Re: [AD] Problem with remove_mouse() and video bitmaps.

[Stef <stapostol@xxxxxxxxxx>]

I was in hurry so I did not explain myself enough. Let me explain what I  
meant:

As far as I can tell, the problem is that the draw_mouse() function  
(called by the show_mouse()) tries to draw the mouse pointer to a  
non-valid bitmap (one that has been deallocated). If we had a way to tell  
whether a bitmap is valid, draw_mouse() could bail out without crashing.  
(Note: There is NO reason to put mouse specific code in destroy_bitmap() -  
that's out of the question. It is the mouse code that checks if the target  
bitmap is valid!)

The follwoing code provides a (half-correct) way:

> void destroy_bitmap(BITMAP *bmp)
> {
>    /* do stuff */
>    ...
>    bmp = NULL;
> }

(ideally there would be a bitmap_exists(BITMAP *bmp) function, and all  
allegro functions that use bitmaps (read from them or draw to them) would  
bail out if one of their arguments is not valid.)

Since we don't have a bitmap_exists() function (and for compatibilty  
reasons can't add one now), we could at least place a check against NULL  
in draw_mouse().

This is orthogonal to the documentation issue (ie. that one should not use  
a non-valid bitmap as a target, or crashes may occur).

Does this seem reasonal?