0xrsydn/gameboy-rust
1
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

fix(video): ignore enable bits for backgrounds a mode lacks

Browse source 
DISPCNT enable bits for BG3 in Mode 1, BG0/BG1 in Mode 2, and every background
but BG2 in Modes 3-5 failed the whole frame with UnsupportedLayers, and the
window turned that into a stopped session. Hardware has no such backgrounds and
ignores the bits, so the renderer now masks them. The error variant is removed.

Prohibited OBJ mode 3 and shape 3 stay diagnostics: their hardware output is
not established here.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
This commit is contained in:
0xrsydn 2026-10-14 08:35:32 +07:00
commit 0ef2719c6b
5 changed files with 31 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

18
crates/gba-core/tests/bitmap_modes.rs
View file

@ -1,7 +1,7 @@
use gba_core::{
io::{BG2CNT, BG2PA, BG2X, BG2Y, DISPCNT, GREENSWAP},
memory::{Memory, OAM_START as OAM, PALETTE_START as PAL, VRAM_START as VRAM},
video::{rgb555_to_rgb888, Framebuffer, VideoError, WIDTH},
video::{rgb555_to_rgb888, Framebuffer, WIDTH},
};
fn setup(mode: u16) -> Memory {
@ -423,20 +423,18 @@ fn cpu_bitmap_controls_pan_rotate_zoom_force_page_and_reset() {
}
#[test]
fn unsupported_bitmap_layers_leave_frame_unchanged() {
fn absent_bitmap_layer_bits_are_ignored() {
for mode in [4, 5] {
let mut m = setup(mode);
m.write16(VRAM + 0xa000, 0x0201).unwrap(); // Visible on the selected second page.
m.write16(DISPCNT, 0x410 | mode).unwrap();
let expected = frame(&m);
let mut f = Framebuffer::default();
f.clear(0x001f);
for extra in [0x100, 0x200, 0x800] {
let control = 0x410 | mode | extra;
m.write16(DISPCNT, control).unwrap();
assert_eq!(
m.render_frame(&mut f),
Err(VideoError::UnsupportedLayers(control))
);
m.write16(DISPCNT, 0x410 | mode | extra).unwrap();
m.render_frame(&mut f).unwrap();
assert_eq!(f.pixels(), expected.pixels());
}
assert!(f.pixels().iter().all(|&p| p == 0xff0000));
assert_eq!(m.cycles(), 0);
}
}