Reland "webgl: use immutable texture for the default FBO."

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 266 matching lines @@
     if (m_preserveDrawingBuffer == Discard) {
         std::swap(frontColorBufferMailbox->textureInfo, m_colorBuffer);
         attachColorBufferToReadFramebuffer();
 
         if (m_discardFramebufferSupported) {
             // Explicitly discard framebuffer to save GPU memory bandwidth for tile-based GPU arch.
             const GLenum attachments[3] = { GL_COLOR_ATTACHMENT0, GL_DEPTH_ATTACHMENT, GL_STENCIL_ATTACHMENT };
             m_gl->DiscardFramebufferEXT(GL_FRAMEBUFFER, 3, attachments);
         }
     } else {
-        m_gl->CopyTextureCHROMIUM(m_colorBuffer.textureId, frontColorBufferMailbox->textureInfo.textureId, frontColorBufferMailbox->textureInfo.parameters.internalColorFormat, GL_UNSIGNED_BYTE, GL_FALSE, GL_FALSE, GL_FALSE);
+        m_gl->CopySubTextureCHROMIUM(m_colorBuffer.textureId, frontColorBufferMailbox->textureInfo.textureId,
+            0, 0, 0, 0, m_size.width(), m_size.height(), GL_FALSE, GL_FALSE, GL_FALSE);
     }
 
     restoreFramebufferBindings();
     m_contentsChanged = false;
 
     m_gl->ProduceTextureDirectCHROMIUM(frontColorBufferMailbox->textureInfo.textureId, frontColorBufferMailbox->textureInfo.parameters.target, frontColorBufferMailbox->mailbox.name);
     const GLuint64 fenceSync = m_gl->InsertFenceSyncCHROMIUM();
     if (RuntimeEnabledFeatures::webGLImageChromiumEnabled())
         m_gl->DescheduleUntilFinishedCHROMIUM();
     m_gl->Flush();
@@ skipping 172 matching lines @@
     m_antiAliasingMode = None;
     if (useMultisampling) {
         m_gl->GetIntegerv(GL_MAX_SAMPLES_ANGLE, &maxSampleCount);
         m_antiAliasingMode = MSAAExplicitResolve;
         if (m_extensionsUtil->supportsExtension("GL_EXT_multisampled_render_to_texture")) {
             m_antiAliasingMode = MSAAImplicitResolve;
         } else if (m_extensionsUtil->supportsExtension("GL_CHROMIUM_screen_space_antialiasing")) {
             m_antiAliasingMode = ScreenSpaceAntialiasing;
         }
     }
+    m_storageTextureSupported = m_extensionsUtil->supportsExtension("GL_EXT_texture_storage");

[Zhenyao Mo, 2016/07/06 18:12:06]

What about WebGL 2 / ES3 context?  This extension may no longer be reported as
it's part of core.

[dshwang, 2016/07/07 12:33:26]

Done. Set m_storageTextureSupported to true on WebGL2

     m_sampleCount = std::min(4, maxSampleCount);
 
     m_gl->GenFramebuffers(1, &m_fbo);
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
     if (wantExplicitResolve()) {
         m_gl->GenFramebuffers(1, &m_multisampleFBO);
         m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
         m_gl->GenRenderbuffers(1, &m_multisampleRenderbuffer);
     }
     if (!reset(size))
@@ skipping 444 matching lines @@
     unsigned count = height / 2;
     for (unsigned i = 0; i < count; i++) {
         uint8_t* rowA = framebuffer + i * rowBytes;
         uint8_t* rowB = framebuffer + (height - i - 1) * rowBytes;
         memcpy(scanline, rowB, rowBytes);
         memcpy(rowB, rowA, rowBytes);
         memcpy(rowA, scanline, rowBytes);
     }
 }
 
-void DrawingBuffer::texImage2DResourceSafe(GLenum target, GLint level, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type, GLint unpackAlignment)
+bool DrawingBuffer::createStorageTextureIfPossible(GLenum target, GLenum internalformat, GLsizei width, GLsizei height, GLint border, GLenum format, GLenum type)

[Zhenyao Mo, 2016/07/06 18:12:06]

To me this method should not return anything.  It just returns
m_storageTextureSupported, so why bother? It only leads to confusion.

[Ken Russell (switch to Gerrit), 2016/07/06 23:53:49]

Naming nit: could you please call this "allocate*" instead of "create"? Perhaps
"allocateConditionallyImmutableTexture". To address Mo's feedback, call sites
can set info.immutable = m_storageTextureSupported.

[dshwang, 2016/07/07 12:33:26]

Done.

 {
-    ASSERT(unpackAlignment == 1 || unpackAlignment == 2 || unpackAlignment == 4 || unpackAlignment == 8);
-    m_gl->TexImage2D(target, level, internalformat, width, height, border, format, type, 0);
+    if (m_storageTextureSupported) {
+        GLenum internalStorageFormat = GL_NONE;
+        if (internalformat == GL_RGB) {
+            internalStorageFormat = GL_RGB8;
+        } else if (internalformat == GL_RGBA) {
+            internalStorageFormat = GL_RGBA8;
+        } else {
+            NOTREACHED();
+        }
+        m_gl->TexStorage2DEXT(GL_TEXTURE_2D, 1, internalStorageFormat, width, height);
+        return true;
+    }
+    m_gl->TexImage2D(target, 0, internalformat, width, height, border, format, type, 0);
+    return false;
 }
 
 void DrawingBuffer::deleteChromiumImageForTexture(TextureInfo* info)
 {
     if (info->imageId) {
         m_gl->BindTexture(info->parameters.target, info->textureId);
         m_gl->ReleaseTexImage2DCHROMIUM(info->parameters.target, info->imageId);
         m_gl->DestroyImageCHROMIUM(info->imageId);
         info->imageId = 0;
         info->gpuMemoryBufferId = -1;
@@ skipping 41 matching lines @@
     info.textureId = textureId;
     info.imageId = imageId;
     info.gpuMemoryBufferId = gpuMemoryBufferId;
     info.parameters = parameters;
     clearChromiumImageAlpha(info);
     return info;
 }
 
 DrawingBuffer::TextureInfo DrawingBuffer::createDefaultTextureAndAllocateMemory(const IntSize& size)
 {
+    DrawingBuffer::TextureInfo info;
     TextureParameters parameters = defaultTextureParameters();
-    GLuint textureId = createColorTexture(parameters);
-    texImage2DResourceSafe(parameters.target, 0, parameters.creationInternalColorFormat, size.width(), size.height(), 0, parameters.colorFormat, GL_UNSIGNED_BYTE);
-
-    DrawingBuffer::TextureInfo info;
-    info.textureId = textureId;
     info.parameters = parameters;
+    info.textureId = createColorTexture(parameters);
+    info.immutable = createStorageTextureIfPossible(parameters.target, parameters.creationInternalColorFormat,
+        size.width(), size.height(), 0, parameters.colorFormat, GL_UNSIGNED_BYTE);
     return info;
 }
 
 void DrawingBuffer::resizeTextureMemory(TextureInfo* info, const IntSize& size)
 {
     ASSERT(info->textureId);
     if (!RuntimeEnabledFeatures::webGLImageChromiumEnabled()) {
+        if (info->immutable) {
+            m_gl->DeleteTextures(1, &info->textureId);
+            info->textureId = createColorTexture(info->parameters);
+        }
         m_gl->BindTexture(info->parameters.target, info->textureId);
-        texImage2DResourceSafe(info->parameters.target, 0, info->parameters.creationInternalColorFormat, size.width(), size.height(), 0, info->parameters.colorFormat, GL_UNSIGNED_BYTE);
+        info->immutable = createStorageTextureIfPossible(info->parameters.target, info->parameters.creationInternalColorFormat,
+            size.width(), size.height(), 0, info->parameters.colorFormat, GL_UNSIGNED_BYTE);
         return;
     }
 
+    DCHECK(!info->immutable);
     deleteChromiumImageForTexture(info);
     info->imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(size.width(), size.height(), info->parameters.creationInternalColorFormat, GC3D_SCANOUT_CHROMIUM);
     if (info->imageId) {
         m_gl->BindTexture(info->parameters.target, info->textureId);
         m_gl->BindTexImage2DCHROMIUM(info->parameters.target, info->imageId);
 
         GLint gpuMemoryBufferId = -1;
         m_gl->GetImageivCHROMIUM(info->imageId, GC3D_GPU_MEMORY_BUFFER_ID, &gpuMemoryBufferId);
         DCHECK_NE(-1, gpuMemoryBufferId);
         info->gpuMemoryBufferId = gpuMemoryBufferId;
@@ skipping 50 matching lines @@
 
 void DrawingBuffer::restoreTextureBindings()
 {
     // This class potentially modifies the bindings for GL_TEXTURE_2D and
     // GL_TEXTURE_RECTANGLE. Only GL_TEXTURE_2D needs to be restored since
     // the public interface for WebGL does not support GL_TEXTURE_RECTANGLE.
     m_gl->BindTexture(GL_TEXTURE_2D, m_texture2DBinding);
 }
 
 } // namespace blink