问:
Design Help! java generics in a enum factory transformer!
I am wondering if I could get some input on a good way to design this.  I will put my approach but I think that there is a better solution (hence the question :) ).

I want to create an enum (to make clear the options and to avoid a singleton architecture) that has accessors for creating one object from another.  But what those objects are is pretty flexible.

Think of it as a way to limit the number of options for this transformation.

Let me go into a little of the hierarchy. If I am going from a diverse set of objects to something like this:

```<code>class Base {...}
class ValueA extends Base {...}
class ValueB extends Base {...}
</code>```

I was thinking of doing something like this:

```<code>public enum ValueTransformer{
  VALUE_A{

    @Override
    public <T> T createVo (Class<T> expectedRtn, Object obj) {
      ValueA retObj = null;

      if (expectedRtn == getReturnType ()) {
        if (obj != null && CanBeTranslatedToA.class == obj.getClass ()) {
          retObj = new ValueA ();
          /*...*/
        }
      }

      return retObj;
    }

    @Override
    public Class<ValueA> getReturnType () { return ValueA.class; }

  },
  VALUE_B {
    @Override
    public Class<ValueB> getReturnType () { return ValueB.class; }

    @Override
    public <T> T createVo (Class<T> expectedRtn, Object obj) {
      ValueB retObj = null;

      if (expectedRtn == getReturnType ()) {
        if (obj != null && CanBeTranslatedToB.class == obj.getClass ()) {
          retObj = new ValueB ();
          /*...*/
        }  else if (obj != null && AnotherClassForB.class = obj.getClass ()){
          retObj = new ValueB();
          /* ... */
        }
      }

      return retObj;
    }
  };

  public abstract <T> Class<T> getReturnType ();
  public abstract <T> T createVo (Class<T> expectedRtn, Object obj);
}
</code>```

Is this a decent design?  This enum will probably grow, and what ValueA and ValueB can be created from might change (as the sys grows).  I could return a 'Base' in all those cases, but it would require a cast and a check.  I'd prefer to not have that.

Is it necessary for me to have the expectedRtn parameter?  Should I be using Generics at all?  I am fairly new to Java so I am not always sure the best way to handle this case.

Thanks for any tips!!!!

答:
Regarding Generics, Java doesn't have "real" generics, which can be both beneficial and detrimental in this case. Using generics is tricky when you don't know at compile time exactly what type of object you're dealing with. If the code consuming this information actually knows which type of object it's supposed to expect from a call to ValueTransformer.ValueA.createVo, then it should honestly be expected to cast the returned value. I would expect the call to look more like this:

```<code>MyTypeA myType = (MyTypeA)ValueTransformer.ValueA.createVo(sourceObject);
</code>```

If I'm getting the wrong type out of this method, I would rather see a Cast exception on this line (where the problem really happened) than a null pointer exception later on. This is correct "fail-fast" practice.

If you really don't like the explicit casting, I've seen a cool trick that lets you cast these things implicitly. I think it goes something like this:

```<code>public abstract <T> T createVo (Object obj) {...}

MyTypeA myType = ValueTransformer.ValueA.createVo(sourceObject);
</code>```

However, I don't really recommend this approach because it still performs the cast at runtime, but nobody would suspect that by looking at your usage code.

I can see a few goals that you may be hoping to achieve:

Have a single "source of truth" to go to for all objects of the given Base class.

Allow the creation of an instance of a given object every time you request one.

Have type-safety and avoid casting at runtime.

Unless you have other requirements I'm not thinking of, it seems like a factory would be preferable:

```<code>public class ValueFactory
{
    public ValueA getValueA(Object obj) {return new ValueA();}
    public ValueB getValueB(Object obj) {return new ValueB();}
}
</code>```

This satisfies all the requirements mentioned above. Furthermore, if you know what type of object is required to produce a ValueA object, you can use a more explicit type on the input value.

Body:
I am wondering if I could get some input on a good way to design this.  I will put my approach but I think that there is a better solution (hence the question :) ).

I want to create an enum (to make clear the options and to avoid a singleton architecture) that has accessors for creating one object from another.  But what those objects are is pretty flexible.

Think of it as a way to limit the number of options for this transformation.

Let me go into a little of the hierarchy. If I am going from a diverse set of objects to something like this:

class Base {...}
class ValueA extends Base {...}
class ValueB extends Base {...}

I was thinking of doing something like this:

public enum ValueTransformer{
  VALUE_A{

    @Override
    public <T> T createVo (Class<T> expectedRtn, Object obj) {
      ValueA retObj = null;

      if (expectedRtn == getReturnType ()) {
        if (obj != null && CanBeTranslatedToA.class == obj.getClass ()) {
          retObj = new ValueA ();
          /*...*/
        }
      }

      return retObj;
    }

    @Override
    public Class<ValueA> getReturnType () { return ValueA.class; }

  },
  VALUE_B {
    @Override
    public Class<ValueB> getReturnType () { return ValueB.class; }

    @Override
    public <T> T createVo (Class<T> expectedRtn, Object obj) {
      ValueB retObj = null;

      if (expectedRtn == getReturnType ()) {
        if (obj != null && CanBeTranslatedToB.class == obj.getClass ()) {
          retObj = new ValueB ();
          /*...*/
        }  else if (obj != null && AnotherClassForB.class = obj.getClass ()){
          retObj = new ValueB();
          /* ... */
        }
      }

      return retObj;
    }
  };

  public abstract <T> Class<T> getReturnType ();
  public abstract <T> T createVo (Class<T> expectedRtn, Object obj);
}

Is this a decent design?  This enum will probably grow, and what ValueA and ValueB can be created from might change (as the sys grows).  I could return a 'Base' in all those cases, but it would require a cast and a check.  I'd prefer to not have that.

Is it necessary for me to have the expectedRtn parameter?  Should I be using Generics at all?  I am fairly new to Java so I am not always sure the best way to handle this case.

Thanks for any tips!!!!

Body:
Regarding Generics, Java doesn't have "real" generics, which can be both beneficial and detrimental in this case. Using generics is tricky when you don't know at compile time exactly what type of object you're dealing with. If the code consuming this information actually knows which type of object it's supposed to expect from a call to ValueTransformer.ValueA.createVo, then it should honestly be expected to cast the returned value. I would expect the call to look more like this:

MyTypeA myType = (MyTypeA)ValueTransformer.ValueA.createVo(sourceObject);

If I'm getting the wrong type out of this method, I would rather see a Cast exception on this line (where the problem really happened) than a null pointer exception later on. This is correct "fail-fast" practice.

If you really don't like the explicit casting, I've seen a cool trick that lets you cast these things implicitly. I think it goes something like this:

public abstract <T> T createVo (Object obj) {...}

MyTypeA myType = ValueTransformer.ValueA.createVo(sourceObject);

However, I don't really recommend this approach because it still performs the cast at runtime, but nobody would suspect that by looking at your usage code.

I can see a few goals that you may be hoping to achieve:

Have a single "source of truth" to go to for all objects of the given Base class.

Allow the creation of an instance of a given object every time you request one.

Have type-safety and avoid casting at runtime.

Unless you have other requirements I'm not thinking of, it seems like a factory would be preferable:

public class ValueFactory
{
    public ValueA getValueA(Object obj) {return new ValueA();}
    public ValueB getValueB(Object obj) {return new ValueB();}
}

This satisfies all the requirements mentioned above. Furthermore, if you know what type of object is required to produce a ValueA object, you can use a more explicit type on the input value.


来源: stackexchange

问:
How is Instant Articles updated on the Android App?
It seems like Instant Articles are cached on Android's Facebook App. Does anyone know how this works in terms of getting articles updated?

We published an article, but then made some typo changes a few hours later. The changes came through on the iOS App, but not on the Android App.

Both apps had the first version of the article loaded. Does Android Facebook App cache it in another way, or something?

答:
Actually that's a confirmed bug in the Android Facebook app, at least up to version 117. See the following link:

https://developers.facebook.com/bugs/731508133684525/

ContentLicense: CC BY-SA 3.0


问:
Why does strptime from Time::Piece not parse my format?
My collegue (who has left the company) has written a bunch of scripts, including batch and Perl scripts, and I'm getting rid of the regional settings dependencies.

In the last Perl script, he's written the following piece of code:

```<code>my $format = "%d.%m.%Y %H:%M";
my $today_converted = Time::Piece->strptime($today, $format) - ONE_HOUR - ONE_HOUR - ONE_HOUR - ONE_HOUR - ONE_HOUR;
</code>```

(the idea is to get five hours before midnight of that particular date)

The value of $today seems to be "03/04/2017" (which stands for the third of April (European dateformat)), which seems not to be understood by Time::Piece implementation:

```<code>Error parsing time at C:/Perl64/lib/Time/Piece.pm line 481.
</code>```

Which format can I use which is understood by Time::Piece Perl implementation?

答: In the format you have dots . as the date delimiter, but in the data you have slashes /. That's why it doesn't parse. It needs an exact match.

Body:
My collegue (who has left the company) has written a bunch of scripts, including batch and Perl scripts, and I'm getting rid of the regional settings dependencies.

In the last Perl script, he's written the following piece of code:

my $format = "%d.%m.%Y %H:%M";
my $today_converted = Time::Piece->strptime($today, $format) - ONE_HOUR - ONE_HOUR - ONE_HOUR - ONE_HOUR - ONE_HOUR;

(the idea is to get five hours before midnight of that particular date)

The value of $today seems to be "03/04/2017" (which stands for the third of April (European dateformat)), which seems not to be understood by Time::Piece implementation:

Error parsing time at C:/Perl64/lib/Time/Piece.pm line 481.

Which format can I use which is understood by Time::Piece Perl implementation?


问:
Region.IsVisible(PointF) has very slow performance for large floating point values
I have run into a strange performance issue, and it would be great with an explanation to the behavior I'm experiencing.

I'm using System.Drawing.Region.IsVisible(PointF) to determine if a point is inside a polygon. This usually works very well, but yesterday I noticed that the performance of the IsVisible method becomes very slow if the polygon is complex and it consists of large x- and y values.

Below is some code to reproduce the issue (and an image that shows the shape of the polygon), sorry for the large array sizes, but the polygon needs to be quite complex before the issue appears.

When calling IsVisible on the original points my machine takes 460 651 milliseconds to finish, whereas when I first divide all points by 1000, and then call the method, it takes 1 millisecond. Why I'm I seeing such a big difference in the timing? I did not think the actual values of a float would affect performance.

```using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;

namespace PerformanceTest
{
    class Program
    {
        static void Main(string[] args)
        {

            // Create complex polygon with large x and y values
            float[] xValues = {1.014498E+07f, 1.016254E+07f, 1.019764E+07f, 1.021519E+07f, 1.023274E+07f, 1.026785E+07f, 1.026785E+07f, 1.02854E+07f, 1.02854E+07f, 1.030295E+07f, 1.03205E+07f, 1.033805E+07f, 1.035561E+07f, 1.037316E+07f, 1.039071E+07f, 1.040826E+07f, 1.042581E+07f, 1.044337E+07f, 1.046092E+07f, 1.047847E+07f, 1.049602E+07f, 1.051357E+07f, 1.054868E+07f, 1.056623E+07f, 1.058378E+07f, 1.060133E+07f, 1.061888E+07f, 1.061888E+07f, 1.063644E+07f, 1.065399E+07f, 1.068909E+07f, 1.068909E+07f, 1.070664E+07f, 1.07242E+07f, 1.074175E+07f, 1.074175E+07f, 1.07593E+07f, 1.07593E+07f, 1.077685E+07f, 1.07944E+07f, 1.07944E+07f, 1.081196E+07f, 1.081196E+07f, 1.081196E+07f, 1.082951E+07f, 1.084706E+07f, 1.084706E+07f, 1.086461E+07f, 1.086461E+07f, 1.088216E+07f, 1.089971E+07f, 1.091727E+07f, 1.093482E+07f, 1.098747E+07f, 1.100503E+07f, 1.102258E+07f, 1.104013E+07f, 1.105768E+07f, 1.107523E+07f, 1.107523E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.112789E+07f, 1.112789E+07f, 1.112789E+07f, 1.114544E+07f, 1.116299E+07f, 1.118054E+07f, 1.11981E+07f, 1.12332E+07f, 1.125075E+07f, 1.12683E+07f, 1.128586E+07f, 1.130341E+07f, 1.135606E+07f, 1.137361E+07f, 1.139117E+07f, 1.140872E+07f, 1.144382E+07f, 1.146137E+07f, 1.147893E+07f, 1.149648E+07f, 1.151403E+07f, 1.153158E+07f, 1.154913E+07f, 1.156669E+07f, 1.156669E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.156669E+07f, 1.156669E+07f, 1.151403E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.153158E+07f, 1.154913E+07f, 1.156669E+07f, 1.156669E+07f, 1.158424E+07f, 1.160179E+07f, 1.160179E+07f, 1.161934E+07f, 1.165444E+07f, 1.1672E+07f, 1.168955E+07f, 1.17071E+07f, 1.172465E+07f, 1.17422E+07f, 1.175976E+07f, 1.177731E+07f, 1.179486E+07f, 1.181241E+07f, 1.182996E+07f, 1.184752E+07f, 1.186507E+07f, 1.188262E+07f, 1.190017E+07f, 1.190017E+07f, 1.191772E+07f, 1.191772E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.193528E+07f, 1.195283E+07f, 1.197038E+07f, 1.198793E+07f, 1.200548E+07f, 1.202303E+07f, 1.204059E+07f, 1.205814E+07f, 1.207569E+07f, 1.209324E+07f, 1.211079E+07f, 1.212835E+07f, 1.21459E+07f, 1.216345E+07f, 1.2181E+07f, 1.219855E+07f, 1.221611E+07f, 1.221611E+07f, 1.223366E+07f, 1.225121E+07f, 1.226876E+07f, 1.226876E+07f, 1.228631E+07f, 1.230386E+07f, 1.230386E+07f, 1.230386E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.232142E+07f, 1.235652E+07f, 1.235652E+07f, 1.237407E+07f, 1.237407E+07f, 1.239162E+07f, 1.239162E+07f, 1.240918E+07f, 1.242673E+07f, 1.242673E+07f, 1.244428E+07f, 1.247938E+07f, 1.249694E+07f, 1.251449E+07f, 1.253204E+07f, 1.254959E+07f, 1.256714E+07f, 1.258469E+07f, 1.260225E+07f, 1.263735E+07f, 1.26549E+07f, 1.267245E+07f, 1.269001E+07f, 1.270756E+07f, 1.272511E+07f, 1.272511E+07f, 1.274266E+07f, 1.274266E+07f, 1.276021E+07f, 1.276021E+07f, 1.277776E+07f, 1.277776E+07f, 1.277776E+07f, 1.277776E+07f, 1.279532E+07f, 1.279532E+07f, 1.279532E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.281287E+07f, 1.279532E+07f, 1.277776E+07f, 1.276021E+07f, 1.276021E+07f, 1.274266E+07f, 1.274266E+07f, 1.272511E+07f, 1.272511E+07f, 1.272511E+07f, 1.274266E+07f, 1.276021E+07f, 1.279532E+07f, 1.281287E+07f, 1.283042E+07f, 1.284797E+07f, 1.286552E+07f, 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8352763f, 8352763f, 8352763f, 8370237f, 8370237f, 8387712f, 8387712f, 8405186f, 8422661f, 8422661f, 8440134f, 8457609f, 8492558f, 8527506f, 8544981f, 8562456f, 8579930f, 8597405f, 8614878f, 8632353f, 8649828f, 8667302f, 8702250f, 8719725f, 8737200f, 8772149f, 8789622f, 8807097f, 8824572f, 8842046f, 8876994f, 8894469f, 8911944f, 8929418f, 8946893f, 8964366f, 8964366f, 8981841f, 8999316f, 9016790f, 9034265f, 9034265f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9016790f, 8999316f, 8964366f, 8946893f, 8929418f, 8911944f, 8876994f, 8859521f, 8842046f, 8824572f, 8807097f, 8789622f, 8772149f, 8754674f, 8702250f, 8667302f, 8649828f, 8632353f, 8614878f, 8597405f, 8579930f, 8562456f, 8544981f, 8510033f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8510033f, 8544981f, 8544981f, 8562456f, 8562456f, 8597405f, 8614878f, 8632353f, 8667302f, 8702250f, 8719725f, 8754674f, 8789622f, 8824572f, 8842046f, 8859521f, 8876994f, 8911944f, 8929418f, 8964366f, 8964366f, 8999316f, 9016790f, 9034265f, 9086688f, 9104162f, 9139110f, 9156585f, 9174060f, 9209009f, 9243957f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9243957f, 9226482f, 9191534f, 9174060f, 9156585f, 9086688f, 9051738f, 9034265f, 8999316f, 8981841f, 8964366f, 8929418f, 8894469f, 8876994f, 8842046f, 8824572f, 8807097f, 8789622f, 8772149f, 8754674f, 8702250f, 8684777f, 8667302f, 8667302f, 8649828f, 8614878f, 8597405f, 8579930f, 8562456f, 8562456f, 8527506f, 8510033f, 8492558f, 8475084f, 8440134f, 8422661f, 8422661f, 8387712f, 8370237f, 8370237f, 8370237f, 8370237f, 8370237f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8352763f, 8370237f, 8405186f, 8440134f, 8457609f, 8492558f, 8510033f, 8527506f, 8562456f, 8579930f, 8597405f, 8597405f, 8632353f, 8632353f, 8667302f, 8702250f, 8719725f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8737200f, 8719725f, 8702250f, 8684777f, 8667302f, 8649828f, 8632353f, 8614878f, 8562456f, 8527506f, 8440134f, 8422661f, 8387712f, 8352763f, 8317815f, 8300340f, 8282865f, 8265391f, 8247917f, 8212968f, 8212968f, 8160545f, 8143071f, 8125596f, 8108121f, 8108121f, 8090647f, 8090647f, 8073173f, 8073173f, 8055699f, 8055699f, 8055699f, 8038224f, 8038224f, 8038224f, 8038224f, 8038224f, 8020749f, 8020749f, 8003275f, 8003275f, 7985801f, 7950852f, 7933377f, 7915903f, 7915903f, 7880955f, 7863480f, 7846005f, 7828531f, 7793583f, 7776108f, 7758633f, 7741159f, 7723685f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7723685f, 7723685f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7723685f, 7723685f, 7688736f, 7671261f, 7653787f, 7583889f, 7566415f, 7513992f, 7461569f, 7444095f, 7409145f, 7374197f, 7356723f, 7321773f, 7304299f, 7286825f, 7269351f, 7251876f, 7234401f, 7199453f, 7181979f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7181979f, 7199453f };

            PointF[] points = xValues.Zip(yValues, (x, y) => new PointF(x, y)).ToArray();

            // Create a region with the original values
            GraphicsPath pathWithOriginalPoints = new GraphicsPath();
            pathWithOriginalPoints.AddPolygon(points);
            Region regionFromOriginalPoints = new Region(pathWithOriginalPoints);

            // Create a region with the values divided by 1000
            GraphicsPath pathDividedBy1000 = new GraphicsPath();
            pathDividedBy1000.AddPolygon(points.Select(p => new PointF(p.X/1000f, p.Y/1000f)).ToArray());
            Region regionDividedby1000 = new Region(pathDividedBy1000);

            // Time call to Region.IsVisible(PointF)
            var stopwatch = Stopwatch.StartNew();
            Console.WriteLine("Computing region.IsVisible for points divided by 1000:");
            regionDividedby1000.IsVisible(new PointF(0f, 0f));
            var dividedBy1000Timing = stopwatch.ElapsedMilliseconds;
            Console.WriteLine($"Elapsed time: {dividedBy1000Timing} ms");

            stopwatch.Restart();
            Console.WriteLine("Computing region.IsVisible for original points");
            regionFromOriginalPoints.IsVisible(new PointF(0f, 0f));
            var originalTiming = stopwatch.ElapsedMilliseconds;
            Console.WriteLine($"Elapsed time: {originalTiming} ms");
        }
    }
}
```

答:
TLTR

The time it takes to do one Region.IsVisible(Point) call doesn't depend on the number of points at all. Instead it depends on the number of rectangles it takes to fully and precisely cover the region. Which depends on..:

the shapes those points describe and usually

the size of the shape.

Example 1: A rectangular region has four points and it always takes one rectangle to cover it. This would not change if you would add a large number of points as long as they all lie on the sides of the rectangle!

Example 2: A circular region also (!) has four points () but the number of rectangles you need to cover it fully **depends on the diameter of that circle. See the graphics at the bottom!

Full Story

Region is not what I would call a 'well-documented' class.

You can see that the inner working seems to rely on the RegionData, which can can accessed by calling var RData = your Region.GetRegionData().

Here the very same holds: Not well-documented, to say the least. Maybe I just can't find it, but there seems to be no info on how those bytes are structured..

(The numbers below suggest that each point needed takes 1 byte as a type indicator plus 2+4 bytes for the two float coordinates. This would be like the PathPoints&PathTypes in the GraphicsPath.  In your example with 924+1 points and 1+2*4 bytes this makes up 8325 bytes; another 27 bytes are there; 8 could hold the scaling..)

One thing is interesting though: Looking into the RegionData from both of your Regions one can easily see that they have the same size..: 8352. This is an indication that the RegionData are not directly relevant for the additional time anyway..

But there is another, somewhat equally mysterious, read: ill-documented call: GetRegionScans. MSDN says this about it:

Returns an array of RectangleF structures that approximate this Region
  after the specified matrix transformation is applied.

First lets see what happens if we pull out thoses 'scans'  for both of your Regions:

```<code>Matrix M = new Matrix();

var scans1 = regionFromOriginalPoints.GetRegionScans(M);
var scans2 = regionDividedby1000.GetRegionScans(M);
</code>```

I use the simple identity matrix (*), i.e. no transformation and these are the reults:

```<code>scans1.Length = 5.960.690
scans2.Length = 5.956
</code>```

So it creates 1000 times more rectangles to approximate the Region, and, lo and behold for doing so it also takes a lot of time..:

This is not really surprising: The unscaled path covers a huge area and to approximate it I would expect many more rectangles are needed. I don't know how the approximation works, but it might decide that, even though RectangleF are returned,  no rectangle with any side being less than 1 pixel is needed.

So I conclude that the IsVisible call internally needs to create those approximation rectangles and it needs enough of them to cover every full pixel inside the region. (Note that Region does not support partial/anti-aliased pixels!)  The larger the region's bounds the more pixels fit in and the longer the scanning process takes.

I also assume that it is strictly the scanning process that eats up the time.

Next: Doing a RectangleF.Contains(Point) should be extremely fast, even for a million calls. Let's see; when I measure this:

```<code>int hits = 0;
PointF pt = new PointF(123.456f, 789.012f);
foreach (RectangleF r in scans1) if (r.Contains(pt)) hits++;
</code>```

..it takes only  42ms to complete.  So once you have cached the scan rectangles you can easily do a lot of hit tests on them instead of doing separate IsVisible calls..

Here is a summary of the numbers :

Your original path:

number of polygon points = 924

  regionData1.Length = 8.352

  scans1.Length = 5.960.690

  Elapsed time1: 453.187 ms

The path scaled down by 1000:

number of polygon points = 924

  regionData2.Length = 8.352

  scans2.Length= 5.956

  Elapsed time2: 2 ms

Elapsed time for full set of scans: 41 ms

Finally: To better understand the scan rectangles I approximated a circle with alternating colors:

```<code>for (int i = 0; i < scans.Length; i++)
     g.FillRectangle(i%2 == 0 ? Brushes.ForestGreen : Brushes.Salmon, scans[i]);
</code>```

You can see that at the top and bottom every row is one rectangle because here the curve is flat and the x coordinates move outward quickly. The closer we get to the middle the larger (i..e. taller) the rectangles can get... So we can see that the approximation strictly follows the rows..

This holds true even if the bounding rectangle is taller than wide and, using the columns, one might do with fewer rectangles:

Here both ellipses (222x111 and 111x222) are approximated with 85 horizontal stripes. That is less than the circle because of the different curvature..

(*) - We have skipped over the Matrix; but it could be used to modify the result by either scaling the data up or down. The circle has a Height of 222 pixels and it takes 135 scan rectangles to approximate it. If we scale up the Matrix, (i.e. the Graphics object used to represent the Region): m.Scale(10,10); it takes 1315 scan rectangles to cover the upscaled circle.

So a matrix scaled down by 0.001f could be used instead of scaling your data points; but it would test only the scaled down version and will likely either miss pixels around the borders or include wrong ones. So best use only the correct scale you actually need..

(* *) Note that the circular GraphicsPath does have 13 PathPoints; but these are really just four real points (plus the 1st one repeated to close the figure) plus two control points in between each pair of points; so 5 + 4*2 = 13. Also note that any line in a GraphicsPath is either straight or a bezier curve. This includes arcs, ellipses and circles!

Body:
I have run into a strange performance issue, and it would be great with an explanation to the behavior I'm experiencing.

I'm using System.Drawing.Region.IsVisible(PointF) to determine if a point is inside a polygon. This usually works very well, but yesterday I noticed that the performance of the IsVisible method becomes very slow if the polygon is complex and it consists of large x- and y values.

Below is some code to reproduce the issue (and an image that shows the shape of the polygon), sorry for the large array sizes, but the polygon needs to be quite complex before the issue appears.

When calling IsVisible on the original points my machine takes 460 651 milliseconds to finish, whereas when I first divide all points by 1000, and then call the method, it takes 1 millisecond. Why I'm I seeing such a big difference in the timing? I did not think the actual values of a float would affect performance.

using System;
using System.Diagnostics;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;

namespace PerformanceTest
{
    class Program
    {
        static void Main(string[] args)
        {

            // Create complex polygon with large x and y values
            float[] xValues = {1.014498E+07f, 1.016254E+07f, 1.019764E+07f, 1.021519E+07f, 1.023274E+07f, 1.026785E+07f, 1.026785E+07f, 1.02854E+07f, 1.02854E+07f, 1.030295E+07f, 1.03205E+07f, 1.033805E+07f, 1.035561E+07f, 1.037316E+07f, 1.039071E+07f, 1.040826E+07f, 1.042581E+07f, 1.044337E+07f, 1.046092E+07f, 1.047847E+07f, 1.049602E+07f, 1.051357E+07f, 1.054868E+07f, 1.056623E+07f, 1.058378E+07f, 1.060133E+07f, 1.061888E+07f, 1.061888E+07f, 1.063644E+07f, 1.065399E+07f, 1.068909E+07f, 1.068909E+07f, 1.070664E+07f, 1.07242E+07f, 1.074175E+07f, 1.074175E+07f, 1.07593E+07f, 1.07593E+07f, 1.077685E+07f, 1.07944E+07f, 1.07944E+07f, 1.081196E+07f, 1.081196E+07f, 1.081196E+07f, 1.082951E+07f, 1.084706E+07f, 1.084706E+07f, 1.086461E+07f, 1.086461E+07f, 1.088216E+07f, 1.089971E+07f, 1.091727E+07f, 1.093482E+07f, 1.098747E+07f, 1.100503E+07f, 1.102258E+07f, 1.104013E+07f, 1.105768E+07f, 1.107523E+07f, 1.107523E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.109279E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.111034E+07f, 1.112789E+07f, 1.112789E+07f, 1.112789E+07f, 1.114544E+07f, 1.116299E+07f, 1.118054E+07f, 1.11981E+07f, 1.12332E+07f, 1.125075E+07f, 1.12683E+07f, 1.128586E+07f, 1.130341E+07f, 1.135606E+07f, 1.137361E+07f, 1.139117E+07f, 1.140872E+07f, 1.144382E+07f, 1.146137E+07f, 1.147893E+07f, 1.149648E+07f, 1.151403E+07f, 1.153158E+07f, 1.154913E+07f, 1.156669E+07f, 1.156669E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.158424E+07f, 1.156669E+07f, 1.156669E+07f, 1.151403E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.149648E+07f, 1.153158E+07f, 1.154913E+07f, 1.156669E+07f, 1.156669E+07f, 1.158424E+07f, 1.160179E+07f, 1.160179E+07f, 1.161934E+07f, 1.165444E+07f, 1.1672E+07f, 1.168955E+07f, 1.17071E+07f, 1.172465E+07f, 1.17422E+07f, 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6762593f, 6745119f, 6727644f, 6710169f, 6692695f, 6675221f, 6657747f, 6657747f, 6640272f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6622797f, 6640272f, 6657747f, 6692695f, 6692695f, 6710169f, 6727644f, 6745119f, 6762593f, 6780067f, 6780067f, 6797541f, 6815016f, 6832491f, 6849965f, 6867439f, 6884913f, 6902388f, 6919863f, 6937337f, 6954811f, 6972285f, 6989760f, 7007235f, 7024709f, 7042183f, 7059657f, 7077132f, 7094607f, 7112081f, 7129555f, 7147029f, 7164504f, 7181979f, 7199453f, 7234401f, 7234401f, 7251876f, 7251876f, 7269351f, 7286825f, 7304299f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7321773f, 7304299f, 7286825f, 7269351f, 7251876f, 7234401f, 7216927f, 7199453f, 7181979f, 7164504f, 7147029f, 7129555f, 7112081f, 7094607f, 7077132f, 7042183f, 7024709f, 7007235f, 6989760f, 6954811f, 6937337f, 6919863f, 6902388f, 6849965f, 6832491f, 6815016f, 6797541f, 6780067f, 6780067f, 6762593f, 6762593f, 6762593f, 6745119f, 6745119f, 6745119f, 6745119f, 6745119f, 6745119f, 6762593f, 6762593f, 6797541f, 6832491f, 6867439f, 6884913f, 6884913f, 6919863f, 6954811f, 6954811f, 6972285f, 6989760f, 7007235f, 7042183f, 7042183f, 7059657f, 7077132f, 7094607f, 7094607f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7112081f, 7094607f, 7077132f, 7042183f, 7024709f, 7024709f, 7007235f, 6989760f, 6989760f, 6972285f, 6954811f, 6937337f, 6937337f, 6919863f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6902388f, 6919863f, 6919863f, 6954811f, 6972285f, 6972285f, 6989760f, 7024709f, 7042183f, 7059657f, 7094607f, 7112081f, 7129555f, 7164504f, 7181979f, 7199453f, 7234401f, 7251876f, 7269351f, 7286825f, 7321773f, 7321773f, 7339248f, 7339248f, 7356723f, 7374197f, 7374197f, 7374197f, 7374197f, 7374197f, 7391671f, 7391671f, 7409145f, 7409145f, 7426620f, 7426620f, 7426620f, 7444095f, 7444095f, 7461569f, 7479043f, 7496517f, 7513992f, 7513992f, 7513992f, 7531467f, 7548941f, 7548941f, 7566415f, 7601364f, 7618839f, 7636313f, 7653787f, 7671261f, 7688736f, 7706211f, 7741159f, 7793583f, 7828531f, 7846005f, 7880955f, 7880955f, 7898429f, 7898429f, 7915903f, 7933377f, 7933377f, 7950852f, 7950852f, 7950852f, 7950852f, 7950852f, 7950852f, 7950852f, 7968327f, 7985801f, 8003275f, 8020749f, 8038224f, 8055699f, 8073173f, 8090647f, 8108121f, 8125596f, 8160545f, 8178019f, 8195493f, 8212968f, 8212968f, 8230443f, 8247917f, 8265391f, 8282865f, 8282865f, 8282865f, 8282865f, 8282865f, 8282865f, 8282865f, 8282865f, 8265391f, 8230443f, 8212968f, 8195493f, 8178019f, 8160545f, 8160545f, 8143071f, 8143071f, 8125596f, 8108121f, 8108121f, 8090647f, 8090647f, 8073173f, 8038224f, 8038224f, 8020749f, 8020749f, 8003275f, 7985801f, 7985801f, 7968327f, 7950852f, 7950852f, 7933377f, 7933377f, 7933377f, 7933377f, 7915903f, 7898429f, 7898429f, 7898429f, 7898429f, 7898429f, 7898429f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7880955f, 7898429f, 7898429f, 7933377f, 7968327f, 7985801f, 8003275f, 8020749f, 8055699f, 8073173f, 8108121f, 8108121f, 8143071f, 8178019f, 8178019f, 8212968f, 8212968f, 8230443f, 8247917f, 8265391f, 8282865f, 8282865f, 8317815f, 8335289f, 8352763f, 8387712f, 8405186f, 8422661f, 8440134f, 8457609f, 8475084f, 8510033f, 8527506f, 8544981f, 8562456f, 8614878f, 8632353f, 8667302f, 8684777f, 8737200f, 8772149f, 8789622f, 8824572f, 8842046f, 8859521f, 8876994f, 8894469f, 8929418f, 8929418f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8946893f, 8911944f, 8894469f, 8859521f, 8824572f, 8789622f, 8772149f, 8702250f, 8684777f, 8667302f, 8632353f, 8614878f, 8597405f, 8562456f, 8544981f, 8510033f, 8492558f, 8475084f, 8457609f, 8440134f, 8422661f, 8405186f, 8387712f, 8370237f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8352763f, 8370237f, 8370237f, 8387712f, 8387712f, 8405186f, 8422661f, 8422661f, 8440134f, 8457609f, 8492558f, 8527506f, 8544981f, 8562456f, 8579930f, 8597405f, 8614878f, 8632353f, 8649828f, 8667302f, 8702250f, 8719725f, 8737200f, 8772149f, 8789622f, 8807097f, 8824572f, 8842046f, 8876994f, 8894469f, 8911944f, 8929418f, 8946893f, 8964366f, 8964366f, 8981841f, 8999316f, 9016790f, 9034265f, 9034265f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9051738f, 9016790f, 8999316f, 8964366f, 8946893f, 8929418f, 8911944f, 8876994f, 8859521f, 8842046f, 8824572f, 8807097f, 8789622f, 8772149f, 8754674f, 8702250f, 8667302f, 8649828f, 8632353f, 8614878f, 8597405f, 8579930f, 8562456f, 8544981f, 8510033f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8492558f, 8510033f, 8544981f, 8544981f, 8562456f, 8562456f, 8597405f, 8614878f, 8632353f, 8667302f, 8702250f, 8719725f, 8754674f, 8789622f, 8824572f, 8842046f, 8859521f, 8876994f, 8911944f, 8929418f, 8964366f, 8964366f, 8999316f, 9016790f, 9034265f, 9086688f, 9104162f, 9139110f, 9156585f, 9174060f, 9209009f, 9243957f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9261432f, 9243957f, 9226482f, 9191534f, 9174060f, 9156585f, 9086688f, 9051738f, 9034265f, 8999316f, 8981841f, 8964366f, 8929418f, 8894469f, 8876994f, 8842046f, 8824572f, 8807097f, 8789622f, 8772149f, 8754674f, 8702250f, 8684777f, 8667302f, 8667302f, 8649828f, 8614878f, 8597405f, 8579930f, 8562456f, 8562456f, 8527506f, 8510033f, 8492558f, 8475084f, 8440134f, 8422661f, 8422661f, 8387712f, 8370237f, 8370237f, 8370237f, 8370237f, 8370237f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8335289f, 8352763f, 8370237f, 8405186f, 8440134f, 8457609f, 8492558f, 8510033f, 8527506f, 8562456f, 8579930f, 8597405f, 8597405f, 8632353f, 8632353f, 8667302f, 8702250f, 8719725f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8754674f, 8737200f, 8719725f, 8702250f, 8684777f, 8667302f, 8649828f, 8632353f, 8614878f, 8562456f, 8527506f, 8440134f, 8422661f, 8387712f, 8352763f, 8317815f, 8300340f, 8282865f, 8265391f, 8247917f, 8212968f, 8212968f, 8160545f, 8143071f, 8125596f, 8108121f, 8108121f, 8090647f, 8090647f, 8073173f, 8073173f, 8055699f, 8055699f, 8055699f, 8038224f, 8038224f, 8038224f, 8038224f, 8038224f, 8020749f, 8020749f, 8003275f, 8003275f, 7985801f, 7950852f, 7933377f, 7915903f, 7915903f, 7880955f, 7863480f, 7846005f, 7828531f, 7793583f, 7776108f, 7758633f, 7741159f, 7723685f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7706211f, 7723685f, 7723685f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7741159f, 7723685f, 7723685f, 7688736f, 7671261f, 7653787f, 7583889f, 7566415f, 7513992f, 7461569f, 7444095f, 7409145f, 7374197f, 7356723f, 7321773f, 7304299f, 7286825f, 7269351f, 7251876f, 7234401f, 7199453f, 7181979f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7164504f, 7181979f, 7199453f };

            PointF[] points = xValues.Zip(yValues, (x, y) => new PointF(x, y)).ToArray();

            // Create a region with the original values
            GraphicsPath pathWithOriginalPoints = new GraphicsPath();
            pathWithOriginalPoints.AddPolygon(points);
            Region regionFromOriginalPoints = new Region(pathWithOriginalPoints);

            // Create a region with the values divided by 1000
            GraphicsPath pathDividedBy1000 = new GraphicsPath();
            pathDividedBy1000.AddPolygon(points.Select(p => new PointF(p.X/1000f, p.Y/1000f)).ToArray());
            Region regionDividedby1000 = new Region(pathDividedBy1000);

            // Time call to Region.IsVisible(PointF)
            var stopwatch = Stopwatch.StartNew();
            Console.WriteLine("Computing region.IsVisible for points divided by 1000:");
            regionDividedby1000.IsVisible(new PointF(0f, 0f));
            var dividedBy1000Timing = stopwatch.ElapsedMilliseconds;
            Console.WriteLine($"Elapsed time: {dividedBy1000Timing} ms");

            stopwatch.Restart();
            Console.WriteLine("Computing region.IsVisible for original points");
            regionFromOriginalPoints.IsVisible(new PointF(0f, 0f));
            var originalTiming = stopwatch.ElapsedMilliseconds;
            Console.WriteLine($"Elapsed time: {originalTiming} ms");
        }
    }
}

Body:
TLTR

The time it takes to do one Region.IsVisible(Point) call doesn't depend on the number of points at all. Instead it depends on the number of rectangles it takes to fully and precisely cover the region. Which depends on..:

the shapes those points describe and usually

the size of the shape.

Example 1: A rectangular region has four points and it always takes one rectangle to cover it. This would not change if you would add a large number of points as long as they all lie on the sides of the rectangle!

Example 2: A circular region also (!) has four points () but the number of rectangles you need to cover it fully **depends on the diameter of that circle. See the graphics at the bottom!

Full Story

Region is not what I would call a 'well-documented' class.

You can see that the inner working seems to rely on the RegionData, which can can accessed by calling var RData = your Region.GetRegionData().

Here the very same holds: Not well-documented, to say the least. Maybe I just can't find it, but there seems to be no info on how those bytes are structured..

(The numbers below suggest that each point needed takes 1 byte as a type indicator plus 2+4 bytes for the two float coordinates. This would be like the PathPoints&PathTypes in the GraphicsPath.  In your example with 924+1 points and 1+2*4 bytes this makes up 8325 bytes; another 27 bytes are there; 8 could hold the scaling..)

One thing is interesting though: Looking into the RegionData from both of your Regions one can easily see that they have the same size..: 8352. This is an indication that the RegionData are not directly relevant for the additional time anyway..

But there is another, somewhat equally mysterious, read: ill-documented call: GetRegionScans. MSDN says this about it:

Returns an array of RectangleF structures that approximate this Region
  after the specified matrix transformation is applied.

First lets see what happens if we pull out thoses 'scans'  for both of your Regions:

Matrix M = new Matrix();

var scans1 = regionFromOriginalPoints.GetRegionScans(M);
var scans2 = regionDividedby1000.GetRegionScans(M);

I use the simple identity matrix (*), i.e. no transformation and these are the reults:

scans1.Length = 5.960.690
scans2.Length = 5.956

So it creates 1000 times more rectangles to approximate the Region, and, lo and behold for doing so it also takes a lot of time..:

This is not really surprising: The unscaled path covers a huge area and to approximate it I would expect many more rectangles are needed. I don't know how the approximation works, but it might decide that, even though RectangleF are returned,  no rectangle with any side being less than 1 pixel is needed.

So I conclude that the IsVisible call internally needs to create those approximation rectangles and it needs enough of them to cover every full pixel inside the region. (Note that Region does not support partial/anti-aliased pixels!)  The larger the region's bounds the more pixels fit in and the longer the scanning process takes.

I also assume that it is strictly the scanning process that eats up the time.

Next: Doing a RectangleF.Contains(Point) should be extremely fast, even for a million calls. Let's see; when I measure this:

int hits = 0;
PointF pt = new PointF(123.456f, 789.012f);
foreach (RectangleF r in scans1) if (r.Contains(pt)) hits++;

..it takes only  42ms to complete.  So once you have cached the scan rectangles you can easily do a lot of hit tests on them instead of doing separate IsVisible calls..

Here is a summary of the numbers :

Your original path:

number of polygon points = 924

  regionData1.Length = 8.352

  scans1.Length = 5.960.690

  Elapsed time1: 453.187 ms

The path scaled down by 1000:

number of polygon points = 924

  regionData2.Length = 8.352

  scans2.Length= 5.956

  Elapsed time2: 2 ms

Elapsed time for full set of scans: 41 ms

Finally: To better understand the scan rectangles I approximated a circle with alternating colors:

for (int i = 0; i < scans.Length; i++)
     g.FillRectangle(i%2 == 0 ? Brushes.ForestGreen : Brushes.Salmon, scans[i]);

You can see that at the top and bottom every row is one rectangle because here the curve is flat and the x coordinates move outward quickly. The closer we get to the middle the larger (i..e. taller) the rectangles can get... So we can see that the approximation strictly follows the rows..

This holds true even if the bounding rectangle is taller than wide and, using the columns, one might do with fewer rectangles:

Here both ellipses (222x111 and 111x222) are approximated with 85 horizontal stripes. That is less than the circle because of the different curvature..

(*) - We have skipped over the Matrix; but it could be used to modify the result by either scaling the data up or down. The circle has a Height of 222 pixels and it takes 135 scan rectangles to approximate it. If we scale up the Matrix, (i.e. the Graphics object used to represent the Region): m.Scale(10,10); it takes 1315 scan rectangles to cover the upscaled circle.

So a matrix scaled down by 0.001f could be used instead of scaling your data points; but it would test only the scaled down version and will likely either miss pixels around the borders or include wrong ones. So best use only the correct scale you actually need..

(* *) Note that the circular GraphicsPath does have 13 PathPoints; but these are really just four real points (plus the 1st one repeated to close the figure) plus two control points in between each pair of points; so 5 + 4*2 = 13. Also note that any line in a GraphicsPath is either straight or a bezier curve. This includes arcs, ellipses and circles!


问:
Uploading images with customizing  in html
I'm a newbie in html and trying to upload image to my homepage.

I already set up the uploading part like below in html,

```<code><div class="collapse navbar-collapse" id="navbar-collapse">
  <ul class="nav navbar-nav navbar-right">
     <li>
       <form action="/upload", method="post", enctype="multipart/form-data">
         <input type="file" style="max-width: 30%; max-height: 50%;"  name="upFile" id="upFile" onchange="getCmaFileView(this,'name')" target="dropzone_1">
         <input type="submit" name="Upload" >
       </form>
     </li>
     <li>
       <form action="/jsondata", method="get", id="jsd", enctype="multipart/form-data"  ></form>
     </li>
     <li><a onclick="save2()" id="imageSave">Save</a></li>
  </ul>
</code>```

However, it shows a button like old-fashioned typical button like below,

and I want it to make my own customized button using  with clicking..

I tried to find in google, but they used
 instead of <form> of mine..
So I posted here customize the file button for image upload

I know this might be a stupid question, but I just want to learn!

How can I make that...?

Thanks in advance!

答:
Here is working example how to style your upload button. Basically you have to hide your html input.

.fileUpload {
    position: relative;
    overflow: hidden;
    margin: 10px;
}
.fileUpload input.upload {
    position: absolute;
    top: 0;
    right: 0;
    margin: 0;
    padding: 0;
    font-size: 20px;
    cursor: pointer;
    opacity: 0;
    filter: alpha(opacity=0);
}```
<pre class="snippet-code-html lang-html prettyprint-override"><code><!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

<!-- Optional theme -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" crossorigin="anonymous">

<div class="fileUpload btn btn-success">
    <span>Click to upload new file</span>
    <input type="file" class="upload" />
</div></code>```

Body:
I'm a newbie in html and trying to upload image to my homepage.

I already set up the uploading part like below in html,

       <form action="/upload", method="post", enctype="multipart/form-data">
         <input type="file" style="max-width: 30%; max-height: 50%;"  name="upFile" id="upFile" onchange="getCmaFileView(this,'name')" target="dropzone_1">
         <input type="submit" name="Upload" >
       </form>

       <form action="/jsondata", method="get", id="jsd", enctype="multipart/form-data"  ></form>

Save

However, it shows a button like old-fashioned typical button like below,

and I want it to make my own customized button using  with clicking..

I tried to find in google, but they used
 instead of <form> of mine..
So I posted here customize the file button for image upload

I know this might be a stupid question, but I just want to learn!

How can I make that...?

Thanks in advance!

Body:
Here is working example how to style your upload button. Basically you have to hide your html input.

.fileUpload {
    position: relative;
    overflow: hidden;
    margin: 10px;
}
.fileUpload input.upload {
    position: absolute;
    top: 0;
    right: 0;
    margin: 0;
    padding: 0;
    font-size: 20px;
    cursor: pointer;
    opacity: 0;
    filter: alpha(opacity=0);
}

<!-- Latest compiled and minified CSS -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">

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问:
How to make 2 threads work on one panel in winform c#?
I am trying to make two threads work at the same time on the same panel in a windows form, the threads are the same. I have looked for answers already but no question treated this thing (at least from what i saw). here is the code :

The code in the form.cs :

```<code>semaphore = new Semaphore();

    p1t1 = new PanelThread(new Point(10, 10),
                         150, Direction.West, Track.track1, pnl1, typetrain.loco,
                         Color.Blue,
                         semaphore
                         );

    p2t2 = new PanelThread(new Point(390, 390),
                         150, Direction.East, Track.track2, panel5, typetrain.loco,
                         Color.Red,
                         semaphore
                         );

    green1t1 = new PanelThread(new Point(10, 10),
                         150, Direction.North, Track.track1, pnl1, typetrain.wagon,
                         Color.Green,
                         semaphore
                         );

    semThread = new Thread(new ThreadStart(semaphore.Start));

    thread1 = new Thread(new ThreadStart(p1t1.Start));

    thread2 = new Thread(new ThreadStart(p2t2.Start));

    thread3 = new Thread(new ThreadStart(green1t1.Start));

    this.Closing += new CancelEventHandler(this.Form1_Closing);

    semThread.Start();
    thread1.Start();
    thread2.Start();
    thread3.Start();
</code>```

the code in the panelthread.cs :

```<code>public PanelThread(Point origin,
                       int delay,
                       Direction direction,
                       Track track,
                       Panel panel,
                       typetrain locwag,
                       Color colour,
                       Semaphore semaphore)
    {
        this.origin = origin;
        this.delay = delay;
        this.direction = direction;
        this.panel = panel;
        this.colour = colour;
        this.plane = origin;
        this.panel.Paint += new PaintEventHandler(this.panel_Paint);
        this.track = track;
        this.locwag = locwag;
        switch (this.direction)
        {
            case Direction.East:
                this.xDelta = -10;
                this.yDelta = 0;
                break;

            case Direction.West:
                this.xDelta = +10;
                this.yDelta = 0;
                break;

            case Direction.North:
                this.xDelta = 0;
                this.yDelta = -10;
                break;

            case Direction.South:
                this.xDelta = 0;
                this.yDelta = +10;
                break;
        }

        this.semaphore = semaphore;
    }
</code>```

When I launch the program, the program bugs at the paint event handler with an System.ArgumentException at the line g.FillRectangle:

```<code>private void panel_Paint(object sender, PaintEventArgs e)
{
    Graphics g = e.Graphics;

    SolidBrush brush = new SolidBrush(colour);
    g.FillRectangle(brush, plane.X, plane.Y, 10, 10);

    brush.Dispose();    //  Dispose of graphic
    g.Dispose();        //  resources
}
</code>```

UPDATE :
I have tried using invoke in the panelthread.cs like this :

```<code>if (this.panel.InvokeRequired)
    {
        this.panel.Invoke((MethodInvoker)delegate { this.panel.Paint += new PaintEventHandler(this.panel_Paint); });
    }
</code>```

I don't have any error now, but the squares are not being created, so i don't go at all in the panel_paint function. I surely have written something wrong in the Invoke calling, or I wrote it in the wrong place.

答: I actually found the error, and having found that the panel_paint is actually always on the main thread, the error was somewhere else. In the end, I saw that I only needed to take out the g.dispose command in panel_paint, as it destroyed the graphic before painted the next object.</p>

ContentLicense: CC BY-SA 4.0

Body:
I am trying to make two threads work at the same time on the same panel in a windows form, the threads are the same. I have looked for answers already but no question treated this thing (at least from what i saw). here is the code :

The code in the form.cs :

semaphore = new Semaphore();

    p1t1 = new PanelThread(new Point(10, 10),
                         150, Direction.West, Track.track1, pnl1, typetrain.loco,
                         Color.Blue,
                         semaphore
                         );

    p2t2 = new PanelThread(new Point(390, 390),
                         150, Direction.East, Track.track2, panel5, typetrain.loco,
                         Color.Red,
                         semaphore
                         );

    green1t1 = new PanelThread(new Point(10, 10),
                         150, Direction.North, Track.track1, pnl1, typetrain.wagon,
                         Color.Green,
                         semaphore
                         );

    semThread = new Thread(new ThreadStart(semaphore.Start));

    thread1 = new Thread(new ThreadStart(p1t1.Start));

    thread2 = new Thread(new ThreadStart(p2t2.Start));

    thread3 = new Thread(new ThreadStart(green1t1.Start));

    this.Closing += new CancelEventHandler(this.Form1_Closing);

    semThread.Start();
    thread1.Start();
    thread2.Start();
    thread3.Start();

the code in the panelthread.cs :

public PanelThread(Point origin,
                       int delay,
                       Direction direction,
                       Track track,
                       Panel panel,
                       typetrain locwag,
                       Color colour,
                       Semaphore semaphore)
    {
        this.origin = origin;
        this.delay = delay;
        this.direction = direction;
        this.panel = panel;
        this.colour = colour;
        this.plane = origin;
        this.panel.Paint += new PaintEventHandler(this.panel_Paint);
        this.track = track;
        this.locwag = locwag;
        switch (this.direction)
        {
            case Direction.East:
                this.xDelta = -10;
                this.yDelta = 0;
                break;

            case Direction.West:
                this.xDelta = +10;
                this.yDelta = 0;
                break;

            case Direction.North:
                this.xDelta = 0;
                this.yDelta = -10;
                break;

            case Direction.South:
                this.xDelta = 0;
                this.yDelta = +10;
                break;
        }

        this.semaphore = semaphore;
    }

When I launch the program, the program bugs at the paint event handler with an System.ArgumentException at the line g.FillRectangle:

private void panel_Paint(object sender, PaintEventArgs e)
{
    Graphics g = e.Graphics;

    SolidBrush brush = new SolidBrush(colour);
    g.FillRectangle(brush, plane.X, plane.Y, 10, 10);

    brush.Dispose();    //  Dispose of graphic
    g.Dispose();        //  resources
}

UPDATE :
I have tried using invoke in the panelthread.cs like this :

if (this.panel.InvokeRequired)
    {
        this.panel.Invoke((MethodInvoker)delegate { this.panel.Paint += new PaintEventHandler(this.panel_Paint); });
    }

I don't have any error now, but the squares are not being created, so i don't go at all in the panel_paint function. I surely have written something wrong in the Invoke calling, or I wrote it in the wrong place.


问:
FlashVars works locally but not live server
I did some code for making a flash audio player .. This player takes the sound source by its FlashVars param. Its working locally fine .. But when it is in server only shows swf file but does dot play sound as expected. Why this happens. My actionscript code is bellow..

```<code>var keyStr:String;
var valueStr:String;
var paramObj:Object = LoaderInfo(this.root.loaderInfo).parameters;   //set the paramObj variable to the parameters property of the LoaderInfo object
for (keyStr in paramObj)
{
    valueStr = String(paramObj[keyStr]);
    var req:URLRequest = new URLRequest(valueStr);

}

    sound_icon.visible =  true
sound_icon.addEventListener(MouseEvent.CLICK, playSound);
var s:Sound = new Sound(req);
gotoAndStop("f2");//firstly  animated sound icon is stopped at the beginning position

function playSound(e:MouseEvent):void{
    sound_icon.visible =  false; //hide sound icon
    gotoAndPlay("f2");           //play animated sound icon from beginning

var mySoundChannel:SoundChannel = s.play(); //reference for getting complete event

mySoundChannel.addEventListener(Event.SOUND_COMPLETE, songFinished);
function songFinished(ev:Event):void
{
   sound_icon.visible =  true;
   gotoAndStop("f2");
}
</code>```

}

and php code is below

```<code>    <div id="flashContent">

        <?php

        $swfSourcePath = "soundtest.swf";
        $soundSourcePath = "4.mp3";

        ?>

        <object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" width="40" height="40" id="soundtest" align="middle">
            <param name="movie" value="<?php echo $swfSourcePath;?>" />
                <param name=FlashVars value="myVariable=<?php echo $soundSourcePath;?>" />

            <!--[if !IE]>-->
            <object type="application/x-shockwave-flash" data="soundtest.swf" width="40" height="40">
                <param name="movie" value="<?php echo $swfSourcePath;?>" />
                    <param name=FlashVars value="myVariable=<?php echo  $soundSourcePath;?>" />

            <!--<![endif]-->
                <a href="http://www.adobe.com/go/getflash">
                    <img src="http://www.adobe.com/images/shared/download_buttons/get_flash_player.gif" alt="Get Adobe Flash player" />
                </a>
            <!--[if !IE]>-->
            </object>
            <!--<![endif]-->
        </object>
    </div>
</code>```

答:
There are some options:

If you use Flash Professional / Animate open File - Publish Settings - Local playback security, set it to Access Network only.

Try to use "flashvars" instead of FlashVars

Try to set source as "soundtest.swf?myVariable=4.mp3"

Body:
I did some code for making a flash audio player .. This player takes the sound source by its FlashVars param. Its working locally fine .. But when it is in server only shows swf file but does dot play sound as expected. Why this happens. My actionscript code is bellow..

var keyStr:String;
var valueStr:String;
var paramObj:Object = LoaderInfo(this.root.loaderInfo).parameters;   //set the paramObj variable to the parameters property of the LoaderInfo object
for (keyStr in paramObj)
{
    valueStr = String(paramObj[keyStr]);
    var req:URLRequest = new URLRequest(valueStr);

}

    sound_icon.visible =  true
sound_icon.addEventListener(MouseEvent.CLICK, playSound);
var s:Sound = new Sound(req);
gotoAndStop("f2");//firstly  animated sound icon is stopped at the beginning position

function playSound(e:MouseEvent):void{
    sound_icon.visible =  false; //hide sound icon
    gotoAndPlay("f2");           //play animated sound icon from beginning

var mySoundChannel:SoundChannel = s.play(); //reference for getting complete event

mySoundChannel.addEventListener(Event.SOUND_COMPLETE, songFinished);
function songFinished(ev:Event):void
{
   sound_icon.visible =  true;
   gotoAndStop("f2");
}

}

and php code is below

        <?php

        $swfSourcePath = "soundtest.swf";
        $soundSourcePath = "4.mp3";

        ?>

        <object classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" width="40" height="40" id="soundtest" align="middle">
            <param name="movie" value="<?php echo $swfSourcePath;?>" />
                <param name=FlashVars value="myVariable=<?php echo $soundSourcePath;?>" />

            <object type="application/x-shockwave-flash" data="soundtest.swf" width="40" height="40">
                <param name="movie" value="<?php echo $swfSourcePath;?>" />
                    <param name=FlashVars value="myVariable=<?php echo  $soundSourcePath;?>" />

            </object>

        </object>


问:
Best way to select n elements at a time in jQuery
I have an ul of li elements, what I want to do is this:

If there are 6 or less li elements, select them all and put them into a new ul.

For any number greater than 6 elements, loop through, selecting 6 elements, put into new ul, start at the next li element and continue.

If there are less than 6 element left at the end, they get put into a new ul as well.

If I start out with 5 li elements, I would hope to end up with 1 ul element with 5 li children.

If I start out with 40 li elements, I would hope to end up with 7 ul elements, 6 with 6 li children and 1 with 4.

What would be the most efficient way of handling this in jQuery?

答:
I would recommend that you keep track of how many elements are inside the UL. For example, you can set a global variable like this at the top of the page:

```<code><script type="text/javascript">
var listItems = 0;
</script>
</code>```

Increment that variable whenever new items are added to the list. If they're added while looping through a PHP array (or equivalent in other languages), do this:

```<code><? foreach ($items as $item):?>
  <script type="text/javascript">
  listItems++;
  </script>
  <li><?=$item;?>
<?endforeach;?>
</code>```

If they're added through javascript, do something like this:

```<code>function addToList(item)
{
   listItems++;
   $("#list").append("<li>" + item + "</li>");
}
</code>```

Then, you can use that variable to determine how many elements are in the ul, e.g:

```<code>if (listItems < 6)
   //Do something
else
   // Do something else
</code>```

ContentLicense: CC BY-SA 2.5

Body:
I would recommend that you keep track of how many elements are inside the UL. For example, you can set a global variable like this at the top of the page:

<script type="text/javascript">
var listItems = 0;
</script>

Increment that variable whenever new items are added to the list. If they're added while looping through a PHP array (or equivalent in other languages), do this:

<? foreach ($items as $item):?>
  <script type="text/javascript">
  listItems++;
  </script>
  <li><?=$item;?>
<?endforeach;?>

If they're added through javascript, do something like this:

function addToList(item)
{
   listItems++;
   $("#list").append("<li>" + item + "</li>");
}

Then, you can use that variable to determine how many elements are in the ul, e.g:

if (listItems < 6)
   //Do something
else
   // Do something else


问:
Android Studio throwing warnings on everything
The first project I created since I updated Android Studio to 2.3, I get that everything on MainActivity is marked with a warning. At first I thought it was because I was creating the project inside another folder within AndroidStudioProjects, so I corrected that but still no dice.

Here's a picture of MainActivity:

I get errors like package-info.java file missing or Single class import blablabla, or package name too long (even though I once tried with a very short one) and more.

I updated Android SDK tools but nothing changed. One thing to notice is that previously created projects do work as normal, and even now I keep working on them. Any help would be appreciated

答: Try to remove support library (replace extends AppCompatActivity to extends Activity). Then Sync Project and Clean</p>