Clamp dialog bounds to be fully visible on the nearest display

components/constrained_window/constrained_window_views_unittest.cc

 // Copyright 2013 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 "components/constrained_window/constrained_window_views.h"
 
 #include <memory>
+#include <vector>
 
 #include "base/macros.h"
 #include "components/constrained_window/constrained_window_views_client.h"
 #include "components/web_modal/test_web_contents_modal_dialog_host.h"
+#include "ui/display/display.h"
+#include "ui/display/screen.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/border.h"
 #include "ui/views/test/views_test_base.h"
 #include "ui/views/widget/widget.h"
 #include "ui/views/window/dialog_delegate.h"
 
 using views::Widget;
@@ skipping 199 matching lines @@
   SetConstrainedWindowViewsClient(
       base::MakeUnique<TestConstrainedWindowViewsClient>());
   DialogContents* contents = new DialogContents;
   contents->set_modal_type(ui::MODAL_TYPE_WINDOW);
   views::Widget* widget = CreateBrowserModalDialogViews(contents, nullptr);
   widget->Show();
   EXPECT_TRUE(widget->IsVisible());
   widget->CloseNow();
 }
 
+// Make sure dialogs presented off-screen are properly clamped to the nearest
+// screen.
+TEST_F(ConstrainedWindowViewsTest, ClampDialogToNearestDisplay) {
+  // First, make sure the host and dialog are sized and positioned.
+  UpdateWebContentsModalDialogPosition(dialog(), dialog_host());
+
+  const display::Screen* screen = display::Screen::GetScreen();
+  const display::Display display = screen->GetPrimaryDisplay();
+  // Within the tests there is only 1 display. Error if that ever changes.
+  EXPECT_EQ(screen->GetNumDisplays(), 1);
+  const gfx::Rect extents = display.work_area();
+
+  // Move the host completely off the screen.
+  views::Widget* host_widget =
+      views::Widget::GetWidgetForNativeView(dialog_host()->GetHostView());
+  gfx::Rect host_bounds = host_widget->GetWindowBoundsInScreen();
+  host_bounds.set_origin(gfx::Point(extents.right(), extents.bottom()));
+  host_widget->SetBounds(host_bounds);
+
+  // Make sure the host is fully off the screen.
+  EXPECT_FALSE(extents.Intersects(host_widget->GetWindowBoundsInScreen()));
+
+  // Now reposition the modal dialog into the display.
+  UpdateWebContentsModalDialogPosition(dialog(), dialog_host());
+
+  const gfx::Rect dialog_bounds = dialog()->GetRootView()->GetBoundsInScreen();
+
+  // As long as the dialog intersects the display, it has been moved to be
+  // visible. Due to the constraints set, it may extend off the display.

[msw, 2016/12/15 21:44:56]

Can you explain what constraints you're referring to here? It seems like we
should expect the display's work area to contain the dialog bounds, unless the
dialog is bigger than the work area? (Or they share an edge and that doesn't
count as 'contains'...)

[kylix_rd, 2016/12/15 21:57:56]

The default dialog constraints (min/max size) setup in the surrounding testing
class. The min size is slightly larger, vertically, than the display.

[msw, 2016/12/15 22:17:40]

It's a little silly that the test's SetUp makes the dialog too big to fit on the
default test display... Anyway, in this specific test fixture, can we do
something like this to ensure the bounds are contained?
  // Set a small preferred size that fits in the display's work area.
  contents()->set_preferred_size(gfx::Size(200, 100));
  ...
  EXPECT_TRUE(extents.Contains(dialog_bounds));

[kylix_rd, 2016/12/15 22:21:53]

I agree. However, out of the abundance of caution, I didn't make that kind of
change in case there were some other oddity I'd missed.

I'll verify that it is indeed only that change that is needed.

+  EXPECT_TRUE(extents.Intersects(dialog_bounds));
+}
+
 }  // namespace constrained_window