things!
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veclavtlica
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#include "display.h"
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#include <stdint.h>
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#include <string.h>
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#define WIDTH 640
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#define HEIGHT 480
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#define MODE_VGA_320_200_8 0x13
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#define MODE_VESA_640_480_8 0x101
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// 8-color VGA palette gradient, lighter shades of lavender to pink
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#define COLOR_OFFSET 0x50
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#define COLOR_NUM 8
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#define COLOR_STEP (HEIGHT / COLOR_NUM)
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/* https://wiki.osdev.org/VESA_Video_Modes */
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_Packed struct VbeInfoBlock {
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char VbeSignature[4]; // == "VESA"
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uint16_t VbeVersion; // == 0x0300 for VBE 3.0
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uint16_t OemStringPtr[2]; // isa vbeFarPtr
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uint8_t Capabilities[4];
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uint16_t VideoModePtr[2]; // isa vbeFarPtr
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uint16_t TotalMemory; // as # of 64KB blocks
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uint8_t Reserved[492];
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};
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_Packed struct ModeInfoBlock {
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uint16_t
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attributes; // deprecated, only bit 7 should be of interest to you, and it
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// indicates the mode supports a linear frame buffer.
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uint8_t window_a; // deprecated
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uint8_t window_b; // deprecated
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uint16_t granularity; // deprecated; used while calculating bank numbers
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uint16_t window_size;
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uint16_t segment_a;
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uint16_t segment_b;
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uint32_t win_func_ptr; // deprecated; used to switch banks from protected mode
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// without returning to real mode
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uint16_t pitch; // number of bytes per horizontal line
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uint16_t width; // width in pixels
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uint16_t height; // height in pixels
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uint8_t w_char; // unused...
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uint8_t y_char; // ...
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uint8_t planes;
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uint8_t bpp; // bits per pixel in this mode
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uint8_t banks; // deprecated; total number of banks in this mode
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uint8_t memory_model;
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uint8_t bank_size; // deprecated; size of a bank, almost always 64 KB but may
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// be 16 KB...
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uint8_t image_pages;
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uint8_t reserved0;
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uint8_t red_mask;
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uint8_t red_position;
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uint8_t green_mask;
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uint8_t green_position;
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uint8_t blue_mask;
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uint8_t blue_position;
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uint8_t reserved_mask;
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uint8_t reserved_position;
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uint8_t direct_color_attributes;
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uint32_t framebuffer; // physical address of the linear frame buffer; write
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// here to draw to the screen
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uint32_t off_screen_mem_off;
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uint16_t off_screen_mem_size; // size of memory in the framebuffer but not
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// being displayed on the screen
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uint8_t reserved1[206];
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};
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static char get_video_mode();
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#pragma aux get_video_mode = "mov ah, 0x0f" \
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"int 0x10" value[al] modify[ah];
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static void set_video_mode(unsigned char);
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#pragma aux set_video_mode = "mov ah, 0x00" \
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"int 0x10" parm[al] modify[ah];
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static void set_vesa_video_mode(unsigned short);
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#pragma aux set_vesa_video_mode = "mov ax, 0x4f02" \
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"int 0x10" parm[bx] modify[ah];
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static void wait_for_key();
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#pragma aux wait_for_key = "mov ah, 0x00" \
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"int 0x16" modify[ah];
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static short get_vesa_controller_info(struct VbeInfoBlock *);
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#pragma aux get_vesa_controller_info = "mov ax, 0x4f00" \
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"int 0x10" parm[es di] value[ax];
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static short get_vesa_mode_info(uint16_t mode, struct ModeInfoBlock *);
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#pragma aux get_vesa_mode_info = "mov ax, 0x4F01" \
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"int 0x10" parm[cx][es di] value[ax];
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/* https://wiki.osdev.org/User:Omarrx024/VESA_Tutorial*/
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static char *find_display_memory(void) {
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struct VbeInfoBlock *ctrl = (struct VbeInfoBlock *)0x2000;
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struct ModeInfoBlock *inf = (struct ModeInfoBlock *)0x3000;
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uint16_t *modes;
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int i;
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strncpy(ctrl->VbeSignature, "VBE2", 4);
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if (get_vesa_controller_info(ctrl) != 0x004F)
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return NULL;
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modes = (uint16_t *)(ctrl->VideoModePtr);
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for (i = 0; modes[i] != 0xFFFF; ++i) {
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if (get_vesa_mode_info(modes[i], inf) != 0x004F)
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continue;
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// Check if this is a graphics mode with linear frame buffer support
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if ((inf->attributes & 0x80) != 0x80)
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continue;
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// Check if this is a packed pixel or direct color mode
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if (inf->memory_model != 4 && inf->memory_model != 6)
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continue;
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// Check if this is exactly the mode we're looking for
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if (WIDTH == inf->width && HEIGHT == inf->height && 256 == inf->pitch)
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return (char *)inf->framebuffer;
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}
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return NULL;
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}
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extern int plr_display_dos_main(int argc, char *argv[]) {
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char far *buf = (char far *)0xA0000; // VGA memory address
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int x, y;
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unsigned char saved_mode = get_video_mode(); // Save original mode
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set_vesa_video_mode(MODE_VESA_640_480_8); // Set our VGA mode
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buf = find_display_memory();
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/* TODO: Fetch info about the mode, to know the availability */
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/* as well as base address in memory */
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/* https://wiki.osdev.org/VESA_Video_Modes */
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// Now draw. We draw pixel-by-pixel by directly setting the video memory like
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// it was an array. We step the color every 25 pixels so that we have 8 bands
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// of even height.
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for (y = 0; y < HEIGHT; y++) {
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for (x = 0; x < WIDTH; x++) {
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buf[y * WIDTH + x] = COLOR_OFFSET + y / COLOR_STEP;
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}
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}
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wait_for_key();
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set_video_mode(saved_mode); // Restore original mode
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return 0;
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}
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