To: sdl@libsdl.org From: Christian Walther <cwalther@gmx.ch> Date: Thu, 15 Dec 2005 21:19:53 +0100 Subject: [SDL] More mouse enhancements for Mac OS X The attached patch brings two more enhancements to mouse handling on Mac OS X (Quartz): 1. Currently, after launching an SDL application, SDL's notion of the mouse position is stuck in the top left corner (0,0) until the first time the mouse is moved. That's because the UpdateMouse() function isn't implemented in the Quartz driver. This patch adds it. 2. When grabbing input while the mouse cursor is hidden, the function CGAssociateMouseAndMouseCursorPosition(0) is called, which prevents the system's notion of the mouse location from moving (and therefore leaving the SDL window) even when the mouse is moved. However, apparently the Wacom tablet driver (and maybe other special pointing device drivers) doesn't care about that setting and still allows the mouse location to go outside of the window. Interestingly, the system cursor, which is made visible by the existing code in SDL in that case, does not follow the mouse location, but appears in the middle of the SDL window. The mouse location being outside of the window however means that mouse button events go to background applications (or the dock or whatever is there), which is very confusing to the user who sees no cursor outside of the SDL window. I have not found any way of intercepting these events (and that's probably by design, as "normal" applications shouldn't prevent the user from bringing other applications' windows to the front by clicking on them). An idea would be placing a fully transparent, screen-filling window in front of everything, but I fear that this might affect rendering performance (by doing unnecessary compositing, using up memory, or whatever). The deluxe solution to the problem would be talking to the tablet driver using AppleEvents to tell it to constrain its mapped area to the window (see Wacom's "TabletEventDemo" sample app, http://www.wacomeng.com/devsupport/mac/downloads.html), but I think that the bloat that solution would add to SDL would outweigh its usefulness. What I did instead in my patch is reassociating mouse and cursor when the mouse leaves the window while an invisible grab is in effect, and restoring the grab when the window is entered. That way, the grab can still be effectively broken by a tablet, but at least it's obvious to the user that it is broken. That change is minimal - it doesn't affect operation with a mouse (or a trackpad), and the code that it adds is not executed on every PumpEvents() call, only when entering and leaving the window. Unless there are any concerns about the patch, please apply. Feel free to shorten the lengthy comment in SDL_QuartzEvents.m if you think it's too verbose. Thanks -Christian

/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002  Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

#ifdef SAVE_RCSID
static char rcsid =
 "@(#) $Id$";
#endif

/*
 *	VBL queue routine
 *
 *	Patrice Mandin
 */

#define _vbl_queue 0x456

	.text

	.globl	_SDL_AtariVblInstall
	.globl	_SDL_AtariVblUninstall

/*--- Vector installer ---*/

_SDL_AtariVblInstall:
	movel	sp@(4),my_vector
	lea		_my_vbl,a0

	clrw	vbl_mutex

	/* Stop interrupts */

	movew	#0x2700,sr

	/* Read vbl_queue pointer */
	movel	_vbl_queue.w,a1

	/* Search a free place */
	moveq	#7,d0
bcl_search_place:
	movel	(a1),d1
	beqs	place_found
	addql	#4,a1
	dbra	d0,bcl_search_place

	/* Not found */
	moveq	#1,d0
	bras	exit_vbl_queue

	/* Then install ourselves */
place_found:
	movel	a0,(a1)
	moveq	#0,d0	

exit_vbl_queue:
	/* Restart interrupts */
	movew	#0x2300,sr

	rts

/*--- Vector uninstaller ---*/

_SDL_AtariVblUninstall:
	movel	sp@(4),d0
	cmpl	my_vector,d0
	bnes	badvector
	
	movel	#_my_vbl,d0

	/* Stop interrupts */

	movew	#0x2700,sr

	/* Read vbl_queue pointer */
	movel	_vbl_queue.w,a1

	/* Search where we are */
	moveq	#7,d1
bcl2_search_place:
	cmpl	(a1),d0
	bnes	next_place
	clrl	(a1)
	moveq	#0,d1
next_place:
	addql	#4,a1
	dbra	d1,bcl2_search_place

	/* Restart interrupts */
	movew	#0x2300,sr
badvector:
	rts

/*--- Our vbl ---*/

_my_vbl:
	/* Verify if this is not already running */

	tstw	vbl_mutex
	bnes	vbl_end
	notw	vbl_mutex

	moveml	d0-d7/a0-a6,sp@-
	movel	my_vector,a0
	jsr		a0@
	moveml	sp@+,d0-d7/a0-a6

	clrw	vbl_mutex
vbl_end:
	rts

	.data
	.even
	.comm	vbl_mutex,2*1
	.even
	.comm	my_vector,4*1