Fix several problem with wxMemoryDC in wxQt

Under wxQT, wxMemoryDC was previously rendering to a temporary image
which was only being blitted back to the original wxBitmap when either
the DC wx destroyed or a new bitmap was selected (via SelectObject).

With these change wxMemoryDCImpl now draws directly to the bitmap
managed by wxBitmap, this makes the behaviour more consistent with the
MSW and GTK implementations.

Closes https://github.com/wxWidgets/wxWidgets/pull/1083

include/wx/qt/dc.h

@@ -111,10 +111,10 @@ public:
     virtual void* GetHandle() const { return (void*) m_qtPainter; }
 
 protected:
-    virtual QImage *GetQImage() { return m_qtImage; }
+    virtual QPixmap *GetQPixmap() { return m_qtPixmap; }
     
     QPainter *m_qtPainter;
-    QImage *m_qtImage;
+    QPixmap *m_qtPixmap;
 
     wxRegion *m_clippingRegion;
 private:

include/wx/qt/dcscreen.h

@@ -19,9 +19,7 @@ public:
 
 protected:
     virtual void DoGetSize(int *width, int *height) const wxOVERRIDE;
-    virtual bool DoGetPixel(wxCoord x, wxCoord y, wxColour *col) const;
-
-    virtual QImage *GetQImage();
+    virtual QPixmap *GetQPixmap() wxOVERRIDE;
 
     wxDECLARE_ABSTRACT_CLASS(wxScreenDCImpl);
 };

src/qt/dc.cpp

@@ -47,7 +47,7 @@ wxQtDCImpl::wxQtDCImpl( wxDC *owner )
     : wxDCImpl( owner )
 {
     m_clippingRegion = new wxRegion;
-    m_qtImage = NULL;
+    m_qtPixmap = NULL;
     m_rasterColourOp = wxQtNONE;
     m_qtPenColor = new QColor;
     m_qtBrushColor = new QColor;
@@ -474,15 +474,18 @@ bool wxQtDCImpl::DoGetPixel(wxCoord x, wxCoord y, wxColour *col) const
 
     if ( col )
     {
-        wxCHECK_MSG( m_qtImage != NULL, false, "This DC doesn't support GetPixel()" );
-
-        QColor pixel = m_qtImage->pixel( x, y );
+        wxCHECK_MSG( m_qtPixmap != NULL, false, "This DC doesn't support GetPixel()" );
+        QPixmap pixmap1px = m_qtPixmap->copy( x, y, 1, 1 );
+        QImage image = pixmap1px.toImage();
+        QColor pixel = image.pixel( 0, 0 );
         col->Set( pixel.red(), pixel.green(), pixel.blue(), pixel.alpha() );
 
         return true;
     }
     else
+    {
         return false;
+    }
 }
 
 void wxQtDCImpl::DoDrawPoint(wxCoord x, wxCoord y)
@@ -739,23 +742,31 @@ bool wxQtDCImpl::DoBlit(wxCoord xdest, wxCoord ydest,
 {
     wxQtDCImpl *implSource = (wxQtDCImpl*)source->GetImpl();
 
-    QImage *qtSource = implSource->GetQImage();
+    QPixmap *qtSource = implSource->GetQPixmap();
 
     // Not a CHECK on purpose
     if ( !qtSource )
         return false;
 
-    QImage qtSourceConverted = *qtSource;
-    if ( !useMask )
-        qtSourceConverted = qtSourceConverted.convertToFormat( QImage::Format_RGB32 );
-
     // Change logical function
     wxRasterOperationMode savedMode = GetLogicalFunction();
     SetLogicalFunction( rop );
 
-    m_qtPainter->drawImage( QRect( xdest, ydest, width, height ),
-                           qtSourceConverted,
-                           QRect( xsrc, ysrc, width, height ) );
+    if ( useMask )
+    {
+        m_qtPainter->drawPixmap( QRect( xdest, ydest, width, height ),
+                                *qtSource,
+                                QRect( xsrc, ysrc, width, height ) );
+    }
+    else
+    {
+        QImage qtSourceConverted = qtSource->toImage();
+        qtSourceConverted = qtSourceConverted.convertToFormat(QImage::Format_RGB32);
+
+        m_qtPainter->drawImage( QRect( xdest, ydest, width, height ),
+                                qtSourceConverted,
+                                QRect( xsrc, ysrc, width, height ) );
+    }
 
     SetLogicalFunction( savedMode );
 

src/qt/dcclient.cpp

@@ -31,7 +31,6 @@ wxWindowDCImpl::wxWindowDCImpl( wxDC *owner )
     : wxQtDCImpl( owner )
 {
     m_window = NULL;
-    m_qtImage = NULL;
     m_ok = false;
     m_qtPainter = new QPainter();
 }
@@ -40,7 +39,6 @@ wxWindowDCImpl::wxWindowDCImpl( wxDC *owner, wxWindow *win )
     : wxQtDCImpl( owner )
 {
     m_window = win;
-    m_qtImage = NULL;
     m_qtPainter = m_window->QtGetPainter();
     // if we're not inside a Paint event, painter will invalid
     m_ok = m_qtPainter != NULL;

src/qt/dcmemory.cpp

@@ -16,7 +16,6 @@
 wxMemoryDCImpl::wxMemoryDCImpl( wxMemoryDC *owner )
     : wxQtDCImpl( owner )
 {
-    m_qtImage = NULL;
     m_ok = false;
     m_qtPainter = new QPainter();
 }
@@ -24,7 +23,6 @@ wxMemoryDCImpl::wxMemoryDCImpl( wxMemoryDC *owner )
 wxMemoryDCImpl::wxMemoryDCImpl( wxMemoryDC *owner, wxBitmap& bitmap )
     : wxQtDCImpl( owner )
 {
-    m_qtImage = NULL;
     m_ok = false;
     m_qtPainter = new QPainter();
     DoSelect( bitmap );
@@ -33,7 +31,6 @@ wxMemoryDCImpl::wxMemoryDCImpl( wxMemoryDC *owner, wxBitmap& bitmap )
 wxMemoryDCImpl::wxMemoryDCImpl( wxMemoryDC *owner, wxDC *WXUNUSED(dc) )
     : wxQtDCImpl( owner )
 {
-    m_qtImage = NULL;
     m_ok = false;
     m_qtPainter = new QPainter();
 }
@@ -50,34 +47,21 @@ void wxMemoryDCImpl::DoSelect( const wxBitmap& bitmap )
     {
         // Finish the painting in the intermediate image device:
         m_qtPainter->end();
-
-        if (m_selected.IsOk() && !m_selected.GetHandle()->isNull())
-        {
-            // Copy intermediate image to the bitmap
-            m_qtPainter->begin( m_selected.GetHandle() );
-            m_qtPainter->drawImage( QPoint( 0, 0 ), *m_qtImage );
-            m_qtPainter->end();
-        }
         m_ok = false;
     }
 
     // clean up the intermediate image device:
-    if ( m_qtImage )
-    {
-        delete m_qtImage;
-        m_qtImage = NULL;
-    }
-
     m_selected = bitmap;
-    if ( bitmap.IsOk() && !bitmap.GetHandle()->isNull() ) {
-        QPixmap pixmap(*bitmap.GetHandle());
-        // apply mask before converting to image
-        if ( bitmap.GetMask() && bitmap.GetMask()->GetHandle() )
-            pixmap.setMask(*bitmap.GetMask()->GetHandle());
-        // create the intermediate image for the pixmap:
-        m_qtImage = new QImage( pixmap.toImage() );
+    m_qtPixmap = bitmap.GetHandle();
+    if ( bitmap.IsOk() && !m_qtPixmap->isNull() )
+    {
+        // apply mask before drawing
+        wxMask *mask = bitmap.GetMask();
+        if ( mask && mask->GetHandle() )
+            m_qtPixmap->setMask(*mask->GetHandle());
+
         // start drawing on the intermediary device:
-        m_ok = m_qtPainter->begin( m_qtImage );
+        m_ok = m_qtPainter->begin( m_qtPixmap );
 
         SetPen(m_pen);
         SetBrush(m_brush);

src/qt/dcscreen.cpp

@@ -21,12 +21,11 @@ wxIMPLEMENT_ABSTRACT_CLASS(wxScreenDCImpl, wxWindowDCImpl);
 wxScreenDCImpl::wxScreenDCImpl( wxScreenDC *owner )
     : wxWindowDCImpl( owner )
 {
-    m_qtImage = NULL;
 }
 
 wxScreenDCImpl::~wxScreenDCImpl( )
 {
-    delete m_qtImage;
+    delete m_qtPixmap;
 }
 
 void wxScreenDCImpl::DoGetSize(int *width, int *height) const
@@ -34,19 +33,10 @@ void wxScreenDCImpl::DoGetSize(int *width, int *height) const
     wxDisplaySize(width, height);
 }
 
-bool wxScreenDCImpl::DoGetPixel(wxCoord x, wxCoord y, wxColour *col) const
-{
-//    const_cast<wxScreenDCImpl*>(this)->GetQImage();
-//    return wxQtDCImpl::DoGetPixel(x, y, col);
-    x = y = 0;
-    col = 0;
-    return false;
-}
-
 // defered allocation for blit
-QImage *wxScreenDCImpl::GetQImage()
+QPixmap *wxScreenDCImpl::GetQPixmap()
 {
-    if ( !m_qtImage )
-        m_qtImage = new QImage(QApplication::primaryScreen()->grabWindow(QApplication::desktop()->winId()).toImage());
-    return m_qtImage;
+    if ( !m_qtPixmap )
+        m_qtPixmap = new QPixmap(QApplication::primaryScreen()->grabWindow(QApplication::desktop()->winId()));
+    return m_qtPixmap;
 }