Re: [AD] set_display_mode and screen update handling

[Chris <kcat@xxxxxxxxxx>]

Elias Pschernig wrote:
> > Plain text document attachment (modefuncs.c)
> > /* The bitmaps we'll be drawing to */
> > static BITMAP *page[3];
>
> I don't know, in my implementations of this function (I guess everyone
> uses a wrapper around set_gfx_mode :), I use this:
>
> BITMAP *front_buffer, *back_buffer, *middle_buffer;
>
> And swap those variables around. No need for a current_page variable,
> and the code gets cleaner IMO.

I don't really like the idea of swapping pointer values like that when 
all you have to do is update an int variable. Also the names seem a 
little ambiguous.

> If you request: TRIPLE_BUFFER | PAGE_FLIP, should it do page flipping if
> triple buffering isn't possible?

That's what my code currently does, yeah.

> I think, the bpp could be defines as well.

Then the question comes in, as to what should have priority? 
Windowed/fullscreen or bitdepth? If the bitdepth and screen mode combo 
isn't available, should the screen mode switch first or bitdepth?

> I guess the vs should be not a parameter here, but specified in the call
> to set_display_mode. After all, it has no meaning for anything but
> double buffer.

Hmm.. perhaps it should be another function altogether? I don't like the 
idea of having to reset the gfx mode just to toggle vsync.

> Very often, you also need the front buffer. E.g. when doing page
> flipping, but then you use the GUI file selector. screen could be the
> back page in that case. With my method, there'd be 3 global variables to
> get up to 3 pages (or just a wrapper get_front_page would do as well).

Again, these names are a little ambiguous. If you're doing something 
like Allegro's GUI (dirty rectangles), then I'd think you'd either use 
no buffering, or double buffering (making sure to blit the buffer 
whenever it changes), or to blit the current screen to the current 
buffer (which would be fast since it'd likely be vram->vram 
accelerated), modify that, and then show the new buffer.

- Kitty Cat