bionic (3) al_use_projection_transform.3alleg5.gz

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 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)