Offset scissor and viewport when using SetDrawRectangle on surface.

gpu/ipc/service/direct_composition_surface_win.cc

 // Copyright 2017 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 "gpu/ipc/service/direct_composition_surface_win.h"
 
 #include "base/optional.h"
 #include "gpu/ipc/service/gpu_channel_manager.h"
 #include "gpu/ipc/service/gpu_channel_manager_delegate.h"
 #include "ui/gfx/native_widget_types.h"
@@ skipping 277 matching lines @@
   if (gfx::Rect(size_) != rectangle && !has_been_rendered_to_) {
     DLOG(ERROR) << "First draw to surface must draw to everything";
     return false;
   }
 
   DCHECK(!real_surface_);
   CHECK(!g_current_surface);
   ScopedReleaseCurrent release_current(this);
 
   RECT rect = rectangle.ToRECT();
-  // TODO(jbauman): Use update_offset
   POINT update_offset;
 
   HRESULT hr = dcomp_surface_->BeginDraw(
       &rect, IID_PPV_ARGS(draw_texture_.Receive()), &update_offset);
   CHECK(SUCCEEDED(hr));
   has_been_rendered_to_ = true;
 
+  draw_offset_ = gfx::Point(update_offset) - gfx::Rect(rect).origin();
+
   g_current_surface = dcomp_surface_.get();
 
   std::vector<EGLint> pbuffer_attribs{
       EGL_WIDTH,
       size_.width(),
       EGL_HEIGHT,
       size_.height(),
       EGL_FLEXIBLE_SURFACE_COMPATIBILITY_SUPPORTED_ANGLE,
       EGL_TRUE,
       EGL_NONE};
 
   EGLClientBuffer buffer =
       reinterpret_cast<EGLClientBuffer>(draw_texture_.get());
   real_surface_ = eglCreatePbufferFromClientBuffer(
       GetDisplay(), EGL_D3D_TEXTURE_ANGLE, buffer, GetConfig(),
       &pbuffer_attribs[0]);
 
   return true;
 }
 
+gfx::Vector2d DirectCompositionSurfaceWin::GetDrawOffset() const {
+  return draw_offset_;
+}
+
 scoped_refptr<base::TaskRunner>
 DirectCompositionSurfaceWin::GetWindowTaskRunnerForTesting() {
   return child_window_.GetTaskRunnerForTesting();
 }
 
 DirectCompositionSurfaceWin::Overlay::Overlay(int z_order,
                                               gfx::OverlayTransform transform,
                                               scoped_refptr<gl::GLImage> image,
                                               gfx::Rect bounds_rect,
                                               gfx::RectF crop_rect)
     : z_order(z_order),
       transform(transform),
       image(image),
       bounds_rect(bounds_rect),
       crop_rect(crop_rect) {}
 
 DirectCompositionSurfaceWin::Overlay::Overlay(const Overlay& overlay) = default;
 
 DirectCompositionSurfaceWin::Overlay::~Overlay() {}
 
 }  // namespace gpu