[Mac] Improve modal sheet positioning during window resizing.

chrome/browser/ui/cocoa/constrained_window/constrained_window_sheet_controller_unittest.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_sheet_controller.h"
 
 #import "chrome/browser/ui/cocoa/cocoa_test_helper.h"
 #import "chrome/browser/ui/cocoa/constrained_window/constrained_window_custom_sheet.h"
 #import "testing/gtest_mac.h"
 
@@ skipping 118 matching lines @@
     return rect;
   }
 
   void VerifySheetXPosition(NSRect sheet_frame, NSView* parent_view) {
     NSRect parent_frame = GetViewFrameInScreenCoordinates(parent_view);
     CGFloat expected_x = NSMinX(parent_frame) +
         (NSWidth(parent_frame) - NSWidth(sheet_frame)) / 2.0;
     EXPECT_EQ(expected_x, NSMinX(sheet_frame));
   }
 
+  CGFloat GetSheetYOffset(NSRect sheet_frame, NSView* parent_view) {
+    return NSMaxY(sheet_frame) -
+           NSMaxY(GetViewFrameInScreenCoordinates(parent_view));
+  }
+
   base::scoped_nsobject<NSWindow> sheet_window_;
   base::scoped_nsobject<CustomConstrainedWindowSheet> sheet_;
   base::scoped_nsobject<ConstrainedWindowSheetController> controller_;
   base::scoped_nsobject<NSMutableArray> tab_views_;
   base::scoped_nsobject<NSView> active_tab_view_;
   base::scoped_nsobject<NSView> tab0_;
   base::scoped_nsobject<NSView> tab1_;
 };
 
 // Test showing then hiding the sheet.
@@ skipping 98 matching lines @@
   [sheet_window_ setFrame:new_inactive_frame display:YES];
 
   ActivateTabView(tab0_);
   EXPECT_EQ(1.0, [sheet_window_ alphaValue]);
 
   NSRect new_active_frame = [sheet_window_ frame];
   EXPECT_EQ(NSWidth(new_inactive_frame), NSWidth(new_active_frame));
   EXPECT_EQ(NSHeight(new_inactive_frame), NSHeight(new_active_frame));
 }
 
+// Test resizing parent window keeps the sheet anchored.
+TEST_F(ConstrainedWindowSheetControllerTest, ResizeParentWindow) {
+  [controller_ showSheet:sheet_ forParentView:active_tab_view_];
+  CGFloat sheet_offset =
+      GetSheetYOffset([sheet_window_ frame], active_tab_view_);
+
+  // Test 3x3 different parent window sizes.
+  CGFloat insets[] = {-10, 0, 10};
+  NSRect old_frame = [test_window() frame];
+
+  for (size_t x = 0; x < sizeof(insets) / sizeof(CGFloat); x++) {
+    for (size_t y = 0; y < sizeof(insets) / sizeof(CGFloat); y++) {
+      NSRect resized_frame = NSInsetRect(old_frame, insets[x], insets[y]);
+      [test_window() setFrame:resized_frame display:YES];
+      NSRect sheet_frame = [sheet_window_ frame];
+
+      // Y pos should track parent view's position.
+      EXPECT_EQ(sheet_offset, GetSheetYOffset(sheet_frame, active_tab_view_));
+
+      // X pos should be centered on parent view.
+      VerifySheetXPosition(sheet_frame, active_tab_view_);
+    }
+  }
+}
+
 // Test system sheets.
 TEST_F(ConstrainedWindowSheetControllerTest, SystemSheet) {
   base::scoped_nsobject<ConstrainedWindowSystemSheetTest> system_sheet(
       [[ConstrainedWindowSystemSheetTest alloc] init]);
   base::scoped_nsobject<NSAlert> alert([[NSAlert alloc] init]);
   [system_sheet setAlert:alert];
 
   EXPECT_FALSE([[alert window] isVisible]);
   [controller_ showSheet:system_sheet
                  forParentView:active_tab_view_];
@@ skipping 15 matching lines @@
   [controller_ showSheet:system_sheet
                  forParentView:tab1_];
   EXPECT_FALSE([[alert window] isVisible]);
 
   ActivateTabView(tab1_);
   EXPECT_TRUE([[alert window] isVisible]);
   EXPECT_EQ(1.0, [[alert window] alphaValue]);
 
   [controller_ closeSheet:system_sheet];
 }