Mercurial > sdl-ios-xcode
view docs/man3/SDL_SetAlpha.3 @ 1120:8e1fde455471
Patch by me to fix crash described below.
--ryan.
To: sdl@libsdl.org
From: Rainer Deyke <rainerd@eldwood.com>
Date: Tue, 16 Aug 2005 01:08:18 -0600
Subject: [SDL] Bug report: SDL_CreateRGBSurface with SDL_HWSURFACE crashes
If SDL is in full-screen mode with a hardware video surface on OS X,
SDL_CreateRGBSurface with SDL_HWSURFACE crashes. The crash occurs on
line 109 of SDL_Surface.c. This was tested on OS X 10.3.9 with both SDL
1.2.8 and the latest CVS. Here is a small C++ program that demonstrates
the problem:
#include "SDL.h"
#include <stdio.h>
namespace {
void wait_for_key()
{
SDL_Event e;
printf("%d\n", SDL_GetAppState());
while (SDL_WaitEvent(&e)) {
if (e.type == SDL_KEYDOWN || e.type == SDL_QUIT) return;
}
}
}
int main(int, char *[])
{
SDL_Init(SDL_INIT_VIDEO);
SDL_Surface *screen
= SDL_SetVideoMode(640, 480, 32, SDL_FULLSCREEN | SDL_HWSURFACE);
SDL_Surface *s = SDL_CreateRGBSurface(SDL_HWSURFACE, 640, 480, 32,
screen->format->Rmask, screen->format->Gmask,
screen->format->Bmask, screen->format->Amask);
wait_for_key();
if (s) SDL_FreeSurface(s);
SDL_Quit();
printf("Success!\n");
return 0;
}
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Thu, 18 Aug 2005 06:46:32 +0000 |
| parents | e5bc29de3f0a |
| children | 546f7c1eb755 |
line wrap: on
line source
.TH "SDL_SetAlpha" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_SetAlpha\- Adjust the alpha properties of a surface .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBint \fBSDL_SetAlpha\fP\fR(\fBSDL_Surface *surface, Uint32 flag, Uint8 alpha\fR); .SH "DESCRIPTION" .PP .RS \fBNote: .PP This function and the semantics of SDL alpha blending have changed since version 1\&.1\&.4\&. Up until version 1\&.1\&.5, an alpha value of 0 was considered opaque and a value of 255 was considered transparent\&. This has now been inverted: 0 (\fBSDL_ALPHA_TRANSPARENT\fP) is now considered transparent and 255 (\fBSDL_ALPHA_OPAQUE\fP) is now considered opaque\&. .RE .PP \fBSDL_SetAlpha\fP is used for setting the per-surface alpha value and/or enabling and disabling alpha blending\&. .PP The\fBsurface\fR parameter specifies which surface whose alpha attributes you wish to adjust\&. \fBflags\fR is used to specify whether alpha blending should be used (\fBSDL_SRCALPHA\fP) and whether the surface should use RLE acceleration for blitting (\fBSDL_RLEACCEL\fP)\&. \fBflags\fR can be an OR\&'d combination of these two options, one of these options or 0\&. If \fBSDL_SRCALPHA\fP is not passed as a flag then all alpha information is ignored when blitting the surface\&. The \fBalpha\fR parameter is the per-surface alpha value; a surface need not have an alpha channel to use per-surface alpha and blitting can still be accelerated with \fBSDL_RLEACCEL\fP\&. .PP .RS \fBNote: .PP The per-surface alpha value of 128 is considered a special case and is optimised, so it\&'s much faster than other per-surface values\&. .RE .PP Alpha effects surface blitting in the following ways: .TP 20 RGBA->RGB with \fBSDL_SRCALPHA\fP The source is alpha-blended with the destination, using the alpha channel\&. \fBSDL_SRCCOLORKEY\fP and the per-surface alpha are ignored\&. .TP 20 RGBA->RGB without \fBSDL_SRCALPHA\fP The RGB data is copied from the source\&. The source alpha channel and the per-surface alpha value are ignored\&. .TP 20 RGB->RGBA with \fBSDL_SRCALPHA\fP The source is alpha-blended with the destination using the per-surface alpha value\&. If \fBSDL_SRCCOLORKEY\fP is set, only the pixels not matching the colorkey value are copied\&. The alpha channel of the copied pixels is set to opaque\&. .TP 20 RGB->RGBA without \fBSDL_SRCALPHA\fP The RGB data is copied from the source and the alpha value of the copied pixels is set to opaque\&. If \fBSDL_SRCCOLORKEY\fP is set, only the pixels not matching the colorkey value are copied\&. .TP 20 RGBA->RGBA with \fBSDL_SRCALPHA\fP The source is alpha-blended with the destination using the source alpha channel\&. The alpha channel in the destination surface is left untouched\&. \fBSDL_SRCCOLORKEY\fP is ignored\&. .TP 20 RGBA->RGBA without \fBSDL_SRCALPHA\fP The RGBA data is copied to the destination surface\&. If \fBSDL_SRCCOLORKEY\fP is set, only the pixels not matching the colorkey value are copied\&. .TP 20 RGB->RGB with \fBSDL_SRCALPHA\fP The source is alpha-blended with the destination using the per-surface alpha value\&. If \fBSDL_SRCCOLORKEY\fP is set, only the pixels not matching the colorkey value are copied\&. .TP 20 RGB->RGB without \fBSDL_SRCALPHA\fP The RGB data is copied from the source\&. If \fBSDL_SRCCOLORKEY\fP is set, only the pixels not matching the colorkey value are copied\&. .PP .RS \fBNote: .PP Note that RGBA->RGBA blits (with SDL_SRCALPHA set) keep the alpha of the destination surface\&. This means that you cannot compose two arbitrary RGBA surfaces this way and get the result you would expect from "overlaying" them; the destination alpha will work as a mask\&. .PP Also note that per-pixel and per-surface alpha cannot be combined; the per-pixel alpha is always used if available .RE .SH "RETURN VALUE" .PP This function returns \fB0\fR, or \fB-1\fR if there was an error\&. .SH "SEE ALSO" .PP \fI\fBSDL_MapRGBA\fP\fR, \fI\fBSDL_GetRGBA\fP\fR, \fI\fBSDL_DisplayFormatAlpha\fP\fR, \fI\fBSDL_BlitSurface\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01