Skip to content

Graphics System

Jump to bottom
NtinosTheGamer2324 edited this page Feb 11, 2026 · 2 revisions

Graphics System

ModuOS supports both legacy VGA text mode and pixel framebuffer graphics.

The modern graphics path is based on a kernel framebuffer abstraction plus SQRM GPU modules (loadable drivers) that provide a framebuffer to the rest of the system.

Graphics Overview

At a high level:

  • Early boot / fallback: VGA text mode (0xB8000)
  • Graphics mode: a linear framebuffer (LFB) provided by a GPU driver
    • The framebuffer is consumed by the kernel graphics subsystem (2D drawing, console, UI)

VGA Text Mode

Resolution: 80 columns × 25 rows Character cells: 16 colors foreground + 8 colors background

VGA Driver

File: src/drivers/graphics/VGA.c

VGA Memory

Memory-mapped: 0xB8000

Character format (16-bit):

Bits 0-7:   ASCII character
Bits 8-11:  Foreground color
Bits 12-14: Background color
Bit 15:     Blink attribute

Color Codes

Code Color
0x0 Black
0x1 Blue
0x2 Green
0x3 Cyan
0x4 Red
0x5 Magenta
0x6 Brown
0x7 Light Gray
0x8 Dark Gray
0x9 Light Blue
0xA Light Green
0xB Light Cyan
0xC Light Red
0xD Light Magenta
0xE Yellow
0xF White

VGA API

// Initialize VGA
void VGA_init(void);

// Clear screen
void VGA_clear_screen(void);

// Print string
void VGA_print(const char *str);

// Print with color
void VGA_print_color(const char *str, uint8_t color);

// Set cursor position
void VGA_set_cursor(int x, int y);

// Get cursor position
void VGA_get_cursor(int *x, int *y);

Framebuffer Graphics (SQRM GPU Modules)

ModuOS uses SQRM modules to provide graphics framebuffers at runtime.

In-tree GPU SQRM modules

  • QXL GPU (virtual GPU in QEMU/Spice)
    • Source: modules/QXL/src/qxl_gpu_sqrm.c
  • VMware SVGA / VMSVGA (virtual GPU in VMware / some QEMU configs)
    • Source: modules/VMSVGA/vmsvga_gpu_sqrm.c
  • MD VGA Compatible Display Driver (fallback VGA graphics; typically Mode 13h 320×200×8)
    • Source: modules/md_vga_compatible_display_sqrm.c

How GPU modules are chosen

GPU modules may defer to a more specific driver when they detect a known adapter. For example, the MD VGA compatible driver will defer when it detects QXL or VMSVGA so that those drivers can claim the device.

What a GPU module provides

A GPU module registers a framebuffer descriptor with the kernel (width/height/pitch/bpp/address). Higher-level components (framebuffer console, 2D UI, apps) render to that framebuffer.

VBE / VESA BIOS Extensions

VBE can be used as a generic firmware-provided way to set up a linear framebuffer, but it is not the primary graphics driver path in ModuOS now that SQRM GPU drivers exist.

If/when a VBE-based driver exists, it should likely live as an SQRM GPU module that exposes the VBE linear framebuffer through the same framebuffer interface.

Next Steps

Clone this wiki locally