From a159e377932c8def76c2d77495b94f70083defcd Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Fri, 21 Apr 2017 03:15:39 -0700
Subject: [PATCH] GBA Video: Don't update background scanline params in mode 0
 (fixes #377)

---
 CHANGES                            |  1 +
 src/gba/renderers/video-software.c | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/CHANGES b/CHANGES
index 66c37278a..a8a1106c3 100644
--- a/CHANGES
+++ b/CHANGES
@@ -40,6 +40,7 @@ Bugfixes:
  - Qt: Fix crash when changing audio settings after a game is closed
  - GBA BIOS: Fix ArcTan sign in HLE BIOS
  - GBA BIOS: Fix ArcTan2 sign in HLE BIOS (fixes mgba.io/i/689)
+ - GBA Video: Don't update background scanline params in mode 0 (fixes mgba.io/i/377)
 Misc:
  - SDL: Remove scancode key input
  - GBA Video: Clean up unused timers
diff --git a/src/gba/renderers/video-software.c b/src/gba/renderers/video-software.c
index 2c20a475a..70dac8811 100644
--- a/src/gba/renderers/video-software.c
+++ b/src/gba/renderers/video-software.c
@@ -807,10 +807,12 @@ static void _drawScanline(struct GBAVideoSoftwareRenderer* renderer, int y) {
 			}
 		}
 	}
-	renderer->bg[2].sx += renderer->bg[2].dmx;
-	renderer->bg[2].sy += renderer->bg[2].dmy;
-	renderer->bg[3].sx += renderer->bg[3].dmx;
-	renderer->bg[3].sy += renderer->bg[3].dmy;
+	if (GBARegisterDISPCNTGetMode(renderer->dispcnt) != 0) {
+		renderer->bg[2].sx += renderer->bg[2].dmx;
+		renderer->bg[2].sy += renderer->bg[2].dmy;
+		renderer->bg[3].sx += renderer->bg[3].dmx;
+		renderer->bg[3].sy += renderer->bg[3].dmy;
+	}
 }
 
 static void _updatePalettes(struct GBAVideoSoftwareRenderer* renderer) {