NAME

       drawing_mode - Sets the graphics drawing mode. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       void drawing_mode(int mode, BITMAP *pattern, int x_anchor, int y_anchor);

DESCRIPTION

       Sets  the  graphics  drawing  mode.  This  only  affects  the  geometric  routines  like putpixel, lines,
       rectangles, circles, polygons,  floodfill,  etc,  not  the  text  output,  blitting,  or  sprite  drawing
       functions. The mode should be one of the following constants:

          DRAW_MODE_SOLID               - the default, solid color
                                          drawing
          DRAW_MODE_XOR                 - exclusive-or drawing
          DRAW_MODE_COPY_PATTERN        - multicolored pattern fill
          DRAW_MODE_SOLID_PATTERN       - single color pattern fill
          DRAW_MODE_MASKED_PATTERN      - masked pattern fill
          DRAW_MODE_TRANS               - translucent color blending

       In  DRAW_MODE_SOLID,  pixels  of the bitmap being drawn onto are simply replaced by those produced by the
       drawing function.

       In DRAW_MODE_XOR, pixels are written to the bitmap with an exclusive-or operation rather  than  a  simple
       copy,  so  drawing the same shape twice will erase it. Because it involves reading as well as writing the
       bitmap memory, xor drawing is a lot slower than the normal replace mode.

       With the patterned modes, you provide a pattern bitmap which is tiled across the surface  of  the  shape.
       Allegro  stores a pointer to this bitmap rather than copying it, so you must not destroy the bitmap while
       it is still selected as the pattern. The width and height of the pattern must be powers of two, but  they
       can  be  different,  eg.  a  64x16 pattern is fine, but a 17x3 one is not. The pattern is tiled in a grid
       starting at point (x_anchor, y_anchor). Normally you should just pass zero for these values,  which  lets
       you  draw  several  adjacent  shapes  and  have the patterns meet up exactly along the shared edges. Zero
       alignment may look peculiar if you are moving a patterned shape around the screen, however,  because  the
       shape  will  move  but  the  pattern  alignment will not, so in some situations you may wish to alter the
       anchor position.

       When you select DRAW_MODE_COPY_PATTERN, pixels are  simply  copied  from  the  pattern  bitmap  onto  the
       destination  bitmap.  This  allows the use of multicolored patterns, and means that the color you pass to
       the drawing routine is ignored. This is the fastest of the patterned modes.

       In DRAW_MODE_SOLID_PATTERN, each pixel in the pattern bitmap is compared with the mask  color,  which  is
       zero  in  256-color  modes  or  bright pink for truecolor data (maximum red and blue, zero green). If the
       pattern pixel is solid, a pixel of the color you  passed  to  the  drawing  routine  is  written  to  the
       destination  bitmap,  otherwise  a  zero is written. The pattern is thus treated as a monochrome bitmask,
       which lets you use the same pattern to draw different shapes in different colors, but prevents the use of
       multicolored patterns.

       DRAW_MODE_MASKED_PATTERN is almost the same as DRAW_MODE_SOLID_PATTERN, but the masked pixels are skipped
       rather than being written as zeros, so the background shows through the gaps.

       In DRAW_MODE_TRANS, the global color_map table or truecolor blender functions are used to overlay  pixels
       on  top  of the existing image. This must only be used after you have set up the color mapping table (for
       256 color modes) or blender functions (for truecolor modes). Because  it  involves  reading  as  well  as
       writing  the  bitmap  memory,  translucent  drawing  is  very  slow if you draw directly to video RAM, so
       wherever possible you should use a memory bitmap instead.

SEE ALSO

       xor_mode(3alleg4), solid_mode(3alleg4), color_map(3alleg4), set_trans_blender(3alleg4), exalpha(3alleg4),
       excolmap(3alleg4), exjoy(3alleg4), expat(3alleg4), extrans(3alleg4)