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>SDL_BlitSurface< /TITLE
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>SDL Library Documentation< /TH
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>< H1
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>SDL_BlitSurface< /H1
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>< DIV
CLASS="REFNAMEDIV"
>< A
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NAME="AEN2299"
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>< /A
>< H2
>Name< /H2
>SDL_BlitSurface -- This performs a fast blit from the source surface to the destination surface.< /DIV
>< DIV
CLASS="REFSYNOPSISDIV"
>< A
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>< /A
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>Synopsis< /H2
>< DIV
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NAME="AEN2303"
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>< /A
>< P
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>< PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"< /PRE
>< P
>< CODE
>< CODE
CLASS="FUNCDEF"
>int < B
CLASS="FSFUNC"
>SDL_BlitSurface< /B
>< /CODE
>(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);< /CODE
>< /P
>< P
>< /P
>< /DIV
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>< A
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NAME="AEN2309"
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>< /A
>< H2
>Description< /H2
>< P
>This performs a fast blit from the source surface to the destination surface.< /P
>< P
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>The width and height in < TT
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CLASS="PARAMETER"
>< I
>srcrect< /I
>< /TT
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> determine the
size of the copied rectangle. Only the position is used in the
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< TT
CLASS="PARAMETER"
>< I
>dstrect< /I
>< /TT
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> (the width and height are ignored).< /P
>< P
>If < TT
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CLASS="PARAMETER"
>< I
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>srcrect< /I
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>< /TT
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> is < TT
CLASS="LITERAL"
>NULL< /TT
>, the
entire surface is copied. If < TT
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CLASS="PARAMETER"
>< I
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>dstrect< /I
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>< /TT
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> is
< TT
CLASS="LITERAL"
>NULL< /TT
>, then the destination position (upper left
corner) is (0, 0).< /P
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>< P
>The final blit rectangle is saved in
< TT
CLASS="PARAMETER"
>< I
>dstrect< /I
>< /TT
> after all clipping is performed
(< TT
CLASS="PARAMETER"
>< I
>srcrect< /I
>< /TT
> is not modified).< /P
>< P
>The blit function should not be called on a locked surface.< /P
>< P
>The results of blitting operations vary greatly depending on whether < TT
CLASS="LITERAL"
>SDL_SRCAPLHA< /TT
> is set or not. See < A
HREF="sdlsetalpha.html"
>SDL_SetAlpha< /A
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> for an explaination of how this affects your results. Colorkeying and alpha attributes also interact with surface blitting, as the following pseudo-code should hopefully explain.
< PRE
CLASS="PROGRAMLISTING"
>if (source surface has SDL_SRCALPHA set) {
if (source surface has alpha channel (that is, format-> Amask != 0))
blit using per-pixel alpha, ignoring any colour key
else {
if (source surface has SDL_SRCCOLORKEY set)
blit using the colour key AND the per-surface alpha value
else
blit using the per-surface alpha value
}
} else {
if (source surface has SDL_SRCCOLORKEY set)
blit using the colour key
else
ordinary opaque rectangular blit
}< /PRE
>< /P
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>< /DIV
>< DIV
CLASS="REFSECT1"
>< A
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NAME="AEN2328"
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>< /A
>< H2
>Return Value< /H2
>< P
>If the blit is successful, it returns < SPAN
CLASS="RETURNVALUE"
>0< /SPAN
>,
otherwise it returns < SPAN
CLASS="RETURNVALUE"
>-1< /SPAN
>.< /P
>< P
>If either of the surfaces were in video memory, and the blit returns
< SPAN
CLASS="RETURNVALUE"
>-2< /SPAN
>, the video memory was lost, so it should be
reloaded with artwork and re-blitted:
< PRE
CLASS="PROGRAMLISTING"
> while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
while ( SDL_LockSurface(image)) < 0 )
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SDL_Delay(10);
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-- Write image pixels to image-> pixels --
SDL_UnlockSurface(image);
}< /PRE
>
This happens under DirectX 5.0 when the system switches away from your
fullscreen application. Locking the surface will also fail until you
have access to the video memory again.< /P
>< /DIV
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>< A
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NAME="AEN2336"
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>< /A
>< H2
>See Also< /H2
>< P
>< A
HREF="sdllocksurface.html"
>< TT
CLASS="FUNCTION"
>SDL_LockSurface< /TT
>< /A
>,
< A
HREF="sdlfillrect.html"
>< TT
CLASS="FUNCTION"
>SDL_FillRect< /TT
>< /A
>,
< A
HREF="sdlsurface.html"
>< SPAN
CLASS="STRUCTNAME"
>SDL_Surface< /SPAN
>< /A
>,
< A
HREF="sdlrect.html"
>< SPAN
CLASS="STRUCTNAME"
>SDL_Rect< /SPAN
>< /A
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