## Display Device Driver Reference for OS/2

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### Text Output

After BitBlt is functioning, create text output. (If more than one developer is working on the driver, then text and BitBlt can be done simultaneously, when the driver is correctly initialized and some of the rudiments of BitBlt are functional.)

1.The first task is to modify the caching code in EDDNCACH.C so it copies the character bit maps into off-screen VRAM in a format suitable for your hardware. If your hardware is incapable of VRAM-to-VRAM monochrome expansion, set CharTooBig to be TRUE in EDDNGCHS.ASM, and let BitBlt handle text output until a non-cached scheme is created.

2.The routines that handle caching are eddt_CacheCharacter, in EDDNCACH.C, and Cache8514Char, in EDDHGCHS.ASM. Cache8514Char may be unnecessary for your device. A memcpy may work just as well.

3.Modify eddh_DrawText in EDDHGCHS.ASM. Most of the modifications will probably be confined to the sections marked IFDEF HARD_DRAW ... IFDEF _ 8514.

4.Debug the above code. It is difficult to debug the character-caching code without actually drawing any characters. Unless the character-caching code is working, it is impossible to draw any characters correctly.