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

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

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
index 32416b2befbeabbe7bb114d8140b223cad285ab8..ce16c86666138f98266eb9759a7e2ec7783c7363 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -284,7 +284,8 @@ bool DrawingBuffer::prepareMailbox(WebExternalTextureMailbox* outMailbox, WebExt
             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();
@@ -477,6 +478,7 @@ bool DrawingBuffer::initialize(const IntSize& size, bool useMultisampling)
             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);
@@ -941,10 +943,22 @@ void DrawingBuffer::flipVertically(uint8_t* framebuffer, int width, int height)
     }
 }
 
-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)
@@ -1006,13 +1020,12 @@ DrawingBuffer::TextureInfo DrawingBuffer::createTextureAndAllocateMemory(const I
 
 DrawingBuffer::TextureInfo DrawingBuffer::createDefaultTextureAndAllocateMemory(const IntSize& size)
 {
-    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;
+    TextureParameters parameters = defaultTextureParameters();
     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;
 }
 
@@ -1020,11 +1033,17 @@ 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) {