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view docs/man3/SDL_UpdateRects.3 @ 1543:98f9b16f565c
From: "Alex Volkov"
Date: Thu, 10 Nov 2005 21:53:40 -0500
Subject: [SDL] BUG[?]: 32bpp RGBA->RGB colorkey blit, no SDL_SRCALPHA
It seems there is either a documentation vs. reality mismatch or a real bug
in SDL_blit_N.c:BlitNtoNKey().
The exact blit in question is a 32bpp RGBA->RGB, where RGBA has SDL_COLORKEY
and *no* SDL_SRCALPHA flags. The doc in SDL_video.h states:
* RGBA->RGB:
* SDL_SRCALPHA not set:
* copy RGB.
* if SDL_SRCCOLORKEY set, only copy the pixels matching the
* RGB values of the source colour key, ignoring alpha in the
* comparison.
BlitNtoNKey(), however, forgets to "ignore alpha in the comparison". The
documentation makes perfect sense, so I think it is the code that is faulty.
The attached patch corrects the code.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Wed, 15 Mar 2006 15:43:15 +0000 |
| parents | e5bc29de3f0a |
| children | 546f7c1eb755 |
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.TH "SDL_UpdateRects" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" .SH "NAME" SDL_UpdateRects\- Makes sure the given list of rectangles is updated on the given screen\&. .SH "SYNOPSIS" .PP \fB#include "SDL\&.h" .sp \fBvoid \fBSDL_UpdateRects\fP\fR(\fBSDL_Surface *screen, int numrects, SDL_Rect *rects\fR); .SH "DESCRIPTION" .PP Makes sure the given list of rectangles is updated on the given screen\&. The rectangles must all be confined within the screen boundaries (no clipping is done)\&. .PP This function should not be called while \fBscreen\fR is \fIlocked\fR\&. .PP .RS \fBNote: .PP It is adviced to call this function only once per frame, since each call has some processing overhead\&. This is no restriction since you can pass any number of rectangles each time\&. .PP The rectangles are not automatically merged or checked for overlap\&. In general, the programmer can use his knowledge about his particular rectangles to merge them in an efficient way, to avoid overdraw\&. .RE .SH "SEE ALSO" .PP \fI\fBSDL_UpdateRect\fP\fR, \fI\fBSDL_Rect\fR\fR, \fI\fBSDL_Surface\fR\fR, \fI\fBSDL_LockSurface\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01