better ownership handling

[wxWidgets.git] / src / common / dcbufcmn.cpp

diff --git a/src/common/dcbufcmn.cpp b/src/common/dcbufcmn.cpp
index b38b4f1f67921c65093f3bcbc69c3517a42b30e8..2a8314d43e3a5495d803e03479fac09595b2b4e0 100644 (file)
--- a/src/common/dcbufcmn.cpp
+++ b/src/common/dcbufcmn.cpp
@@ -34,6 +34,9 @@
 // implementation
 // ============================================================================
 
+IMPLEMENT_DYNAMIC_CLASS(wxBufferedDC,wxMemoryDC)
+IMPLEMENT_ABSTRACT_CLASS(wxBufferedPaintDC,wxBufferedDC)
+
 // ----------------------------------------------------------------------------
 // wxSharedDCBufferManager: helper class maintaining backing store bitmap
 // ----------------------------------------------------------------------------
@@ -56,6 +59,14 @@ public:
                     h > ms_buffer->GetHeight() )
         {
             delete ms_buffer;
+
+            // we must always return a valid bitmap but creating a bitmap of
+            // size 0 would fail, so create a 1*1 bitmap in this case
+            if ( !w )
+                w = 1;
+            if ( !h )
+                h = 1;
+
             ms_buffer = new wxBitmap(w, h);
         }
 
@@ -94,6 +105,8 @@ IMPLEMENT_DYNAMIC_CLASS(wxSharedDCBufferManager, wxModule)
 
 void wxBufferedDC::UseBuffer(wxCoord w, wxCoord h)
 {
+    wxCHECK_RET( w >= -1 && h >= -1, "Invalid buffer size" );
+
     if ( !m_buffer || !m_buffer->IsOk() )
     {
         if ( w == -1 || h == -1 )
@@ -104,21 +117,42 @@ void wxBufferedDC::UseBuffer(wxCoord w, wxCoord h)
     }
 
     SelectObject(*m_buffer);
+
+    // now that the DC is valid we can inherit the attributes (fonts, colours,
+    // layout direction, ...) from the original DC
+    if ( m_dc && m_dc->IsOk() )
+        CopyAttributes(*m_dc);
 }
 
 void wxBufferedDC::UnMask()
 {
-    wxCHECK_RET( m_dc, _T("no underlying wxDC?") );
-    wxASSERT_MSG( m_buffer && m_buffer->IsOk(), _T("invalid backing store") );
+    wxCHECK_RET( m_dc, wxT("no underlying wxDC?") );
+    wxASSERT_MSG( m_buffer && m_buffer->IsOk(), wxT("invalid backing store") );
 
     wxCoord x = 0,
             y = 0;
 
+    // Ensure the scale matches the device
+    SetUserScale(1.0, 1.0);
+
     if ( m_style & wxBUFFER_CLIENT_AREA )
         GetDeviceOrigin(&x, &y);
 
-    m_dc->Blit(0, 0, m_buffer->GetWidth(), m_buffer->GetHeight(),
-               this, -x, -y );
+    // avoid blitting too much: if we were created for a bigger bitmap (and
+    // reused for a smaller one later) we should only blit the real bitmap area
+    // and not the full allocated back buffer
+    int widthDC,
+        heightDC;
+
+    m_dc->GetSize(&widthDC, &heightDC);
+
+    int widthBuf = m_buffer->GetWidth(),
+        heightBuf = m_buffer->GetHeight();
+
+    m_dc->Blit(0, 0,
+               wxMin(widthDC, widthBuf), wxMin(heightDC, heightBuf),
+               this,
+               -x, -y);
     m_dc = NULL;
 
     if ( m_style & wxBUFFER_USES_SHARED_BUFFER )