Re: [pygame] freetype module

[Lenard Lindstrom <len-l@xxxxxxxxx>]

Hi Marcus,

On 13/01/11 11:13 PM, Marcus von Appen wrote:
> On, Fri Jan 14, 2011, Lenard Lindstrom wrote:
>
>    
> > Hi everyone,
> >
> > A few months back I had a look at the new freetype pygame module. It is
> > meant to replace the SDL_font based font module, and adds new features
> > such as text rotation and full Unicode character support. Unfortunately
> > it also has a serious bug in determining the text bounding rectangle
> > when the text contains a mix of character with ascenders and descenders.
> >      
> The bug can be solved by storing the relative text bbox width and
> height.
>
>    
I'm not sure how you get the bboxes. I could only get reliable bounding 
boxes by calling FT_Glyph_Get_CBox on loaded and transformed glyphs. At 
this point much of the work is done, with just rendering and blitting 
left. So the freetype.get_size method becomes extra expensive. Saving 
transformed glyphs would add extra complexity to the cache mechanism. So 
the architecture of the freetype module class(es) will need to be rethought.

>    
> > This can cause a Python interpreter crash.
> >      
> I did not encounter that so far. Can you provide an example for that?
>
>    
The render_raw method crashed on "gh" when returning a bytes string. 
Byte strings have less padding so the python instance and malloc headers 
are corrupted. The boundary problem is not noticeable when rendering to 
an existing surface with render. But the attached chop.py program 
displays "gn", chopping off the h's accender. I would have tried this 
with pygame2, but only have SDL_mixer 1.2.8 available for Debian 
squeeze. (The pygame2 build fails with these errors:

src/sdlmixer/constantsmod.c: In function ‘initconstants’:
src/sdlmixer/constantsmod.c:72: error: ‘MIX_INIT_FLAC’ undeclared (first 
use in this function)
src/sdlmixer/constantsmod.c:72: error: (Each undeclared identifier is 
reported only once
src/sdlmixer/constantsmod.c:72: error: for each function it appears in.)
src/sdlmixer/constantsmod.c:73: error: ‘MIX_INIT_MOD’ undeclared (first 
use in this function)
src/sdlmixer/constantsmod.c:74: error: ‘MIX_INIT_MP3’ undeclared (first 
use in this function)
src/sdlmixer/constantsmod.c:75: error: ‘MIX_INIT_OGG’ undeclared (first 
use in this function)
error: command 'gcc' failed with exit status 1

And I do have the development packages installed.)

> > In the pygame freetype branch I added a method which correctly
> > calculates a bounding rect. But it uses a different approach than
> > pygame.freetype. The fix may require a significant rewrite. So it is
> > worthwhile to consider other possibilities. One would be to wrap pango,
> > then all formatting woes are taken care of. A pango for SDL library
> > already exits -http://sourceforge.net/projects/sdlpango  - but nothing
> > has been done with it for over a year. I don't suggest using it
> > directly, but rather as a template for writing Pygame's own wrapper as
> > an extension module. Using pango is just an idea. It may turn out
> > building pango on Windows is too involved to be practical. Any thoughts?
> >      
> Pulling in pango means pulling in Glib20 and friends. Personally I would
> not recommend that.
>
>    
Noted, along with Stas Zytkiewicz's post. Wrapping pango can go on the 
"Things to *not* do" list.

Lenard Lindstrom

import pygame
display = pygame.display.set_mode((300, 200))
display.fill(pygame.Color('white'))
pygame.display.flip()

import pygame.freetype
pygame.freetype.init()
text = "gh"
f = pygame.freetype.Font(None)
s, r = f.render(None, text, pygame.Color('black'), ptsize=90)
display.blit(s, (10, 30))
pygame.display.flip()

while (1):
    e = pygame.event.wait()
    if e.type == pygame.QUIT:
        break
    if (e.type == pygame.KEYDOWN and 
        e.key == pygame.K_ESCAPE     ):
        break
    pygame.display.flip()
pygame.quit()