Re: [pygame] Ugly fonts (yes, I use AA)

["Lenard Lindstrom" <len-l@xxxxxxxxx>]

On 10 Nov 2006 at 4:32, Karlo Lozovina wrote:

> My app is based on three classes, one widget class, one scene class
> (something like a frame, or window in GUI world, and app class which
> manages all the details. Now, the problem is that when widget class
> renders fonts they look really crappy. Turning AA on/off does make a
> difference in their appearance, but even with AA switched on, the
> result is rather bad.
> 
> The thing that puzzles me the most is the fact that when I render the
> same font on my display surface, without using widget->scene->app
> classes I get perfectly fine looking fonts :(. What could I have done
> wrong so that my fonts get messed up?
> 
> My design is as follows: widget uses its own Surface to do the
> drawing, and renders text to that surface. Then, when update is needed
> scene class takes widgets Surface and blits that with it's own
> Surface, and then scene Surface finally gets blitted to main display
> surface.
> 
> Does anyone have any idea what could possibly go wrong during this
> process? If needed, I'll attach my code later...
> 
> Here is the code to the widget class, because I suspect that's where
> my problem lies:
> 
> --- cut here ---
> class Viewport:
>     def __init__(self, parent, size, pos, bgimage, margin, font_path,
> font_size):
[snip __init__ code]
> 
>     def update(self):
>         text_row = 0
>         for item in self.items:
>             item_text = self.font.render(item, 0, (249, 249, 249))
>             self.canvas.blit(item_text, self.ritems.move(0, text_row))
>             text_row += self.font_size + 1
>
The problem is the backgound, font.canvas, is not cleared before each 
update. The font image is blitted onto the font image already there 
from the previous update. Font.render uses per-pixel alpha for anti-
aliasing with a transparent background. Repeated alpha blitting makes 
partially transparent pixels more opaque, undoing anti-aliasing. A 
pygame 1.7 bug can also turn the background black.

Lenard Lindstrom
<len-l@xxxxxxxxx>