From e0ef6a51de8bf406c8620e2f1f78cde82673bfab Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Sat, 26 Sep 2020 21:34:18 -0700
Subject: [PATCH] GBA Video: Improve speed of window texture generation on AMD

---
 CHANGES                |  2 ++
 src/gba/renderers/gl.c | 31 +++++++++++++++----------------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/CHANGES b/CHANGES
index 9147c86d2..265b7d56a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -24,6 +24,8 @@ Other fixes:
  - mGUI: Fix closing down a game if an exit is signalled
  - mVL: Fix injecting accidentally draining non-injection buffer
  - VFS: Fix directory node listing on some filesystems
+Misc:
+ - GBA Video: Improve speed of window texture generation on AMD
 
 0.8.3: (2020-08-03)
 Emulation fixes:
diff --git a/src/gba/renderers/gl.c b/src/gba/renderers/gl.c
index 9787b77ef..7f5d96cb6 100644
--- a/src/gba/renderers/gl.c
+++ b/src/gba/renderers/gl.c
@@ -513,7 +513,7 @@ static const char* const _renderWindow =
 	"uniform ivec4 win1[160];\n"
 	"OUT(0) out ivec4 window;\n"
 
-	"void crop(vec4 windowParams, int flags, inout ivec3 windowFlags) {\n"
+	"bool crop(vec4 windowParams) {\n"
 	"	bvec4 compare = lessThan(texCoord.xxyy, windowParams);\n"
 	"	compare = equal(compare, bvec4(true, false, true, false));\n"
 	"	if (any(compare)) {\n"
@@ -521,25 +521,23 @@ static const char* const _renderWindow =
 	"		vec2 v = windowParams.zw;\n"
 	"		if (v.x > v.y) {\n"
 	"			if (compare.z && compare.w) {\n"
-	"				return;\n"
+	"				return false;\n"
 	"			}\n"
 	"		} else if (compare.z || compare.w) {\n"
-	"			return;\n"
+	"			return false;\n"
 	"		}\n"
 	"		if (h.x > h.y) {\n"
 	"			if (compare.x && compare.y) {\n"
-	"				return;\n"
+	"				return false;\n"
 	"			}\n"
 	"		} else if (compare.x || compare.y) {\n"
-	"			return;\n"
+	"			return false;\n"
 	"		}\n"
 	"	}\n"
-	"	windowFlags.x = flags;\n"
+	"	return true;\n"
 	"}\n"
 
-	"vec4 interpolate(ivec4 win[160]) {\n"
-	"	vec4 bottom = vec4(win[int(texCoord.y) - 1]);\n"
-	"	vec4 top = vec4(win[int(texCoord.y)]);\n"
+	"vec4 interpolate(vec4 top, vec4 bottom) {\n"
 	"	if (distance(top, bottom) > 40.) {\n"
 	"		return top;\n"
 	"	}\n"
@@ -551,14 +549,15 @@ static const char* const _renderWindow =
 	"	if ((dispcnt & 0xE0) == 0) {\n"
 	"		window = ivec4(dispflags, blend, 0);\n"
 	"	} else {\n"
-	"		ivec3 windowFlags = ivec3(flags.z, blend);\n"
-	"		if ((dispcnt & 0x40) != 0) { \n"
-	"			crop(interpolate(win1), flags.y, windowFlags);\n"
+	"		ivec4 windowFlags = ivec4(flags.z, blend, 0);\n"
+	"		int top = int(texCoord.y);\n"
+	"		int bottom = max(top - 1, 0);\n"
+	"		if ((dispcnt & 0x20) != 0 && crop(interpolate(vec4(win0[top]), vec4(win0[bottom])))) { \n"
+	"			windowFlags.x = flags.x;\n"
+	"		} else if ((dispcnt & 0x40) != 0 && crop(interpolate(vec4(win1[top]), vec4(win1[bottom])))) {\n"
+	"			windowFlags.x = flags.y;\n"
 	"		}\n"
-	"		if ((dispcnt & 0x20) != 0) { \n"
-	"			crop(interpolate(win0), flags.x, windowFlags);\n"
-	"		}\n"
-	"		window = ivec4(windowFlags, 0);\n"
+	"		window = windowFlags;\n"
 	"	}\n"
 	"}\n";