Add flush command to external painter command set

src/kernel/qpaintdevice.h

@@ -204,7 +204,9 @@ public:
 	PdcSaveWMatrix = 56,
 	PdcRestoreWMatrix = 57,
 	PdcSetClip = 60, // ival
-	PdcSetClipRegion = 61, // rgn
+	PdcSetClipRegion = 61, // rgn,cmode
+	PdcFlush = 62, //  <void>
+	PdcFlushRegion = 63, // rgn,cmode
 
 	PdcReservedStart = 0, // codes 0-199 are reserved
 	PdcReservedStop = 199 //   for Qt

src/kernel/qpainter_x11.cpp

@@ -1264,8 +1264,16 @@ bool QPainter::end()                            // end painting
     \sa flush() CoordinateMode
 */
 
-void QPainter::flush(const QRegion &, CoordinateMode)
+void QPainter::flush(const QRegion &rgn, CoordinateMode m)
 {
+    if ( testf(ExtDev) ) {
+        QPDevCmdParam param[2];
+        param[0].rgn = &rgn;
+        param[1].ival = m;
+        pdev->cmd( QPaintDevice::PdcFlushRegion, this, param );
+        return;
+    }
+
     flush();
 }
 
@@ -1278,6 +1286,11 @@ void QPainter::flush(const QRegion &, CoordinateMode)
 
 void QPainter::flush()
 {
+    if ( testf(ExtDev) ) {
+        pdev->cmd( QPaintDevice::PdcFlush, this, 0 );
+        return;
+    }
+
     if ( isActive() && dpy )
         XFlush( dpy );
 }