Partially account for the shifted origin in wxBufferedDC.

This change slightly improves wxBufferedDC and wxBufferedPaintDC behaviour
when the origin of the DC is shifted, but they still don't work quite right in
this case as they don't use the buffer area of correct size in this case,
which results in cropping the final bitmap (as can be seen in the drawing
sample, which was modified to show wxBufferedPaintDC in action).

Closes #15497.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74951 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/drawing/drawing.cpp

@@ -32,6 +32,7 @@
 #include "wx/colordlg.h"
 #include "wx/image.h"
 #include "wx/artprov.h"
+#include "wx/dcbuffer.h"
 #include "wx/dcgraph.h"
 #include "wx/overlay.h"
 #include "wx/graphics.h"
@@ -101,6 +102,7 @@ public:
 #if wxUSE_GRAPHICS_CONTEXT
     void OnGraphicContext(wxCommandEvent& event);
 #endif
+    void OnBuffer(wxCommandEvent& event);
     void OnCopy(wxCommandEvent& event);
     void OnSave(wxCommandEvent& event);
     void OnShow(wxCommandEvent &event);
@@ -148,6 +150,8 @@ public:
 #if wxUSE_GRAPHICS_CONTEXT
     void UseGraphicContext(bool use) { m_useContext = use; Refresh(); }
 #endif
+    void UseBuffer(bool use) { m_useBuffer = use; Refresh(); }
+
     void Draw(wxDC& dc);
 
 protected:
@@ -189,6 +193,7 @@ private:
 #if wxUSE_GRAPHICS_CONTEXT
     bool         m_useContext ;
 #endif
+    bool         m_useBuffer;
 
     DECLARE_EVENT_TABLE()
 };
@@ -227,6 +232,7 @@ enum
 #if wxUSE_GRAPHICS_CONTEXT
     File_GraphicContext,
 #endif
+    File_Buffer,
     File_Copy,
     File_Save,
 
@@ -410,6 +416,7 @@ MyCanvas::MyCanvas(MyFrame *parent)
 #if wxUSE_GRAPHICS_CONTEXT
     m_useContext = false;
 #endif
+    m_useBuffer = false;
 }
 
 void MyCanvas::DrawTestBrushes(wxDC& dc)
@@ -1494,8 +1501,16 @@ void MyCanvas::DrawRegionsHelper(wxDC& dc, wxCoord x, bool firstTime)
 
 void MyCanvas::OnPaint(wxPaintEvent &WXUNUSED(event))
 {
-    wxPaintDC pdc(this);
+    if ( m_useBuffer )
-    Draw(pdc);
+    {
+        wxBufferedPaintDC bpdc(this);
+        Draw(bpdc);
+    }
+    else
+    {
+        wxPaintDC pdc(this);
+        Draw(pdc);
+    }
 }
 
 void MyCanvas::Draw(wxDC& pdc)
@@ -1729,6 +1744,7 @@ BEGIN_EVENT_TABLE(MyFrame, wxFrame)
 #if wxUSE_GRAPHICS_CONTEXT
     EVT_MENU      (File_GraphicContext, MyFrame::OnGraphicContext)
 #endif
+    EVT_MENU      (File_Buffer,   MyFrame::OnBuffer)
     EVT_MENU      (File_Copy,     MyFrame::OnCopy)
     EVT_MENU      (File_Save,     MyFrame::OnSave)
 
@@ -1769,6 +1785,7 @@ MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
 #if wxUSE_GRAPHICS_CONTEXT
     menuFile->AppendCheckItem(File_GraphicContext, wxT("&Use GraphicContext\tCtrl-Y"), wxT("Use GraphicContext"));
 #endif
+    menuFile->AppendCheckItem(File_Buffer, wxT("&Use wx&BufferedPaintDC\tCtrl-Z"), wxT("Buffer painting"));
     menuFile->AppendSeparator();
 #if wxUSE_METAFILE && defined(wxMETAFILE_IS_ENH)
     menuFile->Append(File_Copy, wxT("Copy to clipboard"));
@@ -1881,6 +1898,11 @@ void MyFrame::OnGraphicContext(wxCommandEvent& event)
 }
 #endif
 
+void MyFrame::OnBuffer(wxCommandEvent& event)
+{
+    m_canvas->UseBuffer(event.IsChecked());
+}
+
 void MyFrame::OnCopy(wxCommandEvent& WXUNUSED(event))
 {
 #if wxUSE_METAFILE && defined(wxMETAFILE_IS_ENH)

src/common/dcbufcmn.cpp

@@ -157,7 +157,8 @@ void wxBufferedDC::UnMask()
         height = wxMin(height, heightDC);
     }
 
-    m_dc->Blit(0, 0, width, height, this, -x, -y);
+    const wxPoint origin = GetLogicalOrigin();
+    m_dc->Blit(-origin.x, -origin.y, width, height, this, -x, -y);
     m_dc = NULL;
 
     if ( m_style & wxBUFFER_USES_SHARED_BUFFER )