Support primary display swapping for >2 displays

Primary display swapping using Alt + F4 only recognized two displays.
Fixed by returning secondary display that is next to the primary display
in active_display_list_.

Bug: 867966
Change-Id: Icd395582bf48123c0a463e663b0db62c51e352d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2019474Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Commit-Queue: Su Hong Koo <sukoo@google.com>
Cr-Commit-Position: refs/heads/master@{#738290}

ash/accelerators/accelerator_commands.cc

@@ -4,6 +4,7 @@
 
 #include "ash/accelerators/accelerator_commands.h"
 
+#include "ash/display/display_configuration_controller.h"
 #include "ash/shell.h"
 #include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/screen_pinning_controller.h"
@@ -97,5 +98,35 @@ void UnpinWindow() {
     WindowState::Get(pinned_window)->Restore();
 }
 
+void ShiftPrimaryDisplay() {
+  display::DisplayManager* display_manager = Shell::Get()->display_manager();
+
+  CHECK_GE(display_manager->GetNumDisplays(), 2U);
+
+  const int64_t primary_display_id =
+      display::Screen::GetScreen()->GetPrimaryDisplay().id();
+
+  const display::Displays& active_display_list =
+      display_manager->active_display_list();
+
+  auto primary_display_iter =
+      std::find_if(active_display_list.begin(), active_display_list.end(),
+                   [id = primary_display_id](const display::Display& display) {
+                     return display.id() == id;
+                   });
+
+  DCHECK(primary_display_iter != active_display_list.end());
+
+  ++primary_display_iter;
+
+  // If we've reach the end of |active_display_list|, wrap back around to the
+  // front.
+  if (primary_display_iter == active_display_list.end())
+    primary_display_iter = active_display_list.begin();
+
+  Shell::Get()->display_configuration_controller()->SetPrimaryDisplayId(
+      primary_display_iter->id(), true /* throttle */);
+}
+
 }  // namespace accelerators
 }  // namespace ash

ash/accelerators/accelerator_commands.h

@@ -38,6 +38,10 @@ ASH_EXPORT bool CanUnpinWindow();
 // If a window is pinned (aka forced fullscreen), exit from pinned mode.
 ASH_EXPORT void UnpinWindow();
 
+// Change primary display to the secondary display next to current primary
+// display
+ASH_EXPORT void ShiftPrimaryDisplay();
+
 }  // namespace accelerators
 }  // namespace ash
 

ash/accelerators/accelerator_commands_unittest.cc

@@ -10,6 +10,9 @@
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
+#include "ui/display/manager/display_manager.h"
+#include "ui/display/screen.h"
+#include "ui/display/test/display_manager_test_api.h"
 
 namespace ash {
 namespace accelerators {
@@ -82,5 +85,56 @@ TEST_F(AcceleratorCommandsTest, Unpin) {
   EXPECT_FALSE(window_state1->IsPinned());
 }
 
+TEST_F(AcceleratorCommandsTest, CycleSwapPrimaryDisplay) {
+  display::test::DisplayManagerTestApi(display_manager())
+      .SetFirstDisplayAsInternalDisplay();
+  UpdateDisplay("800x600,800x600,800x600");
+
+  display::DisplayIdList id_list = display_manager()->GetCurrentDisplayIdList();
+
+  ShiftPrimaryDisplay();
+  int64_t primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[1], primary_id);
+
+  ShiftPrimaryDisplay();
+  primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[2], primary_id);
+
+  ShiftPrimaryDisplay();
+  primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[0], primary_id);
+}
+
+TEST_F(AcceleratorCommandsTest, CycleMixedMirrorModeSwapPrimaryDisplay) {
+  UpdateDisplay("300x400,400x500,500x600");
+  display::DisplayIdList id_list = display_manager()->GetCurrentDisplayIdList();
+
+  // Turn on mixed mirror mode. (Mirror from the first display to the second
+  // display)
+  display::DisplayIdList dst_ids;
+  dst_ids.emplace_back(id_list[1]);
+  base::Optional<display::MixedMirrorModeParams> mixed_params(
+      base::in_place, id_list[0], dst_ids);
+
+  display_manager()->SetMirrorMode(display::MirrorMode::kMixed, mixed_params);
+
+  EXPECT_TRUE(display_manager()->IsInSoftwareMirrorMode());
+  EXPECT_EQ(id_list[0], display_manager()->mirroring_source_id());
+  EXPECT_TRUE(display_manager()->mixed_mirror_mode_params());
+  EXPECT_EQ(2U, display_manager()->GetNumDisplays());
+
+  ShiftPrimaryDisplay();
+  int64_t primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[2], primary_id);
+
+  ShiftPrimaryDisplay();
+  primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[0], primary_id);
+
+  ShiftPrimaryDisplay();
+  primary_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
+  EXPECT_EQ(id_list[2], primary_id);
+}
+
 }  // namespace accelerators
 }  // namespace ash

ash/accelerators/accelerator_controller_impl.cc

@@ -733,13 +733,7 @@ void HandleShowTaskManager() {
 
 void HandleSwapPrimaryDisplay() {
   base::RecordAction(UserMetricsAction("Accel_Swap_Primary_Display"));
-
-  // TODO(rjkroege): This is not correct behaviour on devices with more than
-  // two screens. Behave the same as mirroring: fail and notify if there are
-  // three or more screens.
-  Shell::Get()->display_configuration_controller()->SetPrimaryDisplayId(
-      Shell::Get()->display_manager()->GetSecondaryDisplay().id(),
-      true /* throttle */);
+  accelerators::ShiftPrimaryDisplay();
 }
 
 bool CanHandleSwitchIme(const ui::Accelerator& accelerator) {