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

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  Using SDL with PicoGUI
 ========================

- Originally contributed by Micah Dowty <micahjd@users.sourceforge.net>

PicoGUI is a scalable GUI system with a unique architecture, primarily focused
on scalability to various embedded systems. You can find more information
including a FAQ at http://picogui.org

To use the patch:

  1. When compiling, add the "--enable-video-picogui" switch to ./configure

  2. When running your program, ensure that the picogui driver for SDL
     is in use by setting the SDL_VIDEODRIVER environment variable 
     to "picogui".

  3. The program must also be linked to the C client library for PicoGUI
     (libpgui.so). If the program is being compiled with a patched SDL 
     installed this should be done automatically. If you want to use an
     existing binary with PicoGUI, you can set the LD_PRELOAD environment
     variable to the path of your libpgui.so file.

Capabilities:

  So far only basic functionality is provided on true color (linear16/24/32)
  devices. Accessing a memory mapped bitmap, updating the display, and handling
  mouse/keyboard input. This functionality has been tested with several
  applications, including mplayer, Xine, sldroids, and Abuse.

TODO list:

  - YUV overlays will be helpful for watching video on set top boxes or other
    embedded devices that have some graphics acceleration hardware

  - Account for rotated bitmap storage in pgserver

  - Support for hiding or changing the cursor

  - The display should be centered when the SDL application is smaller
    than the PicoGUI panel

  - Fullscreen or any other special modes

  - Support for indexed and grayscale modes

  - Probably much more...

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