Bad performance with Canvas and extensive clipping

[Tom Schindl]

In the current usecase it is a rect all time but that's just in this special use case. 

I guess that rect clipping is the most common one so having an optimization for rects and a slow path for none rects might help.

Tom

Von meinem iPhone gesendet

> Am 23.05.2014 um 23:35 schrieb Jim Graham <james.graham at oracle.com>:
> 
> Are you clipping to an arbitrary path in all cases or just a rectangle?  Unfortunately we only offer the arbitrary clip-to-current-path method that isn't optimized for basic rectangular clipping and it implements soft clipping.
> 
> There is an outstanding tweak that we added faster clipping support for WebNode and we need to start using it for Node.setClipNode(non-rectangle) and Canvas, but we haven't implemented that yet.  (https://javafx-jira.kenai.com/browse/RT-30107)  It basically is a direct "render this texture through that other texture as a clip" operation instead of the current code that runs it through some Blend effect filters.  It would definitely improve your run times, but I'm not sure how much.
> 
> Even more savings could be had for rectangular clips if we provided some way to communicate them to the GC...
> 
>            ...jim
> 
>> On 5/23/14 11:47 AM, Tom Schindl wrote:
>> Hi,
>> 
>> Maybe as some of you might know I've been working since sometime on SWT
>> on JavaFX and to implement direct drawing operations we use JavaFX-Canvas.
>> 
>> I've today tried to run a heavy direct drawing grid implementation and
>> it performed very bad because it makes heavy use of clipping.
>> 
>> For a grid I've counted ~1500 clipping operations the library works
>> something like this:
>> 
>> boolean activeClip;
>> Canvas canvas = new Canvas();
>> 
>> public void setClipping(PathIterator pathIterator) {
>>   GraphicsContext gc = canvas.getGraphicsContext2D();
>>   if(activeClip) {
>>     gc.restore();
>>     activeClip= false;
>>   }
>> 
>>   if( pathIterator == null ) {
>>     return;
>>   }
>> 
>>   activeClip = true;
>>   float coords[] = new float[6];
>>   gc.save();
>>        gc.beginPath();
>>        
>>        float x = 0;
>>        float y = 0;
>>        
>>        
>>        gc.moveTo(0, 0);
>>        
>>        while( ! pathIterator.isDone() ) {
>>            switch (pathIterator.currentSegment(coords)) {
>>            case PathIterator.SEG_CLOSE:
>>                gc.lineTo(x, y);
>>                break;
>>            case PathIterator.SEG_CUBICTO:
>>                gc.bezierCurveTo(coords[0], coords[1], coords[2], coords[3],
>> coords[4], coords[5]);
>>                break;
>>            case PathIterator.SEG_LINETO:
>>                gc.lineTo(coords[0], coords[1]);
>>                break;
>>            case PathIterator.SEG_MOVETO:
>>                gc.moveTo(coords[0], coords[1]);
>>                x = coords[0];
>>                y = coords[1];
>>                break;
>>            case PathIterator.SEG_QUADTO:
>>                gc.quadraticCurveTo(coords[0], coords[1], coords[2], coords[3]);
>>                break;
>>            default:
>>                break;
>>            }
>>            pathIterator.next();
>>        }
>>        
>>        gc.clip();
>>        gc.closePath();
>> }
>> 
>> Am I doing something ultimately wrong, totally wrong? Has anyone an idea
>> how I would work around the problem?
>> 
>> Tom
>>