brightstone/Player/Display/dos.c

#include "display.h"
#include <stdint.h>
#include <string.h>

#define WIDTH 640
#define HEIGHT 480
#define MODE_VGA_320_200_8 0x13
#define MODE_VESA_640_480_8 0x101

/*
  TODO: https://github.com/depp/elf2dos/blob/master/elf/elf.go
        https://www.edm2.com/index.php/LX_-_Linear_eXecutable_Module_Format_Description
  Do not use anything but Clang in the end.
  */

// 8-color VGA palette gradient, lighter shades of lavender to pink
#define COLOR_OFFSET 0x50
#define COLOR_NUM 8
#define COLOR_STEP (HEIGHT / COLOR_NUM)

// /* https://wiki.osdev.org/VESA_Video_Modes */
// _Packed struct VbeInfoBlock {
//   char VbeSignature[4];     // == "VESA"
//   uint16_t VbeVersion;      // == 0x0300 for VBE 3.0
//   uint16_t OemStringPtr[2]; // isa vbeFarPtr
//   uint8_t Capabilities[4];
//   uint16_t VideoModePtr[2]; // isa vbeFarPtr
//   uint16_t TotalMemory;     // as # of 64KB blocks
//   uint8_t Reserved[492];
// };

// _Packed struct ModeInfoBlock {
//   uint16_t
//       attributes; // deprecated, only bit 7 should be of interest to you, and
//       it
//                   // indicates the mode supports a linear frame buffer.
//   uint8_t window_a;     // deprecated
//   uint8_t window_b;     // deprecated
//   uint16_t granularity; // deprecated; used while calculating bank numbers
//   uint16_t window_size;
//   uint16_t segment_a;
//   uint16_t segment_b;
//   uint32_t win_func_ptr; // deprecated; used to switch banks from protected
//   mode
//                          // without returning to real mode
//   uint16_t pitch;        // number of bytes per horizontal line
//   uint16_t width;        // width in pixels
//   uint16_t height;       // height in pixels
//   uint8_t w_char;        // unused...
//   uint8_t y_char;        // ...
//   uint8_t planes;
//   uint8_t bpp;   // bits per pixel in this mode
//   uint8_t banks; // deprecated; total number of banks in this mode
//   uint8_t memory_model;
//   uint8_t bank_size; // deprecated; size of a bank, almost always 64 KB but
//   may
//                      // be 16 KB...
//   uint8_t image_pages;
//   uint8_t reserved0;

//   uint8_t red_mask;
//   uint8_t red_position;
//   uint8_t green_mask;
//   uint8_t green_position;
//   uint8_t blue_mask;
//   uint8_t blue_position;
//   uint8_t reserved_mask;
//   uint8_t reserved_position;
//   uint8_t direct_color_attributes;

//   uint32_t framebuffer; // physical address of the linear frame buffer; write
//                         // here to draw to the screen
//   uint32_t off_screen_mem_off;
//   uint16_t off_screen_mem_size; // size of memory in the framebuffer but not
//                                 // being displayed on the screen
//   uint8_t reserved1[206];
// };

// static char get_video_mode();
// #pragma aux get_video_mode = "mov ah, 0x0f" \
//                              "int 0x10" value[al] modify[ah];

// static void set_video_mode(unsigned char);
// #pragma aux set_video_mode = "mov ah, 0x00" \
//                              "int 0x10" parm[al] modify[ah];

// static void set_vesa_video_mode(unsigned short);
// #pragma aux set_vesa_video_mode = "mov ax, 0x4f02" \
//                                   "int 0x10" parm[bx] modify[ah];

// static void wait_for_key();
// #pragma aux wait_for_key = "mov ah, 0x00" \
//                            "int 0x16" modify[ah];

// static short get_vesa_controller_info(struct VbeInfoBlock *);
// #pragma aux get_vesa_controller_info = "mov ax, 0x4f00" \
//                                        "int 0x10" parm[es di] value[ax];

// static short get_vesa_mode_info(uint16_t mode, struct ModeInfoBlock *);
// #pragma aux get_vesa_mode_info = "mov ax, 0x4F01" \
//                                  "int 0x10" parm[cx][es di] value[ax];

// /* https://wiki.osdev.org/User:Omarrx024/VESA_Tutorial*/
// static char *find_display_memory(void) {
//   struct VbeInfoBlock *ctrl = (struct VbeInfoBlock *)0x2000;
//   struct ModeInfoBlock *inf = (struct ModeInfoBlock *)0x3000;
//   uint16_t *modes;
//   int i;

//   strncpy(ctrl->VbeSignature, "VBE2", 4);
//   if (get_vesa_controller_info(ctrl) != 0x004F)
//     return NULL;

//   modes = (uint16_t *)(ctrl->VideoModePtr);
//   for (i = 0; modes[i] != 0xFFFF; ++i) {
//     if (get_vesa_mode_info(modes[i], inf) != 0x004F)
//       continue;

//     // Check if this is a graphics mode with linear frame buffer support
//     if ((inf->attributes & 0x80) != 0x80)
//       continue;

//     // Check if this is a packed pixel or direct color mode
//     if (inf->memory_model != 4 && inf->memory_model != 6)
//       continue;

//     // Check if this is exactly the mode we're looking for
//     if (WIDTH == inf->width && HEIGHT == inf->height && 256 == inf->pitch)
//       return (char *)inf->framebuffer;
//   }

//   return NULL;
// }

// extern int plr_display_dos_main(int argc, char *argv[]) {
extern int plr_display_dos_main(void) {
  char *buf = (char *)0xA0000; // VGA memory address
  int x, y;

  // unsigned char saved_mode = get_video_mode(); // Save original mode
  // set_vesa_video_mode(MODE_VESA_640_480_8);    // Set our VGA mode

  // buf = find_display_memory();

  /* TODO: Fetch info about the mode, to know the availability */
  /*       as well as base address in memory */
  /*       https://wiki.osdev.org/VESA_Video_Modes */

  // Now draw. We draw pixel-by-pixel by directly setting the video memory
  // like it was an array. We step the color every 25 pixels so that we have 8
  // bands of even height.
  // for (y = 0; y < HEIGHT; y++) {
  //   for (x = 0; x < WIDTH; x++) {
  //     buf[y * WIDTH + x] = COLOR_OFFSET + y / COLOR_STEP;
  //   }
  // }

  // wait_for_key();
  // set_video_mode(saved_mode); // Restore original mode

  while (1) {
    for (y = 0; y < HEIGHT; y++) {
      for (x = 0; x < WIDTH; x++) {
        buf[y * WIDTH + x] = COLOR_OFFSET + y / COLOR_STEP;
      }
    }
  }

  return 0;
}