From 84bddfad69bb0760d2c5734ac6a74c17f56da87b Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Mon, 20 Jan 2020 18:09:26 -0800
Subject: [PATCH] GBA Video: Fix mosaic in modes 1-5 in OpenGL (fixes #1620)

---
 CHANGES                |  1 +
 src/gba/renderers/gl.c | 12 ++++++------
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/CHANGES b/CHANGES
index 396c882a5..04108c128 100644
--- a/CHANGES
+++ b/CHANGES
@@ -102,6 +102,7 @@ Other fixes:
  - Core: Fix uninitialized memory issues with graphics caches
  - Core: Return null for out of bounds cached tile VRAM querying
  - GBA Video: Fix OpenGL fragment data binding
+ - GBA Video: Fix mosaic in modes 1-5 in OpenGL (fixes mgba.io/i/1620)
  - Debugger: Fix tracing skipping instructions (fixes mgba.io/i/1614)
  - OpenGL: Only invalidate texture if dimensions change (fixes mgba.io/i/1612)
  - Qt: Fix fast forward mute being reset (fixes mgba.io/i/1574)
diff --git a/src/gba/renderers/gl.c b/src/gba/renderers/gl.c
index 5b73f7c2c..3c433e81f 100644
--- a/src/gba/renderers/gl.c
+++ b/src/gba/renderers/gl.c
@@ -268,10 +268,10 @@ static const char* const _renderMode2 =
 	"	ivec2 offset[4];\n"
 	"	vec2 incoord = texCoord;\n"
 	"	if (mosaic.x > 1) {\n"
-	"		incoord.x = float(int(incoord.x) % mosaic.x);\n"
+	"		incoord.x = floor(incoord.x - float(int(incoord.x) % mosaic.x));\n"
 	"	}\n"
 	"	if (mosaic.y > 1) {\n"
-	"		incoord.y = float(int(incoord.y) % mosaic.y);\n"
+	"		incoord.y = floor(incoord.y - float(int(incoord.y) % mosaic.y));\n"
 	"	}\n"
 	"	loadAffine(int(incoord.y), mat, offset);\n"
 	"	float y = fract(incoord.y);\n"
@@ -321,10 +321,10 @@ static const char* const _renderMode35 =
 	"	ivec2 offset[4];\n"
 	"	vec2 incoord = texCoord;\n"
 	"	if (mosaic.x > 1) {\n"
-	"		incoord.x = float(int(incoord.x) % mosaic.x);\n"
+	"		incoord.x = floor(incoord.x - float(int(incoord.x) % mosaic.x));\n"
 	"	}\n"
 	"	if (mosaic.y > 1) {\n"
-	"		incoord.y = float(int(incoord.y) % mosaic.y);\n"
+	"		incoord.y = floor(incoord.y - float(int(incoord.y) % mosaic.y));\n"
 	"	}\n"
 	"	loadAffine(int(incoord.y), mat, offset);\n"
 	"	float y = fract(incoord.y);\n"
@@ -386,10 +386,10 @@ static const char* const _renderMode4 =
 	"	ivec2 offset[4];\n"
 	"	vec2 incoord = texCoord;\n"
 	"	if (mosaic.x > 1) {\n"
-	"		incoord.x = float(int(incoord.x) % mosaic.x);\n"
+	"		incoord.x = floor(incoord.x - float(int(incoord.x) % mosaic.x));\n"
 	"	}\n"
 	"	if (mosaic.y > 1) {\n"
-	"		incoord.y = float(int(incoord.y) % mosaic.y);\n"
+	"		incoord.y = floor(incoord.y - float(int(incoord.y) % mosaic.y));\n"
 	"	}\n"
 	"	loadAffine(int(incoord.y), mat, offset);\n"
 	"	float y = fract(incoord.y);\n"