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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
>General</TITLE
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><DIV
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>Chapter 5. General</H1
><DIV
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><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="sdlinit.html"
>SDL_Init</A
>&nbsp;--&nbsp;Initializes SDL</DT
><DT
><A
HREF="sdlinitsubsystem.html"
>SDL_InitSubSystem</A
>&nbsp;--&nbsp;Initialize subsystems</DT
><DT
><A
HREF="sdlquitsubsystem.html"
>SDL_QuitSubSystem</A
>&nbsp;--&nbsp;Shut down a subsystem</DT
><DT
><A
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>SDL_Quit</A
>&nbsp;--&nbsp;Shut down SDL</DT
><DT
><A
HREF="sdlwasinit.html"
>SDL_WasInit</A
>&nbsp;--&nbsp;Check which subsystems are initialized</DT
><DT
><A
HREF="sdlgeterror.html"
>SDL_GetError</A
>&nbsp;--&nbsp;Get SDL error string</DT
><DT
><A
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>SDL_envvars</A
>&nbsp;--&nbsp;SDL environment variables</DT
></DL
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><P
>Before SDL can be used in a program it must be initialized with <A
HREF="sdlinit.html"
><TT
CLASS="FUNCTION"
>SDL_Init</TT
></A
>. <TT
CLASS="FUNCTION"
>SDL_Init</TT
> initializes all the subsystems that the user requests (video, audio, joystick, timers and/or cdrom). Once SDL is initialized with <TT
CLASS="FUNCTION"
>SDL_Init</TT
> subsystems can be shut down and initialized as needed using <A
HREF="sdlinitsubsystem.html"
><TT
CLASS="FUNCTION"
>SDL_InitSubSystem</TT
></A
> and <A
HREF="sdlquitsubsystem.html"
><TT
CLASS="FUNCTION"
>SDL_QuitSubSystem</TT
></A
>.</P
><P
>SDL must also be shut down before the program exits to make sure it cleans up correctly. Calling <A
HREF="sdlquit.html"
><TT
CLASS="FUNCTION"
>SDL_Quit</TT
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> shuts down all subsystems and frees any resources allocated to SDL.</P
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