sdl_joystickgetball.3

网络MPEG4IP流媒体开发源代码

.TH "SDL_JoystickGetBall" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_JoystickGetBall\- Get relative trackball motion
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBint \fBSDL_JoystickGetBall\fP\fR(\fBSDL_Joystick *joystick, int ball, int *dx, int *dy\fR);
.SH "DESCRIPTION"
.PP
Get the \fBball\fR axis change\&.
.PP
Trackballs can only return relative motion since the last call to \fBSDL_JoystickGetBall\fP, these motion deltas a placed into \fBdx\fR and \fBdy\fR\&.
.SH "RETURN VALUE"
.PP
Returns \fB0\fR on success or \fB-1\fR on failure
.SH "EXAMPLES"
.PP
.PP
.nf
\f(CWint delta_x, delta_y;
SDL_Joystick *joy;
\&.
\&.
\&.
SDL_JoystickUpdate();
if(SDL_JoystickGetBall(joy, 0, &delta_x, &delta_y)==-1)
  printf("TrackBall Read Error!
");
printf("Trackball Delta- X:%d, Y:%d
", delta_x, delta_y);\fR
.fi
.PP
.SH "SEE ALSO"
.PP
\fI\fBSDL_JoystickNumBalls\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00