The output routines that draw arcs, ellipses, and other primitive figures do not specify color or line-style information. Instead, they rely on properties set independently by other routines.
GETCOLORRGB (or GETCOLOR) and SETCOLORRGB (or SETCOLOR) obtain or set the current color value (or color index), which FLOODFILLRGB (or FLOODFILL), OUTGTEXT, and the shape-drawing routines all use. Similarly, GETBKCOLORRGB (or GETBKCOLOR) and SETBKCOLORRGB (or SETBKCOLOR) retrieve or set the current background color.
GETFILLMASK and SETFILLMASK return or set the current fill mask. The mask is an 8-by-8-bit array with each bit representing a pixel. If a bit is 0, the pixel in memory is left untouched: the mask is transparent to that pixel. If a bit is 1, the pixel is assigned the current color value. The array acts as a template that repeats over the entire fill area. It "masks" the background with a pattern of pixels drawn in the current color, creating a large number of fill patterns. These routines are particularly useful for shading.
GETWRITEMODE and SETWRITEMODE return or set the current logical write mode used when drawing lines. The logical write mode, which can be set to $GAND, $GOR, $GPRESET, $GPSET, or $GXOR, determines the interaction between the new drawing and the existing screen and current graphics color. The logical write mode affects the LINETO, RECTANGLE, and POLYGON routines.
GETLINESTYLE and SETLINESTYLE retrieve and set the current line style. The line style is determined by a 16-bit-long mask that determines which of the five available styles is chosen. You can use these two routines to create a wide variety of dashed lines that affect the LINETO, RECTANGLE, and POLYGON routines.
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