drawing_mode(3alleg4)						  Allegro manual					     drawing_mode(3alleg4)

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)

Allegro 							   version 4.4.2					     drawing_mode(3alleg4)