[NONE] Prevent flickering of scrollbars during zoom.

- During zoom it may happen that the contents bounds min and max values do only imprecisely match those of the viewport bounds. While optically the content is fully contained in the viewport, mathematically it isn't. Thus scroll bars are made visible. During zoom that can lead to unintended visibility changes of the scroll bars, which looks like flickering. We can prevent it by using impresicion to detect whether scroll bars should be visible or not (while the underliyng values may still be computed precisely).

org.eclipse.gef.fx/src/org/eclipse/gef/fx/nodes/InfiniteCanvas.java

@@ -1577,8 +1577,8 @@ protected void updateScrollBars() {
 
 		// show/hide horizontal scrollbar
 		ScrollBarPolicy hbarPolicy = horizontalScrollBarPolicyProperty.get();
-		boolean hbarIsNeeded = contentBounds[0] < 0
-				|| contentBounds[2] > getWidth();
+		boolean hbarIsNeeded = contentBounds[0] < -0.01
+				|| contentBounds[2] > getWidth() + 0.01;
 		if (hbarPolicy.equals(ScrollBarPolicy.ALWAYS)
 				|| hbarPolicy.equals(ScrollBarPolicy.AS_NEEDED)
 						&& hbarIsNeeded) {
@@ -1589,8 +1589,8 @@ protected void updateScrollBars() {
 
 		// show/hide vertical scrollbar
 		ScrollBarPolicy vbarPolicy = verticalScrollBarPolicyProperty.get();
-		boolean vbarIsNeeded = contentBounds[1] < 0
-				|| contentBounds[3] > getHeight();
+		boolean vbarIsNeeded = contentBounds[1] < -0.01
+				|| contentBounds[3] > getHeight() + 0.01;
 		if (vbarPolicy.equals(ScrollBarPolicy.ALWAYS)
 				|| vbarPolicy.equals(ScrollBarPolicy.AS_NEEDED)
 						&& vbarIsNeeded) {