-VicSim- v1.1

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This is a small utility library for designing hi-res and multi-color bitmap routines for the Commodore 64 on a DOS box (or "pee sea"). It simply simulates access to screen/color/bitmap ram, the multi-color bit of $d016, and the background color ($d021), while allowing you to use your favorite high-level language (BASIC or C). I use this program while translating programs from pseudocode to assembly, slowly changing portions of the program to assemblyish (by using atomic instructions on variables named areg, xreg, and yreg). This way, I can write and edit assemblyish code while being able to use a VIC-II bitmap screen and the built-in debugging functions of the IDE.

The file FONT.C64 should be included with this program as well, as it includes the font data for the font routines. Everything will work fine without it, but the BASIC version will leave a 0-byte FONT.C64 file in your directory.

This software is free and public domain. Feel free to use it as is, change the code to suit your program, or port it to another language (and go ahead and distribute the ported version if you want to).

Main Subroutines:

- vicinit

Sets up the 320x200 VGA screen and a rough estimate of the 64's palette, initializes scrn, bitmap, colr, backg, and mcm to standard 64 bootup values, loads the fonts into memory, and sets up the squish array. Simply change the "SCREEN 13" command to "SCREEN 12" in order to use 640x480 mode, if you want to display stuff onscreen without disturbing the 320x200 VicSim area. The aspect ratio will be a little skewed, though.

- gfxpoke memloc, byte

Stores 8 bits of byte into the bitmap array and updates the byte on the screen. Standard calling method usually looks something like "gfxpoke mem, bitmap(mem) OR bits".

- scrnpoke memloc, byte

Stores 8 bits of byte into the scrn array and updates the 8x8 block on the screen.

- colrpoke memloc, byte

Stores 4 bits of byte into the colr array and updates the 8x8 block on the screen.

- refresh

Redraws the entire screen. When many changes to the screen are made, it is faster to store values straight into the bitmap/scrn/colr arrays and then call this function, as opposed to using gfxpoke/scrnpoke/colrpoke for each memory access.

Helper Functions and Subroutines:

- fontcopy upper, char, x, y

Copies a character from the 64's default font onto the specified character block (0,0 to 39,24). Upper should be non-zero to read from the uppercase font; zero will result in using the lowercase font. This uses gfxpoke, so results are immediately onscreen.

- fontcopyl upper, char, x, y
- fontcopyr upper, char, x, y

Like fontcopy, but draws a squished version of the specified character into either the left or right nybble. The other nybble is unharmed.

- charcopy a(), x, y

Copies the first eight bytes out of the specified array. x and y work as in fontcopy. For the C version, send an unsigned char pointer (#defined as "byte" in vicsim.h) for the character data.

- block(x, y)

Returns the memory location of the first byte in the 8x8 block specified. x and y range from 0-39 and 0-24 respectively.

- byte(x, y)

Returns the memory location of the byte which contains the bit specified. x and y range from 0-319 and 0-199 respectively.

- mbyte(x, y)

Works like the above routine, but for multicolor mode. x and y range from 0-159 and 0-199 respectively.

Cheater Subroutines: ;)

- set x, y
- clr x, y

Sets or clears a bit. Uses gfxpoke, so results appear immediately. x and y range from 0-319 and 0-199 respectively.

- mset x, y, bits

Works like the above routine, but in multicolor, so x ranges from 0-159. bits should be 0, 1, 2, or 3, regardless of the x position in the block.

Global variables:

- scrn(0 to 999)
- bitmap(0 to 7999)
- colr(0 to 999)
- backg

These are pretty self-explanatory. Remember to call refresh if you change these directly.

- mcm

Set to non-zero for multi-color mode, zero for hi-res. Then call refresh.

- squish(0 to 255)

Given an 8-bit byte, this returns a graphically shrunk version of the original byte in both nybbles. AND this with $f0 or $0f to get a 4-pixel wide representation of the original, depending on which nybble you need to access. Handy for displaying 8x8 fonts as 4x8 fonts.

- lfont(0 to 2047)
- ufont(0 to 2047)

These are where the fonts are located, in standard C64 format. Upon startup, these are loaded from the file FONT.C64.

To Do:

- Sprites.
- Raster effects.
- Text modes.

Download it! (8196 bytes)