Paint a black rectangle under patterns to prevent glitches (#3759)

src/gui/AutomationPatternView.cpp

@@ -257,7 +257,10 @@ void AutomationPatternView::paintEvent( QPaintEvent * )
 
 	lingrad.setColorAt( 1, c.darker( 300 ) );
 	lingrad.setColorAt( 0, c );
-	
+
+	// paint a black rectangle under the pattern to prevent glitches with transparent backgrounds
+	p.fillRect( rect(), QColor( 0, 0, 0 ) );
+
 	if( gradient() )
 	{
 		p.fillRect( rect(), lingrad );
@@ -492,8 +495,3 @@ void AutomationPatternView::scaleTimemapToFit( float oldMin, float oldMax )
 
 	m_pat->generateTangents();
 }
-
-
-
-
-

src/tracks/BBTrack.cpp

@@ -237,7 +237,10 @@ void BBTCOView::paintEvent( QPaintEvent * )
 	
 	lingrad.setColorAt( 0, c.light( 130 ) );
 	lingrad.setColorAt( 1, c.light( 70 ) );
-	
+
+	// paint a black rectangle under the pattern to prevent glitches with transparent backgrounds
+	p.fillRect( rect(), QColor( 0, 0, 0 ) );
+
 	if( gradient() )
 	{
 		p.fillRect( rect(), lingrad );

src/tracks/Pattern.cpp

@@ -890,6 +890,9 @@ void PatternView::paintEvent( QPaintEvent * )
 	lingrad.setColorAt( beatPattern ? 0 : 1, c.darker( 300 ) );
 	lingrad.setColorAt( beatPattern ? 1 : 0, c );
 
+	// paint a black rectangle under the pattern to prevent glitches with transparent backgrounds
+	p.fillRect( rect(), QColor( 0, 0, 0 ) );
+
 	if( gradient() )
 	{
 		p.fillRect( rect(), lingrad );

src/tracks/SampleTrack.cpp

@@ -475,6 +475,9 @@ void SampleTCOView::paintEvent( QPaintEvent * pe )
 	lingrad.setColorAt( 1, c.darker( 300 ) );
 	lingrad.setColorAt( 0, c );
 
+	// paint a black rectangle under the pattern to prevent glitches with transparent backgrounds
+	p.fillRect( rect(), QColor( 0, 0, 0 ) );
+
 	if( gradient() )
 	{
 		p.fillRect( rect(), lingrad );