Some improvements needed on icedtea Java2D renderers.

[Omair Majid]

Hi Xerxes,

Xerxes Rånby wrote:
> Hello, during bug testing of icedtea6 on various embedded and stationary 
> hardware i have stumbled across some rendering issues of java2d when 
> running under icedtea6.

What version of icedtea6 are you using?

> 
> Testcase:
> http://java.sun.com/products/java-media/2D/samples/java2demo/Java2Demo.html
> 
> Sourcecode available from:
> http://java.sun.com/products/java-media/2D/samples/java2demo/Java2D.zip
> 
> The attached picture displays my rendering error findings:
> 
> 1. When the window are refreshed, the component borders gets redrawn 
> with a mix of soft and sharp borders.
> 
> 2. The rendering of the black box have been requested to be rendererd 
> using a dotted CAP_ROUND BasicStroke: it should be dotted!
>        BasicStroke dotted = new BasicStroke(3, BasicStroke.CAP_ROUND,
>                     BasicStroke.JOIN_ROUND, 0, new float[]{0,6,0,6}, 0);
>        g2.setStroke(dotted);
>        g2.drawRect(3,3,w-6,h-6);

This appears to be one of the issues pointed out in icedtea bug 197[1]. 
Java2d was starting the drawing process by considering the first element 
of the dash array to be length of the space rather than length of the 
dash. It was fixed in rev 0641929711bf [2]. Unfortunately, this fix 
didnt make it into icedtea6-1.4.1.

The other issue is the difference in how a length of 0 is treated by the 
jdk. The comment in 
icedtea6/openjdk/jdk/src/share/classes/sun/java2d/pisces/Dasher.java 
line 34 points out the issue:
  *
  * <p> Issues: in J2Se, a zero length dash segment as drawn as a very
  * short dash, whereas Pisces does not draw anything.  The PostScript
  * semantics are unclear.
  *
So the above code in JSE would draw a dashed border but icedtea6 would 
draw a blank border. "new float[]{0.01,6,0.01,6}" should work.

> 
> 3. The six dotted lines should start with displaying a fill instead of a 
> gap especially since phase are set to 0.0f.
>        float j = 1.1f;
>        for (int i = 0; i < bs.length; i++, j += 1.0f) {
>            float dash[] = { j };
>            BasicStroke b = new BasicStroke(1.0f, BasicStroke.CAP_BUTT,
>                                BasicStroke.JOIN_MITER, 10.0f, dash, 0.0f);
>            g2.setStroke(b);
>            g2.drawLine(20, y, w-20, y);
> 
Please see the comments above. The first element of the dash array is 
taken as the space length rather than the dash length.

> 4. The panel are not resized properly to fit the slider component.
Looks like the components above are taking up too much vertical space. 
This looks like bug 255 [3]. I have not been able to reproduce this 
locally. Any help reproducing this is appreciated.
> 
> 5. and 6.  The last two issues are related. the specified joinType are 
> not applyed to lines that gets inserted using closePath.
>    public void drawDemo(int w, int h, Graphics2D g2) {
>        BasicStroke bs = new BasicStroke(bswidth,
>                                    BasicStroke.CAP_BUTT, joinType);
>        GeneralPath p = new GeneralPath();
>        p.moveTo(- w / 4.0f, - h / 12.0f);
>        p.lineTo(+ w / 4.0f, - h / 12.0f);
>        p.lineTo(- w / 6.0f, + h / 4.0f);
>        p.lineTo(+     0.0f, - h / 4.0f);
>        p.lineTo(+ w / 6.0f, + h / 4.0f);
>        p.closePath();                                          //      
> <-----  issue 6: this should have create a correct join. instead a round 
> join are allways used.
>        p.closePath();                                          //      
> <-----  issue 5: this should have create a correct join. the rendering 
> of the start line should
>                                                                        
> //                have  been updated when the second closepath was 
> instructed.
>        g2.translate(w/2, h/2);
>        g2.setColor(Color.black);
>        g2.draw(bs.createStrokedShape(p));
>    }
> 
> The second attached picture without pink markings displays how the 
> testcase looks using Sun's properitary java2d for reference.
> 
> Cheers.
> Xerxes
> 

Cheers,
Omair

[1] http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=197
[2] http://icedtea.classpath.org/hg/icedtea6/rev/0641929711bf
[3] http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=255