added test for Blit()ting OnEraseBackground() results in OnPaint()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@31979 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/erase/erase.cpp

@@ -54,35 +54,46 @@ public:
 };
 
 
-class MyFrame : public wxFrame
-{
-public:
-    MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size);
-
-    void OnQuit(wxCommandEvent& event);
-    void OnAbout(wxCommandEvent& event);
-
-private:
-    DECLARE_EVENT_TABLE()
-};
-
-
 class MyCanvas : public wxScrolledWindow
 {
 public:
-    MyCanvas( MyFrame *parent );
+    MyCanvas( wxFrame *parent );
 
+    void UseBuffer(bool useBuffer) { m_useBuffer = useBuffer; Refresh(); }
+
+private:
     void OnPaint( wxPaintEvent &event );
     void OnChar( wxKeyEvent &event );
     void OnEraseBackground( wxEraseEvent &event );
 
+    void DoPaint(wxDC& dc);
+
+
     wxBitmap    m_bitmap;
     wxString    m_text;
 
-private:
+    // use wxMemoryDC in OnPaint()?
+    bool m_useBuffer;
+
     DECLARE_EVENT_TABLE()
 };
 
+class MyFrame : public wxFrame
+{
+public:
+    MyFrame();
+
+    void OnUseBuffer(wxCommandEvent& event);
+    void OnQuit(wxCommandEvent& event);
+    void OnAbout(wxCommandEvent& event);
+
+private:
+    MyCanvas *m_canvas;
+
+    DECLARE_EVENT_TABLE()
+};
+
+
 // ----------------------------------------------------------------------------
 // constants
 // ----------------------------------------------------------------------------
@@ -90,7 +101,9 @@ private:
 enum
 {
     // menu items
-    ID_MENU_QUIT = 1,
+    Erase_Menu_UseBuffer = 100,
+    Erase_Menu_Exit = wxID_EXIT,
+    Erase_Menu_About = wxID_ABOUT
 };
 
 
@@ -102,8 +115,7 @@ IMPLEMENT_APP(MyApp)
 
 bool MyApp::OnInit()
 {
-    MyFrame *frame = new MyFrame(_T("Erase sample"),
-                                 wxPoint(50, 50), wxSize(450, 340));
+    MyFrame *frame = new MyFrame;
 
     frame->Show(true);
 
@@ -115,22 +127,26 @@ bool MyApp::OnInit()
 // ----------------------------------------------------------------------------
 
 BEGIN_EVENT_TABLE(MyFrame, wxFrame)
-    EVT_MENU(ID_MENU_QUIT,  MyFrame::OnQuit)
-    EVT_MENU(wxID_ABOUT, MyFrame::OnAbout)
+    EVT_MENU(Erase_Menu_UseBuffer,  MyFrame::OnUseBuffer)
+    EVT_MENU(Erase_Menu_Exit,  MyFrame::OnQuit)
+    EVT_MENU(Erase_Menu_About, MyFrame::OnAbout)
 END_EVENT_TABLE()
 
 // frame constructor
-MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
-       : wxFrame((wxFrame *)NULL, wxID_ANY, title, pos, size)
+MyFrame::MyFrame()
+       : wxFrame(NULL, wxID_ANY, _T("Erase sample"),
+                 wxPoint(50, 50), wxSize(450, 340))
 {
     SetIcon(wxICON(mondrian));
 
     wxMenu *menuFile = new wxMenu(_T(""), wxMENU_TEAROFF);
+    menuFile->AppendCheckItem(Erase_Menu_UseBuffer, _T("&Use memory DC\tCtrl-M"));
+    menuFile->AppendSeparator();
+    menuFile->Append(Erase_Menu_Exit, _T("E&xit\tAlt-X"), _T("Quit this program"));
+
 
     wxMenu *helpMenu = new wxMenu;
-    helpMenu->Append(wxID_ABOUT, _T("&About...\tCtrl-A"), _T("Show about dialog"));
-
-    menuFile->Append(ID_MENU_QUIT, _T("E&xit\tAlt-X"), _T("Quit this program"));
+    helpMenu->Append(Erase_Menu_About, _T("&About...\tCtrl-A"), _T("Show about dialog"));
 
     wxMenuBar *menuBar = new wxMenuBar();
     menuBar->Append(menuFile, _T("&File"));
@@ -144,10 +160,15 @@ MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
     SetStatusText(_T("Welcome to wxWidgets erase sample!"));
 #endif // wxUSE_STATUSBAR
 
-    (void)new MyCanvas( this );
+    m_canvas = new MyCanvas( this );
 }
 
 
+void MyFrame::OnUseBuffer(wxCommandEvent& event)
+{
+    m_canvas->UseBuffer(event.IsChecked());
+}
+
 void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
 {
     Close(true);
@@ -166,12 +187,12 @@ BEGIN_EVENT_TABLE(MyCanvas, wxScrolledWindow)
     EVT_ERASE_BACKGROUND(  MyCanvas::OnEraseBackground)
 END_EVENT_TABLE()
 
-MyCanvas::MyCanvas( MyFrame *parent )
+MyCanvas::MyCanvas( wxFrame *parent )
         : wxScrolledWindow( parent, wxID_ANY, wxDefaultPosition, wxDefaultSize,
-                            wxScrolledWindowStyle |
-                            wxNO_FULL_REPAINT_ON_RESIZE|
-                            wxSUNKEN_BORDER )
+                            wxScrolledWindowStyle | wxSUNKEN_BORDER )
 {
+    m_useBuffer = false;
+
     SetScrollbars( 10, 10, 40, 100, 0, 0 );
 
     m_bitmap = wxBitmap( wxICON(mondrian) );
@@ -200,14 +221,10 @@ void MyCanvas::OnChar( wxKeyEvent &event )
         case WXK_RETURN: m_text += wxT( "<ENTER>" ); break;
         default: m_text += (wxChar)event.m_keyCode; break;
     }
-
 }
 
-void MyCanvas::OnPaint( wxPaintEvent &WXUNUSED(event) )
+void MyCanvas::DoPaint(wxDC& dc)
 {
-    wxPaintDC dc(this);
-    PrepareDC( dc );
-
     dc.SetBrush( *wxBLACK_BRUSH );
     dc.DrawRectangle( 0,0,200,50 );
 
@@ -271,15 +288,39 @@ void MyCanvas::OnPaint( wxPaintEvent &WXUNUSED(event) )
 #endif // 0
 }
 
+void MyCanvas::OnPaint( wxPaintEvent &WXUNUSED(event) )
+{
+    wxPaintDC dcWin(this);
+    PrepareDC( dcWin );
+
+    if ( m_useBuffer )
+    {
+        const wxSize size = GetClientSize();
+        wxMemoryDC dc;
+        wxBitmap bmp(size.x, size.y);
+        dc.SelectObject(bmp);
+        dc.Blit(0, 0, size.x, size.y, &dcWin, 0, 0);
+        dc.DrawText(_T("(copy of background)"), 5, 120 );
+
+        DoPaint(dc);
+
+        dcWin.Blit(0, 0, size.x, size.y, &dc, 0, 0);
+    }
+    else
+    {
+        DoPaint(dcWin);
+    }
+}
+
 void MyCanvas::OnEraseBackground( wxEraseEvent& event )
 {
     wxDC& dc = *event.GetDC();
     dc.SetPen(*wxGREEN_PEN);
 
-    // this line is needed, otherwise the junk is left on win the background
+    // clear any junk currently displayed
     dc.Clear();
 
-    wxSize size = GetClientSize();
+    const wxSize size = GetClientSize();
     for ( int x = 0; x < size.x; x += 10 )
     {
         dc.DrawLine(x, 0, x, size.y);