A while back I asked about screen scaling. For the immediate moment I solved my problem with proportional increases to my drawing items.

During this time Edgar make a comment about transformations and/or translate that would increase / decrease overall screen without the need for mouse action adjustments based on screen size.

Now I can't find the topic with Allegro search or Google. Can someone tell me if I'm remembering wrong on the abilities of transform?

Thanks.

While I didn't say that specifically Ace, you are right on track.

If you use the full screen size, a smaller buffer and transformations, you can use an inverted transform to find your mouse on the smaller buffer.

ALLEGRO_TRANSFORM t;
al_identity_transform(&t);
al_scale_transform(&t , SCREEN_WIDTH/BUFFER_WIDTH , SCREEN_HEIGHT/BUFFER_HEIGHT);

ALLEGRO_TRANSFORM tinverse;
al_copy_transform(&t , &tinverse);
al_inverse_transform(&tinverse);

if (ev.type == ALLEGRO_EVENT_MOUSE_AXES) {
   int rmx =  ev.mouse.x, rmy = ev.mouse.y;
   al_apply_transform(&tinverse , &rmx , &rmy);
}

An ALLEGRO_TRANSFORM is just a generic data type. Manipulate them with the API. You can scale, translate, and rotate, as well as inverse it and apply it to a set of coordinates. Use the transform to affect your screen, and the inverse transform to get your mouse coordinates.

Normally a display starts at 0,0, no tint, no rotation, etc. Transformations allow you to change that.

1. position: set the transform to position (x, y) then when you draw any item at (i, j) you're actually drawing to (x + i, y + j)

2. color: set the tint to ALL objects drawn

3. rotation: Set the rotation of all objects

3. scale: set the size of all objects

all this can be in 1 transform

Identity transform resets all back to zero.

Proper steps
1. backup the current transform
2. reset the new transform to identity
3. set the aspects of transform (position, scales, etc)
4. set the new transform as current transform
5. do the drawing
6. set the backup transform as current transform

Look at the source for this function

Transforms are just basic numbers. Your target bitmap is still target bitmap. transforms just inform the system how and where to draw to the target.

If you have a 640x480 real buffer, but you want a 1200x800 imaginary buffer then set the transform using the scale function.

void al_scale_transform(ALLEGRO_TRANSFORM *trans, float sx, float sy);

al_scale_transform(my_transform, 640 / 1200, 480 / 800);

If you use this transform then when you draw to (1000, 600) it multiplies your position and scale. So you are actually drawing to (1000 * 640/1200), (600 * 640/1200) = (533, 360)

I use a set size buffer and scale it to whatever the display size is. This is a transform. If the display changes, the scale changes. However, my buffer doesn't change size.

Thanks all,

This clarifies a lot. I'm going to play around with the commands and see how they work on screen. I appreciate it.