Skip drawing points when gl_PointSize isn't written.

src/common/version.h

 #define MAJOR_VERSION 1
 #define MINOR_VERSION 0
 #define BUILD_VERSION 0
-#define BUILD_REVISION 1275
+#define BUILD_REVISION 1277
 
 #define STRINGIFY(x) #x
 #define MACRO_STRINGIFY(x) STRINGIFY(x)

src/libGLESv2/Context.cpp

@@ -3051,7 +3051,7 @@ void Context::drawArrays(GLenum mode, GLint first, GLsizei count, GLsizei instan
         return error(GL_INVALID_OPERATION);
     }
 
-    if (!cullSkipsDraw(mode))
+    if (!skipDraw(mode))
     {
         mDisplay->startScene();
         
@@ -3141,7 +3141,7 @@ void Context::drawElements(GLenum mode, GLsizei count, GLenum type, const GLvoid
         return error(GL_INVALID_OPERATION);
     }
 
-    if (!cullSkipsDraw(mode))
+    if (!skipDraw(mode))
     {
         mDisplay->startScene();
 
@@ -3733,9 +3733,31 @@ Texture *Context::getIncompleteTexture(TextureType type)
     return t;
 }
 
-bool Context::cullSkipsDraw(GLenum drawMode)
+bool Context::skipDraw(GLenum drawMode)
 {
-    return mState.cullFace && mState.cullMode == GL_FRONT_AND_BACK && isTriangleMode(drawMode);
+    if (drawMode == GL_POINTS)
+    {
+        // ProgramBinary assumes non-point rendering if gl_PointSize isn't written,
+        // which affects varying interpolation. Since the value of gl_PointSize is
+        // undefined when not written, just skip drawing to avoid unexpected results.
+        if (!getCurrentProgramBinary()->usesPointSize())
+        {
+            // This is stictly speaking not an error, but developers should be 
+            // notified of risking undefined behavior.
+            ERR("Point rendering without writing to gl_PointSize.");
+
+            return true;
+        }
+    }
+    else if (isTriangleMode(drawMode))
+    {
+        if (mState.cullFace && mState.cullMode == GL_FRONT_AND_BACK)
+        {
+            return true;
+        }
+    }
+
+    return false;
 }
 
 bool Context::isTriangleMode(GLenum drawMode)

src/libGLESv2/Context.h

@@ -538,7 +538,7 @@ class Context
 
     Texture *getIncompleteTexture(TextureType type);
 
-    bool cullSkipsDraw(GLenum drawMode);
+    bool skipDraw(GLenum drawMode);
     bool isTriangleMode(GLenum drawMode);
 
     void initExtensionString();

src/libGLESv2/ProgramBinary.cpp

@@ -176,6 +176,11 @@ GLint ProgramBinary::getUsedSamplerRange(SamplerType type)
     }
 }
 
+bool ProgramBinary::usesPointSize() const
+{
+    return mUsesPointSize;
+}
+
 // Returns the index of the texture image unit (0-19) corresponding to a Direct3D 9 sampler
 // index (0-15 for the pixel shader and 0-3 for the vertex shader).
 GLint ProgramBinary::getSamplerMapping(SamplerType type, unsigned int samplerIndex)
@@ -1319,7 +1324,8 @@ bool ProgramBinary::linkVaryings(InfoLog &infoLog, std::string& pixelHLSL, std::
         }
     }
 
-    std::string varyingSemantic = (vertexShader->mUsesPointSize && sm3 ? "COLOR" : "TEXCOORD");
+    mUsesPointSize = vertexShader->mUsesPointSize;
+    std::string varyingSemantic = (mUsesPointSize && sm3) ? "COLOR" : "TEXCOORD";
 
     vertexHLSL += "struct VS_INPUT\n"
                    "{\n";

src/libGLESv2/ProgramBinary.h

@@ -110,6 +110,7 @@ class ProgramBinary : public RefCountObject
     GLint getSamplerMapping(SamplerType type, unsigned int samplerIndex);
     TextureType getSamplerTextureType(SamplerType type, unsigned int samplerIndex);
     GLint getUsedSamplerRange(SamplerType type);
+    bool usesPointSize() const;
 
     GLint getUniformLocation(std::string name);
     bool setUniform1fv(GLint location, GLsizei count, const GLfloat *v);
@@ -208,6 +209,7 @@ class ProgramBinary : public RefCountObject
     Sampler mSamplersVS[MAX_VERTEX_TEXTURE_IMAGE_UNITS_VTF];
     GLuint mUsedVertexSamplerRange;
     GLuint mUsedPixelSamplerRange;
+    bool mUsesPointSize;
 
     typedef std::vector<Uniform*> UniformArray;
     UniformArray mUniforms;