We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Screenshot test failing on main (due to vispy 0.10?)
## 🐛 Bug

The test `napari/_tests/test_with_screenshot.py:test_z_order_image_points_after_ndisplay` is failing on main:

https://github.com/napari/napari/runs/6069251907?check_suite_focus=true#step:7:294

I suspect that this is due to the VisPy 0.10 release, which happened in the last 24h or so.

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `napari/_vispy/visuals/volume.py`
Content:
```
1 from vispy.scene.visuals import Volume as BaseVolume
2 
3 FUNCTION_DEFINITIONS = """
4 // the tolerance for testing equality of floats with floatEqual and floatNotEqual
5 const float equality_tolerance = 1e-8;
6 
7 bool floatNotEqual(float val1, float val2)
8 {
9     // check if val1 and val2 are not equal
10     bool not_equal = abs(val1 - val2) > equality_tolerance;
11 
12     return not_equal;
13 }
14 
15 bool floatEqual(float val1, float val2)
16 {
17     // check if val1 and val2 are equal
18     bool equal = abs(val1 - val2) < equality_tolerance;
19 
20     return equal;
21 }
22 
23 
24 // the background value for the iso_categorical shader
25 const float categorical_bg_value = 0;
26 
27 int detectAdjacentBackground(float val_neg, float val_pos)
28 {
29     // determine if the adjacent voxels along an axis are both background
30     int adjacent_bg = int( floatEqual(val_neg, categorical_bg_value) );
31     adjacent_bg = adjacent_bg * int( floatEqual(val_pos, categorical_bg_value) );
32     return adjacent_bg;
33 }
34 
35 vec4 calculateCategoricalColor(vec4 betterColor, vec3 loc, vec3 step)
36 {
37     // Calculate color by incorporating ambient and diffuse lighting
38     vec4 color0 = $sample(u_volumetex, loc);
39     vec4 color1;
40     vec4 color2;
41     float val0 = colorToVal(color0);
42     float val1 = 0;
43     float val2 = 0;
44     int n_bg_borders = 0;
45 
46     // View direction
47     vec3 V = normalize(view_ray);
48 
49     // calculate normal vector from gradient
50     vec3 N; // normal
51     color1 = $sample( u_volumetex, loc+vec3(-step[0],0.0,0.0) );
52     color2 = $sample( u_volumetex, loc+vec3(step[0],0.0,0.0) );
53     val1 = colorToVal(color1);
54     val2 = colorToVal(color2);
55     N[0] = val1 - val2;
56     n_bg_borders += detectAdjacentBackground(val1, val2);
57 
58     color1 = $sample( u_volumetex, loc+vec3(0.0,-step[1],0.0) );
59     color2 = $sample( u_volumetex, loc+vec3(0.0,step[1],0.0) );
60     val1 = colorToVal(color1);
61     val2 = colorToVal(color2);
62     N[1] = val1 - val2;
63     n_bg_borders += detectAdjacentBackground(val1, val2);
64 
65     color1 = $sample( u_volumetex, loc+vec3(0.0,0.0,-step[2]) );
66     color2 = $sample( u_volumetex, loc+vec3(0.0,0.0,step[2]) );
67     val1 = colorToVal(color1);
68     val2 = colorToVal(color2);
69     N[2] = val1 - val2;
70     n_bg_borders += detectAdjacentBackground(val1, val2);
71 
72     // Normalize and flip normal so it points towards viewer
73     N = normalize(N);
74     float Nselect = float(dot(N,V) > 0.0);
75     N = (2.0*Nselect - 1.0) * N;  // ==  Nselect * N - (1.0-Nselect)*N;
76 
77     // Init colors
78     vec4 ambient_color = vec4(0.0, 0.0, 0.0, 0.0);
79     vec4 diffuse_color = vec4(0.0, 0.0, 0.0, 0.0);
80     vec4 final_color;
81 
82     // todo: allow multiple light, define lights on viewvox or subscene
83     int nlights = 1;
84     for (int i=0; i<nlights; i++)
85     {
86         // Get light direction (make sure to prevent zero devision)
87         vec3 L = normalize(view_ray);  //lightDirs[i];
88         float lightEnabled = float( length(L) > 0.0 );
89         L = normalize(L+(1.0-lightEnabled));
90 
91         // Calculate lighting properties
92         float lambertTerm = clamp( dot(N,L), 0.0, 1.0 );
93         if (n_bg_borders > 0) {
94             // to fix dim pixels due to poor normal estimation,
95             // we give a default lambda to pixels surrounded by background
96             lambertTerm = 0.5;
97         }
98 
99         // Calculate mask
100         float mask1 = lightEnabled;
101 
102         // Calculate colors
103         ambient_color +=  mask1 * u_ambient;  // * gl_LightSource[i].ambient;
104         diffuse_color +=  mask1 * lambertTerm;
105     }
106 
107     // Calculate final color by componing different components
108     final_color = betterColor * ( ambient_color + diffuse_color);
109     final_color.a = betterColor.a;
110 
111     // Done
112     return final_color;
113 }
114 """
115 
116 ISO_CATEGORICAL_SNIPPETS = dict(
117     before_loop="""
118         vec4 color3 = vec4(0.0);  // final color
119         vec3 dstep = 1.5 / u_shape;  // step to sample derivative, set to match iso shader
120         gl_FragColor = vec4(0.0);
121         """,
122     in_loop="""
123         // check if value is different from the background value
124         if ( floatNotEqual(val, categorical_bg_value) ) {
125             // Take the last interval in smaller steps
126             vec3 iloc = loc - step;
127             for (int i=0; i<10; i++) {
128                 color = $sample(u_volumetex, iloc);
129                 if (floatNotEqual(color.g, categorical_bg_value) ) {
130                     // when the non-background value is reached
131                     // calculate the color (apply lighting effects)
132                     color = applyColormap(color.g);
133                     color = calculateCategoricalColor(color, iloc, dstep);
134                     gl_FragColor = color;
135 
136                     // set the variables for the depth buffer
137                     surface_point = iloc * u_shape;
138                     surface_found = true;
139 
140                     iter = nsteps;
141                     break;
142                 }
143                 iloc += step * 0.1;
144             }
145         }
146         """,
147     after_loop="""
148         if (surface_found == false) {
149             discard;
150         }
151         """,
152 )
153 
154 shaders = BaseVolume._shaders.copy()
155 before, after = shaders['fragment'].split('void main()')
156 shaders['fragment'] = before + FUNCTION_DEFINITIONS + 'void main()' + after
157 
158 rendering_methods = BaseVolume._rendering_methods.copy()
159 rendering_methods['iso_categorical'] = ISO_CATEGORICAL_SNIPPETS
160 
161 
162 class Volume(BaseVolume):
163     # add the new rendering method to the snippets dict
164     _shaders = shaders
165     _rendering_methods = rendering_methods
166
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/napari/_vispy/visuals/volume.py b/napari/_vispy/visuals/volume.py
--- a/napari/_vispy/visuals/volume.py
+++ b/napari/_vispy/visuals/volume.py
@@ -118,6 +118,7 @@
         vec4 color3 = vec4(0.0);  // final color
         vec3 dstep = 1.5 / u_shape;  // step to sample derivative, set to match iso shader
         gl_FragColor = vec4(0.0);
+        bool discard_fragment = true;
         """,
     in_loop="""
         // check if value is different from the background value
@@ -134,8 +135,8 @@
                     gl_FragColor = color;
 
                     // set the variables for the depth buffer
-                    surface_point = iloc * u_shape;
-                    surface_found = true;
+                    frag_depth_point = iloc * u_shape;
+                    discard_fragment = false;
 
                     iter = nsteps;
                     break;
@@ -145,9 +146,8 @@
         }
         """,
     after_loop="""
-        if (surface_found == false) {
+        if (discard_fragment)
             discard;
-        }
         """,
 )

{"golden_diff": "diff --git a/napari/_vispy/visuals/volume.py b/napari/_vispy/visuals/volume.py\n--- a/napari/_vispy/visuals/volume.py\n+++ b/napari/_vispy/visuals/volume.py\n@@ -118,6 +118,7 @@\n         vec4 color3 = vec4(0.0);  // final color\n         vec3 dstep = 1.5 / u_shape;  // step to sample derivative, set to match iso shader\n         gl_FragColor = vec4(0.0);\n+        bool discard_fragment = true;\n         \"\"\",\n     in_loop=\"\"\"\n         // check if value is different from the background value\n@@ -134,8 +135,8 @@\n                     gl_FragColor = color;\n \n                     // set the variables for the depth buffer\n-                    surface_point = iloc * u_shape;\n-                    surface_found = true;\n+                    frag_depth_point = iloc * u_shape;\n+                    discard_fragment = false;\n \n                     iter = nsteps;\n                     break;\n@@ -145,9 +146,8 @@\n         }\n         \"\"\",\n     after_loop=\"\"\"\n-        if (surface_found == false) {\n+        if (discard_fragment)\n             discard;\n-        }\n         \"\"\",\n )\n", "issue": "Screenshot test failing on main (due to vispy 0.10?)\n## \ud83d\udc1b Bug\r\n\r\nThe test `napari/_tests/test_with_screenshot.py:test_z_order_image_points_after_ndisplay` is failing on main:\r\n\r\nhttps://github.com/napari/napari/runs/6069251907?check_suite_focus=true#step:7:294\r\n\r\nI suspect that this is due to the VisPy 0.10 release, which happened in the last 24h or so.\n", "before_files": [{"content": "from vispy.scene.visuals import Volume as BaseVolume\n\nFUNCTION_DEFINITIONS = \"\"\"\n// the tolerance for testing equality of floats with floatEqual and floatNotEqual\nconst float equality_tolerance = 1e-8;\n\nbool floatNotEqual(float val1, float val2)\n{\n    // check if val1 and val2 are not equal\n    bool not_equal = abs(val1 - val2) > equality_tolerance;\n\n    return not_equal;\n}\n\nbool floatEqual(float val1, float val2)\n{\n    // check if val1 and val2 are equal\n    bool equal = abs(val1 - val2) < equality_tolerance;\n\n    return equal;\n}\n\n\n// the background value for the iso_categorical shader\nconst float categorical_bg_value = 0;\n\nint detectAdjacentBackground(float val_neg, float val_pos)\n{\n    // determine if the adjacent voxels along an axis are both background\n    int adjacent_bg = int( floatEqual(val_neg, categorical_bg_value) );\n    adjacent_bg = adjacent_bg * int( floatEqual(val_pos, categorical_bg_value) );\n    return adjacent_bg;\n}\n\nvec4 calculateCategoricalColor(vec4 betterColor, vec3 loc, vec3 step)\n{\n    // Calculate color by incorporating ambient and diffuse lighting\n    vec4 color0 = $sample(u_volumetex, loc);\n    vec4 color1;\n    vec4 color2;\n    float val0 = colorToVal(color0);\n    float val1 = 0;\n    float val2 = 0;\n    int n_bg_borders = 0;\n\n    // View direction\n    vec3 V = normalize(view_ray);\n\n    // calculate normal vector from gradient\n    vec3 N; // normal\n    color1 = $sample( u_volumetex, loc+vec3(-step[0],0.0,0.0) );\n    color2 = $sample( u_volumetex, loc+vec3(step[0],0.0,0.0) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[0] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    color1 = $sample( u_volumetex, loc+vec3(0.0,-step[1],0.0) );\n    color2 = $sample( u_volumetex, loc+vec3(0.0,step[1],0.0) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[1] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    color1 = $sample( u_volumetex, loc+vec3(0.0,0.0,-step[2]) );\n    color2 = $sample( u_volumetex, loc+vec3(0.0,0.0,step[2]) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[2] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    // Normalize and flip normal so it points towards viewer\n    N = normalize(N);\n    float Nselect = float(dot(N,V) > 0.0);\n    N = (2.0*Nselect - 1.0) * N;  // ==  Nselect * N - (1.0-Nselect)*N;\n\n    // Init colors\n    vec4 ambient_color = vec4(0.0, 0.0, 0.0, 0.0);\n    vec4 diffuse_color = vec4(0.0, 0.0, 0.0, 0.0);\n    vec4 final_color;\n\n    // todo: allow multiple light, define lights on viewvox or subscene\n    int nlights = 1;\n    for (int i=0; i<nlights; i++)\n    {\n        // Get light direction (make sure to prevent zero devision)\n        vec3 L = normalize(view_ray);  //lightDirs[i];\n        float lightEnabled = float( length(L) > 0.0 );\n        L = normalize(L+(1.0-lightEnabled));\n\n        // Calculate lighting properties\n        float lambertTerm = clamp( dot(N,L), 0.0, 1.0 );\n        if (n_bg_borders > 0) {\n            // to fix dim pixels due to poor normal estimation,\n            // we give a default lambda to pixels surrounded by background\n            lambertTerm = 0.5;\n        }\n\n        // Calculate mask\n        float mask1 = lightEnabled;\n\n        // Calculate colors\n        ambient_color +=  mask1 * u_ambient;  // * gl_LightSource[i].ambient;\n        diffuse_color +=  mask1 * lambertTerm;\n    }\n\n    // Calculate final color by componing different components\n    final_color = betterColor * ( ambient_color + diffuse_color);\n    final_color.a = betterColor.a;\n\n    // Done\n    return final_color;\n}\n\"\"\"\n\nISO_CATEGORICAL_SNIPPETS = dict(\n    before_loop=\"\"\"\n        vec4 color3 = vec4(0.0);  // final color\n        vec3 dstep = 1.5 / u_shape;  // step to sample derivative, set to match iso shader\n        gl_FragColor = vec4(0.0);\n        \"\"\",\n    in_loop=\"\"\"\n        // check if value is different from the background value\n        if ( floatNotEqual(val, categorical_bg_value) ) {\n            // Take the last interval in smaller steps\n            vec3 iloc = loc - step;\n            for (int i=0; i<10; i++) {\n                color = $sample(u_volumetex, iloc);\n                if (floatNotEqual(color.g, categorical_bg_value) ) {\n                    // when the non-background value is reached\n                    // calculate the color (apply lighting effects)\n                    color = applyColormap(color.g);\n                    color = calculateCategoricalColor(color, iloc, dstep);\n                    gl_FragColor = color;\n\n                    // set the variables for the depth buffer\n                    surface_point = iloc * u_shape;\n                    surface_found = true;\n\n                    iter = nsteps;\n                    break;\n                }\n                iloc += step * 0.1;\n            }\n        }\n        \"\"\",\n    after_loop=\"\"\"\n        if (surface_found == false) {\n            discard;\n        }\n        \"\"\",\n)\n\nshaders = BaseVolume._shaders.copy()\nbefore, after = shaders['fragment'].split('void main()')\nshaders['fragment'] = before + FUNCTION_DEFINITIONS + 'void main()' + after\n\nrendering_methods = BaseVolume._rendering_methods.copy()\nrendering_methods['iso_categorical'] = ISO_CATEGORICAL_SNIPPETS\n\n\nclass Volume(BaseVolume):\n    # add the new rendering method to the snippets dict\n    _shaders = shaders\n    _rendering_methods = rendering_methods\n", "path": "napari/_vispy/visuals/volume.py"}], "after_files": [{"content": "from vispy.scene.visuals import Volume as BaseVolume\n\nFUNCTION_DEFINITIONS = \"\"\"\n// the tolerance for testing equality of floats with floatEqual and floatNotEqual\nconst float equality_tolerance = 1e-8;\n\nbool floatNotEqual(float val1, float val2)\n{\n    // check if val1 and val2 are not equal\n    bool not_equal = abs(val1 - val2) > equality_tolerance;\n\n    return not_equal;\n}\n\nbool floatEqual(float val1, float val2)\n{\n    // check if val1 and val2 are equal\n    bool equal = abs(val1 - val2) < equality_tolerance;\n\n    return equal;\n}\n\n\n// the background value for the iso_categorical shader\nconst float categorical_bg_value = 0;\n\nint detectAdjacentBackground(float val_neg, float val_pos)\n{\n    // determine if the adjacent voxels along an axis are both background\n    int adjacent_bg = int( floatEqual(val_neg, categorical_bg_value) );\n    adjacent_bg = adjacent_bg * int( floatEqual(val_pos, categorical_bg_value) );\n    return adjacent_bg;\n}\n\nvec4 calculateCategoricalColor(vec4 betterColor, vec3 loc, vec3 step)\n{\n    // Calculate color by incorporating ambient and diffuse lighting\n    vec4 color0 = $sample(u_volumetex, loc);\n    vec4 color1;\n    vec4 color2;\n    float val0 = colorToVal(color0);\n    float val1 = 0;\n    float val2 = 0;\n    int n_bg_borders = 0;\n\n    // View direction\n    vec3 V = normalize(view_ray);\n\n    // calculate normal vector from gradient\n    vec3 N; // normal\n    color1 = $sample( u_volumetex, loc+vec3(-step[0],0.0,0.0) );\n    color2 = $sample( u_volumetex, loc+vec3(step[0],0.0,0.0) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[0] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    color1 = $sample( u_volumetex, loc+vec3(0.0,-step[1],0.0) );\n    color2 = $sample( u_volumetex, loc+vec3(0.0,step[1],0.0) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[1] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    color1 = $sample( u_volumetex, loc+vec3(0.0,0.0,-step[2]) );\n    color2 = $sample( u_volumetex, loc+vec3(0.0,0.0,step[2]) );\n    val1 = colorToVal(color1);\n    val2 = colorToVal(color2);\n    N[2] = val1 - val2;\n    n_bg_borders += detectAdjacentBackground(val1, val2);\n\n    // Normalize and flip normal so it points towards viewer\n    N = normalize(N);\n    float Nselect = float(dot(N,V) > 0.0);\n    N = (2.0*Nselect - 1.0) * N;  // ==  Nselect * N - (1.0-Nselect)*N;\n\n    // Init colors\n    vec4 ambient_color = vec4(0.0, 0.0, 0.0, 0.0);\n    vec4 diffuse_color = vec4(0.0, 0.0, 0.0, 0.0);\n    vec4 final_color;\n\n    // todo: allow multiple light, define lights on viewvox or subscene\n    int nlights = 1;\n    for (int i=0; i<nlights; i++)\n    {\n        // Get light direction (make sure to prevent zero devision)\n        vec3 L = normalize(view_ray);  //lightDirs[i];\n        float lightEnabled = float( length(L) > 0.0 );\n        L = normalize(L+(1.0-lightEnabled));\n\n        // Calculate lighting properties\n        float lambertTerm = clamp( dot(N,L), 0.0, 1.0 );\n        if (n_bg_borders > 0) {\n            // to fix dim pixels due to poor normal estimation,\n            // we give a default lambda to pixels surrounded by background\n            lambertTerm = 0.5;\n        }\n\n        // Calculate mask\n        float mask1 = lightEnabled;\n\n        // Calculate colors\n        ambient_color +=  mask1 * u_ambient;  // * gl_LightSource[i].ambient;\n        diffuse_color +=  mask1 * lambertTerm;\n    }\n\n    // Calculate final color by componing different components\n    final_color = betterColor * ( ambient_color + diffuse_color);\n    final_color.a = betterColor.a;\n\n    // Done\n    return final_color;\n}\n\"\"\"\n\nISO_CATEGORICAL_SNIPPETS = dict(\n    before_loop=\"\"\"\n        vec4 color3 = vec4(0.0);  // final color\n        vec3 dstep = 1.5 / u_shape;  // step to sample derivative, set to match iso shader\n        gl_FragColor = vec4(0.0);\n        bool discard_fragment = true;\n        \"\"\",\n    in_loop=\"\"\"\n        // check if value is different from the background value\n        if ( floatNotEqual(val, categorical_bg_value) ) {\n            // Take the last interval in smaller steps\n            vec3 iloc = loc - step;\n            for (int i=0; i<10; i++) {\n                color = $sample(u_volumetex, iloc);\n                if (floatNotEqual(color.g, categorical_bg_value) ) {\n                    // when the non-background value is reached\n                    // calculate the color (apply lighting effects)\n                    color = applyColormap(color.g);\n                    color = calculateCategoricalColor(color, iloc, dstep);\n                    gl_FragColor = color;\n\n                    // set the variables for the depth buffer\n                    frag_depth_point = iloc * u_shape;\n                    discard_fragment = false;\n\n                    iter = nsteps;\n                    break;\n                }\n                iloc += step * 0.1;\n            }\n        }\n        \"\"\",\n    after_loop=\"\"\"\n        if (discard_fragment)\n            discard;\n        \"\"\",\n)\n\nshaders = BaseVolume._shaders.copy()\nbefore, after = shaders['fragment'].split('void main()')\nshaders['fragment'] = before + FUNCTION_DEFINITIONS + 'void main()' + after\n\nrendering_methods = BaseVolume._rendering_methods.copy()\nrendering_methods['iso_categorical'] = ISO_CATEGORICAL_SNIPPETS\n\n\nclass Volume(BaseVolume):\n    # add the new rendering method to the snippets dict\n    _shaders = shaders\n    _rendering_methods = rendering_methods\n", "path": "napari/_vispy/visuals/volume.py"}]}