I'm currently using page flipping with my new project, but it has a few problems. It flickers occasionally and I don't think I'm doing it correctly. I'm using an accurate timer richard phillps(sp?) gave to me as well.

I don't think theres anything wrong with my code, but I want to check.

Which page do you draw to and where? You must draw to the page that is NOT being shown on screen at the time.

You should separate logic from drawing. Right now it seems you have it all mixed together.

This is how it hould be done:

while (!done) {
    while (timer_ticked) {
        process_input();
        process_logic();
    }

    draw_to_active_page();
    show_active_page();
    swap_pages();
}

Ahh ok, I was doing it inproperly. (I had drawing code in the detectSelection and the handleMouse) I went ahead and fixed it up, and this is how it looks.

I believe that's the correct way to do it, but I have two questions.

In handleMouse, I just pick out what action to do depending on what I have selected when I click on the left mouse button, is that considered logic?

And whenever I close the game and I'm selecting something, it occassionally crashes the game. I'm not sure why, but this is the code I have for when I close the game:

void endGame()
{
 destroy_bitmap(page1);
 destroy_bitmap(page2);
 destroy_bitmap(activepage);
 unload_datafile(media);
 allegro_exit();
}

It's called right after the mainLoop is called if you wanted to know. I don't think there is anything wrong with that, but obviously something is wrong. Oh, and thanks miran.

are you drawing the mouse to any of those bitmaps you destroy?

destroying a bitmap to which the mouse is drawn will crash your game.

No, I only draw the mouse to the screen when the game is initalized.

EDIT: To test your theory, I ran scare_mouse(); when the game is ending and it fixed most the problem, but whenever I have my mouse in the lower parts of the screen when I close it, it closes fine, but it has a stupid error saying "Shimp Pong has encountered an error and needs to close". I don't think this is anything to worry about, but it's still annoying.

You must make sure that you call show_mouse(NULL) before destroying the surface the mouse is on.

Oh, well does scare_mouse() do the same thing? Or do I actually need to call show_mouse(NULL); ? And do I even need to destroy the activepage bitmap when I close the game? Shawn doesn't in his page flipping example.

scare_mouse just tells allegro not to SHOW the mouse cursor.

but the mouse is still ASSIGNED to the selected bitmap.

with show_mouse(NULL) you deselect the mouse from any bitmap.

Maybe this is not 100% correct in technical terms, but that should explain what it does.

Certainly not.

Not quite - it tells Allegro not to draw a soft mouse cursor. If the mouse cursor is drawn by teh OS, it does nothing.

Depends: if the mouse is displayed to screen (which it normally is), then you only need to call show_mouse(NULL) if you explicitly call set_gfx_mode().

Yes, you do. In practice, Allegro may free all video bitmaps when it closes down (memory bitmaps are immaterial, they are freed automatically by the OS), but you should always free memory that you allocate.

That's an oversight, then.

Ahh ok, thanks for clearing that up for me guys. It turns out that the scare_mouse(); wasn't doing the trick, so I changed it to show_mouse(NULL) and it did fixed it up good. Thanks a lot guys. If you don't mind I have one more question, and that's if I call

char *marquee;

as a global variable, do I need to call

free(marquee);

in the end game script?

Yeah, but you also have to malloc() or new it someplace too.

Oh ok, I "malloced" it before hand, I was just wondering if it was required since it was a global variable. Thanks a lot guys.

 destroy_bitmap(page1);
 destroy_bitmap(page2);
 destroy_bitmap(activepage);

Slight problem there, you never actually created a third bitmap, activepage is just a "pointer" or alias for which ever of page1 or page2 is the activepage, so you really aught not to be calling destroy_bitmap on it, since the bitmap it was pointing to, has already been destroyed.

Well I still declared it as a global variable, but it's only a pointer so I don't need to destroy it after all?

Nope. Only call destroy_* on items that were specifically created with create_*. Otherwise you're freeing it twice, which is a rather bad thing.

What? How does one implicitly call set_gfx_mode?

Ok well I removed it and it works well, but shouldn't I set the activepage to NULL anyway when I close the game?

It is a good habit to get into.

Oh ok, I went ahead and did that. Thanks a lot guys.