Implicitly ensure backbuffer creation on draw

Instead of having a special IPC channel to ensure a backbuffer is allocated
for a given GL context, we can create it implicitly on the first draw attempt
into FBO 0. If this fails, the context is considered lost.

BUG=181120

Review URL: https://codereview.chromium.org/112303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240797 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 61 insertions, 24 deletions

diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index 49330b4..0f2e49a 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -2876,17 +2876,18 @@ COMPILE_ASSERT(offsetof(%(cmd_name)s::Result, %(field_name)s) == %(offset)d,
 
   def WriteHandlerDeferReadWrite(self, func, file):
     """Writes the code to handle deferring reads or writes."""
-    defer_reads = func.GetInfo('defer_reads')
     defer_draws = func.GetInfo('defer_draws')
-    conditions = []
+    defer_reads = func.GetInfo('defer_reads')
+    if defer_draws or defer_reads:
+      file.Write("  error::Error error;\n")
     if defer_draws:
-      conditions.append('ShouldDeferDraws()');
+      file.Write("  error = WillAccessBoundFramebufferForDraw();\n")
+      file.Write("  if (error != error::kNoError)\n")
+      file.Write("    return error;\n")
     if defer_reads:
-      conditions.append('ShouldDeferReads()');
-    if not conditions:
-      return
-    file.Write("  if (%s)\n" % ' || '.join(conditions))
-    file.Write("    return error::kDeferCommandUntilLater;\n")
+      file.Write("  error = WillAccessBoundFramebufferForRead();\n")
+      file.Write("  if (error != error::kNoError)\n")
+      file.Write("    return error;\n")
 
   def WriteValidUnitTest(self, func, file, test, extra = {}):
     """Writes a valid unit test."""
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index a68cd66..724d537 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1539,6 +1539,26 @@ class GLES2DecoderImpl : public GLES2Decoder,
            surface_->DeferDraws();
   }
 
+  error::Error WillAccessBoundFramebufferForDraw() {
+    if (ShouldDeferDraws())
+      return error::kDeferCommandUntilLater;
+    if (!offscreen_target_frame_buffer_.get() &&
+        !framebuffer_state_.bound_draw_framebuffer.get() &&
+        !surface_->SetBackbufferAllocation(true))
+      return error::kLostContext;
+    return error::kNoError;
+  }
+
+  error::Error WillAccessBoundFramebufferForRead() {
+    if (ShouldDeferReads())
+      return error::kDeferCommandUntilLater;
+    if (!offscreen_target_frame_buffer_.get() &&
+        !framebuffer_state_.bound_read_framebuffer.get() &&
+        !surface_->SetBackbufferAllocation(true))
+      return error::kLostContext;
+    return error::kNoError;
+  }
+
   void ProcessPendingReadPixels();
   void FinishReadPixels(const cmds::ReadPixels& c, GLuint buffer);
 
@@ -6342,8 +6362,9 @@ error::Error GLES2DecoderImpl::DoDrawArrays(
     GLint first,
     GLsizei count,
     GLsizei primcount) {
-  if (ShouldDeferDraws())
-    return error::kDeferCommandUntilLater;
+  error::Error error = WillAccessBoundFramebufferForDraw();
+  if (error != error::kNoError)
+    return error;
   if (!validators_->draw_mode.IsValid(mode)) {
     LOCAL_SET_GL_ERROR_INVALID_ENUM(function_name, mode, "mode");
     return error::kNoError;
@@ -6442,8 +6463,9 @@ error::Error GLES2DecoderImpl::DoDrawElements(
     GLenum type,
     int32 offset,
     GLsizei primcount) {
-  if (ShouldDeferDraws())
-    return error::kDeferCommandUntilLater;
+  error::Error error = WillAccessBoundFramebufferForDraw();
+  if (error != error::kNoError)
+    return error;
   if (!state_.vertex_attrib_manager->element_array_buffer()) {
     LOCAL_SET_GL_ERROR(
         GL_INVALID_OPERATION, function_name, "No element array buffer bound");
@@ -7223,8 +7245,9 @@ void GLES2DecoderImpl::FinishReadPixels(
 
 error::Error GLES2DecoderImpl::HandleReadPixels(
     uint32 immediate_data_size, const cmds::ReadPixels& c) {
-  if (ShouldDeferReads())
-    return error::kDeferCommandUntilLater;
+  error::Error fbo_error = WillAccessBoundFramebufferForRead();
+  if (fbo_error != error::kNoError)
+    return fbo_error;
   GLint x = c.x;
   GLint y = c.y;
   GLsizei width = c.width;
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h b/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
index a349583..ddc00fc 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_autogen.h
@@ -236,8 +236,10 @@ error::Error GLES2DecoderImpl::HandleCheckFramebufferStatus(
 
 error::Error GLES2DecoderImpl::HandleClear(
     uint32 immediate_data_size, const gles2::cmds::Clear& c) {
-  if (ShouldDeferDraws())
-    return error::kDeferCommandUntilLater;
+  error::Error error;
+  error = WillAccessBoundFramebufferForDraw();
+  if (error != error::kNoError)
+    return error;
   GLbitfield mask = static_cast<GLbitfield>(c.mask);
   DoClear(mask);
   return error::kNoError;
@@ -357,8 +359,10 @@ error::Error GLES2DecoderImpl::HandleCompressedTexSubImage2D(
 
 error::Error GLES2DecoderImpl::HandleCopyTexImage2D(
     uint32 immediate_data_size, const gles2::cmds::CopyTexImage2D& c) {
-  if (ShouldDeferReads())
-    return error::kDeferCommandUntilLater;
+  error::Error error;
+  error = WillAccessBoundFramebufferForRead();
+  if (error != error::kNoError)
+    return error;
   GLenum target = static_cast<GLenum>(c.target);
   GLint level = static_cast<GLint>(c.level);
   GLenum internalformat = static_cast<GLenum>(c.internalformat);
@@ -395,8 +399,10 @@ error::Error GLES2DecoderImpl::HandleCopyTexImage2D(
 
 error::Error GLES2DecoderImpl::HandleCopyTexSubImage2D(
     uint32 immediate_data_size, const gles2::cmds::CopyTexSubImage2D& c) {
-  if (ShouldDeferReads())
-    return error::kDeferCommandUntilLater;
+  error::Error error;
+  error = WillAccessBoundFramebufferForRead();
+  if (error != error::kNoError)
+    return error;
   GLenum target = static_cast<GLenum>(c.target);
   GLint level = static_cast<GLint>(c.level);
   GLint xoffset = static_cast<GLint>(c.xoffset);
@@ -669,8 +675,10 @@ error::Error GLES2DecoderImpl::HandleEnableVertexAttribArray(
 
 error::Error GLES2DecoderImpl::HandleFinish(
     uint32 immediate_data_size, const gles2::cmds::Finish& c) {
-  if (ShouldDeferReads())
-    return error::kDeferCommandUntilLater;
+  error::Error error;
+  error = WillAccessBoundFramebufferForRead();
+  if (error != error::kNoError)
+    return error;
   DoFinish();
   return error::kNoError;
 }
@@ -2631,8 +2639,13 @@ error::Error GLES2DecoderImpl::HandleViewport(
 error::Error GLES2DecoderImpl::HandleBlitFramebufferCHROMIUM(
     uint32 immediate_data_size,
     const gles2::cmds::BlitFramebufferCHROMIUM& c) {
-  if (ShouldDeferDraws() || ShouldDeferReads())
-    return error::kDeferCommandUntilLater;
+  error::Error error;
+  error = WillAccessBoundFramebufferForDraw();
+  if (error != error::kNoError)
+    return error;
+  error = WillAccessBoundFramebufferForRead();
+  if (error != error::kNoError)
+    return error;
   GLint srcX0 = static_cast<GLint>(c.srcX0);
   GLint srcY0 = static_cast<GLint>(c.srcY0);
   GLint srcX1 = static_cast<GLint>(c.srcX1);