From c4cfff45819d261ef6c158dabff9e4c2082fb3c1 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Sun, 25 Sep 2016 19:18:46 -0700
Subject: [PATCH] GB Video: Improved video timings

---
 CHANGES        |  1 +
 src/gb/video.c | 10 ++++++----
 src/gb/video.h |  6 +++---
 3 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/CHANGES b/CHANGES
index c89446be9..960bed6df 100644
--- a/CHANGES
+++ b/CHANGES
@@ -21,6 +21,7 @@ Misc:
  - All: Only update version info if needed
  - FFmpeg: Encoding cleanup
  - GB Memory: Initialize RAM pattern for GBC
+ - GB Video: Improved video timings
 
 0.5.0: (2016-09-19)
 Features:
diff --git a/src/gb/video.c b/src/gb/video.c
index a5d154476..21c887086 100644
--- a/src/gb/video.c
+++ b/src/gb/video.c
@@ -110,7 +110,7 @@ int32_t GBVideoProcessEvents(struct GBVideo* video, int32_t cycles) {
 				video->p->memory.io[REG_LY] = video->ly;
 				video->stat = GBRegisterSTATSetLYC(video->stat, lyc == video->ly);
 				if (video->ly < GB_VIDEO_VERTICAL_PIXELS) {
-					video->nextMode = GB_VIDEO_MODE_2_LENGTH;
+					video->nextMode = GB_VIDEO_MODE_2_LENGTH + (video->p->memory.io[REG_SCX] & 7);
 					video->mode = 2;
 					if (!GBRegisterSTATIsHblankIRQ(video->stat) && GBRegisterSTATIsOAMIRQ(video->stat)) {
 						video->p->memory.io[REG_IF] |= (1 << GB_IRQ_LCDSTAT);
@@ -142,7 +142,8 @@ int32_t GBVideoProcessEvents(struct GBVideo* video, int32_t cycles) {
 				if (video->ly == GB_VIDEO_VERTICAL_TOTAL_PIXELS + 1) {
 					video->ly = 0;
 					video->p->memory.io[REG_LY] = video->ly;
-					video->nextMode = GB_VIDEO_MODE_2_LENGTH;
+					// TODO: Cache SCX & 7 in case it changes during mode 2
+					video->nextMode = GB_VIDEO_MODE_2_LENGTH + (video->p->memory.io[REG_SCX] & 7);
 					video->mode = 2;
 					if (GBRegisterSTATIsOAMIRQ(video->stat)) {
 						video->p->memory.io[REG_IF] |= (1 << GB_IRQ_LCDSTAT);
@@ -175,11 +176,12 @@ int32_t GBVideoProcessEvents(struct GBVideo* video, int32_t cycles) {
 				video->dotCounter = 0;
 				video->nextEvent = GB_VIDEO_HORIZONTAL_LENGTH;
 				video->x = 0;
-				video->nextMode = GB_VIDEO_MODE_3_LENGTH_BASE + video->objMax * 12;
+				// TODO: Estimate sprite timings better
+				video->nextMode = GB_VIDEO_MODE_3_LENGTH_BASE + video->objMax * 11 - (video->p->memory.io[REG_SCX] & 7);
 				video->mode = 3;
 				break;
 			case 3:
-				video->nextMode = GB_VIDEO_MODE_0_LENGTH_BASE - video->objMax * 12;
+				video->nextMode = GB_VIDEO_MODE_0_LENGTH_BASE - video->objMax * 11;
 				video->mode = 0;
 				if (GBRegisterSTATIsHblankIRQ(video->stat)) {
 					video->p->memory.io[REG_IF] |= (1 << GB_IRQ_LCDSTAT);
diff --git a/src/gb/video.h b/src/gb/video.h
index 05f84c913..1f81d6ee4 100644
--- a/src/gb/video.h
+++ b/src/gb/video.h
@@ -19,9 +19,9 @@ enum {
 	GB_VIDEO_VERTICAL_TOTAL_PIXELS = GB_VIDEO_VERTICAL_PIXELS + GB_VIDEO_VBLANK_PIXELS,
 
 	// TODO: Figure out exact lengths
-	GB_VIDEO_MODE_2_LENGTH = 78,
-	GB_VIDEO_MODE_3_LENGTH_BASE = 160,
-	GB_VIDEO_MODE_0_LENGTH_BASE = 218,
+	GB_VIDEO_MODE_2_LENGTH = 83,
+	GB_VIDEO_MODE_3_LENGTH_BASE = 158,
+	GB_VIDEO_MODE_0_LENGTH_BASE = 215,
 
 	GB_VIDEO_HORIZONTAL_LENGTH = GB_VIDEO_MODE_0_LENGTH_BASE + GB_VIDEO_MODE_2_LENGTH + GB_VIDEO_MODE_3_LENGTH_BASE,