Exclude caption button bounds from non-client frame hit testing

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 <dwmapi.h>
 #include <utility>
 
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/windows_version.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/app/chrome_dll_resource.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/ui/layout_constants.h"
 #include "chrome/browser/ui/views/frame/browser_view.h"
 #include "chrome/browser/ui/views/profiles/profile_indicator_icon.h"
 #include "chrome/browser/ui/views/tabs/tab.h"
 #include "chrome/browser/ui/views/tabs/tab_strip.h"
 #include "chrome/browser/ui/views/toolbar/toolbar_view.h"
 #include "components/prefs/pref_service.h"
 #include "components/signin/core/browser/signin_header_helper.h"
 #include "components/signin/core/common/profile_management_switches.h"
 #include "grit/theme_resources.h"
 #include "skia/ext/image_operations.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/resource/resource_bundle_win.h"
 #include "ui/base/theme_provider.h"
 #include "ui/display/win/dpi.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/geometry/dip_util.h"
 #include "ui/gfx/icon_util.h"
 #include "ui/gfx/image/image.h"
 #include "ui/gfx/scoped_canvas.h"
 #include "ui/resources/grit/ui_resources.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/layout/layout_constants.h"
 #include "ui/views/resources/grit/views_resources.h"
 #include "ui/views/win/hwnd_util.h"
 #include "ui/views/window/client_view.h"
 
@@ skipping 22 matching lines @@
 const int kNewTabCaptionRestoredSpacing = 5;
 // In maximized mode, where the New Tab button and the caption buttons are at
 // similar vertical coordinates, we need to reserve a larger, 16 px gap to avoid
 // looking too cluttered.
 const int kNewTabCaptionMaximizedSpacing = 16;
 // Height of the profile switcher button. Same as the height of the Windows 7/8
 // caption buttons.
 // TODO(bsep): Windows 10 caption buttons look very different and we would like
 // the profile switcher button to match on that platform.
 const int kProfileSwitcherButtonHeight = 20;
+// There is a small one-pixel strip right above the caption buttons in which the
+// resize border "peeks" through.
+const int kCaptionButtonTopInset = 1;
 
 // Converts the |image| to a Windows icon and returns the corresponding HICON
 // handle. |image| is resized to desired |width| and |height| if needed.
 base::win::ScopedHICON CreateHICONFromSkBitmapSizedTo(
     const gfx::ImageSkia& image,
     int width,
     int height) {
   return IconUtil::CreateHICONFromSkBitmap(
       width == image.width() && height == image.height()
           ? *image.bitmap()
@@ skipping 155 matching lines @@
   gfx::Rect sys_menu_region(client_border_thickness,
                             display::win::GetSystemMetricsInDIP(SM_CYSIZEFRAME),
                             display::win::GetSystemMetricsInDIP(SM_CXSMICON),
                             display::win::GetSystemMetricsInDIP(SM_CYSMICON));
   if (sys_menu_region.Contains(point))
     return (frame_component == HTCLIENT) ? HTCLIENT : HTSYSMENU;
 
   if (frame_component != HTNOWHERE)
     return frame_component;
 
+  // On Windows 8+, the caption buttons are almost butted up to the top right
+  // corner of the window. This code ensures the mouse isn't set to a size
+  // cursor while hovering over the caption buttons, thus giving the incorrect
+  // impression that the user can resize the window.
+  if (base::win::GetVersion() >= base::win::VERSION_WIN8) {
+    RECT button_bounds = {0};
+    if (SUCCEEDED(DwmGetWindowAttribute(views::HWNDForWidget(frame()),
+                                        DWMWA_CAPTION_BUTTON_BOUNDS,
+                                        &button_bounds,
+                                        sizeof(button_bounds)))) {
+      gfx::Rect buttons = gfx::ConvertRectToDIP(display::win::GetDPIScale(),
+                                                gfx::Rect(button_bounds));
+      // Even though the tiny area above the caption buttons is very difficult
+      // to hit, this ensures behavioral consistency with other top-level
+      // windows. It is worth noting that this area is the same size (1px)
+      // regardless of the current scale factor. For that reason the rect is
+      // inset after it is adjusted for the device scale. Even so, this is less
+      // than ideal since conversion to DIPs may lose some precision. Given
+      // that the API doesn't take that into account, at this point this is the
+      // best we can do.

[Peter Kasting, 2016/07/20 18:47:44]

Nit: This still reads pretty confusingly to me.  What do you think of this?:

The sizing region at the window edge is 1 px regardless of scale factor.  But if
we inset by 1 before converting to DIPs, the precision loss might eliminate this
region entirely.  The best we can do is to inset after conversion, which
guarantees we'll show the resize cursor when resizing is possible, at the cost
of also showing it over the portion of the DIP that isn't the outermost pixel.

+      buttons.Inset(0, kCaptionButtonTopInset, 0, 0);
+      if (buttons.Contains(point))
+        return HTNOWHERE;
+    }
+  }
+
   int top_border_thickness = FrameTopBorderThickness(false);
   // We want the resize corner behavior to apply to the kResizeCornerWidth
   // pixels at each end of the top and bottom edges.  Because |point|'s x
   // coordinate is based on the DWM-inset portion of the window (so, it's 0 at
   // the first pixel inside the left DWM margin), we need to subtract the DWM
   // margin thickness, which we calculate as the total frame border thickness
   // minus the nonclient border thickness.
   const int dwm_margin = FrameBorderThickness() - client_border_thickness;
   int window_component = GetHTComponentForFrame(
       point, top_border_thickness, client_border_thickness,
@@ skipping 419 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;
   }
 }