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Fixed bug #33 Mike Frysinger wrote: > with libsdl-1.2.9, some games (like bomberclone) started > segfaulting in Gentoo [...snip...] > the last change in the last hunk: [...snip...] > if i change the statement to read: > (table[which].blit_features & GetBlitFeatures()) == GetBlitFeatures() > bomberclone no longer segfaults on my box Alex Volkov wrote: > The test "(table[which].blit_features & GetBlitFeatures()) == > table[which].blit_features)" is correct, and the previous > "(table[which].cpu_mmx == SDL_HasMMX())" was actually broken. I think there is potentially a slightly different cause of the above problem. During the introduction of the Altivec code, the blit_table struct field 'alpha' got changed from a straightforward enum to a bitmask, which makes perfect sense by itself. However, now the table driven blitter selection code in SDL_CalculateBlitN() can choose the wrong blitters when searching for a NO_ALPHA blitter because of the following code: int a_need = 0; ... (a_need & table[which].alpha) == a_need && When searching through the normal_blit_2[] table, a SET_ALPHA blitter (like Blit_RGB565_ARGB8888) can now be selected instead of a NO_ALPHA one, causing alpha channel bits to appear in a non-alpha destination surface. I suppose this could theoretically be an indirect cause of the segfault mentioned above. I *think* this can be fixed by changing to int a_need = NO_ALPHA;
author Sam Lantinga <slouken@libsdl.org>
date Wed, 15 Mar 2006 15:47:49 +0000
parents e5bc29de3f0a
children 546f7c1eb755
line wrap: on
line source

.TH "SDL_Surface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_Surface\- Graphical Surface Structure
.SH "STRUCTURE DEFINITION"
.PP
.nf
\f(CWtypedef struct SDL_Surface {
        Uint32 flags;                           /* Read-only */
        SDL_PixelFormat *format;                /* Read-only */
        int w, h;                               /* Read-only */
        Uint16 pitch;                           /* Read-only */
        void *pixels;                           /* Read-write */

        /* clipping information */
        SDL_Rect clip_rect;                     /* Read-only */

        /* Reference count -- used when freeing surface */
        int refcount;                           /* Read-mostly */

	/* This structure also contains private fields not shown here */
} SDL_Surface;\fR
.fi
.PP
.SH "STRUCTURE DATA"
.TP 20
\fBflags\fR
Surface flags
.TP 20
\fBformat\fR
Pixel \fIformat\fR
.TP 20
\fBw, h\fR
Width and height of the surface
.TP 20
\fBpitch\fR
Length of a surface scanline in bytes
.TP 20
\fBpixels\fR
Pointer to the actual pixel data
.TP 20
\fBclip_rect\fR
surface clip \fIrectangle\fR
.SH "DESCRIPTION"
.PP
\fBSDL_Surface\fR\&'s represent areas of "graphical" memory, memory that can be drawn to\&. The video framebuffer is returned as a \fBSDL_Surface\fR by \fI\fBSDL_SetVideoMode\fP\fR and \fI\fBSDL_GetVideoSurface\fP\fR\&. Most of the fields should be pretty obvious\&. \fBw\fR and \fBh\fR are the width and height of the surface in pixels\&. \fBpixels\fR is a pointer to the actual pixel data, the surface should be \fIlocked\fR before accessing this field\&. The \fBclip_rect\fR field is the clipping rectangle as set by \fI\fBSDL_SetClipRect\fP\fR\&.
.PP
The following are supported in the \fBflags\fR field\&.
.TP 20
\fBSDL_SWSURFACE\fP
Surface is stored in system memory
.TP 20
\fBSDL_HWSURFACE\fP
Surface is stored in video memory
.TP 20
\fBSDL_ASYNCBLIT\fP
Surface uses asynchronous blits if possible
.TP 20
\fBSDL_ANYFORMAT\fP
Allows any pixel-format (Display surface)
.TP 20
\fBSDL_HWPALETTE\fP
Surface has exclusive palette
.TP 20
\fBSDL_DOUBLEBUF\fP
Surface is double buffered (Display surface)
.TP 20
\fBSDL_FULLSCREEN\fP
Surface is full screen (Display Surface)
.TP 20
\fBSDL_OPENGL\fP
Surface has an OpenGL context (Display Surface)
.TP 20
\fBSDL_OPENGLBLIT\fP
Surface supports OpenGL blitting (Display Surface)
.TP 20
\fBSDL_RESIZABLE\fP
Surface is resizable (Display Surface)
.TP 20
\fBSDL_HWACCEL\fP
Surface blit uses hardware acceleration
.TP 20
\fBSDL_SRCCOLORKEY\fP
Surface use colorkey blitting
.TP 20
\fBSDL_RLEACCEL\fP
Colorkey blitting is accelerated with RLE
.TP 20
\fBSDL_SRCALPHA\fP
Surface blit uses alpha blending
.TP 20
\fBSDL_PREALLOC\fP
Surface uses preallocated memory
.SH "SEE ALSO"
.PP
\fI\fBSDL_PixelFormat\fR\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01