Fix issue with count=0 for DrawArrays and DrawElements

TEST=unit tests
BUG=52752


Review URL: http://codereview.chromium.org/3180025

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@57450 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 35 insertions, 0 deletions

diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 7fdb582..6940f8d 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2839,6 +2839,11 @@ void GLES2DecoderImpl::DoDrawArrays(
     SetGLError(GL_INVALID_ENUM, "glDrawArrays: first < 0");
     return;
   }
+
+  if (count == 0) {
+    return;
+  }
+
   if (IsDrawValid(first + count - 1)) {
     bool simulated_attrib_0 = SimulateAttrib0(first + count - 1);
     bool textures_set = SetBlackTextureForNonRenderableTextures();
@@ -3602,6 +3607,10 @@ error::Error GLES2DecoderImpl::HandleDrawElements(
     return error::kNoError;
   }
 
+  if (count == 0) {
+    return error::kNoError;
+  }
+
   GLuint max_vertex_accessed;
   if (!bound_element_array_buffer_->GetMaxValueForRange(
       offset, count, type, &max_vertex_accessed)) {
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc b/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
index c282507..c929847 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_unittest.cc
@@ -131,6 +131,18 @@ TEST_F(GLES2DecoderWithShaderTest, DrawArraysMissingAttributesFails) {
   EXPECT_EQ(GL_INVALID_OPERATION, GetGLError());
 }
 
+TEST_F(GLES2DecoderWithShaderTest,
+       DrawArraysMissingAttributesZeroCountSucceeds) {
+  DoEnableVertexAttribArray(1);
+
+  EXPECT_CALL(*gl_, DrawArrays(_, _, _))
+      .Times(0);
+  DrawArrays cmd;
+  cmd.Init(GL_TRIANGLES, 0, 0);
+  EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
+  EXPECT_EQ(GL_NO_ERROR, GetGLError());
+}
+
 TEST_F(GLES2DecoderWithShaderTest, DrawArraysValidAttributesSucceeds) {
   SetupTexture();
   SetupVertexBuffer();
@@ -256,6 +268,20 @@ TEST_F(GLES2DecoderWithShaderTest, DrawElementsMissingAttributesFails) {
   EXPECT_EQ(GL_INVALID_OPERATION, GetGLError());
 }
 
+TEST_F(GLES2DecoderWithShaderTest,
+       DrawElementsMissingAttributesZeroCountSucceeds) {
+  SetupIndexBuffer();
+  DoEnableVertexAttribArray(1);
+
+  EXPECT_CALL(*gl_, DrawElements(_, _, _, _))
+      .Times(0);
+  DrawElements cmd;
+  cmd.Init(GL_TRIANGLES, 0, GL_UNSIGNED_SHORT,
+           kValidIndexRangeStart * 2);
+  EXPECT_EQ(error::kNoError, ExecuteCmd(cmd));
+  EXPECT_EQ(GL_NO_ERROR, GetGLError());
+}
+
 TEST_F(GLES2DecoderWithShaderTest, DrawElementsExtraAttributesFails) {
   SetupIndexBuffer();
   DoEnableVertexAttribArray(6);