Add GL entry points for DiscardBackbufferCHROMIUM

This adds and uses a GL command buffer command for DiscardBackbufferCHROMIUM
instead of having a WebGraphicsContext3D entry point + common/ IPC message.
This is used to deallocate, if possible, the backbuffer when no longer in use.

BUG=181120

Review URL: https://codereview.chromium.org/104823005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240583 0039d316-1c4b-4281-b951-d872f2087c98

17 files changed, 106 insertions, 0 deletions

diff --git a/gpu/GLES2/gl2chromium_autogen.h b/gpu/GLES2/gl2chromium_autogen.h
index c18386b..53e5728 100644
--- a/gpu/GLES2/gl2chromium_autogen.h
+++ b/gpu/GLES2/gl2chromium_autogen.h
@@ -237,6 +237,7 @@
 #define glInsertSyncPointCHROMIUM GLES2_GET_FUN(InsertSyncPointCHROMIUM)
 #define glWaitSyncPointCHROMIUM GLES2_GET_FUN(WaitSyncPointCHROMIUM)
 #define glDrawBuffersEXT GLES2_GET_FUN(DrawBuffersEXT)
+#define glDiscardBackbufferCHROMIUM GLES2_GET_FUN(DiscardBackbufferCHROMIUM)
 
 #endif  // GPU_GLES2_GL2CHROMIUM_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index 0e1ce86..49330b4 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -2481,6 +2481,12 @@ _FUNCTION_INFO = {
     'extension': True,
     'chromium': True,
   },
+  'DiscardBackbufferCHROMIUM': {
+    'type': 'Custom',
+    'impl_func': True,
+    'extension': True,
+    'chromium': True,
+  },
 }
 
 
diff --git a/gpu/command_buffer/client/gles2_c_lib_autogen.h b/gpu/command_buffer/client/gles2_c_lib_autogen.h
index 4f7ee07..f2eb837 100644
--- a/gpu/command_buffer/client/gles2_c_lib_autogen.h
+++ b/gpu/command_buffer/client/gles2_c_lib_autogen.h
@@ -764,6 +764,9 @@ void GLES2WaitSyncPointCHROMIUM(GLuint sync_point) {
 void GLES2DrawBuffersEXT(GLsizei count, const GLenum* bufs) {
   gles2::GetGLContext()->DrawBuffersEXT(count, bufs);
 }
+void GLES2DiscardBackbufferCHROMIUM() {
+  gles2::GetGLContext()->DiscardBackbufferCHROMIUM();
+}
 
 namespace gles2 {
 
@@ -1121,6 +1124,8 @@ extern const NameToFunc g_gles2_function_table[] = {
       glWaitSyncPointCHROMIUM), },
   { "glDrawBuffersEXT", reinterpret_cast<GLES2FunctionPointer>(
       glDrawBuffersEXT), },
+  { "glDiscardBackbufferCHROMIUM", reinterpret_cast<GLES2FunctionPointer>(
+      glDiscardBackbufferCHROMIUM), },
   { NULL, NULL, },
 };
 
diff --git a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
index 625ee89..76a9f4a 100644
--- a/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
+++ b/gpu/command_buffer/client/gles2_cmd_helper_autogen.h
@@ -2014,5 +2014,13 @@
     }
   }
 
+  void DiscardBackbufferCHROMIUM() {
+    gles2::cmds::DiscardBackbufferCHROMIUM* c =
+        GetCmdSpace<gles2::cmds::DiscardBackbufferCHROMIUM>();
+    if (c) {
+      c->Init();
+    }
+  }
+
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_CMD_HELPER_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_implementation_autogen.h b/gpu/command_buffer/client/gles2_implementation_autogen.h
index b578914..5703956 100644
--- a/gpu/command_buffer/client/gles2_implementation_autogen.h
+++ b/gpu/command_buffer/client/gles2_implementation_autogen.h
@@ -555,5 +555,7 @@ virtual void WaitSyncPointCHROMIUM(GLuint sync_point) OVERRIDE;
 
 virtual void DrawBuffersEXT(GLsizei count, const GLenum* bufs) OVERRIDE;
 
+virtual void DiscardBackbufferCHROMIUM() OVERRIDE;
+
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_implementation_impl_autogen.h b/gpu/command_buffer/client/gles2_implementation_impl_autogen.h
index fb6b362..3b92eb2 100644
--- a/gpu/command_buffer/client/gles2_implementation_impl_autogen.h
+++ b/gpu/command_buffer/client/gles2_implementation_impl_autogen.h
@@ -1759,5 +1759,12 @@ void GLES2Implementation::DrawBuffersEXT(GLsizei count, const GLenum* bufs) {
   CheckGLError();
 }
 
+void GLES2Implementation::DiscardBackbufferCHROMIUM() {
+  GPU_CLIENT_SINGLE_THREAD_CHECK();
+  GPU_CLIENT_LOG("[" << GetLogPrefix() << "] glDiscardBackbufferCHROMIUM(" << ")");  // NOLINT
+  helper_->DiscardBackbufferCHROMIUM();
+  CheckGLError();
+}
+
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_IMPL_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_implementation_unittest_autogen.h b/gpu/command_buffer/client/gles2_implementation_unittest_autogen.h
index af49f42..38e32a6 100644
--- a/gpu/command_buffer/client/gles2_implementation_unittest_autogen.h
+++ b/gpu/command_buffer/client/gles2_implementation_unittest_autogen.h
@@ -1862,5 +1862,16 @@ TEST_F(GLES2ImplementationTest, DrawBuffersEXT) {
   gl_->DrawBuffersEXT(1, &data[0][0]);
   EXPECT_EQ(0, memcmp(&expected, commands_, sizeof(expected)));
 }
+
+TEST_F(GLES2ImplementationTest, DiscardBackbufferCHROMIUM) {
+  struct Cmds {
+    cmds::DiscardBackbufferCHROMIUM cmd;
+  };
+  Cmds expected;
+  expected.cmd.Init();
+
+  gl_->DiscardBackbufferCHROMIUM();
+  EXPECT_EQ(0, memcmp(&expected, commands_, sizeof(expected)));
+}
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_IMPLEMENTATION_UNITTEST_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_interface_autogen.h b/gpu/command_buffer/client/gles2_interface_autogen.h
index 8b8f74f..029bf69 100644
--- a/gpu/command_buffer/client/gles2_interface_autogen.h
+++ b/gpu/command_buffer/client/gles2_interface_autogen.h
@@ -322,5 +322,6 @@ virtual void LoseContextCHROMIUM(GLenum current, GLenum other) = 0;
 virtual GLuint InsertSyncPointCHROMIUM() = 0;
 virtual void WaitSyncPointCHROMIUM(GLuint sync_point) = 0;
 virtual void DrawBuffersEXT(GLsizei count, const GLenum* bufs) = 0;
+virtual void DiscardBackbufferCHROMIUM() = 0;
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_INTERFACE_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_interface_stub_autogen.h b/gpu/command_buffer/client/gles2_interface_stub_autogen.h
index 7e21389..59c0ce9 100644
--- a/gpu/command_buffer/client/gles2_interface_stub_autogen.h
+++ b/gpu/command_buffer/client/gles2_interface_stub_autogen.h
@@ -353,5 +353,6 @@ virtual void LoseContextCHROMIUM(GLenum current, GLenum other) OVERRIDE;
 virtual GLuint InsertSyncPointCHROMIUM() OVERRIDE;
 virtual void WaitSyncPointCHROMIUM(GLuint sync_point) OVERRIDE;
 virtual void DrawBuffersEXT(GLsizei count, const GLenum* bufs) OVERRIDE;
+virtual void DiscardBackbufferCHROMIUM() OVERRIDE;
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_INTERFACE_STUB_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_interface_stub_impl_autogen.h b/gpu/command_buffer/client/gles2_interface_stub_impl_autogen.h
index d17a6ad..e6a26d4 100644
--- a/gpu/command_buffer/client/gles2_interface_stub_impl_autogen.h
+++ b/gpu/command_buffer/client/gles2_interface_stub_impl_autogen.h
@@ -665,5 +665,7 @@ void GLES2InterfaceStub::WaitSyncPointCHROMIUM(GLuint /* sync_point */) {
 void GLES2InterfaceStub::DrawBuffersEXT(
     GLsizei /* count */, const GLenum* /* bufs */) {
 }
+void GLES2InterfaceStub::DiscardBackbufferCHROMIUM() {
+}
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_INTERFACE_STUB_IMPL_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_trace_implementation_autogen.h b/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
index 9d42f58..d811db5 100644
--- a/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
+++ b/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
@@ -353,5 +353,6 @@ virtual void LoseContextCHROMIUM(GLenum current, GLenum other) OVERRIDE;
 virtual GLuint InsertSyncPointCHROMIUM() OVERRIDE;
 virtual void WaitSyncPointCHROMIUM(GLuint sync_point) OVERRIDE;
 virtual void DrawBuffersEXT(GLsizei count, const GLenum* bufs) OVERRIDE;
+virtual void DiscardBackbufferCHROMIUM() OVERRIDE;
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_TRACE_IMPLEMENTATION_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/client/gles2_trace_implementation_impl_autogen.h b/gpu/command_buffer/client/gles2_trace_implementation_impl_autogen.h
index e3d7c78..49d7ab2 100644
--- a/gpu/command_buffer/client/gles2_trace_implementation_impl_autogen.h
+++ b/gpu/command_buffer/client/gles2_trace_implementation_impl_autogen.h
@@ -1237,5 +1237,10 @@ void GLES2TraceImplementation::DrawBuffersEXT(
   gl_->DrawBuffersEXT(count, bufs);
 }
 
+void GLES2TraceImplementation::DiscardBackbufferCHROMIUM() {
+  TRACE_EVENT_BINARY_EFFICIENT0("gpu", "GLES2Trace::DiscardBackbufferCHROMIUM");
+  gl_->DiscardBackbufferCHROMIUM();
+}
+
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_TRACE_IMPLEMENTATION_IMPL_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/cmd_buffer_functions.txt b/gpu/command_buffer/cmd_buffer_functions.txt
index 00505f3..eeb4760 100644
--- a/gpu/command_buffer/cmd_buffer_functions.txt
+++ b/gpu/command_buffer/cmd_buffer_functions.txt
@@ -219,5 +219,6 @@ GL_APICALL void         GL_APIENTRY glLoseContextCHROMIUM (GLenum current, GLenu
 GL_APICALL GLuint       GL_APIENTRY glInsertSyncPointCHROMIUM (void);
 GL_APICALL void         GL_APIENTRY glWaitSyncPointCHROMIUM (GLuint sync_point);
 GL_APICALL void         GL_APIENTRY glDrawBuffersEXT (GLsizei count, const GLenum* bufs);
+GL_APICALL void         GL_APIENTRY glDiscardBackbufferCHROMIUM (void);
 
 
diff --git a/gpu/command_buffer/common/gles2_cmd_format_autogen.h b/gpu/command_buffer/common/gles2_cmd_format_autogen.h
index b8ff951..248ad46 100644
--- a/gpu/command_buffer/common/gles2_cmd_format_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_format_autogen.h
@@ -10596,6 +10596,36 @@ COMPILE_ASSERT(offsetof(DrawBuffersEXTImmediate, header) == 0,
 COMPILE_ASSERT(offsetof(DrawBuffersEXTImmediate, count) == 4,
                OffsetOf_DrawBuffersEXTImmediate_count_not_4);
 
+struct DiscardBackbufferCHROMIUM {
+  typedef DiscardBackbufferCHROMIUM ValueType;
+  static const CommandId kCmdId = kDiscardBackbufferCHROMIUM;
+  static const cmd::ArgFlags kArgFlags = cmd::kFixed;
+
+  static uint32 ComputeSize() {
+    return static_cast<uint32>(sizeof(ValueType));  // NOLINT
+  }
+
+  void SetHeader() {
+    header.SetCmd<ValueType>();
+  }
+
+  void Init() {
+    SetHeader();
+  }
+
+  void* Set(void* cmd) {
+    static_cast<ValueType*>(cmd)->Init();
+    return NextCmdAddress<ValueType>(cmd);
+  }
+
+  gpu::CommandHeader header;
+};
+
+COMPILE_ASSERT(sizeof(DiscardBackbufferCHROMIUM) == 4,
+               Sizeof_DiscardBackbufferCHROMIUM_is_not_4);
+COMPILE_ASSERT(offsetof(DiscardBackbufferCHROMIUM, header) == 0,
+               OffsetOf_DiscardBackbufferCHROMIUM_header_not_0);
+
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_FORMAT_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h b/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
index b3d9380..9672db4 100644
--- a/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_format_test_autogen.h
@@ -4474,5 +4474,17 @@ TEST_F(GLES2FormatTest, DrawBuffersEXTImmediate) {
   // TODO(gman): Check that data was inserted;
 }
 
+TEST_F(GLES2FormatTest, DiscardBackbufferCHROMIUM) {
+  cmds::DiscardBackbufferCHROMIUM& cmd =
+      *GetBufferAs<cmds::DiscardBackbufferCHROMIUM>();
+  void* next_cmd = cmd.Set(
+      &cmd);
+  EXPECT_EQ(static_cast<uint32>(cmds::DiscardBackbufferCHROMIUM::kCmdId),
+            cmd.header.command);
+  EXPECT_EQ(sizeof(cmd), cmd.header.size * 4u);
+  CheckBytesWrittenMatchesExpectedSize(
+      next_cmd, sizeof(cmd));
+}
+
 #endif  // GPU_COMMAND_BUFFER_COMMON_GLES2_CMD_FORMAT_TEST_AUTOGEN_H_
 
diff --git a/gpu/command_buffer/common/gles2_cmd_ids_autogen.h b/gpu/command_buffer/common/gles2_cmd_ids_autogen.h
index 371e576..e26e8d2 100644
--- a/gpu/command_buffer/common/gles2_cmd_ids_autogen.h
+++ b/gpu/command_buffer/common/gles2_cmd_ids_autogen.h
@@ -244,6 +244,7 @@
   OP(WaitSyncPointCHROMIUM)                                    /* 487 */ \
   OP(DrawBuffersEXT)                                           /* 488 */ \
   OP(DrawBuffersEXTImmediate)                                  /* 489 */ \
+  OP(DiscardBackbufferCHROMIUM)                                /* 490 */ \
 
 enum CommandId {
   kStartPoint = cmd::kLastCommonId,  // All GLES2 commands start after this.
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 575a1b5..a68cd66 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -9298,6 +9298,18 @@ error::Error GLES2DecoderImpl::HandleWaitSyncPointCHROMIUM(
       error::kNoError : error::kDeferCommandUntilLater;
 }
 
+error::Error GLES2DecoderImpl::HandleDiscardBackbufferCHROMIUM(
+    uint32 immediate_data_size, const cmds::DiscardBackbufferCHROMIUM& c) {
+  if (surface_->DeferDraws())
+    return error::kDeferCommandUntilLater;
+  if (!surface_->SetBackbufferAllocation(false))
+    return error::kLostContext;
+  backbuffer_needs_clear_bits_ |= GL_COLOR_BUFFER_BIT;
+  backbuffer_needs_clear_bits_ |= GL_DEPTH_BUFFER_BIT;
+  backbuffer_needs_clear_bits_ |= GL_STENCIL_BUFFER_BIT;
+  return error::kNoError;
+}
+
 bool GLES2DecoderImpl::GenQueriesEXTHelper(
     GLsizei n, const GLuint* client_ids) {
   for (GLsizei ii = 0; ii < n; ++ii) {