DEMO Attempt to recreate github #33 without success

This is an osmesa demo using shaders and vertex attribute pointers

tests/gh_bug33_osmesa_attribute_pointer.py

@@ -0,0 +1,151 @@
+from __future__ import print_function
+import os
+if not os.environ.get( 'PYOPENGL_PLATFORM' ):
+    os.environ['PYOPENGL_PLATFORM'] = 'osmesa'
+import OpenGL
+OpenGL.USE_ACCELERATE = False
+from OpenGL.GL import *
+from OpenGL.arrays import vbo
+from OpenGL import extensions
+from OpenGL.GL.ARB.fragment_program import glGenProgramsARB
+from OpenGL.GLU import *
+from OpenGL.osmesa import *
+from OpenGL.GL import shaders
+from numpy import arange, array
+import contextlib
+
+def write_ppm(buf, filename):
+    """Write traditional ASCII PPM file from buffer"""
+    with open(filename, "w") as f:
+        h, w, c = buf.shape
+        print( "P3", file=f)
+        print( "# ascii ppm file created by osmesa",file=f)
+        print( "%i %i" % (w, h),file=f)
+        print("255",file=f)
+        for y in range(h - 1, -1, -1):
+            for x in range(w):
+                pixel = buf[y, x]
+                l = " %3d %3d %3d" % (pixel[0], pixel[1], pixel[2])
+                f.write(l)
+            f.write("\n")
+
+@contextlib.contextmanager
+def osmesa_context(width=400, height=400, output='output.ppm'):
+    """Do OSMesa rendering context setup and write to output if non-null"""
+    from OpenGL import arrays
+    ctx = OSMesaCreateContext(OSMESA_RGBA, None)
+    buf = arrays.GLubyteArray.zeros((height, width, 4))
+    assert(OSMesaMakeCurrent(ctx, buf, GL_UNSIGNED_BYTE, width, height))
+    assert(OSMesaGetCurrentContext())
+    yield (ctx, buf)
+    if output:
+        write_ppm(buf,output)
+    OSMesaDestroyContext(ctx)
+
+def setup():
+    """Setup the rendering passes
+    
+    Taken from `OpenGLContext/tests/shader_4.py`
+    """
+    vertex = shaders.compileShader(
+        """
+        uniform float tween;
+        attribute vec3 position;
+        attribute vec3 tweened;
+        attribute vec3 color;
+        varying vec4 baseColor;
+        void main() {
+            gl_Position = gl_ModelViewProjectionMatrix * mix(
+                vec4( position,1.0),
+                vec4( tweened,1.0),
+                tween
+            );
+            baseColor = vec4(color,1.0);
+        }""",
+        GL_VERTEX_SHADER
+    )
+    fragment = shaders.compileShader(
+        """
+        varying vec4 baseColor;
+        void main() {
+            gl_FragColor = baseColor;
+        }""",
+        GL_FRAGMENT_SHADER
+    )
+    shader = shaders.compileProgram(vertex,fragment)
+    vertices = vbo.VBO(
+        array( [
+            [  0, 1, 0, 1,3,0,  0,1,0 ],
+            [ -1,-1, 0, -1,-1,0,  1,1,0 ],
+            [  1,-1, 0, 1,-1,0, 0,1,1 ],
+
+            [  2,-1, 0, 2,-1,0, 1,0,0 ],
+            [  4,-1, 0, 4,-1,0, 0,1,0 ],
+            [  4, 1, 0, 4,9,0, 0,0,1 ],
+            [  2,-1, 0, 2,-1,0, 1,0,0 ],
+            [  4, 1, 0, 1,3,0, 0,0,1 ],
+            [  2, 1, 0, 1,-1,0, 0,1,1 ],
+        ],'f')
+    )
+    position_location = glGetAttribLocation( 
+        shader, 'position' 
+    )
+    tweened_location = glGetAttribLocation(
+        shader, 'tweened',
+    )
+    color_location = glGetAttribLocation( 
+        shader, 'color' 
+    )
+    tween_location = glGetUniformLocation(
+        shader, 'tween',
+    )
+    return {
+        'shader': shader,
+        'position_location': position_location,
+        'tweened_location': tweened_location,
+        'color_location': color_location,
+        'tween_location': tween_location,
+        'vertices': vertices,
+    }
+def render(names, fraction=.5):
+    glUseProgram(names['shader'])
+    glUniform1f(names['tween_location'],  fraction)
+    with names['vertices']:
+        try:
+            glEnableVertexAttribArray( names['position_location'] )
+            glEnableVertexAttribArray( names['tweened_location'] )
+            glEnableVertexAttribArray( names['color_location'] )
+            stride = 9*4
+            glVertexAttribPointer( 
+                names['position_location'], 
+                3, GL_FLOAT,False, stride, names['vertices'] 
+            )
+            glVertexAttribPointer( 
+                names['tweened_location'], 
+                3, GL_FLOAT,False, stride, names['vertices']+12
+            )
+            glVertexAttribPointer( 
+                names['color_location'], 
+                3, GL_FLOAT,False, stride, names['vertices']+24
+            )
+            glDrawArrays(GL_TRIANGLES, 0, 9)
+        finally:
+            glDisableVertexAttribArray( names['position_location'] )
+            glDisableVertexAttribArray( names['tweened_location'] )
+            glDisableVertexAttribArray( names['color_location'] )
+
+def main():
+    with osmesa_context(400,400) as context:
+        print('Queried extensions:', sorted(extensions.GLQuerier.pullExtensions()))
+        print('Queried version:', extensions.GLQuerier.pullVersion())
+        names = setup()
+        for fraction in arange(0,.5,.1):
+            glClearColor(0.0,0.0,1.0,1.0)
+            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT )
+            print("Rendering: %s"%(fraction,))
+            render(names,fraction)
+            glFinish()
+
+
+if __name__ == '__main__':
+    main()