From 60f722b0a9bca552475e2d721c23287e5457994a Mon Sep 17 00:00:00 2001
From: scrawl <scrawl@baseoftrash.de>
Date: Sat, 24 Jan 2015 17:28:05 +0100
Subject: [PATCH] Treat the first mouse motion event as non-relative

This fixes incorrect starting camera orientation when using --skip-menu or --load-savegame.
---
 extern/sdl4ogre/sdlinputwrapper.cpp | 10 +++++++++-
 extern/sdl4ogre/sdlinputwrapper.hpp |  2 ++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/extern/sdl4ogre/sdlinputwrapper.cpp b/extern/sdl4ogre/sdlinputwrapper.cpp
index 0c29be939..a6c7d3e5c 100644
--- a/extern/sdl4ogre/sdlinputwrapper.cpp
+++ b/extern/sdl4ogre/sdlinputwrapper.cpp
@@ -30,7 +30,8 @@ namespace SFO
         mWantMouseVisible(false),
         mAllowGrab(grab),
         mWarpX(0),
-        mWarpY(0)
+        mWarpY(0),
+        mFirstMouseMove(true)
     {
         _setupOISKeys();
     }
@@ -316,6 +317,13 @@ namespace SFO
             pack_evt.y = mMouseY = evt.motion.y;
             pack_evt.xrel = evt.motion.xrel;
             pack_evt.yrel = evt.motion.yrel;
+            if (mFirstMouseMove)
+            {
+                // first event should be treated as non-relative, since there's no point of reference
+                // SDL then (incorrectly) uses (0,0) as point of reference, on Linux at least...
+                pack_evt.xrel = pack_evt.yrel = 0;
+                mFirstMouseMove = false;
+            }
         }
         else if(evt.type == SDL_MOUSEWHEEL)
         {
diff --git a/extern/sdl4ogre/sdlinputwrapper.hpp b/extern/sdl4ogre/sdlinputwrapper.hpp
index 339e99de1..af16ab68d 100644
--- a/extern/sdl4ogre/sdlinputwrapper.hpp
+++ b/extern/sdl4ogre/sdlinputwrapper.hpp
@@ -71,6 +71,8 @@ namespace SFO
         bool mGrabPointer;
         bool mMouseRelative;
 
+        bool mFirstMouseMove;
+
         Sint32 mMouseZ;
         Sint32 mMouseX;
         Sint32 mMouseY;