## Display Device Driver Reference for OS/2

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### BitBlt

Unlike the SVGA driver, the S3 driver does not compile BitBlts onto the stack. Instead, eddb_BitBlt analyzes the raster operator and various source and destination options, and breaks the blt down into simpler cases. Each of these cases can take advantage of the graphics accelerator hardware . All BitBlts are broken down into combinations of the following four cases:

eddh_SrcDestBlt

eddh_PatDestBlt

eddh_DestOnlyBlt

Software BitBlt by way of eddf_MESS

Any BitBlt to the display ultimately ends up in one of the cases, and they are among the first pieces of code that must be modified when this driver is ported to a different chip set. These functions are located in the EDDHBBLT.ASM file. They handle the first three cases that an S3 chip can accelerate in hardware: a source, destination, and a raster operation; a pattern, destination, and a raster operation; or a destination-only raster operation.