exo: Don't shift root surface in fullscreen shell

The expectation is that the root surface fills the display space. This
ensures that sub-surfaces with negative origins don't cause the root
surface to be shifted and the host window resized.

Bug: 1015185
Test: Manually with test fullscreen_wayland_client
Test: Compare behavior while running with "weston --shell fullscreen-shell.so"
Change-Id: Id67f6e0584002329bf9941843ae6eb27c01c7225
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1866608
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707019}

components/exo/fullscreen_shell_surface.cc

@@ -10,6 +10,7 @@
 #include "third_party/skia/include/core/SkPath.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_observer.h"
+#include "ui/aura/window_occlusion_tracker.h"
 #include "ui/aura/window_targeter.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/dip_util.h"
@@ -208,6 +209,17 @@ void FullscreenShellSurface::OnWindowDestroying(aura::Window* window) {
   window->RemoveObserver(this);
 }
 
+void FullscreenShellSurface::UpdateHostWindowBounds() {
+  // This method applies multiple changes to the window tree. Use ScopedPause
+  // to ensure that occlusion isn't recomputed before all changes have been
+  // applied.
+  aura::WindowOcclusionTracker::ScopedPause pause_occlusion;
+
+  host_window()->SetBounds(
+      gfx::Rect(root_surface()->window()->bounds().size()));
+  host_window()->SetTransparent(!root_surface()->FillsBoundsOpaquely());
+}
+
 void FullscreenShellSurface::CreateFullscreenShellSurfaceWidget(
     ui::WindowShowState show_state) {
   DCHECK(GetEnabled());

components/exo/fullscreen_shell_surface.h

@@ -86,6 +86,9 @@ class FullscreenShellSurface : public SurfaceTreeHost,
   void SetChildAxTreeId(ui::AXTreeID child_ax_tree_id);
 
  private:
+  // Keep the bounds in sync with the root surface bounds.
+  void UpdateHostWindowBounds() override;
+
   void CreateFullscreenShellSurfaceWidget(ui::WindowShowState show_state);
   void CommitWidget();
   bool OnPreWidgetCommit();

components/exo/fullscreen_shell_surface_unittest.cc

@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "components/exo/buffer.h"
 #include "components/exo/shell_surface_util.h"
+#include "components/exo/sub_surface.h"
 #include "components/exo/surface.h"
 #include "components/exo/test/exo_test_base_views.h"
 #include "components/exo/wm_helper.h"
@@ -191,6 +192,40 @@ TEST_F(FullscreenShellSurfaceTest, Bounds) {
   EXPECT_EQ(fullscreen_bounds, expected_bounds);
 }
 
+TEST_F(FullscreenShellSurfaceTest, BoundsWithPartiallyOffscreenSubSurface) {
+  aura::Window* root_window =
+      WMHelper::GetInstance()->GetRootWindowForNewWindows();
+  gfx::Rect new_root_bounds(10, 10, 100, 100);
+  gfx::Rect expected_bounds(new_root_bounds.size());
+  root_window->SetBounds(new_root_bounds);
+
+  gfx::Size buffer_size(100, 100);
+  auto buffer = std::make_unique<Buffer>(
+      CreateGpuMemoryBuffer(buffer_size, gfx::BufferFormat::RGBA_8888));
+  auto parent = std::make_unique<Surface>();
+  auto fullscreen_surface = std::make_unique<FullscreenShellSurface>();
+  fullscreen_surface->SetSurface(parent.get());
+
+  parent->Attach(buffer.get());
+  parent->Commit();
+  EXPECT_EQ(fullscreen_surface->GetWidget()->GetWindowBoundsInScreen(),
+            expected_bounds);
+  EXPECT_EQ(parent->window()->bounds(), expected_bounds);
+
+  auto surface = std::make_unique<Surface>();
+  auto sub_surface = std::make_unique<SubSurface>(surface.get(), parent.get());
+  surface->Attach(buffer.get());
+  sub_surface->SetPosition(gfx::Point(-50, -50));
+
+  parent->Commit();
+  // Make sure the sub-surface doesn't affect the Fullscreen Shell's Window
+  // size/position.
+  EXPECT_EQ(fullscreen_surface->GetWidget()->GetWindowBoundsInScreen(),
+            expected_bounds);
+  // The root surface should also have the same position/size as before.
+  EXPECT_EQ(parent->window()->bounds(), expected_bounds);
+}
+
 TEST_F(FullscreenShellSurfaceTest, SetAXChildTree) {
   std::unique_ptr<Surface> surface(new Surface);
   std::unique_ptr<FullscreenShellSurface> fullscreen_surface(

components/exo/surface_tree_host.h

@@ -95,8 +95,9 @@ class SurfaceTreeHost : public SurfaceDelegate,
   // need to be released back to the client.
   void SubmitEmptyCompositorFrame();
 
-  // Update the host window's size to cover entire surfaces.
-  void UpdateHostWindowBounds();
+  // Update the host window's size to cover sufaces that must be visible and
+  // not clipped.
+  virtual void UpdateHostWindowBounds();
 
  private:
   viz::CompositorFrame PrepareToSubmitCompositorFrame();