Inherit notebook background recursively under wxMSW.

With MSWSetTransparentBackground() hack only the panel which was the immediate
child of wxNotebook (i.e. its page) inherited the notebook background but not
its children. This resulted in jarring background discontinuities when nested
panels were used.

Fix this by inheriting notebook background in all child panels by testing for
the return value of the parents MSWHasInheritableBackground() method in
wxPanel::HasTransparentBackground() recursively.

Closes #12317.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65238 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/panelg.h

@@ -77,17 +77,10 @@ public:
 #endif
 
 #ifdef __WXMSW__
-    // This is a hack to support inheriting of background through child
-    // wxPanel: at least wxNotebook needs this under wxMSW as its background
-    // should apply to its children which are usually wxPanels which normally
-    // don't have a transparent background. Calling this function allows to
-    // change this for the panels which are used as notebook pages.
-    void MSWSetTransparentBackground(bool isTransparent = true)
-    {
-        m_isTransparent = isTransparent;
-    }
-
-    virtual bool HasTransparentBackground() { return m_isTransparent; }
+    // This is overridden for MSW to return true for all panels that are child
+    // of a window with themed background (such as wxNotebook) which should
+    // show through the child panels.
+    virtual bool HasTransparentBackground();
 #endif // __WXMSW__
 
     WX_DECLARE_CONTROL_CONTAINER();
@@ -100,10 +93,6 @@ protected:
     virtual wxBorder GetDefaultBorder() const { return wxWindowBase::GetDefaultBorder(); }
 
 private:
-#ifdef __WXMSW__
-    bool m_isTransparent;
-#endif // __WXMSW__
-
     DECLARE_DYNAMIC_CLASS_NO_COPY(wxPanel)
     DECLARE_EVENT_TABLE()
 };

include/wx/msw/notebook.h

@@ -187,6 +187,8 @@ public:
 
   // draw child background
   virtual bool MSWPrintChild(WXHDC hDC, wxWindow *win);
+
+  virtual bool MSWHasInheritableBackground() const { return true; }
 #endif // wxUSE_UXTHEME
 
   // translate wxWin styles to the Windows ones

include/wx/msw/window.h

@@ -438,6 +438,11 @@ public:
         return true;
     }
 
+    // This should be overridden to return true for the controls which have
+    // themed background that should through their children. Currently only
+    // wxNotebook uses this.
+    virtual bool MSWHasInheritableBackground() const { return false; }
+
 #if !defined(__WXWINCE__) && !defined(__WXUNIVERSAL__)
     #define wxHAS_MSW_BACKGROUND_ERASE_HOOK
 #endif

samples/controls/controls.cpp

@@ -949,9 +949,10 @@ MyPanel::MyPanel( wxFrame *frame, int x, int y, int w, int h )
     dc.DrawText(wxT("Bitmap"), 30, 40);
     dc.SelectObject( wxNullBitmap );
 
-    (void)new wxBitmapButton(panel, ID_BITMAP_BTN, bitmap, wxPoint(100, 20));
-    (void)new wxToggleButton(panel, ID_BITMAP_BTN_ENABLE,
-                             wxT("Enable/disable &bitmap"), wxPoint(100, 140));
+    wxPanel *panel2 = new wxPanel(panel, -1, wxPoint(100, 0), wxSize(100, 200));
+    (void)new wxBitmapButton(panel2, ID_BITMAP_BTN, bitmap, wxPoint(0, 20));
+    (void)new wxToggleButton(panel2, ID_BITMAP_BTN_ENABLE,
+                             wxT("Enable/disable &bitmap"), wxPoint(0, 140));
 
 #if defined(__WXMSW__) || defined(__WXMOTIF__)
     // test for masked bitmap display

src/generic/panelg.cpp

@@ -104,10 +104,6 @@ WX_DELEGATE_TO_CONTROL_CONTAINER(wxPanel, wxWindow)
 void wxPanel::Init()
 {
     WX_INIT_CONTROL_CONTAINER();
-
-#ifdef __WXMSW__
-    m_isTransparent = false;
-#endif // __WXMSW__
 }
 
 bool wxPanel::Create(wxWindow *parent, wxWindowID id,
@@ -141,3 +137,20 @@ void wxPanel::InitDialog()
     GetEventHandler()->ProcessEvent(event);
 }
 
+#ifdef __WXMSW__
+
+bool wxPanel::HasTransparentBackground()
+{
+    for ( wxWindow *win = GetParent(); win; win = win->GetParent() )
+    {
+        if ( win->MSWHasInheritableBackground() )
+            return true;
+
+        if ( win->IsTopLevel() )
+            break;
+    }
+
+    return false;
+}
+
+#endif // __WXMSW__

src/msw/notebook.cpp

@@ -819,14 +819,6 @@ bool wxNotebook::InsertPage(size_t nPage,
     // succeeded: save the pointer to the page
     m_pages.Insert(pPage, nPage);
 
-    // also ensure that the notebook background is used for its pages by making
-    // them transparent: this ensures that MSWGetBgBrush() queries the notebook
-    // for the background brush to be used for erasing them
-    if ( wxPanel *panel = wxDynamicCast(pPage, wxPanel) )
-    {
-        panel->MSWSetTransparentBackground();
-    }
-
     // we may need to adjust the size again if the notebook size changed:
     // normally this only happens for the first page we add (the tabs which
     // hadn't been there before are now shown) but for a multiline notebook it