Fix drawing semi-transparent windows in double buffering mode

ARTI1208 · ARTI1208 · commit bce0735c2a4a · 2022-03-22T16:26:21.000+03:00
diff --git a/projector-client-common/src/commonMain/kotlin/org/jetbrains/projector/client/common/canvas/buffering/DoubleBufferedRenderingSurface.kt b/projector-client-common/src/commonMain/kotlin/org/jetbrains/projector/client/common/canvas/buffering/DoubleBufferedRenderingSurface.kt
@@ -49,7 +49,11 @@ class DoubleBufferedRenderingSurface(bufferCanvasFactory: CanvasFactory, private
     // optimization: flush only if the buffer is changed
     if (buffer.changed) {
       buffer.resetChanged()
-      target.context2d.drawImage(buffer.imageSource, 0.0, 0.0)
+      target.context2d.apply {
+        // clear canvas so that semi-transparent parts won't stack on top of each other
+        clearRect(0.0, 0.0, buffer.width.toDouble(), buffer.height.toDouble())
+        drawImage(buffer.imageSource, 0.0, 0.0)
+      }
     }
   }
 

Original file line number	Diff line number	Diff line change
`@@ -49,7 +49,11 @@ class DoubleBufferedRenderingSurface(bufferCanvasFactory: CanvasFactory, private`
`49`	`49`	`// optimization: flush only if the buffer is changed`
`50`	`50`	`if (buffer.changed) {`
`51`	`51`	`buffer.resetChanged()`
`52`		`- target.context2d.drawImage(buffer.imageSource, 0.0, 0.0)`
	`52`	`+ target.context2d.apply {`
	`53`	`+ // clear canvas so that semi-transparent parts won't stack on top of each other`
	`54`	`+ clearRect(0.0, 0.0, buffer.width.toDouble(), buffer.height.toDouble())`
	`55`	`+ drawImage(buffer.imageSource, 0.0, 0.0)`
	`56`	`+ }`
`53`	`57`	`}`
`54`	`58`	`}`
`55`	`59`