Add WebGraphicsContext support for readbacks from any framebuffer.

webkit/gpu/webgraphicscontext3d_in_process_impl.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/gpu/webgraphicscontext3d_in_process_impl.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 570 matching lines @@
     // user specifies the "premultiplyAlpha" flag in the context
     // creation attributes.
     memcpy(scanline, row_b, row_bytes);
     memcpy(row_b, row_a, row_bytes);
     memcpy(row_a, scanline, row_bytes);
   }
 }
 #endif
 
 bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
-    unsigned char* pixels, size_t bufferSize) {
-  if (bufferSize != static_cast<size_t>(4 * width() * height()))
+    unsigned char* pixels, size_t bufferSize, WebGLId framebuffer,
+    int width, int height) {
+  if (bufferSize != static_cast<size_t>(4 * width * height))
     return false;
 
   makeContextCurrent();
 
   // Earlier versions of this code used the GPU to flip the
   // framebuffer vertically before reading it back for compositing
   // via software. This code was quite complicated, used a lot of
   // GPU memory, and didn't provide an obvious speedup. Since this
   // vertical flip is only a temporary solution anyway until Chrome
   // is fully GPU composited, it wasn't worth the complexity.
 
-  ResolveMultisampledFramebuffer(0, 0, cached_width_, cached_height_);
-  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo_);
+  // In this implementation fbo_, not 0, is the drawing buffer, so
+  // special-case that.
+  if (framebuffer == 0)
+    framebuffer = fbo_;
+
+  if (framebuffer == fbo_)
+    ResolveMultisampledFramebuffer(0, 0, width, height);
+  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebuffer);
 
   GLint pack_alignment = 4;
   bool must_restore_pack_alignment = false;
   glGetIntegerv(GL_PACK_ALIGNMENT, &pack_alignment);
   if (pack_alignment > 4) {
     glPixelStorei(GL_PACK_ALIGNMENT, 4);
     must_restore_pack_alignment = true;
   }
 
   if (is_gles2_) {
     // FIXME: consider testing for presence of GL_OES_read_format
     // and GL_EXT_read_format_bgra, and using GL_BGRA_EXT here
     // directly.
-    glReadPixels(0, 0, cached_width_, cached_height_,
+    glReadPixels(0, 0, width, height,
                  GL_RGBA, GL_UNSIGNED_BYTE, pixels);
     for (size_t i = 0; i < bufferSize; i += 4) {
       std::swap(pixels[i], pixels[i + 2]);
     }
   } else {
-    glReadPixels(0, 0, cached_width_, cached_height_,
+    glReadPixels(0, 0, width, height,
                  GL_BGRA, GL_UNSIGNED_BYTE, pixels);
   }
 
   if (must_restore_pack_alignment)
     glPixelStorei(GL_PACK_ALIGNMENT, pack_alignment);
 
   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, bound_fbo_);
 
 #ifdef FLIP_FRAMEBUFFER_VERTICALLY
   if (pixels)
-    FlipVertically(pixels, cached_width_, cached_height_);
+    FlipVertically(pixels, width, height);
 #endif
 
   return true;
 }
 
+bool WebGraphicsContext3DInProcessImpl::readBackFramebuffer(
+    unsigned char* pixels, size_t bufferSize) {
+  return readBackFramebuffer(pixels, bufferSize, fbo_, width(), height());
+}
+
 void WebGraphicsContext3DInProcessImpl::synthesizeGLError(WGC3Denum error) {
   if (synthetic_errors_set_.find(error) == synthetic_errors_set_.end()) {
     synthetic_errors_set_.insert(error);
     synthetic_errors_list_.push_back(error);
   }
 }
 
 void* WebGraphicsContext3DInProcessImpl::mapBufferSubDataCHROMIUM(
     WGC3Denum target, WGC3Dintptr offset,
     WGC3Dsizeiptr size, WGC3Denum access) {
@@ skipping 986 matching lines @@
   if (length > 1) {
     entry->translated_source.reset(new char[length]);
     ShGetObjectCode(compiler, entry->translated_source.get());
   }
   entry->is_valid = true;
   return true;
 }
 
 }  // namespace gpu
 }  // namespace webkit