Revert of cmaa, gpu: use R8 image texture when GL_NV_image_formats is available.

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 ab7965ae849f0052f7919c96b9450e69c70b5abd..4b9d7e437bde796ed1b568e30b64fe439dd21b5b 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
@@ -25,6 +25,7 @@
       is_in_gamma_correct_mode_(false),
       supports_usampler_(true),
       supports_r8_image_(true),
+      supports_r8_read_format_(true),
       is_gles31_compatible_(false),
       frame_id_(0),
       width_(0),
@@ -58,55 +59,67 @@
   is_gles31_compatible_ =
       decoder->GetGLContext()->GetVersionInfo()->IsAtLeastGLES(3, 1);
 
-  if (is_gles31_compatible_) {
-    supports_r8_image_ =
-        decoder->GetGLContext()->HasExtension("GL_NV_image_formats");
-
-    // ES 3.0 requires GL_RGBA8UI is color renderable.
-    supports_usampler_ = true;
-  } else {
-    // CMAA requires GL_ARB_shader_image_load_store for GL, and it requires r8
-    // image texture.
-    DCHECK(decoder->GetGLContext()->HasExtension(
-        "GL_ARB_shader_image_load_store"));
-    supports_r8_image_ = true;
-
-    // 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 a small extra cost.
-    {
-      glActiveTexture(GL_TEXTURE0);
-
-      GLuint rgba8ui_texture = 0, depth_texture = 0;
-      glGenTextures(1, &rgba8ui_texture);
-      glBindTexture(GL_TEXTURE_2D, rgba8ui_texture);
-      glTexStorage2DEXT(GL_TEXTURE_2D, 1, GL_RGBA8UI, 4, 4);
-
-      glGenTextures(1, &depth_texture);
-      glBindTexture(GL_TEXTURE_2D, depth_texture);
-      glTexStorage2DEXT(GL_TEXTURE_2D, 1, GL_DEPTH_COMPONENT16, 4, 4);
-
-      // Create the FBO
-      GLuint rgba8ui_framebuffer = 0;
-      glGenFramebuffersEXT(1, &rgba8ui_framebuffer);
-      glBindFramebufferEXT(GL_FRAMEBUFFER, rgba8ui_framebuffer);
-
-      // Bind to the FBO to test support
-      glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
-                                GL_TEXTURE_2D, rgba8ui_texture, 0);
-      glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
-                                GL_TEXTURE_2D, depth_texture, 0);
-      GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
-
-      supports_usampler_ = (status == GL_FRAMEBUFFER_COMPLETE);
-
-      glDeleteFramebuffersEXT(1, &rgba8ui_framebuffer);
-      glDeleteTextures(1, &rgba8ui_texture);
-      glDeleteTextures(1, &depth_texture);
-
-      decoder->RestoreTextureUnitBindings(0);
-      decoder->RestoreActiveTexture();
-      decoder->RestoreFramebufferBindings();
+  // 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
+  // a small extra cost.
+  {
+    GLuint rgba8ui_texture = 0, depth_texture = 0;
+    glGenTextures(1, &rgba8ui_texture);
+    glBindTexture(GL_TEXTURE_2D, rgba8ui_texture);
+    glTexStorage2DEXT(GL_TEXTURE_2D, 1, GL_RGBA8UI, 4, 4);
+
+    glGenTextures(1, &depth_texture);
+    glBindTexture(GL_TEXTURE_2D, depth_texture);
+    glTexStorage2DEXT(GL_TEXTURE_2D, 1, GL_DEPTH_COMPONENT16, 4, 4);
+
+    // Create the FBO
+    GLuint rgba8ui_framebuffer = 0;
+    glGenFramebuffersEXT(1, &rgba8ui_framebuffer);
+    glBindFramebufferEXT(GL_FRAMEBUFFER, rgba8ui_framebuffer);
+
+    // Bind to the FBO to test support
+    glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
+                              GL_TEXTURE_2D, rgba8ui_texture, 0);
+    glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT,
+                              GL_TEXTURE_2D, depth_texture, 0);
+    GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER);
+
+    supports_usampler_ = (status == GL_FRAMEBUFFER_COMPLETE);
+
+    glDeleteFramebuffersEXT(1, &rgba8ui_framebuffer);
+    glDeleteTextures(1, &rgba8ui_texture);
+    glDeleteTextures(1, &depth_texture);
+  }
+
+  // Check to see if R8 images are supported
+  // If not supported, images are bound as R32F for write targets, not R8.
+  {
+    GLuint r8_texture = 0;
+    glGenTextures(1, &r8_texture);
+    glBindTexture(GL_TEXTURE_2D, r8_texture);
+    glTexStorage2DEXT(GL_TEXTURE_2D, 1, GL_R8, 4, 4);
+
+    glGetError();  // reset all previous errors
+    glBindImageTextureEXT(0, r8_texture, 0, GL_FALSE, 0, GL_WRITE_ONLY, GL_R8);
+    if (glGetError() != GL_NO_ERROR)
+      supports_r8_image_ = false;
+
+    glDeleteTextures(1, &r8_texture);
+  }
+
+  // Check if R8 GLSL read formats are supported.
+  // If not supported, r32f is used instead.
+  {
+    const char shader_source[] =
+        SHADER(layout(r8) restrict writeonly uniform highp image2D g_r8Image;
+               void main() {
+                 imageStore(g_r8Image, ivec2(0, 0), vec4(1.0, 0.0, 0.0, 0.0));
+               });
+
+    GLuint shader = CreateShader(GL_FRAGMENT_SHADER, "", shader_source);
+    supports_r8_read_format_ = (shader != 0);
+    if (shader != 0) {
+      glDeleteShader(shader);
     }
   }
 
@@ -115,6 +128,9 @@
   VLOG(1) << "ApplyFramebufferAttachmentCMAAINTEL: "
           << "Supports R8 Images is "
           << (supports_r8_image_ ? "true" : "false");
+  VLOG(1) << "ApplyFramebufferAttachmentCMAAINTEL: "
+          << "Supports R8 Read Format is "
+          << (supports_r8_read_format_ ? "true" : "false");
 
   // Create the shaders
   std::ostringstream defines, edge1, edge2, combineEdges, blur, displayEdges,
@@ -132,7 +148,7 @@
     defines << "#define IN_GAMMA_CORRECT_MODE\n";
   }
 
-  if (supports_r8_image_) {
+  if (supports_r8_read_format_) {
     defines << "#define EDGE_READ_FORMAT r8\n";
   } else {
     defines << "#define EDGE_READ_FORMAT r32f\n";
@@ -613,7 +629,7 @@
 
   const char header_es31[] =
       "#version 310 es                                                      \n";
-  const char header_gl130[] =
+  const char header_gl30[] =
       "#version 130                                                         \n"
       "#extension GL_ARB_shading_language_420pack  : require                \n"
       "#extension GL_ARB_texture_gather            : require                \n"
@@ -621,16 +637,14 @@
       "#extension GL_ARB_explicit_attrib_location  : require                \n"
       "#extension GL_ARB_shader_image_load_store   : require                \n";
 
-  std::ostringstream header;
+  const char* header = NULL;
   if (is_gles31_compatible_) {
-    header << header_es31;
-    if (supports_r8_image_)
-      header << "#extension GL_NV_image_formats : require\n";
+    header = header_es31;
   } else {
-    header << header_gl130;
+    header = header_gl30;
   }
 
-  const char* source_array[4] = {header.str().c_str(), defines, "\n", source};
+  const char* source_array[4] = {header, defines, "\n", source};
   glShaderSource(shader, 4, source_array, NULL);
 
   glCompileShader(shader);