Distill the concept of the "tab top exclusion region", an area inside the tab

chrome/browser/ui/views/frame/glass_browser_frame_view.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 "chrome/browser/ui/views/frame/glass_browser_frame_view.h"
 
 #include "base/prefs/pref_service.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
 #include "chrome/app/chrome_command_ids.h"
@@ skipping 25 matching lines @@
 #include "ui/views/win/hwnd_util.h"
 #include "ui/views/window/client_view.h"
 
 HICON GlassBrowserFrameView::throbber_icons_[
     GlassBrowserFrameView::kThrobberIconCount];
 
 namespace {
 // Size of client edge drawn inside the outer frame borders.
 const int kNonClientBorderThicknessPreWin10 = 3;
 const int kNonClientBorderThicknessWin10 = 1;
-// Besides the frame border, there's another 9 px of empty space atop the
-// window in restored mode, to use to drag the window around.
-const int kNonClientRestoredExtraThickness = 9;
+// Besides the frame border, there's empty space atop the window in restored
+// mode, to use to drag the window around.
+const int kNonClientRestoredExtraThickness = 11;
 // In the window corners, the resize areas don't actually expand bigger, but the
 // 16 px at the end of the top and bottom edges triggers diagonal resizing.
 const int kResizeCornerWidth = 16;
 // How far the new avatar button is from the left of the minimize button.
 const int kNewAvatarButtonOffset = 5;
 // The content left/right images have a shadow built into them.
 const int kContentEdgeShadowThickness = 2;
 // In restored mode, the New Tab button isn't at the same height as the caption
 // buttons, but the space will look cluttered if it actually slides under them,
 // so we stop it when the gap between the two is down to 5 px.
@@ skipping 262 matching lines @@
 
   return (base::win::GetVersion() <= base::win::VERSION_WIN8_1)
              ? kNonClientBorderThicknessPreWin10
              : kNonClientBorderThicknessWin10;
 }
 
 int GlassBrowserFrameView::NonClientTopBorderHeight() const {
   if (frame()->IsFullscreen())
     return 0;
 
+  const int top = FrameTopBorderHeight();
   // The tab top inset is equal to the height of any shadow region above the
   // tabs, plus a 1 px top stroke.  In maximized mode, we want to push the
-  // shadow region off the top of the screen.
-  const int tab_shadow_height = GetLayoutInsets(TAB).top() - 1;
-  return FrameTopBorderHeight() +
-      (frame()->IsMaximized() ?
-          -tab_shadow_height : kNonClientRestoredExtraThickness);
+  // shadow region off the top of the screen but leave the top stroke.
+  // Annoyingly, the pre-MD layout uses different heights for the hit-test
+  // exclusion region (which we want here, since we're trying to size the border
+  // so that the region above the tab's hit-test zone matches) versus the shadow
+  // thickness.
+  const int exclusion = GetLayoutConstant(TAB_TOP_EXCLUSION_HEIGHT);
+  return frame()->IsMaximized() ?
+      (top - GetLayoutInsets(TAB).top() + 1) :
+      (top + kNonClientRestoredExtraThickness - exclusion);
 }
 
 void GlassBrowserFrameView::PaintToolbarBackground(gfx::Canvas* canvas) {
   ui::ThemeProvider* tp = GetThemeProvider();
 
   gfx::Rect toolbar_bounds(browser_view()->GetToolbarBounds());
   gfx::Point toolbar_origin(toolbar_bounds.origin());
   View::ConvertPointToTarget(browser_view(), this, &toolbar_origin);
   toolbar_bounds.set_origin(toolbar_origin);
   int x = toolbar_bounds.x();
@@ skipping 280 matching lines @@
   static bool initialized = false;
   if (!initialized) {
     for (int i = 0; i < kThrobberIconCount; ++i) {
       throbber_icons_[i] =
           ui::LoadThemeIconFromResourcesDataDLL(IDI_THROBBER_01 + i);
       DCHECK(throbber_icons_[i]);
     }
     initialized = true;
   }
 }