Question

I’m using the following to draw rounded-corner rectangles in my Android application and it seems to be working alright but with one minor problem:

//  Draw the control buttons
paint.setColor      (Color.DKGRAY);
paint.setStyle      (Style.FILL);
canvas.drawRoundRect    (zPlusRectF,  12, 12, paint);
canvas.drawRoundRect    (zMinusRectF, 12, 12, paint);

paint.setColor      (Color.LTGRAY);
paint.setStyle      (Style.STROKE);
canvas.drawRoundRect    (zPlusRectF,  12, 12, paint);
canvas.drawRoundRect    (zMinusRectF, 12, 12, paint);

paint.setColor      (Color.WHITE);
paint.setStyle      (Style.FILL);
paint.setTextSize   (BUTTON_TEXT_SIZE);

... (Adding labels to the rectF's defined above follows) ...

The strange thing is that the two ends of the rectangle aren’t rounded over the same. The left-side quarter circles are noticeably smaller than the ones on the right.

Anybody experienced anything similar? It’s weird enough that I might change my mind about the round corners if I can’t do anything about it…. And if I knew how to do a screen capture from my Android, I would.

Thanks,
R.

Edit: The rectangles in question are 78 pixels wide and 48 tall, if that helps (and since ykatchou may be onto something).

Answer 1

The problem turned out to be a function of anti-aliasing. When you’re drawing 2D graphics in Android (and probably elsewhere, too), and rule of thumb that works out for me is:

Turn anti-aliasing on for curves and text, but off for straight lines.

Once I paid attention to managing the anti-aliasing state in my drawing methods, this problem was fixed.