haiku: Add support for relative mouse mode.

Partially fixes Bugzilla #4442.

src/main/haiku/SDL_BApp.h

@@ -228,7 +228,6 @@ private:
             return;
         }
         win = GetSDLWindow(winID);
-        SDL_SendMouseMotion(win, 0, 0, x, y);
 
 		// Simple relative mode support for mouse.
 		if ((SDL_GetMouse()->relative_mode ||
@@ -237,10 +236,14 @@ private:
 			int winWidth, winHeight, winPosX, winPosY;
 			SDL_GetWindowSize(win, &winWidth, &winHeight);
 			SDL_GetWindowPosition(win, &winPosX, &winPosY);
+			int dx = x - (winWidth / 2);
+			int dy = y - (winHeight / 2);
+			SDL_SendMouseMotion(win, 0, SDL_GetMouse()->relative_mode, dx, dy);
 			set_mouse_position((winPosX + winWidth / 2), (winPosY + winHeight / 2));
 			if (!be_app->IsCursorHidden())
 				be_app->HideCursor();
 		} else {
+			SDL_SendMouseMotion(win, 0, 0, x, y);
 			if (be_app->IsCursorHidden())
 				be_app->ShowCursor();
 		}

src/video/haiku/SDL_BWin.h

@@ -319,22 +319,17 @@ class SDL_BWin:public BDirectWindow
                 && msg->FindInt32("be:transit", &transit) == B_OK) {
                 _MouseMotionEvent(where, transit);
             }
+            break;
 
-            /* FIXME: Apparently a button press/release event might be dropped
-               if made before before a different button is released.  Does
-               B_MOUSE_MOVED have the data needed to check if a mouse button
-               state has changed? */
+        case B_MOUSE_DOWN:
             if (msg->FindInt32("buttons", &buttons) == B_OK) {
-                _MouseButtonEvent(buttons);
+                _MouseButtonEvent(buttons, SDL_PRESSED);
             }
             break;
 
-        case B_MOUSE_DOWN:
         case B_MOUSE_UP:
-            /* _MouseButtonEvent() detects any and all buttons that may have
-               changed state, as well as that button's new state */
             if (msg->FindInt32("buttons", &buttons) == B_OK) {
-                _MouseButtonEvent(buttons);
+                _MouseButtonEvent(buttons, SDL_RELEASED);
             }
             break;
 
@@ -497,26 +492,17 @@ private:
  if true:  SDL_SetCursor(NULL); */
     }
 
-    void _MouseButtonEvent(int32 buttons) {
+    void _MouseButtonEvent(int32 buttons, Uint8 state) {
         int32 buttonStateChange = buttons ^ _last_buttons;
 
-        /* Make sure at least one button has changed state */
-        if( !(buttonStateChange) ) {
-            return;
-        }
-
-        /* Add any mouse button events */
         if(buttonStateChange & B_PRIMARY_MOUSE_BUTTON) {
-            _SendMouseButton(SDL_BUTTON_LEFT, buttons &
-                B_PRIMARY_MOUSE_BUTTON);
+            _SendMouseButton(SDL_BUTTON_LEFT, state);
         }
         if(buttonStateChange & B_SECONDARY_MOUSE_BUTTON) {
-            _SendMouseButton(SDL_BUTTON_RIGHT, buttons &
-                B_PRIMARY_MOUSE_BUTTON);
+            _SendMouseButton(SDL_BUTTON_RIGHT, state);
         }
         if(buttonStateChange & B_TERTIARY_MOUSE_BUTTON) {
-            _SendMouseButton(SDL_BUTTON_MIDDLE, buttons &
-                B_PRIMARY_MOUSE_BUTTON);
+            _SendMouseButton(SDL_BUTTON_MIDDLE, state);
         }
 
         _last_buttons = buttons;