NAME

       al_use_projection_transform - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              void al_use_projection_transform(const ALLEGRO_TRANSFORM *trans)

DESCRIPTION

       Sets  the  projection  transformation  to be used for the drawing operations on the target
       bitmap (each bitmap maintains its own projection transformation).  Every drawing operation
       after  this  call  will  be  transformed  using  this  transformation.   To return default
       behavior, call this function with an orthographic transform like so:

              ALLEGRO_TRANSFORM trans;
              al_identity_transform(&trans);
              al_orthographic_transform(&trans, 0, 0, -1.0, al_get_bitmap_width(bitmap),
                                        al_get_bitmap_height(bitmap), 1.0);

              al_set_target_bitmap(bitmap);
              al_use_projection_transform(&trans);

       The orthographic transformation above is the default projection transform.

       This function does nothing if there is no target bitmap.  This function also does  nothing
       if the bitmap is a memory bitmap (i.e. memory bitmaps always use an orthographic transform
       like the snippet above).  Note that the projection transform will be reset to default if a
       video  bitmap is converted to a memory bitmap.  Additionally, if the bitmap in question is
       the backbuffer, it’s projection transformation will be reset to default if it is  resized.
       Lastly,  when  you  draw  a  memory  bitmap  to  a  video  bitmap with a custom projection
       transform, this transformation will  be  ignored  (i.e. it’ll  be  as  if  the  projection
       transform of the target bitmap was temporarily reset to default).

       The  parameter  is  passed  by reference as an optimization to avoid the overhead of stack
       copying.  The reference will not be stored in the Allegro library so it is  safe  to  pass
       references to local variables.

SINCE

       5.1.9

SEE ALSO

       al_get_current_projection_transform(3alleg5),           al_perspective_transform(3alleg5),
       al_orthographic_transform(3alleg5)