[Win] Update HWND style when SizeConstraintsChanged.

ui/views/widget/widget_hwnd_utils.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 "ui/views/widget/widget_hwnd_utils.h"
 
 #include <dwmapi.h>
 
 #include "base/command_line.h"
 #include "base/win/windows_version.h"
@@ skipping 63 matching lines @@
   // Set type-dependent style attributes.
   switch (params.type) {
     case Widget::InitParams::TYPE_PANEL:
       *ex_style |= WS_EX_TOPMOST;
       if (params.remove_standard_frame) {
         *style |= WS_POPUP;
         break;
       }
       // Else, no break. Fall through to TYPE_WINDOW.
     case Widget::InitParams::TYPE_WINDOW: {
-      *style |= WS_SYSMENU | WS_CAPTION;
-      bool can_resize = widget_delegate->CanResize();
-      bool can_maximize = widget_delegate->CanMaximize();
-      if (can_maximize) {
-        *style |= WS_OVERLAPPEDWINDOW;
-      } else if (can_resize || params.remove_standard_frame) {
-        *style |= WS_OVERLAPPED | WS_THICKFRAME;
-      }
+      // WS_OVERLAPPEDWINDOW is equivalent to:
+      //   WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU |
+      //   WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX
+      *style |= WS_OVERLAPPEDWINDOW;
+      if (!widget_delegate->CanMaximize())
+        *style &= ~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX);

[sky, 2014/09/18 14:27:09]

Why remove the minimize button if the window can't maximize?

[jackhou1, 2014/09/18 23:28:35]

Hah, I was hoping you would know. There's this bug, http://crbug.com/341010,
referenced in HWNDMessageHandler::OnInitMenu. Essentially we want to disable the
Minimize in the right click menu to prevent certain dialog boxes from being
minimizable.

But it seems that throughout Windows and CrOS, we always hide the minimize
button when a window is not maximizable. Any idea who might know more about
this?

This CL maintains the existing semantics. If I can't find out why we do this,
I'll put together another CL that changes it.

+      if (!widget_delegate->CanResize())
+        *style &= ~(WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX);
+      if (params.remove_standard_frame)
+        *style &= ~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX);
+
       if (native_widget_delegate->IsDialogBox()) {
         *style |= DS_MODALFRAME;
         // NOTE: Turning this off means we lose the close button, which is bad.
         // Turning it on though means the user can maximize or size the window
         // from the system menu, which is worse. We may need to provide our own
         // menu to get the close button to appear properly.
         // style &= ~WS_SYSMENU;
 
         // Set the WS_POPUP style for modal dialogs. This ensures that the owner
         // window is activated on destruction. This style should not be set for
@@ skipping 51 matching lines @@
   DWORD class_style = 0;
   CalculateWindowStylesFromInitParams(params, widget_delegate,
                                       native_widget_delegate, &style, &ex_style,
                                       &class_style);
   handler->set_initial_class_style(class_style);
   handler->set_window_style(handler->window_style() | style);
   handler->set_window_ex_style(handler->window_ex_style() | ex_style);
 }
 
 }  // namespace views