Re: [AD] al_convert_bitmap

[Peter Wang <novalazy@xxxxxxxxxx>]

On 2011-06-03, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> The attached patch adds the ability to convert between memory and video
> bitmaps. It has two new functions:
> 
> al_convert_bitmap: like al_clone_bitmap, but modifies the bitmap
> in-place)
> 
> al_convert_all_video_bitmaps: converts all video bitmaps which have
> silently been converted to memory bitmaps because there was no display
> to actual video bitmaps
> 
> I first implemented this with a very small patch, simply making
> ALLEGRO_BITMAP big enough to hold either the OpenGL or D3D version with
> some static asserts to ensure it. But since that felt a bit messy I then
> changed ALLEGRO_BITMAP to have an .extra field which OpenGL/D3D now use
> to allocate their additional required storage, with no more driver
> specific bitmap structs. This however made the patch grow huge :P

I think the documentation is lacking justification for why you might
want to create pseudo-video bitmaps before creating a display.
(If it's to do with fonts, I think the font addons should actually keep
both memory and video bitmap copies of the glyphs, at least by default.)

Here's an idea: what if we introduce bitmap 'tags', where every bitmap
is tagged with the current tag when it is created.  Logically, each tag
is a list of bitmaps managed by Allegro.  Then we introduce a function
to convert all bitmaps with a particular tag:

    al_convert_bitmaps_with_tag(int tag, int newtag);
    /* After each bitmap is successfully converted, its tag
     * can be changed to newtag.
     */

This might replace al_convert_all_video_bitmaps while opening up
more possibilities.

Peter