diff --git a/src/interface/viewport.c b/src/interface/viewport.c
index 593c6d4d52..0ab7e68bcf 100644
--- a/src/interface/viewport.c
+++ b/src/interface/viewport.c
@@ -298,8 +298,8 @@ void sub_689174(sint16* x, sint16* y, sint16 *z, uint8 curr_rotation){
 //
 //}
 
-void sub_6E7F34(sint16 previous_x, sint16 previous_y, rct_window* w, rct_viewport* viewport){
-	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, previous_x, (int)viewport, (int)w, previous_y);
+void sub_6E7F34(rct_window* w, rct_viewport* viewport, sint16 x_diff, sint16 y_diff){
+	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, x_diff, (int)viewport, (int)w, y_diff);
 	rct_window* orignal_w = w;
 	int left = 0, right = 0, top = 0, bottom = 0;
 
@@ -318,11 +318,11 @@ void sub_6E7F34(sint16 previous_x, sint16 previous_y, rct_window* w, rct_viewpor
 		top = w->y;
 		bottom = w->y + w->height;
 
-		if (left >= viewport->x)left = viewport->x;
-		if (right >= viewport->x + viewport->width) right = viewport->x + viewport->width;
+		if (left < viewport->x)left = viewport->x;
+		if (right > viewport->x + viewport->width) right = viewport->x + viewport->width;
 
-		if (top >= viewport->y)top = viewport->y;
-		if (bottom >= viewport->y + viewport->height) bottom = viewport->y + viewport->height;
+		if (top < viewport->y)top = viewport->y;
+		if (bottom > viewport->y + viewport->height) bottom = viewport->y + viewport->height;
 
 		if (left >= right) continue;
 		if (top >= bottom) continue;
@@ -331,7 +331,7 @@ void sub_6E7F34(sint16 previous_x, sint16 previous_y, rct_window* w, rct_viewpor
 	}
 
 	w = orignal_w;
-	RCT2_CALLPROC_X(0x6E7FF3, 0, 0, 0, previous_x, (int)viewport, (int)w, previous_y);
+	RCT2_CALLPROC_X(0x6E7FF3, 0, 0, 0, x_diff, (int)viewport, (int)w, y_diff);
 }
 
 /* There is a bug in this. */
@@ -340,13 +340,14 @@ void sub_6E7DE1(sint16 x, sint16 y, rct_window* w, rct_viewport* viewport){
 	//return;
 	uint8 zoom = (1 << viewport->zoom);
 
-	sint16 previous_x = viewport->view_x / zoom;
-	sint16 previous_y = viewport->view_y / zoom;
+	sint16 x_diff = (viewport->view_x - x) / zoom;
+	sint16 y_diff = (viewport->view_y - y) / zoom;
 
 	viewport->view_x = x;
 	viewport->view_y = y;
 
-	if (((x / zoom) == previous_x) && ((y / zoom) == previous_y)) return;
+	// If no change in viewing area
+	if ((!x_diff) && (!y_diff))return;
 
 	if (w->flags & WF_7){
 		int left = max(viewport->x, 0);
@@ -400,8 +401,8 @@ void sub_6E7DE1(sint16 x, sint16 y, rct_window* w, rct_viewport* viewport){
 		return;
 	}
 
-	sub_6E7F34(previous_x, previous_y, w, viewport);
-	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, previous_x, (int)viewport, (int)w, previous_y);
+	sub_6E7F34(w, viewport, x_diff, y_diff);
+	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, x_diff, (int)viewport, (int)w, y_diff);
 
 	memcpy(viewport, &view_copy, sizeof(rct_viewport));
 }