diff --git a/src/interface/viewport.c b/src/interface/viewport.c
index 8903cd157c..20d19debc7 100644
--- a/src/interface/viewport.c
+++ b/src/interface/viewport.c
@@ -298,13 +298,13 @@ void sub_689174(sint16* x, sint16* y, sint16 *z, uint8 curr_rotation){
 //
 //}
 
-void sub_6E7F34(rct_window* w, rct_viewport* viewport){
-	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, 0, (int)viewport, (int)w, 0);
+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;
 
 	for (; w < RCT2_GLOBAL(RCT2_ADDRESS_NEW_WINDOW_PTR, rct_window*); w++){
-		if (!w->flags&WF_TRANSPARENT) continue;
+		if (!(w->flags & WF_TRANSPARENT)) continue;
 		if (w->viewport == viewport) continue;
 
 		if (viewport->x + viewport->width <= w->x)continue;
@@ -318,11 +318,11 @@ void sub_6E7F34(rct_window* w, rct_viewport* viewport){
 		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;
@@ -331,22 +331,22 @@ void sub_6E7F34(rct_window* w, rct_viewport* viewport){
 	}
 
 	w = orignal_w;
-	RCT2_CALLPROC_X(0x6E7FF3, 0, 0, 0, right, (int)viewport, (int)w, bottom);
+	RCT2_CALLPROC_X(0x6E7FF3, 0, 0, 0, x_diff, (int)viewport, (int)w, y_diff);
 }
 
-/* There is a bug in this. */
 void sub_6E7DE1(sint16 x, sint16 y, rct_window* w, rct_viewport* viewport){
 	//RCT2_CALLPROC_X(0x6E7DE1, x, y, 0, 0, w, viewport, 0);
 	//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 +400,8 @@ void sub_6E7DE1(sint16 x, sint16 y, rct_window* w, rct_viewport* viewport){
 		return;
 	}
 
-	//sub_6E7F34(w, viewport);
-	//RCT2_CALLPROC_X(0x6E7F34, 0, 0, 0, 0, (int)viewport, (int)w, 0);
+	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));
 }
@@ -430,8 +430,8 @@ void viewport_update_position(rct_window *window)
 		int center_x, center_y;
 		center_2d_coordinates(sprite->unknown.x, sprite->unknown.y, sprite->unknown.z, &center_x, &center_y, window->viewport);
 
-		//sub_6E7DE1(center_x, center_y, window, viewport);
-		RCT2_CALLPROC_X(0x6E7DE1, center_x, center_y, 0, 0, (int)window, (int)viewport, 0);
+		sub_6E7DE1(center_x, center_y, window, viewport);
+		//RCT2_CALLPROC_X(0x6E7DE1, center_x, center_y, 0, 0, (int)window, (int)viewport, 0);
 		return;
 	}
 
@@ -523,8 +523,8 @@ void viewport_update_position(rct_window *window)
 		y += viewport->view_y;
 	}
 
-	//sub_6E7DE1(x, y, window, viewport);
-	RCT2_CALLPROC_X(0x6E7DE1, x, y, 0, 0, (int)window, (int)viewport, 0);
+	sub_6E7DE1(x, y, window, viewport);
+	//RCT2_CALLPROC_X(0x6E7DE1, x, y, 0, 0, (int)window, (int)viewport, 0);
 }
 
 void viewport_paint(rct_viewport* viewport, rct_drawpixelinfo* dpi, int left, int top, int right, int bottom);