Misc/abrash-black-book
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James Gregory 2013-12-31 11:06:31 +11:00
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@ -20,9 +20,21 @@ using write mode 3 because write mode 3 requires a read/write of display
memory (or at least preloading the latches with the background color),
while the write mode 0 approach requires only a write to display memory.
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![](images/i.jpg) *Is write mode 0 always the best way to do text? Not at all. The write mode 0 approach described above draws both foreground and background pixels within the character box, forcing the background pixels to black at the same time that it forces the foreground pixels to white. If you want to draw transparent text (that is, draw only the character pixels, not the surrounding background box), write mode 3 is ideal. Also, matters get far more complicated if characters that aren't 8 pixels wide are drawn, or if characters are drawn starting at arbitrary pixel locations, without the multiple-of-8 column restriction, so that rotation and masking are required. Lastly, the Map Mask register can be used to draw text in colors other than white—but only if the background is black. Otherwise, the data remaining in the planes protected by the Map Mask will remain and can interfere with the colors of the text being drawn.*
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> ![](images/i.jpg)
> Is write mode 0 always the best way to do text? Not at all. The write
> mode 0 approach described above draws both foreground and background
> pixels within the character box, forcing the background pixels to black
> at the same time that it forces the foreground pixels to white. If you
> want to draw transparent text (that is, draw only the character pixels,
> not the surrounding background box), write mode 3 is ideal. Also,
> matters get far more complicated if characters that aren't 8 pixels wide
> are drawn, or if characters are drawn starting at arbitrary pixel
> locations, without the multiple-of-8 column restriction, so that
> rotation and masking are required. Lastly, the Map Mask register can be
> used to draw text in colors other than white—but only if the background
> is black. Otherwise, the data remaining in the planes protected by the
> Map Mask will remain and can interfere with the colors of the text being
> drawn.
I'm not going to delve any deeper into the considerable issues of
drawing VGA text; I just want to sensitize you to the existence of