From 17abada57e1f06222582f83846b8f9304103fd59 Mon Sep 17 00:00:00 2001
From: Duncan Frost <duncans_pumpkin@hotmail.co.uk>
Date: Wed, 3 Jun 2015 19:00:16 +0100
Subject: [PATCH] Fix invalid locations breaking viewports

Fixes #1183. Note this isn't the same fix that rct2 uses. But I feel it solves the main issue
---
 src/interface/viewport.c | 9 +++++++++
 src/world/sprite.c       | 4 ++--
 src/world/sprite.h       | 2 +-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/interface/viewport.c b/src/interface/viewport.c
index 29d450731e..8c8522754b 100644
--- a/src/interface/viewport.c
+++ b/src/interface/viewport.c
@@ -147,6 +147,15 @@ void center_2d_coordinates(int x, int y, int z, int* out_x, int* out_y, rct_view
 		break;
 	}
 
+	// If the start location was invalid
+	// propagate the invalid location to the output.
+	// This fixes a bug that caused the game to enter an infinite loop.
+	if (start_x == (sint16)0x8000){
+		*out_x = (sint16)0x8000;
+		*out_y = 0;
+		return;
+	}
+
 	*out_x = x - viewport->view_width / 2;
 	*out_y = y - viewport->view_height / 2;
 }
diff --git a/src/world/sprite.c b/src/world/sprite.c
index 1ad644cae1..067b62c13a 100644
--- a/src/world/sprite.c
+++ b/src/world/sprite.c
@@ -806,7 +806,7 @@ void sprite_misc_update_all()
  * cx: y
  * dx: z
  */
-void sprite_move(int x, int y, int z, rct_sprite* sprite){
+void sprite_move(sint16 x, sint16 y, sint16 z, rct_sprite* sprite){
 	int new_position = x;
 	if (x == (sint16)0x8000)new_position = 0x10000;
 	else{
@@ -842,7 +842,7 @@ void sprite_move(int x, int y, int z, rct_sprite* sprite){
 		sprite->unknown.z = z;
 		return;
 	}
-	int new_x = x, new_y = y, start_x = x;
+	sint16 new_x = x, new_y = y, start_x = x;
 	switch (RCT2_GLOBAL(RCT2_ADDRESS_CURRENT_ROTATION, uint32)){
 	case 0:
 		new_x = new_y - new_x;
diff --git a/src/world/sprite.h b/src/world/sprite.h
index 190c0efcb0..52d66f2d24 100644
--- a/src/world/sprite.h
+++ b/src/world/sprite.h
@@ -245,7 +245,7 @@ void reset_sprite_list();
 void reset_0x69EBE4();
 void move_sprite_to_list(rct_sprite *sprite, uint8 cl);
 void sprite_misc_update_all();
-void sprite_move(int x, int y, int z, rct_sprite* sprite);
+void sprite_move(sint16 x, sint16 y, sint16 z, rct_sprite* sprite);
 void invalidate_sprite(rct_sprite *sprite);
 void sub_6EC60B(rct_sprite* sprite);
 void sprite_remove(rct_sprite *sprite);