From 1a2db6c030038302bd9b2fc8a3e78c9bc3b16c82 Mon Sep 17 00:00:00 2001
From: "J?rgen P. Tjern?" <jorgen@valvesoftware.com>
Date: Wed, 24 Apr 2013 12:20:51 -0700
Subject: [PATCH] Move cursor into window when enabling relative mode or
 gaining focus in relative mode.

This prevents wonky behavior where the clicks won't go to the window
because the cursor was outside it when we enabled relative mode.
---
 src/events/SDL_mouse.c | 14 ++++++++++++--
 src/video/SDL_video.c  | 14 ++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/events/SDL_mouse.c b/src/events/SDL_mouse.c
index 89ac786d2..ede6a6c46 100644
--- a/src/events/SDL_mouse.c
+++ b/src/events/SDL_mouse.c
@@ -415,6 +415,8 @@ int
 SDL_SetRelativeMouseMode(SDL_bool enabled)
 {
     SDL_Mouse *mouse = SDL_GetMouse();
+    SDL_Window *focusWindow = SDL_GetKeyboardFocus();
+    int original_x = mouse->x, original_y = mouse->y;
 
     if (enabled == mouse->relative_mode) {
         return 0;
@@ -424,6 +426,14 @@ SDL_SetRelativeMouseMode(SDL_bool enabled)
         return SDL_Unsupported();
     }
 
+    if (enabled && focusWindow) {
+        /* Center it in the focused window to prevent clicks from going through
+         * to background windows.
+         */
+        SDL_SetMouseFocus(focusWindow);
+        SDL_WarpMouseInWindow(focusWindow, focusWindow->w/2, focusWindow->h/2);
+    }
+
     if (mouse->SetRelativeMouseMode(enabled) < 0) {
         return -1;
     }
@@ -433,8 +443,8 @@ SDL_SetRelativeMouseMode(SDL_bool enabled)
 
     if (enabled) {
         /* Save the expected mouse position */
-        mouse->original_x = mouse->x;
-        mouse->original_y = mouse->y;
+        mouse->original_x = original_x;
+        mouse->original_y = original_y;
     } else if (mouse->focus) {
         /* Restore the expected mouse position */
         SDL_WarpMouseInWindow(mouse->focus, mouse->original_x, mouse->original_y);
diff --git a/src/video/SDL_video.c b/src/video/SDL_video.c
index 694291022..9f0b03b3f 100644
--- a/src/video/SDL_video.c
+++ b/src/video/SDL_video.c
@@ -2044,10 +2044,17 @@ SDL_OnWindowLeave(SDL_Window * window)
 void
 SDL_OnWindowFocusGained(SDL_Window * window)
 {
+    SDL_Mouse *mouse = SDL_GetMouse();
+
     if (window->gamma && _this->SetWindowGammaRamp) {
         _this->SetWindowGammaRamp(_this, window, window->gamma);
     }
 
+    if (mouse && mouse->relative_mode) {
+        SDL_SetMouseFocus(window);
+        SDL_WarpMouseInWindow(window, window->w/2, window->h/2);
+    }
+
     SDL_UpdateWindowGrab(window);
 }
 
@@ -2067,10 +2074,17 @@ static SDL_bool ShouldMinimizeOnFocusLoss()
 void
 SDL_OnWindowFocusLost(SDL_Window * window)
 {
+    SDL_Mouse *mouse = SDL_GetMouse();
+
     if (window->gamma && _this->SetWindowGammaRamp) {
         _this->SetWindowGammaRamp(_this, window, window->saved_gamma);
     }
 
+    if (mouse && mouse->relative_mode) {
+        /* Restore the expected mouse position */
+        SDL_WarpMouseInWindow(window, mouse->original_x, mouse->original_y);
+    }
+
     SDL_UpdateWindowGrab(window);
 
     /* If we're fullscreen on a single-head system and lose focus, minimize */