Re: [pygame] Strange (uncommon) behaviour of Font.render()

[Gregor Lingl <gregor.lingl@xxxxxx>]

Thanks for your enlightening reply. (I had the suspicion that something 
like this could be the cause)

Am 09.01.2011 23:46, schrieb Saul Spatz:
> The first 3 arguments are positional.  If this were in pure python, 
> then background=None would have the same effect as just passing None. 
>   The font module is programed in C.  If you look at font.c you'll find
>
> font_render (PyObject* self, PyObject* args)
> {
<snip>
...
So one had to consider this to be a bug in the C-Code. Do you think one 
could fix this, by introducing an extra check
if bg_rgba_obj is the Python None obj here:
>        if (bg_rgba_obj)   *AND IT IS NOT None*
>     {
>         if (!RGBAFromColorObj (bg_rgba_obj, rgba))
>             return RAISE (PyExc_TypeError, "Invalid background RGBA 
> argument");
>         backg.r = rgba[0];
>         backg.g = rgba[1];
>         backg.b = rgba[2];
>         backg.unused = 0;
>     }
>     else
>    {
>         backg.r = 0;
>         backg.g = 0;
>         backg.b = 0;
>         backg.unused = 0;
>     }
> <snip>
>
> While I haven't traced through all the code, it seems clear that if 
> you pass a parameter for the background, the function will check if 
> it's a valid RGBA argument, and raise a TypeError if it isn't.
So, as it is, the only possible workaround for the before mentioned 
usecase is like this. Right?

def text_line(surface, font, text, x, y, color, bg=None):
    ...
    if bg is None:
        label = font.render(text, 1, color)
    else:
        label = font.render(text, 1, color, bg)
    ...

Not very elegant :-(

At least, I think, the docs for Font.render() should be fixed.

Best regards,
Gregor


> I have found similar things in pygame before, although I can't recall 
> the details.
>
> In any event, if you don't want a background apramter, leave it out; 
> None won't work whatever you do.
>
> Saul