Using the following code in the main loop:

if (keysDown[ALLEGRO_KEY_F4]) {
if (al_get_display_flags(display) & ALLEGRO_FULLSCREEN)
al_set_new_display_flags(0);
else
al_set_new_display_flags(ALLEGRO_FULLSCREEN);
al_destroy_display(display);
display = al_create_display(640,480);

cdecl::al_set_target_backbuffer(display);
keysDown[ALLEGRO_KEY_F4] = false;
}

I am able to toggle fullscreen on and off. However, while the game runs fine normally in the (initial) windowed mode, when I toggle to fullscreen, it lags badly, and then upon toggling it back the lag remains. What am I doing wrong?

Recreate all your bitmaps after changing modes.

Problem here is, I'm using Allegro 5.0.5, which doesn't have al_convert_bitmap. Also, I store all of my bitmaps in separate "sprite" classes, they'd be a major pain to keep track of separately. Is my only option to compile allegro 5.1 elsewise, though?

I feel very stupid for not thinking of that, or rather noticing that that function existed. Thank you very much for the help.

Only if they are video bitmaps. Or possibly system bitmaps. If they were created via create_bitmap, you're fine.

Seems to me you had to do a set_gfx_mode(GFX_TEXT,0,0,0,0); then you could reset a graphic mode.

Hmm. What you two are saying is about the same. Is the message output necessary for it to work? If not it's good for at least telling the player what's going on.

Yeah, at least for me, the allegro message bit was necessary to properly change resolutions. I just use it to output the new resolution to the user.

If it is just a timing issue, a rest should work.

I'd imagine a full second delay should work for anything.

Nobody noticed that putting that in your main loop would try to create a new display for the number of times you check the keyboard while F4 is pressed down? (Or would the actual switch pause the program long enough to let you lift your finger?) And what does cdecl do?!