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

These are test programs for the SDL library:

	testver		Check the version and dynamic loading and endianness
	testtypes	Check to see if the data types are the correct size
	testhread	Hacked up test of multi-threading
	testlock	Hacked up test of multi-threading and locking
	testerror	Tests multi-threaded error handling
	testsem		Tests SDL's semaphore implementation
	testtimer	Test the timer facilities
	loopwave	Audio test -- loop playing a WAV file
	testcdrom	Sample audio CD control program
	testkeys	List the available keyboard keys
	testvidinfo	Show the pixel format of the display and perfom the benchmark
	checkkeys	Watch the key events to check the keyboard
	testwin		Display a BMP image at various depths
	graywin		Display a gray gradient and center mouse on spacebar
	testsprite	Example of fast sprite movement on the screen
	testbitmap	Test displaying 1-bit bitmaps
	testalpha	Display an alpha faded icon -- paint with mouse
	testwm		Test window manager -- title, icon, events
	threadwin	Test multi-threaded event handling
	testgl		A very simple example of using OpenGL with SDL
	testjoystick	List joysticks and watch joystick events
	testoverlay	Tests the software/hardware overlay functionality.
	testoverlay2	Tests the overlay flickering/scaling during playback.
	testblitspeed	Tests performance of SDL's blitters and converters.