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

Project files for embedded Visual C++ 4.0 can be found in VisualCE.zip

NOTE:
There are several SDL features not available in the WinCE port of SDL.

- DirectX is not yet available
- Semaphores are not available
- Joystick support is not available
- CD-ROM control is not available

In addition, there are several features that run in "degraded" mode:

Preprocessor Symbol		Effect
===================		=================================

SDL_systimer.c:
USE_GETTICKCOUNT		Less accurate values for SDL time functions
USE_SETTIMER			Use only a single marginally accurate timer

SDL_syswm.c:
DISABLE_ICON_SUPPORT		Can't set the runtime window icon

SDL_sysmouse.c:
USE_STATIC_CURSOR		Only the arrow cursor is available

SDL_sysevents.c:
NO_GETKEYBOARDSTATE		Can't get modifier state on keyboard focus

SDL_dibevents.c:
NO_GETKEYBOARDSTATE		Very limited keycode translation

SDL_dibvideo.c:
NO_GETDIBITS			Can't distinguish between 15 bpp and 16 bpp
NO_CHANGEDISPLAYSETTINGS	No fullscreen support
NO_GAMMA_SUPPORT		Gamma correction not available