prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Fixed width saver and loader don't round trip. (Columns expand with increasing number of spaces)
  **Small description**
  
  Open `test.csv`:
  
  ``` csv
  colours,counts
  red,3
  green,5
  blue,8
  ```
  
  Then save it as `test.fixed`:
  
  ```
  colours   counts   
  red       3        
  green     5        
  blue      8        
  ```
  
  Each column is separated by three spaces.
  
  Now, open the newly saved `test.fixed`, and save it as `test.fixed.csv`.
  Upon inspection, you will see that the three spaces have been included as column data, rather than being discarded as a separator:
  
  ```
  colours,counts
  red       ,3     
  green     ,5     
  blue      ,8     
  ```
  
  If you repeat this process, three spaces get appended to each column every time you repeat a round trip.
  
  **Expected result**
  
  I expect to be able to round trip from CSV to Fixed and back without extra spaces being added to the data.
  
  
  **Steps to reproduce with sample data and a .vd**
  
  [test-fixed-saver.zip](https://github.com/saulpw/visidata/files/13938788/test-fixed-saver.zip)
  
  **Additional context**
  
  - saul.pw/VisiData v3.0.1
  - Python 3.10.12
  
  
  </issue>
  <code>
  [start of visidata/loaders/fixed_width.py]
  1 
  2 from visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet
  3 
  4 
  5 vd.option('fixed_rows', 1000, 'number of rows to check for fixed width columns')
  6 vd.option('fixed_maxcols', 0, 'max number of fixed-width columns to create (0 is no max)')
  7 
  8 @VisiData.api
  9 def open_fixed(vd, p):
  10     return FixedWidthColumnsSheet(p.base_stem, source=p, headerlines=[])
  11 
  12 class FixedWidthColumn(Column):
  13     def __init__(self, name, i, j, **kwargs):
  14         super().__init__(name, **kwargs)
  15         self.i, self.j = i, j
  16 
  17     def calcValue(self, row):
  18         return row[0][self.i:self.j]
  19 
  20     def putValue(self, row, value):
  21         value = str(value)[:self.j-self.i]
  22         j = self.j or len(row)
  23         row[0] = row[0][:self.i] + '%-*s' % (j-self.i, value) + row[0][self.j:]
  24 
  25 def columnize(rows):
  26     'Generate (i,j) indexes for fixed-width columns found in rows'
  27 
  28     ## find all character columns that are not spaces ever
  29     allNonspaces = set()
  30     for r in rows:
  31         for i, ch in enumerate(r):
  32             if not ch.isspace():
  33                 allNonspaces.add(i)
  34 
  35     colstart = 0
  36     prev = 0
  37 
  38     # collapse fields
  39     for i in allNonspaces:
  40         if i > prev+1:
  41             yield colstart, i
  42             colstart = i
  43         prev = i
  44 
  45     yield colstart, prev+1   # final column gets rest of line
  46 
  47 
  48 class FixedWidthColumnsSheet(SequenceSheet):
  49     rowtype = 'lines'  # rowdef: [line] (wrapping in list makes it unique and modifiable)
  50     def addRow(self, row, index=None):
  51         Sheet.addRow(self, row, index=index)
  52 
  53     def iterload(self):
  54         itsource = iter(self.source)
  55 
  56         # compute fixed width columns from first fixed_rows lines
  57         maxcols = self.options.fixed_maxcols
  58         self.columns = []
  59         fixedRows = list([x] for x in self.optlines(itsource, 'fixed_rows'))
  60         for i, j in columnize(list(r[0] for r in fixedRows)):
  61             if maxcols and self.nCols >= maxcols-1:
  62                 self.addColumn(FixedWidthColumn('', i, None))
  63                 break
  64             else:
  65                 self.addColumn(FixedWidthColumn('', i, j))
  66 
  67         yield from fixedRows
  68 
  69         self.setColNames(self.headerlines)
  70 
  71         yield from ([line] for line in itsource)
  72 
  73     def setCols(self, headerlines):
  74         self.headerlines = headerlines
  75 
  76 
  77 @VisiData.api
  78 def save_fixed(vd, p, *vsheets):
  79     with p.open(mode='w', encoding=vsheets[0].options.save_encoding) as fp:
  80         for sheet in vsheets:
  81             if len(vsheets) > 1:
  82                 fp.write('%s\n\n' % sheet.name)
  83 
  84             widths = {}  # Column -> width:int
  85             # headers
  86             for col in Progress(sheet.visibleCols, gerund='sizing'):
  87                 widths[col] = col.getMaxWidth(sheet.rows)  #1849
  88                 fp.write(('{0:%s} ' % widths[col]).format(col.name))
  89             fp.write('\n')
  90 
  91             # rows
  92             with Progress(gerund='saving'):
  93                 for dispvals in sheet.iterdispvals(format=True):
  94                     for col, val in dispvals.items():
  95                         fp.write(('{0:%s%s.%s} ' % ('>' if vd.isNumeric(col) else '<', widths[col], widths[col])).format(val))
  96                     fp.write('\n')
  97
  [end of visidata/loaders/fixed_width.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/visidata/loaders/fixed_width.py b/visidata/loaders/fixed_width.py
  --- a/visidata/loaders/fixed_width.py
  +++ b/visidata/loaders/fixed_width.py
  @@ -1,5 +1,5 @@
   
  -from visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet
  +from visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet, Column, dispwidth
   
   
   vd.option('fixed_rows', 1000, 'number of rows to check for fixed width columns')
  @@ -9,6 +9,22 @@
   def open_fixed(vd, p):
       return FixedWidthColumnsSheet(p.base_stem, source=p, headerlines=[])
   
  +@Column.api
  +def getMaxDataWidth(col, rows):  #2255 need real max width for fixed width saver
  +    '''Return the maximum length of any cell in column or its header,
  +    even if wider than window. (Slow for large cells!)'''
  +
  +    w = 0
  +    nlen = dispwidth(col.name)
  +    if len(rows) > 0:
  +        w_max = 0
  +        for r in rows:
  +            row_w = dispwidth(col.getDisplayValue(r))
  +            if w_max < row_w:
  +                w_max = row_w
  +        w = w_max
  +    return max(w, nlen)
  +
   class FixedWidthColumn(Column):
       def __init__(self, name, i, j, **kwargs):
           super().__init__(name, **kwargs)
  @@ -38,7 +54,7 @@
       # collapse fields
       for i in allNonspaces:
           if i > prev+1:
  -            yield colstart, i
  +            yield colstart, prev+1 #2255
               colstart = i
           prev = i
   
  @@ -84,7 +100,7 @@
               widths = {}  # Column -> width:int
               # headers
               for col in Progress(sheet.visibleCols, gerund='sizing'):
  -                widths[col] = col.getMaxWidth(sheet.rows)  #1849
  +                widths[col] = col.getMaxDataWidth(sheet.rows)  #1849 #2255
                   fp.write(('{0:%s} ' % widths[col]).format(col.name))
               fp.write('\n')
  
verification_info: {"golden_diff": "diff --git a/visidata/loaders/fixed_width.py b/visidata/loaders/fixed_width.py\n--- a/visidata/loaders/fixed_width.py\n+++ b/visidata/loaders/fixed_width.py\n@@ -1,5 +1,5 @@\n \n-from visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet\n+from visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet, Column, dispwidth\n \n \n vd.option('fixed_rows', 1000, 'number of rows to check for fixed width columns')\n@@ -9,6 +9,22 @@\n def open_fixed(vd, p):\n     return FixedWidthColumnsSheet(p.base_stem, source=p, headerlines=[])\n \n+@Column.api\n+def getMaxDataWidth(col, rows):  #2255 need real max width for fixed width saver\n+    '''Return the maximum length of any cell in column or its header,\n+    even if wider than window. (Slow for large cells!)'''\n+\n+    w = 0\n+    nlen = dispwidth(col.name)\n+    if len(rows) > 0:\n+        w_max = 0\n+        for r in rows:\n+            row_w = dispwidth(col.getDisplayValue(r))\n+            if w_max < row_w:\n+                w_max = row_w\n+        w = w_max\n+    return max(w, nlen)\n+\n class FixedWidthColumn(Column):\n     def __init__(self, name, i, j, **kwargs):\n         super().__init__(name, **kwargs)\n@@ -38,7 +54,7 @@\n     # collapse fields\n     for i in allNonspaces:\n         if i > prev+1:\n-            yield colstart, i\n+            yield colstart, prev+1 #2255\n             colstart = i\n         prev = i\n \n@@ -84,7 +100,7 @@\n             widths = {}  # Column -> width:int\n             # headers\n             for col in Progress(sheet.visibleCols, gerund='sizing'):\n-                widths[col] = col.getMaxWidth(sheet.rows)  #1849\n+                widths[col] = col.getMaxDataWidth(sheet.rows)  #1849 #2255\n                 fp.write(('{0:%s} ' % widths[col]).format(col.name))\n             fp.write('\\n')\n", "issue": "Fixed width saver and loader don't round trip. (Columns expand with increasing number of spaces)\n**Small description**\r\n\r\nOpen `test.csv`:\r\n\r\n``` csv\r\ncolours,counts\r\nred,3\r\ngreen,5\r\nblue,8\r\n```\r\n\r\nThen save it as `test.fixed`:\r\n\r\n```\r\ncolours   counts   \r\nred       3        \r\ngreen     5        \r\nblue      8        \r\n```\r\n\r\nEach column is separated by three spaces.\r\n\r\nNow, open the newly saved `test.fixed`, and save it as `test.fixed.csv`.\r\nUpon inspection, you will see that the three spaces have been included as column data, rather than being discarded as a separator:\r\n\r\n```\r\ncolours,counts\r\nred       ,3     \r\ngreen     ,5     \r\nblue      ,8     \r\n```\r\n\r\nIf you repeat this process, three spaces get appended to each column every time you repeat a round trip.\r\n\r\n**Expected result**\r\n\r\nI expect to be able to round trip from CSV to Fixed and back without extra spaces being added to the data.\r\n\r\n\r\n**Steps to reproduce with sample data and a .vd**\r\n\r\n[test-fixed-saver.zip](https://github.com/saulpw/visidata/files/13938788/test-fixed-saver.zip)\r\n\r\n**Additional context**\r\n\r\n- saul.pw/VisiData v3.0.1\r\n- Python 3.10.12\r\n\n", "before_files": [{"content": "\nfrom visidata import VisiData, vd, Sheet, Column, Progress, SequenceSheet\n\n\nvd.option('fixed_rows', 1000, 'number of rows to check for fixed width columns')\nvd.option('fixed_maxcols', 0, 'max number of fixed-width columns to create (0 is no max)')\n\n@VisiData.api\ndef open_fixed(vd, p):\n    return FixedWidthColumnsSheet(p.base_stem, source=p, headerlines=[])\n\nclass FixedWidthColumn(Column):\n    def __init__(self, name, i, j, **kwargs):\n        super().__init__(name, **kwargs)\n        self.i, self.j = i, j\n\n    def calcValue(self, row):\n        return row[0][self.i:self.j]\n\n    def putValue(self, row, value):\n        value = str(value)[:self.j-self.i]\n        j = self.j or len(row)\n        row[0] = row[0][:self.i] + '%-*s' % (j-self.i, value) + row[0][self.j:]\n\ndef columnize(rows):\n    'Generate (i,j) indexes for fixed-width columns found in rows'\n\n    ## find all character columns that are not spaces ever\n    allNonspaces = set()\n    for r in rows:\n        for i, ch in enumerate(r):\n            if not ch.isspace():\n                allNonspaces.add(i)\n\n    colstart = 0\n    prev = 0\n\n    # collapse fields\n    for i in allNonspaces:\n        if i > prev+1:\n            yield colstart, i\n            colstart = i\n        prev = i\n\n    yield colstart, prev+1   # final column gets rest of line\n\n\nclass FixedWidthColumnsSheet(SequenceSheet):\n    rowtype = 'lines'  # rowdef: [line] (wrapping in list makes it unique and modifiable)\n    def addRow(self, row, index=None):\n        Sheet.addRow(self, row, index=index)\n\n    def iterload(self):\n        itsource = iter(self.source)\n\n        # compute fixed width columns from first fixed_rows lines\n        maxcols = self.options.fixed_maxcols\n        self.columns = []\n        fixedRows = list([x] for x in self.optlines(itsource, 'fixed_rows'))\n        for i, j in columnize(list(r[0] for r in fixedRows)):\n            if maxcols and self.nCols >= maxcols-1:\n                self.addColumn(FixedWidthColumn('', i, None))\n                break\n            else:\n                self.addColumn(FixedWidthColumn('', i, j))\n\n        yield from fixedRows\n\n        self.setColNames(self.headerlines)\n\n        yield from ([line] for line in itsource)\n\n    def setCols(self, headerlines):\n        self.headerlines = headerlines\n\n\n@VisiData.api\ndef save_fixed(vd, p, *vsheets):\n    with p.open(mode='w', encoding=vsheets[0].options.save_encoding) as fp:\n        for sheet in vsheets:\n            if len(vsheets) > 1:\n                fp.write('%s\\n\\n' % sheet.name)\n\n            widths = {}  # Column -> width:int\n            # headers\n            for col in Progress(sheet.visibleCols, gerund='sizing'):\n                widths[col] = col.getMaxWidth(sheet.rows)  #1849\n                fp.write(('{0:%s} ' % widths[col]).format(col.name))\n            fp.write('\\n')\n\n            # rows\n            with Progress(gerund='saving'):\n                for dispvals in sheet.iterdispvals(format=True):\n                    for col, val in dispvals.items():\n                        fp.write(('{0:%s%s.%s} ' % ('>' if vd.isNumeric(col) else '<', widths[col], widths[col])).format(val))\n                    fp.write('\\n')\n", "path": "visidata/loaders/fixed_width.py"}]}