Fix the issue that a panel window cannot be shrink to very small

views/widget/native_widget_win.cc

 // Copyright (c) 2011 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 "views/widget/native_widget_win.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 
 #include "base/string_util.h"
@@ skipping 2006 matching lines @@
       last_work_area_ = work_area;
     }
   }
 
   if (force_hidden_count_) {
     // Prevent the window from being made visible if we've been asked to do so.
     // See comment in header as to why we might want this.
     window_pos->flags &= ~SWP_SHOWWINDOW;
   }
 
+  // When WM_WINDOWPOSCHANGING message is handled by DefWindowProc, it will
+  // enforce (cx, cy) not to be smaller than (6, 6) for any non-popup window.
+  // We work around this by changing cy back to our intended value.
+  if (!GetParent() && ~(window_pos->flags & SWP_NOSIZE) && window_pos->cy < 6) {
+    LONG old_cy = window_pos->cy;
+    DefWindowProc(GetNativeView(), WM_WINDOWPOSCHANGING, 0,
+        reinterpret_cast<LPARAM>(window_pos));
+    window_pos->cy = old_cy;
+    SetMsgHandled(TRUE);
+    return;
+  }
+
   SetMsgHandled(FALSE);
 }
 
 void NativeWidgetWin::OnWindowPosChanged(WINDOWPOS* window_pos) {
   if (DidClientAreaSizeChange(window_pos))
     ClientAreaSizeChanged();
   if (window_pos->flags & SWP_SHOWWINDOW)
     delegate_->OnNativeWidgetVisibilityChanged(true);
   else if (window_pos->flags & SWP_HIDEWINDOW)
     delegate_->OnNativeWidgetVisibilityChanged(false);
@@ skipping 12 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 // NativeWidgetWin, protected:
 
 int NativeWidgetWin::GetShowState() const {
   return SW_SHOWNORMAL;
 }
 
 gfx::Insets NativeWidgetWin::GetClientAreaInsets() const {
   // Returning an empty Insets object causes the default handling in
   // NativeWidgetWin::OnNCCalcSize() to be invoked.
-  if (!GetWidget()->non_client_view() || GetWidget()->ShouldUseNativeFrame())
+  if (GetWidget()->ShouldUseNativeFrame())
     return gfx::Insets();
 
   if (IsMaximized()) {
     // Windows automatically adds a standard width border to all sides when a
     // window is maximized.
     int border_thickness = GetSystemMetrics(SM_CXSIZEFRAME);
     return gfx::Insets(border_thickness, border_thickness, border_thickness,
                        border_thickness);
   }
   // This is weird, but highly essential. If we don't offset the bottom edge
@@ skipping 451 matching lines @@
   return (GetKeyState(VK_LBUTTON) & 0x80) ||
     (GetKeyState(VK_RBUTTON) & 0x80) ||
     (GetKeyState(VK_MBUTTON) & 0x80) ||
     (GetKeyState(VK_XBUTTON1) & 0x80) ||
     (GetKeyState(VK_XBUTTON2) & 0x80);
 }
 
 }  // namespace internal
 
 }  // namespace views