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><H1
><A
NAME="SDLBLITSURFACE"
>SDL_BlitSurface</A
></H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1915"
></A
><H2
>Name</H2
>SDL_BlitSurface&nbsp;--&nbsp;This performs a fast blit from the source surface to the destination surface.</DIV
><DIV
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><A
NAME="AEN1918"
></A
><H2
>Synopsis</H2
><DIV
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><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
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><DIV
CLASS="REFSECT1"
><A
NAME="AEN1925"
></A
><H2
>Description</H2
><P
>This performs a fast blit from the source surface to the destination surface.</P
><P
>Only the position is used in the <TT
CLASS="PARAMETER"
><I
>dstrect</I
></TT
> (the
width and height are ignored).</P
><P
>If either <TT
CLASS="PARAMETER"
><I
>srcrect</I
></TT
> or
<TT
CLASS="PARAMETER"
><I
>dstrect</I
></TT
> are <TT
CLASS="LITERAL"
>NULL</TT
>, the entire
surface (<TT
CLASS="PARAMETER"
><I
>src</I
></TT
> or <TT
CLASS="PARAMETER"
><I
>dst</I
></TT
>) is
copied.</P
><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
> 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-&#62;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
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1944"
></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)) &#60; 0 )
                        Sleep(10);
                -- Write image pixels to image-&#62;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
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1952"
></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
></P
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author	Sam Lantinga <slouken@libsdl.org>
date	Thu, 07 Mar 2002 20:23:11 +0000
parents	e5bc29de3f0a
children	355632dca928