annotate docs/man3/SDL_Flip.3 @ 1544:ab1e4c41ab71

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
rev   line source
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1 .TH "SDL_Flip" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference"
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2 .SH "NAME"
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3 SDL_Flip\- Swaps screen buffers
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4 .SH "SYNOPSIS"
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5 .PP
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6 \fB#include "SDL\&.h"
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7 .sp
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8 \fBint \fBSDL_Flip\fP\fR(\fBSDL_Surface *screen\fR);
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9 .SH "DESCRIPTION"
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10 .PP
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11 On hardware that supports double-buffering, this function sets up a flip and returns\&. The hardware will wait for vertical retrace, and then swap video buffers before the next video surface blit or lock will return\&. On hardware that doesn\&'t support double-buffering, this is equivalent to calling \fISDL_UpdateRect\fR\fB(screen, 0, 0, 0, 0)\fR
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12 .PP
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13 The \fBSDL_DOUBLEBUF\fP flag must have been passed to \fISDL_SetVideoMode\fR, when setting the video mode for this function to perform hardware flipping\&.
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14 .SH "RETURN VALUE"
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15 .PP
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16 This function returns \fB0\fR if successful, or \fB-1\fR if there was an error\&.
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17 .SH "SEE ALSO"
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18 .PP
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19 \fI\fBSDL_SetVideoMode\fP\fR, \fI\fBSDL_UpdateRect\fP\fR, \fI\fBSDL_Surface\fR\fR
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20 ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01