Fix validation of LUMA formats in glGenerateMipmap.

src/libGLESv2/libGLESv2.cpp

@@ -1996,17 +1996,22 @@ void __stdcall glGenerateMipmap(GLenum target)
             }
 
             GLenum internalFormat = texture->getBaseLevelInternalFormat();
-
-            // Internally, all texture formats are sized so checking if the format
-            // is color renderable and filterable will not fail.
-
             const gl::TextureCaps &formatCaps = context->getCaps().textureCaps.get(internalFormat);
 
-            bool validRenderable = (formatCaps.colorRendering ||
-                                    gl::IsSizedInternalFormat(internalFormat, context->getClientVersion()));
-
-            if (formatCaps.depthRendering || gl::IsFormatCompressed(internalFormat, context->getClientVersion()) ||
-                !formatCaps.filtering || !validRenderable)
+            // GenerateMipmap should not generate an INVALID_OPERATION for textures created with
+            // unsized formats or that are color renderable and filterable.  Since we do not track if
+            // the texture was created with sized or unsized format (only sized formats are stored),
+            // it is not possible to make sure the the LUMA formats can generate mipmaps (they should
+            // be able to) because they aren't color renderable.  Simply do a special case for LUMA
+            // textures since they're the only texture format that can be created with unsized formats
+            // that is not color renderable.  New unsized formats are unlikely to be added, since ES2
+            // was the last version to use add them.
+            bool isLUMA = internalFormat == GL_LUMINANCE8_EXT ||
+                          internalFormat == GL_LUMINANCE8_ALPHA8_EXT ||
+                          internalFormat == GL_ALPHA8_EXT;
+
+            if (formatCaps.depthRendering || !formatCaps.filtering || (!formatCaps.colorRendering && !isLUMA) ||
+                gl::IsFormatCompressed(internalFormat, context->getClientVersion()))
             {
                 return gl::error(GL_INVALID_OPERATION);
             }