gpu, cmaa: copy RGBA8 texture via glCopyTexSubImage2D() instead of imageStore().

gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc

Index: gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc b/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc
index b9209835ff59f42a90c35ec838a81ccef0fb802b..ecab7f037b826307aa5b30770bb75710bd4bb693 100644
--- a/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc
+++ b/gpu/command_buffer/service/gles2_cmd_apply_framebuffer_attachment_cmaa_intel.cc
@@ -29,7 +29,6 @@ ApplyFramebufferAttachmentCMAAINTELResourceManager::
       width_(0),
       height_(0),
       copy_to_framebuffer_shader_(0),
-      copy_to_image_shader_(0),
       edges0_shader_(0),
       edges1_shader_(0),
       edges_combine_shader_(0),
@@ -47,8 +46,7 @@ ApplyFramebufferAttachmentCMAAINTELResourceManager::
       edges1_shader_result_texture_(0),
       edges_combine_shader_result_texture_float4_slot1_(0),
       process_and_apply_shader_result_texture_float4_slot1_(0),
-      edges_combine_shader_result_texture_slot2_(0),
-      copy_to_image_shader_outTexture_(0) {}
+      edges_combine_shader_result_texture_slot2_(0) {}
 
 ApplyFramebufferAttachmentCMAAINTELResourceManager::
     ~ApplyFramebufferAttachmentCMAAINTELResourceManager() {
@@ -61,9 +59,7 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::Initialize(
   is_gles31_compatible_ =
       decoder->GetGLContext()->GetVersionInfo()->IsAtLeastGLES(3, 1);
 
-  copy_to_image_shader_ = CreateProgram("", vert_str_, copy_frag_str_);
-  copy_to_framebuffer_shader_ =
-      CreateProgram("#define OUT_FBO 1\n", vert_str_, copy_frag_str_);
+  copy_to_framebuffer_shader_ = CreateProgram("", vert_str_, copy_frag_str_);
 
   // Check if RGBA8UI is supported as an FBO colour target with depth.
   // If not supported, GLSL needs to convert the data to/from float so there is
@@ -190,8 +186,6 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::Initialize(
       glGetUniformLocation(edges_combine_shader_, "g_resultTextureSlot2");
   process_and_apply_shader_result_texture_float4_slot1_ = glGetUniformLocation(
       process_and_apply_shader_, "g_resultTextureFlt4Slot1");
-  copy_to_image_shader_outTexture_ =
-      glGetUniformLocation(copy_to_image_shader_, "outTexture");
 
   initialized_ = true;
 }
@@ -202,7 +196,6 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::Destroy() {
 
   ReleaseTextures();
 
-  glDeleteProgram(copy_to_image_shader_);
   glDeleteProgram(copy_to_framebuffer_shader_);
   glDeleteProgram(process_and_apply_shader_);
   glDeleteProgram(edges_combine_shader_);
@@ -224,6 +217,11 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::
   if (!framebuffer)
     return;
 
+  glDisable(GL_SCISSOR_TEST);
+  glDisable(GL_STENCIL_TEST);
+  glDisable(GL_CULL_FACE);
+  glDisable(GL_BLEND);

[dshwang, 2016/09/02 15:00:21]

These was in CopyTexture(), but ApplyCMAAEffectTexture() also needs them. so
move it here. It is not related to this CL anyway.

+
   GLuint last_framebuffer = framebuffer->service_id();
 
   // Process each color attachment of the current draw framebuffer.
@@ -251,11 +249,13 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::
 
       // Copy source_texture to rgba8_texture_
       if (do_copy) {
-        CopyTexture(source_texture, rgba8_texture_, false);
+        glBindFramebufferEXT(GL_FRAMEBUFFER, copy_framebuffer_);
+        glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                                  GL_TEXTURE_2D, rgba8_texture_, 0);
+        CopyTexture(source_texture);
       }
 
       // CMAA Effect
-      glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, last_framebuffer);
       if (do_copy) {
         ApplyCMAAEffectTexture(rgba8_texture_, rgba8_texture_);
       } else {
@@ -272,7 +272,7 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::
         glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                   GL_TEXTURE_2D, source_texture, 0);
 
-        CopyTexture(rgba8_texture_, source_texture, true);
+        CopyTexture(rgba8_texture_);
 
         // Restore color attachments
         glBindFramebufferEXT(GL_FRAMEBUFFER, copy_framebuffer_);
@@ -565,28 +565,15 @@ void ApplyFramebufferAttachmentCMAAINTELResourceManager::ReleaseTextures() {
 }
 
 void ApplyFramebufferAttachmentCMAAINTELResourceManager::CopyTexture(
-    GLint source,
-    GLint dest,
-    bool via_fbo) {
+    GLint source) {
   glViewport(0, 0, width_, height_);
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, source);
 
-  if (!via_fbo) {
-    glUseProgram(copy_to_image_shader_);
-    if (!is_gles31_compatible_) {
-      glUniform1i(copy_to_image_shader_outTexture_, 0);
-    }
-    glBindImageTextureEXT(0, dest, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_RGBA8);
-  } else {
-    glDisable(GL_DEPTH_TEST);
-    glDisable(GL_STENCIL_TEST);
-    glDisable(GL_CULL_FACE);
-    glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
-    glDepthMask(GL_FALSE);
-    glDisable(GL_BLEND);
-    glUseProgram(copy_to_framebuffer_shader_);
-  }
+  glDisable(GL_DEPTH_TEST);
+  glDepthMask(GL_FALSE);
+  glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+  glUseProgram(copy_to_framebuffer_shader_);
 
   glDrawArrays(GL_TRIANGLES, 0, 3);
   glUseProgram(0);
@@ -1889,21 +1876,11 @@ const char
       precision highp float;
       layout(binding = 0) uniform highp sampler2D inTexture;
       layout(location = 0) out vec4 outColor;
-      \n#ifdef GL_ES\n
-      layout(binding = 0, rgba8) restrict writeonly uniform highp
-                                                     image2D outTexture;
-      \n#else\n
-      layout(rgba8) restrict writeonly uniform highp image2D outTexture;
-      \n#endif\n
 
       void main() {
         ivec2 screenPosI = ivec2( gl_FragCoord.xy );
         vec4 pixel = texelFetch(inTexture, screenPosI, 0);
-      \n#ifdef OUT_FBO\n
         outColor = pixel;
-      \n#else\n
-        imageStore(outTexture, screenPosI, pixel);

[dshwang, 2016/09/02 15:00:21]

simple fix is adding following line here.
  outColor = vec4(0.);
However, this solution make this code and later CMAA phase entangled. vec4(0.)
hack requires the knowledge of implementation detail of next phase. So I remove
whole imageStore() path.

adrian@, jon@, do you have specific reason to prefer imageStore() to FBO write.
In my opinion, it's not necessary. RGBA8 to RGBA8 copy works well with FBO
write. In addition, ApplyCMAAEffectTexture() already writes something on RGBA8
and R8 FBO.

-      \n#endif\n
       }
     );
 /* clang-format on */