Mercurial > sdl-ios-xcode
view docs/html/sdljoystickgetball.html @ 1259:36f24cdfcda7
te: Thu, 17 Apr 2003 11:25:26 -0700
From: "Jim"
Subject: [SDL] Frame buffer patches...
Would seem that GCC 3.2.2 promotes all signed values to unsigned if any single vlaue is unsigned in an expression...
for instance when calculating an elo touch position....evertyhign is an (int) except for cach_vinfo.xres which is unsigned. THerefore if y
ou reverse the SDL_ELO_MIN_X and SDL_ELO_MAX_X values the resulging negative value pegs the expression to it's max. Attached it the accumu
lated patch to typecast the unsigned values to (int)
- *dx = (cache_vinfo.xres - (cache_vinfo.xres * (input_x - ELO_MIN_X)) / width);
+ *dx = ((int)cache_vinfo.xres - ((int)cache_vinfo.xres * (input_x - ELO_MIN_X)) / width);
and also to provide quite failure to operations which have the screen currently locked...
The touch screen I'm using the original values were exactly opposite of any position I touched on the screen - evaluating the math the expr
ession SHOULD have handled reversing the min and max values - and after casting the unsigned .xres and .yres to a signed int - worked well.
..
Jim
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Tue, 24 Jan 2006 06:36:43 +0000 |
parents | 355632dca928 |
children |
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<HTML ><HEAD ><TITLE >SDL_JoystickGetBall</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Joystick" HREF="joystick.html"><LINK REL="PREVIOUS" TITLE="SDL_JoystickGetButton" HREF="sdljoystickgetbutton.html"><LINK REL="NEXT" TITLE="SDL_JoystickClose" HREF="sdljoystickclose.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdljoystickgetbutton.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdljoystickclose.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLJOYSTICKGETBALL" ></A >SDL_JoystickGetBall</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN6433" ></A ><H2 >Name</H2 >SDL_JoystickGetBall -- Get relative trackball motion</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN6436" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN6437" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >int <B CLASS="FSFUNC" >SDL_JoystickGetBall</B ></CODE >(SDL_Joystick *joystick, int ball, int *dx, int *dy);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6443" ></A ><H2 >Description</H2 ><P >Get the <TT CLASS="PARAMETER" ><I >ball</I ></TT > axis change.</P ><P >Trackballs can only return relative motion since the last call to <TT CLASS="FUNCTION" >SDL_JoystickGetBall</TT >, these motion deltas a placed into <TT CLASS="PARAMETER" ><I >dx</I ></TT > and <TT CLASS="PARAMETER" ><I >dy</I ></TT >.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6451" ></A ><H2 >Return Value</H2 ><P >Returns <SPAN CLASS="RETURNVALUE" >0</SPAN > on success or <SPAN CLASS="RETURNVALUE" >-1</SPAN > on failure</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6456" ></A ><H2 >Examples</H2 ><P ><PRE CLASS="PROGRAMLISTING" >int delta_x, delta_y; SDL_Joystick *joy; . . . SDL_JoystickUpdate(); if(SDL_JoystickGetBall(joy, 0, &delta_x, &delta_y)==-1) printf("TrackBall Read Error!\n"); printf("Trackball Delta- X:%d, Y:%d\n", delta_x, delta_y);</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6460" ></A ><H2 >See Also</H2 ><P ><A HREF="sdljoysticknumballs.html" ><TT CLASS="FUNCTION" >SDL_JoystickNumBalls</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdljoystickgetbutton.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdljoystickclose.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_JoystickGetButton</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="joystick.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_JoystickClose</TD ></TR ></TABLE ></DIV ></BODY ></HTML >