# HG changeset patch
# User peter1138 <peter1138@openttd.org>
# Date 2009-11-18 23:07:29
# Node ID f35947b8cc89e0d16ed5f2c179ba2d8bce89fa54
# Parent  2cc9480a46a1c81f247e05540f81cdc86e4235b5

(svn r18177) -Fix (r18001): [SDL] Viewport could jump when mouse moved and right button pressed at the same time.

diff --git a/src/video/sdl_v.cpp b/src/video/sdl_v.cpp
--- a/src/video/sdl_v.cpp
+++ b/src/video/sdl_v.cpp
@@ -365,25 +365,23 @@ static int PollEvent()
 {
 	SDL_Event ev;
 
-	if (_cursor.fix_at != _last_fix_at) {
-		_last_fix_at = _cursor.fix_at;
-		if (_last_fix_at) {
-			/* Move to centre of window */
-			SDL_CALL SDL_WarpMouse(_screen.width / 2, _screen.height / 2);
-
-		} else {
-			/* Restore position */
-			SDL_CALL SDL_WarpMouse(_cursor.pos.x, _cursor.pos.y);
-		}
-	}
-
 	if (!SDL_CALL SDL_PollEvent(&ev)) return -2;
 
 	switch (ev.type) {
 		case SDL_MOUSEMOTION:
 			if (_cursor.fix_at) {
-				int dx = ev.motion.x - _screen.width / 2;
-				int dy = ev.motion.y - _screen.height / 2;
+				int dx;
+				int dy;
+				if (_last_fix_at) {
+					dx = ev.motion.x - _screen.width / 2;
+					dy = ev.motion.y - _screen.height / 2;
+				} else {
+					/* Mouse hasn't been warped yet, so our movement is
+					 * relative to the old position. */
+					dx = ev.motion.x - _cursor.pos.x;
+					dy = ev.motion.y - _cursor.pos.y;
+					_last_fix_at = true;
+				}
 				if (dx != 0 || dy != 0) {
 					_cursor.delta.x = dx;
 					_cursor.delta.y = dy;
@@ -434,6 +432,13 @@ static int PollEvent()
 				_right_button_down = false;
 			}
 			HandleMouseEvents();
+
+			if (_cursor.fix_at != _last_fix_at) {
+				/* Mouse fixing changed during a mouse button up event, so it
+				 * must have been released. */
+				_last_fix_at = false;
+				SDL_CALL SDL_WarpMouse(_cursor.pos.x, _cursor.pos.y);
+			}
 			break;
 
 		case SDL_ACTIVEEVENT: