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Added a 160x192x2 TGI (graphics) driver to the VIC-20 library.

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The driver requires a special linker configuration: "vic20-tgi.cfg".
The VIC-20 computer needs at least 8K of expansion RAM!

"tgidemo.c" needed to be adjusted because the VIC-20's vertical (y) range is greater than its horizontal (x) range -- the opposite of most other platforms.  Also, the circle demo would jam on the VIC-20.
This commit is contained in:
Greg King
2020-07-08 05:55:30 -04:00
parent d1833cc441
commit 410e4502ee
11 changed files with 1253 additions and 23 deletions
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29
doc/vic20.sgml
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@@ -75,7 +75,6 @@ common to all CBM platforms.
There are currently no special VIC20 functions.
<sect1>CBM-specific functions<p>
Some functions are available for all (or at least most) of the Commodore
@@ -143,7 +142,33 @@ The names in the parentheses denote the symbols to be used for static linking of
<sect1>Graphics drivers<p>
No graphics drivers are currently available for the VIC20.
<descrip>
<tag><tt/vic20-hi.tgi (vic20_hi_tgi)/</tag>
This driver features a resolution of 160&times;192 with two colors. The
background can be chosen from a sixteen-color palette. The foreground can
be chosen from an eight-color palette.
The driver will use memory from addresses $1000 to $1FFF as a graphics
buffer. Therefore, the VIC-20 must have, at least, 8K of expansion RAM.
Programs that use this driver must be linked by the <tt/vic20-tgi.cfg/
configuration file. It will link a special header into the program.
That header will do the housekeeping that's needed by TGI.
An example command line:
<tscreen><verb>
cl65 -D DYN_DRV=0 -t vic20 -C vic20-tgi.cfg samples/mandelbrot.c
</verb></tscreen>
When the program starts, it will move itself up in RAM, to make room for the
buffer. When the program finishes, it will reset the BASIC interpreter.
That means that graphics pictures won't be preserved between the executions
of programs. Also, the graphics buffer shares RAM with the text screen. If
a picture must be saved, then a program must put it somewhere else (such as
a disk file) before returning to the text mode.
</descrip>
<sect1>Extended memory drivers<p>