Allow offset for secondary display position in chrome://settings/display.

ash/display/display_controller.cc

 // Copyright (c) 2012 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 "ash/display/display_controller.h"
 
+#include <algorithm>
+
 #include "ash/ash_switches.h"
 #include "ash/display/multi_display_manager.h"
 #include "ash/root_window_controller.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/wm/coordinate_conversion.h"
 #include "ash/wm/property_util.h"
 #include "ash/wm/window_util.h"
 #include "base/command_line.h"
 #include "ui/aura/client/screen_position_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/screen.h"
 
 namespace ash {
 namespace internal {
+namespace {
+// The number of pixels to overlap between the primary and secondary displays,
+// in case that the offset value is too large.
+const int kMinimumOverlapForInvalidOffset = 50;
+}
 
 DisplayController::DisplayController()
     : secondary_display_layout_(RIGHT),
+      secondary_display_offset_(0),
       dont_warp_mouse_(false) {
   aura::Env::GetInstance()->display_manager()->AddObserver(this);
 }
 
 DisplayController::~DisplayController() {
   aura::Env::GetInstance()->display_manager()->RemoveObserver(this);
   // Delete all root window controllers, which deletes root window
   // from the last so that the primary root window gets deleted last.
   for (std::map<int, aura::RootWindow*>::const_reverse_iterator it =
            root_windows_.rbegin(); it != root_windows_.rend(); ++it) {
@@ skipping 77 matching lines @@
   }
   return controllers;
 }
 
 void DisplayController::SetSecondaryDisplayLayout(
     SecondaryDisplayLayout layout) {
   secondary_display_layout_ = layout;
   UpdateDisplayBoundsForLayout();
 }
 
+void DisplayController::SetSecondaryDisplayOffset(int offset) {
+  secondary_display_offset_ = offset;
+  UpdateDisplayBoundsForLayout();
+}
+
 bool DisplayController::WarpMouseCursorIfNecessary(
     aura::RootWindow* current_root,
     const gfx::Point& point_in_root) {
   if (root_windows_.size() < 2 || dont_warp_mouse_)
     return false;
 
   // The pointer might be outside the |current_root|. Get the root window where
   // the pointer is currently on.
   std::pair<aura::RootWindow*, gfx::Point> actual_location =
       wm::GetRootWindowRelativeToWindow(current_root, point_in_root);
@@ skipping 101 matching lines @@
   }
   DCHECK_EQ(2, gfx::Screen::GetNumDisplays());
   aura::DisplayManager* display_manager =
       aura::Env::GetInstance()->display_manager();
   const gfx::Rect& primary_bounds = display_manager->GetDisplayAt(0)->bounds();
   gfx::Display* secondary_display = display_manager->GetDisplayAt(1);
   const gfx::Rect& secondary_bounds = secondary_display->bounds();
   gfx::Point new_secondary_origin = primary_bounds.origin();
 
   // TODO(oshima|mukai): Implement more flexible layout.
+
+  // Ignore the offset in case that the secondary display doesn't share edges
+  // with the primary display.
+  int offset = secondary_display_offset_;
+  if (secondary_display_layout_ == TOP || secondary_display_layout_ == BOTTOM) {
+    offset = std::min(
+        offset, primary_bounds.width() - kMinimumOverlapForInvalidOffset);
+    offset = std::max(
+        offset, -secondary_bounds.width() + kMinimumOverlapForInvalidOffset);
+  } else {
+    offset = std::min(
+        offset, primary_bounds.height() - kMinimumOverlapForInvalidOffset);
+    offset = std::max(
+        offset, -secondary_bounds.height() + kMinimumOverlapForInvalidOffset);
+  }
   switch (secondary_display_layout_) {
     case TOP:
-      new_secondary_origin.Offset(0, -secondary_bounds.height());
+      new_secondary_origin.Offset(offset, -secondary_bounds.height());
       break;
     case RIGHT:
-      new_secondary_origin.Offset(primary_bounds.width(), 0);
+      new_secondary_origin.Offset(primary_bounds.width(), offset);
       break;
     case BOTTOM:
-      new_secondary_origin.Offset(0, primary_bounds.height());
+      new_secondary_origin.Offset(offset, primary_bounds.height());
       break;
     case LEFT:
-      new_secondary_origin.Offset(-secondary_bounds.width(), 0);
+      new_secondary_origin.Offset(-secondary_bounds.width(), offset);
       break;
   }
   gfx::Insets insets = secondary_display->GetWorkAreaInsets();
   secondary_display->set_bounds(
       gfx::Rect(new_secondary_origin, secondary_bounds.size()));
   secondary_display->UpdateWorkAreaFromInsets(insets);
 }
 
 }  // namespace internal
 }  // namespace ash