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

.TH "SDL_keysym" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_keysym\- Keysym structure
.SH "STRUCTURE DEFINITION"
.PP
.nf
\f(CWtypedef struct{
  Uint8 scancode;
  SDLKey sym;
  SDLMod mod;
  Uint16 unicode;
} SDL_keysym;\fR
.fi
.PP
.SH "STRUCTURE DATA"
.TP 20
\fBscancode\fR
Hardware specific scancode
.TP 20
\fBsym\fR
SDL virtual keysym
.TP 20
\fBmod\fR
Current key modifiers
.TP 20
\fBunicode\fR
Translated character
.SH "DESCRIPTION"
.PP
The \fBSDL_keysym\fR structure is used by reporting key presses and releases since it is a part of the \fI\fBSDL_KeyboardEvent\fR\fR\&.
.PP
The \fBscancode\fR field should generally be left alone, it is the hardware dependent scancode returned by the keyboard\&. The \fBsym\fR field is extremely useful\&. It is the SDL-defined value of the key (see \fISDL Key Syms\fR\&. This field is very useful when you are checking for certain key presses, like so: 
.PP
.nf
\f(CW\&.
\&.
while(SDL_PollEvent(&event)){
  switch(event\&.type){
    case SDL_KEYDOWN:
      if(event\&.key\&.keysym\&.sym==SDLK_LEFT)
        move_left();
      break;
    \&.
    \&.
    \&.
  }
}
\&.
\&.\fR
.fi
.PP
 \fBmod\fR stores the current state of the keyboard modifiers as explained in \fI\fBSDL_GetModState\fP\fR\&. The \fBunicode\fR is only used when UNICODE translation is enabled with \fI\fBSDL_EnableUNICODE\fP\fR\&. If \fBunicode\fR is non-zero then this a the UNICODE character corresponding to the keypress\&. If the high 9 bits of the character are 0, then this maps to the equivalent ASCII character: 
.PP
.nf
\f(CWchar ch;
if ( (keysym\&.unicode & 0xFF80) == 0 ) {
  ch = keysym\&.unicode & 0x7F;
}
else {
  printf("An International Character\&.
");
}\fR
.fi
.PP
 UNICODE translation does have a slight overhead so don\&'t enable it unless its needed\&.
.SH "SEE ALSO"
.PP
\fI\fBSDLKey\fR\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00