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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_JoyBallEvent</TITLE
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><H1
><A
NAME="SDLJOYBALLEVENT"
></A
>SDL_JoyBallEvent</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN4396"
></A
><H2
>Name</H2
>SDL_JoyBallEvent&nbsp;--&nbsp;Joystick trackball motion event structure</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4399"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  Uint8 type;
  Uint8 which;
  Uint8 ball;
  Sint16 xrel, yrel;
} SDL_JoyBallEvent;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4402"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN4404"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>type</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Joystick device index</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Joystick trackball index</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
>, <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>The relative motion in the X/Y direction</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4425"
></A
><H2
>Description</H2
><P
><SPAN
CLASS="STRUCTNAME"
>SDL_JoyBallEvent</SPAN
> is a member of the <A
HREF="sdlevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
> union and is used when an event of type <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> is reported.</P
><P
>A <TT
CLASS="LITERAL"
>SDL_JOYBALLMOTION</TT
> event occurs when a user moves a trackball on the joystick. The field <TT
CLASS="STRUCTFIELD"
><I
>which</I
></TT
> is the index of the joystick that reported the event and <TT
CLASS="STRUCTFIELD"
><I
>ball</I
></TT
> is the index of the trackball (for a more detailed explaination see the <A
HREF="joystick.html"
>Joystick section</A
>). Trackballs only return relative motion, this is the change in position on the ball since it was last polled (last cycle of the event loop) and it is stored in <TT
CLASS="STRUCTFIELD"
><I
>xrel</I
></TT
> and <TT
CLASS="STRUCTFIELD"
><I
>yrel</I
></TT
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN4439"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlevent.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Event</SPAN
></A
>,
<A
HREF="joystick.html"
>Joystick Functions</A
>,
<A
HREF="sdljoystickeventstate.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickEventState</TT
></A
>,
<A
HREF="sdljoystickgetball.html"
><TT
CLASS="FUNCTION"
>SDL_JoystickGetBall</TT
></A
></P
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