#include <stddef.h>
#include <stdio.h>
#include <conio.h>
#include <dos.h>
#include <i86.h>
#include <memory.h>
#include <sys/types.h>

/*

Set up a 640x480x256 Super VGA screen and load a bitmap image into it.
Wait 10 seconds, then exit the program.

Since this is going through DOS/4GW, we need to use the DOS Protected
Mode Interface (DPMI) to work with x86 Real Mode RAM so the VESA
interrupt functions have a place to accept and dump data.

There were a lot of scattered examples as to how to get SVGA going, but:

* most were written in assembler and, while I can read assembler, I don't
  prefer to, especially in the early learning stages of a bunch of new concepts
* very few of them covered the whole pipeline of query display, then
  set it up, then do something real with it

So here's this one. Enjoy.

John

*/

// built from a combination of:
//
// * http://www.pennelynn.com/Documents/CUJ/HTML/14.08/KREHBIEL/KREHL1.HTM
// * https://forum.osdev.org/viewtopic.php?f=2&t=30186
// * https://github.com/joncampbell123/doslib/blob/master/hw/vesa/vesa.c
// * https://stackoverflow.com/questions/3318410/pragma-pack-effect
// * https://www.delorie.com/djgpp/doc/dpmi/ch4.4.html
// * https://delorie.com/djgpp/doc/dpmi/api/310100.html
// * http://www.monstersoft.com/tutorial1/VESA_intro.html
// * http://www.delorie.com/djgpp/doc/ug/graphics/vesa.html.en
// * https://lhlaurini.xyz/VESA_Video_Modes
// * https://stackoverflow.com/questions/58328264/retrieve-list-of-vesa-video-modes-from-int-10h-ax-4f00h
// * https://github.com/execomrt/vesa2/blob/main/vbelib/vbecore.c#L262
// * https://pdos.csail.mit.edu/6.828/2004/readings/hardware/vbe3.pdf

#include "vesa.h"
#include "bmp.h"
#include "dpmi.h"

/**

If you want to enumerate all the possible modes to inspect, you would need
something like this to turn the segment:offset data into array elements you can
address in 32-bit DOS.

uint16_t *modePtr;

modePtr = (uint16_t*)((vbeInfo.VideoModeSegment << 4) + vbeInfo.VideoModeOffset);
for (i = 0; i < 4; ++i) {
  printf("Available mode %d: 0x%x\n", i, modePtr[i]);
}

*/

int main(void) {
  int x, y;
  FILE *bmp;
  struct BMPImage bmpImage;
  struct VESAColor colors[256];
  struct VbeInfo vbeInfo;
  struct VbeModeInfo vbeModeInfo;

  setupVESAHandling();

  vbeGetVBEInfo(&vbeInfo);
  printf("VBE Version: 0x%x\n", vbeInfo.VbeVersion);

  bmp = fopen("chkn640.bmp", "rb");
  readBMPHeader(bmp, &bmpImage);
  bmp256ColorPaletteToVESAColorPalette(&bmpImage, colors);

  // we could enumerate all the modes, but in DOSBox-X's default S3 VGA card,
  // 0x101 is 640x480x256, and that's where I'm running this. it's more correct
  // to select the mode based on examining capabilities for all available
  // modes, but...eh.
  startSVGAMode(0x101, &vbeModeInfo);
  setVESAColorPalette(colors);

  for (y = 0; y < vbeModeInfo.YResolution; ++y) {
    for (x = 0; x < vbeModeInfo.XResolution; ++x) {
      setPixel(x, vbeModeInfo.YResolution - y, fgetc(bmp));
    }
  }

  fclose(bmp);

  delay(10000);

  teardownVESAHandling();

  return 0;
}