view docs/man3/SDL_CreateRGBSurface.3 @ 4168:69bcba65c388 SDL-1.2

Fixed bug #526 Comment #1 From Simon Howard 2009-03-20 16:50:56 Hi, I'm the author of Chocolate Doom, one of the other source ports that James mentioned. This is a patch against the current SVN version of SDL 1.2 that fixes the bug. It has been tested and hopefully should be obviously correct from examining the changes. I'll give a brief explanation. When the palette is set with SDL_SetPalette, the IDirectDrawPalette_SetEntries DirectX function is invoked. However, when this happens, a WM_PALETTECHANGED message is sent to the window. A WM_PALETTECHANGED message can also be received if the palette is changed for some other reason, like if the system palette is changed. Therefore, the palette change handler (DX5_PaletteChanged) has code to deal with this case. It distinguishes "expected" palette changes (set with SDL_SetPalette) from "unexpected" palette changes using the colorchange_expected variable, which is set before calling IDirectDrawPalette_SetEntries. However, the code to set this variable is missing in the fullscreen code path. By setting this variable, the palette change is handled properly and the freezes go away.
author Sam Lantinga <slouken@libsdl.org>
date Mon, 13 Apr 2009 00:53:12 +0000
parents 4e3b250c950e
children 1238da4a7112
line wrap: on
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.TH "SDL_CreateRGBSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_CreateRGBSurface \- Create an empty SDL_Surface
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBSDL_Surface *\fBSDL_CreateRGBSurface\fP\fR(\fBUint32 flags, int width, int height, int depth, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask\fR);
.SH "DESCRIPTION"
.PP
Allocate an empty surface (must be called after \fISDL_SetVideoMode\fR)
.PP
If \fBdepth\fR is 8 bits an empty palette is allocated for the surface, otherwise a \&'packed-pixel\&' \fI\fBSDL_PixelFormat\fR\fR is created using the \fB[RGBA]mask\fR\&'s provided (see \fI\fBSDL_PixelFormat\fR\fR)\&. The \fBflags\fR specifies the type of surface that should be created, it is an OR\&'d combination of the following possible values\&.
.TP 20
\fBSDL_SWSURFACE\fP
SDL will create the surface in system memory\&. This improves the performance of pixel level access, however you may not be able to take advantage of some types of hardware blitting\&.
.TP 20
\fBSDL_HWSURFACE\fP
SDL will attempt to create the surface in video memory\&. This will allow SDL to take advantage of Video->Video blits (which are often accelerated)\&.
.TP 20
\fBSDL_SRCCOLORKEY\fP
This flag turns on colourkeying for blits from this surface\&. If \fBSDL_HWSURFACE\fP is also specified and colourkeyed blits are hardware-accelerated, then SDL will attempt to place the surface in video memory\&. Use \fI\fBSDL_SetColorKey\fP\fR to set or clear this flag after surface creation\&.
.TP 20
\fBSDL_SRCALPHA\fP
This flag turns on alpha-blending for blits from this surface\&. If \fBSDL_HWSURFACE\fP is also specified and alpha-blending blits are hardware-accelerated, then the surface will be placed in video memory if possible\&. Use \fI\fBSDL_SetAlpha\fP\fR to set or clear this flag after surface creation\&.
.PP
.RS
\fBNote:  
.PP
If an alpha-channel is specified (that is, if \fBAmask\fR is nonzero), then the \fBSDL_SRCALPHA\fP flag is automatically set\&. You may remove this flag by calling \fI\fBSDL_SetAlpha\fP\fR after surface creation\&.
.RE
.SH "RETURN VALUE"
.PP
Returns the created surface, or \fBNULL\fR upon error\&.
.SH "EXAMPLE"
.PP
.nf
\f(CW    /* Create a 32-bit surface with the bytes of each pixel in R,G,B,A order,
       as expected by OpenGL for textures */
    SDL_Surface *surface;
    Uint32 rmask, gmask, bmask, amask;

    /* SDL interprets each pixel as a 32-bit number, so our masks must depend
       on the endianness (byte order) of the machine */
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    rmask = 0xff000000;
    gmask = 0x00ff0000;
    bmask = 0x0000ff00;
    amask = 0x000000ff;
#else
    rmask = 0x000000ff;
    gmask = 0x0000ff00;
    bmask = 0x00ff0000;
    amask = 0xff000000;
#endif

    surface = SDL_CreateRGBSurface(SDL_SWSURFACE, width, height, 32,
                                   rmask, gmask, bmask, amask);
    if(surface == NULL) {
        fprintf(stderr, "CreateRGBSurface failed: %s
", SDL_GetError());
        exit(1);
    }\fR
.fi
.PP
.SH "SEE ALSO"
.PP
\fI\fBSDL_CreateRGBSurfaceFrom\fP\fR, \fI\fBSDL_FreeSurface\fP\fR, \fI\fBSDL_SetVideoMode\fP\fR, \fI\fBSDL_LockSurface\fP\fR, \fI\fBSDL_PixelFormat\fR\fR, \fI\fBSDL_Surface\fR\fR \fI\fBSDL_SetAlpha\fP\fR \fI\fBSDL_SetColorKey\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01