Display and the framebuffer

The chain

multiboot2 framebuffer tag (geometry + pitch + masks) -> screen_fb.c (the framebuffer primitives) -> screen_font.c + screen_font_data.c (the 8x16 engine) -> screen_console.c (the console grid) -> the shell line editor and the TUI.

The L1 surface

l1_ext_fb_get_info() (geometry for module renderers) and the font-engine protocol l1_ext_register_font_engine (the Chinese 16x16 font registers through it) + the console hook (l1_ext_set_console_hook) that lets a module intercept output.

Commands and tests

tui-hw (render diagnostics), font/font-test (engines), the TUI suite tui-test. In QEMU the default -vga std gives 800x600x32 - the boot log prints the exact geometry and masks it found.