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

17
crates/gba-core/tests/affine_backgrounds.rs
View file

@ -1,7 +1,7 @@
use gba_core::{
io::*,
memory::{Memory, MemoryError, 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(bg: u32, size: u16, wrap: bool) -> Memory {
@ -252,17 +252,16 @@ fn transformed_backgrounds_composite_with_regular_and_affine_sprites() {
}
#[test]
fn unsupported_layers_leave_output_unchanged_and_disabled_layers_skip_validation() {
fn absent_layer_bits_are_ignored_and_disabled_layers_skip_validation() {
let mut m = setup(2, 3, false);
let mut f = Framebuffer::default();
f.clear(0x001f);
for control in [0xc01, 0xd02, 0xe02] {
// Mode 1 has no BG3 and mode 2 has no BG0 or BG1; their enable bits change nothing.
for (control, present) in [(0xc01, 0x401), (0xd02, 0xc02), (0xe02, 0xc02)] {
m.write16(DISPCNT, present).unwrap();
let expected = frame(&m);
m.write16(DISPCNT, control).unwrap();
assert_eq!(
m.render_frame(&mut f),
Err(VideoError::UnsupportedLayers(control))
);
assert!(f.pixels().iter().all(|&p| p == 0xff0000));
m.render_frame(&mut f).unwrap();
assert_eq!(f.pixels(), expected.pixels());
}
m.write16(DISPCNT, 2).unwrap();
m.render_frame(&mut f).unwrap();