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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
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>SDL_CreateRGBSurfaceFrom</TITLE
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>SDL_CreateRGBSurfaceFrom</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1856"
></A
><H2
>Name</H2
>SDL_CreateRGBSurfaceFrom&nbsp;--&nbsp;Create an SDL_Surface from pixel data</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
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><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
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><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>SDL_Surface *<B
CLASS="FSFUNC"
>SDL_CreateRGBSurfaceFrom</B
></CODE
>(void *pixels, int width, int height, int depth, int pitch, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask);</CODE
></P
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><H2
>Description</H2
><P
>Creates an SDL_Surface from the provided pixel data.</P
><P
>The data stored in <TT
CLASS="PARAMETER"
><I
>pixels</I
></TT
> is assumed to be of the <TT
CLASS="PARAMETER"
><I
>depth</I
></TT
> specified in the parameter list. The pixel data is not copied into the <SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
> structure so it should not be freed until the surface has been freed with a called to <A
HREF="sdlfreesurface.html"
>SDL_FreeSurface</A
>. <TT
CLASS="PARAMETER"
><I
>pitch</I
></TT
> is the length of each scanline in bytes.  </P
><P
>See <A
HREF="sdlcreatergbsurface.html"
><TT
CLASS="FUNCTION"
>SDL_CreateRGBSurface</TT
></A
> for a more detailed description of the other parameters.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1878"
></A
><H2
>Return Value</H2
><P
>Returns the created surface, or <SPAN
CLASS="RETURNVALUE"
>NULL</SPAN
> upon error.</P
></DIV
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><H2
>See Also</H2
><P
><A
HREF="sdlcreatergbsurface.html"
><TT
CLASS="FUNCTION"
>SDL_CreateRGBSurface</TT
></A
>,
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>SDL_FreeSurface</TT
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