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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_Palette</TITLE
><META
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><H1
><A
NAME="SDLPALETTE"
></A
>SDL_Palette</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN3129"
></A
><H2
>Name</H2
>SDL_Palette&nbsp;--&nbsp;Color palette for 8-bit pixel formats</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3132"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  int ncolors;
  SDL_Color *colors;
} SDL_Palette;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3135"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN3137"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>ncolors</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Number of colors used in this palette</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>colors</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Pointer to <A
HREF="sdlcolor.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Color</SPAN
></A
> structures that make up the palette.</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3150"
></A
><H2
>Description</H2
><P
>Each pixel in an 8-bit surface is an index into the <TT
CLASS="STRUCTFIELD"
><I
>colors</I
></TT
> field of the <SPAN
CLASS="STRUCTNAME"
>SDL_Palette</SPAN
> structure store in <A
HREF="sdlpixelformat.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
></A
>. A <SPAN
CLASS="STRUCTNAME"
>SDL_Palette</SPAN
> should never need to be created manually. It is automatically created when SDL allocates a <SPAN
CLASS="STRUCTNAME"
>SDL_PixelFormat</SPAN
> for a surface. The colors values of a <A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
>s palette can be set with the <A
HREF="sdlsetcolors.html"
><TT
CLASS="FUNCTION"
>SDL_SetColors</TT
></A
>.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN3163"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlcolor.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Color</SPAN
></A
>,
<A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
>,
<A
HREF="sdlsetcolors.html"
><TT
CLASS="FUNCTION"
>SDL_SetColors</TT
></A
>
<A
HREF="sdlsetpalette.html"
><TT
CLASS="FUNCTION"
>SDL_SetPalette</TT
></A
></P
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