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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 e5bc29de3f0a
children 546f7c1eb755
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.TH "SDL_MixAudio" "3" "Tue 11 Sep 2001, 22:58" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_MixAudio\- Mix audio data
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBvoid \fBSDL_MixAudio\fP\fR(\fBUint8 *dst, Uint8 *src, Uint32 len, int volume\fR);
.SH "DESCRIPTION"
.PP
This function takes two audio buffers of \fBlen\fR bytes each of the playing audio format and mixes them, performing addition, volume adjustment, and overflow clipping\&. The \fBvolume\fR ranges from 0 to \fBSDL_MIX_MAXVOLUME\fP and should be set to the maximum value for full audio volume\&. Note this does not change hardware volume\&. This is provided for convenience -- you can mix your own audio data\&.
.PP
.RS
\fBNote:  
.PP
Do not use this function for mixing together more than two streams of sample data\&. The output from repeated application of this function may be distorted by clipping, because there is no accumulator with greater range than the input (not to mention this being an inefficient way of doing it)\&. Use mixing functions from SDL_mixer, OpenAL, or write your own mixer instead\&.
.RE
.SH "SEE ALSO"
.PP
\fI\fBSDL_OpenAudio\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:58