dos-vga-arena-shooter-game/system/vga.c

#include "vga.h"
#include "pc_stuff.h"
#include <malloc.h>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <time.h>

#include "../font8x8_basic.h"

int activePage = 0;
byte *drawBuffer;

byte *initializeDrawBuffer() {
  int i;

  drawBuffer = (byte *)malloc(VGA_DISPLAY_WIDTH * VGA_DISPLAY_HEIGHT);

  for (i = 0; i < VGA_DISPLAY_WIDTH * VGA_DISPLAY_HEIGHT; ++i) {
    drawBuffer[i] = 0;
  }

  return drawBuffer;
}

void copyDrawBufferToDisplay() {
  memcpy(VGA, drawBuffer, VGA_DISPLAY_WIDTH * VGA_DISPLAY_HEIGHT);
}

void freeDrawBuffer() {
  free(drawBuffer);
}

byte *getDrawBuffer() {
  return drawBuffer;
}

clock_t startTime, endTime;

void buildSpriteFromSpritesheet(
  struct BMPImage *spritesheetImage,
  struct SpriteRender *spriteRender,
  int positionX,
  int positionY,
  int width,
  int height
) {
  spriteRender->data = spritesheetImage->memoryStart + positionY * spritesheetImage->width + positionX;
  spriteRender->modulo = spritesheetImage->width - width;
  spriteRender->width = width;
  spriteRender->height = height;
  spriteRender->transparentColor = spritesheetImage->transparentColor;
}

void buildCompiledSprite(
  void (*code)(byte *),
  struct CompiledSpriteRender *compiledSpriteRender,
  int width,
  int height,
  int offsetX,
  int offsetY
) {
  compiledSpriteRender->code = code;
  compiledSpriteRender->width = width;
  compiledSpriteRender->height = height;
  compiledSpriteRender->offsetX = offsetX;
  compiledSpriteRender->offsetY = offsetY;
}

void drawPixel(int x, int y, int color) {
  drawBuffer[y * VGA_DISPLAY_WIDTH + x] = color;
}

void drawSprite(struct SpriteRender* sprite) {
  int x, y;
  byte pixel;
  int modulo = VGA_DISPLAY_WIDTH - sprite->width;

  byte* spriteData = sprite->data;
  byte* drawBufferPos =
    drawBuffer +
    sprite->x -
    sprite->offsetX +
    (
      (sprite->y - sprite->offsetY) * VGA_DISPLAY_WIDTH
    );

  for (y = 0; y < sprite->height; ++y) {
    for (x = 0; x < sprite->width; ++x) {
      pixel = *(spriteData++);
      if (pixel != sprite->transparentColor) {
        *(drawBufferPos) = pixel;
      }

      drawBufferPos++;
    }

    drawBufferPos += modulo;
    spriteData += sprite->modulo;
  }
}

void drawCompiledSprite(struct CompiledSpriteRender* compiledSprite) {
  byte *drawBufferPos = drawBuffer +
    compiledSprite->x + compiledSprite->y * VGA_DISPLAY_WIDTH;

  compiledSprite->code(drawBufferPos);
}

void getSpriteBounds(struct CompiledSpriteRender *sprite, struct SpriteBounds *bounds) {
  bounds->top = sprite->y - sprite->offsetY;
  bounds->bottom = bounds->top + sprite->height;

  bounds->left = sprite->x - sprite->offsetX;
  bounds->right = bounds->left + sprite->width;
}

void setVGAColors(struct VGAColor colors[], int totalColors) {
  int i;

  outp(0x3c8,0);
  for (i = 0; i < totalColors; ++i) {
    outp(0x3c9, colors[i].red);
    outp(0x3c9, colors[i].green);
    outp(0x3c9, colors[i].blue);
  }
}

#define RENDER_STRING_FAILSAFE (80)

struct CharRowDetails {
  char c;
  char color;
  char backgroundColor;
  char writeBackgroundColor;
  char* pos;
} charRowDetails;

// Write this in inline assembler for practice!
void plotCharRow();
#pragma aux plotCharRow = \
"mov al, [edi]" \
"mov ah, 8" \
"mov bl, [edi+1]" \
"mov bh, [edi+2]" \
"mov cl, [edi+3]" \
"mov edi, [edi + 4]" \
"nextBit: mov ch, al" \
"and ch,1" \
"cmp ch,1" \
"jne background" \
"mov [edi], bl" \
"jmp maybeKeepGoing" \
"background: cmp cl,0" \
"je maybeKeepGoing" \
"mov [edi], bh" \
"maybeKeepGoing: ror al, 1" \
"inc edi" \
"dec ah" \
"jnz nextBit" \
parm [edi] \
modify [eax ebx ecx edi];

void renderStringToDrawBuffer(char* buffer, int color, int backgroundColor, int x, int y) {
  char *bufferPos = buffer, currentCharacter, charRow;
  int i, fontX, fontY, currentX = x;

  int charX, fontYs[8];

  charRowDetails.color = color;
  if (backgroundColor == -1) {
    charRowDetails.backgroundColor = 0;
  }
  charRowDetails.writeBackgroundColor = backgroundColor != -1;

  for (fontY = 0; fontY < 8; ++fontY) {
    fontYs[fontY] = (y + fontY) * VGA_DISPLAY_WIDTH;
  }

  charX = x;

  for (i = 0; i < RENDER_STRING_FAILSAFE; ++i) {
    currentCharacter = *(bufferPos++);
    if (!currentCharacter) break;

    for (fontY = 0; fontY < 8; ++fontY) {
      charRowDetails.c = font8x8_basic[currentCharacter][fontY];
      charRowDetails.pos = drawBuffer + fontYs[fontY] + charX;

      plotCharRow(&charRowDetails);
    }

    charX += 8;
  }
}