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

                         Simple DirectMedia Layer

                                  (SDL)

                                Version 1.2

---
http://www.libsdl.org/

This is the Simple DirectMedia Layer, a general API that provides low
level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL,
and 2D framebuffer across multiple platforms.

SDL is written in C, but works with C++ natively, and has bindings to
several other languages, including Ada, C#, Eiffel, Java, Lua, ML,
Objective C, Perl, PHP, Pike, Python, and Ruby.

The current version supports Linux, Windows, BeOS, MacOS, MacOS X,
FreeBSD, OpenBSD, BSD/OS, Solaris, IRIX, and QNX.  The code contains
support for Windows CE, AmigaOS, Dreamcast, Atari, NetBSD, AIX, OSF/Tru64,
RISC OS, and SymbianOS, but these are not officially supported.

This library is distributed under GNU LGPL version 2, which can be
found in the file  "COPYING".  This license allows you to use SDL
freely in commercial programs as long as you link with the dynamic
library.

The best way to learn how to use SDL is to check out the header files in
the "include" subdirectory and the programs in the "test" subdirectory.
The header files and test programs are well commented and always up to date.
More documentation is available in HTML format in "./docs/index.html"

The test programs in the "test" subdirectory are in the public domain.

Frequently asked questions are answered online:
	http://www.libsdl.org/faq.php

If you need help with the library, or just want to discuss SDL related
issues, you can join the developers mailing list:
	http://www.libsdl.org/mailing-list.php

Enjoy!
	Sam Lantinga				(slouken@libsdl.org)