Hello all,

I’m using Allegro 5.0.10 and I have some problems when setting up fullscreen displays on « some configurations » (actually I was not able to detect which configuration makes it work)
I would like the keep the 4:3 ratio but nowadays most desktop monitors and laptop monitor are 16:9 (or even 16:10).

Here s my code:

al_set_new_display_option(ALLEGRO_DEPTH_SIZE, 32, ALLEGRO_REQUIRE);
al_set_new_display_flags(ALLEGRO_DIRECT3D| ALLEGRO_FULLSCREEN);
ALLEGRO_DISPLAY* _display = al_create_display(640, 480);

• On a desktop PC [A] / Monitor [A] / Videocard [1] : It works like I want = It displays fullscreen and the 4:3 is kept, showing black rectangles on the sides.

• On a desktop PC [A] / Monitor [A] / Videocard [2] : It works like I want = It displays fullscreen and the 4:3 is kept, showing black rectangles on the sides.

• On a laptop PC [B] / Videocard [3] : It doesn’t works like I want = It displays fullscreen but the ratio is altered (stretched)

• On a laptop PC [B] / Videocard [3] connected to an External Monitor [C] : It doesn’t works like I want = It displays fullscreen but the ratio is altered (stretched)

My questions:
Is there a way to force the ratio to be kept when creating display?
Is ALLEGRO_DIRECT3D a good choice? I can switch my code to ALLEGRO_OPENGL. I can also make the user choose which one to use.

Thank you

I would suggest using the native resolution and implementing the letterboxing and scaling yourself. Running any non-native resolution on flat-screen monitors generally looks terrible, especially if the aspect ratios don't match.

Yea, hardware is consistently inconsistent. You should get and use the native resolution of the display and then scale, stretch, and/or letterbox in your software.

Uhm, you might, but if you set things up correctly it shouldn't make a difference.

What I do is draw everything to a separate ALLEGRO_BITMAP, then scale/stretch to the display on the final pass. So essentially everything in your code is the same as before, except you're drawing to a separate ALLEGRO_BITMAP instead of the bitmap of the ALLEGRO_DISPLAY.

Then, all your scaling and stretching and letter boxing and whatnots are of concern only when you draw that bitmap to the display before flipping.

I'm not sure if that's the best way, but that's what I'm doing now and it keeps things easy and compartmentalized in my code. There might be equally good alternative solutions.

Thanks for your answers.

Btw how do I detect the fullscreen display size using Allegro 5.0 routines?
Is there a way to detect all "possible" fullscreen display sizes for this video card?

As for my code:

ALLEGRO_DISPLAY* _display; // The display (size: SCREEN_W*SCREEN_H 
                           //                    = Allegro constants)      
ALLEGRO_BITMAP* _bufferDisplay;  // My "scene" (size BITMAP_W*BITMAP_H = 640*480)

// ...

int nFullScreenH = SCREEN_H;
int nFullScreenW = 4*SCREEN_H/3;
int nFullScreenOffsetX = (SCREEN_W - nFullScreenW)/2;

My Loop :

al_set_target_bitmap(_bufferDisplay);
al_clear_to_color(COL_BACKGROUND); // equals to color(0,0,0,0)
_pGameHelper->Draw(); // all my draws

al_set_target_backbuffer(_display); 

al_draw_scaled_bitmap(_bufferDisplay, 
  0+nShakeScreenX, 0+nShakeScreenY, // the current screen-shake values
  BITMAP_W, BITMAP_H,  // The size of my "scene" 
  nFullScreenOffsetX, 0, 
  nFullScreenW, nFullScreenH,  
  0x00);

al_flip_display();

Is this what you suggest?

@Thomas , you said to use ALLEGRO_TRANSFORM and al_set_clipping_rectangle
Will that be faster?

Thanks again

OK Then, if it's possible for you to give me an example, I would appreciate.
Thank you.

And it is possible to get all fullscreen display sizes for the current video card, using Allegro routines?

Definitely do it in software (GPU) not on the TV/monitor. Cheap TVs support very little in terms of letter boxing. My current one (which is cheap) supports centered pixel-for-pixel, or stretched... that's it. There are no boxing modes.

[edit] Woah, that's creepy. Someone must have hit send to top, but because my post was last yesterday, it says "Last post was by Chris Katko ~40 minutes ago."

Thanks very much to all of you.

And very good point Elias about the integer scaling when doing pixel art.