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| >SDL_BlitSurface</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN2299" |
| ></A |
| ><H2 |
| >Name</H2 |
| >SDL_BlitSurface -- This performs a fast blit from the source surface to the destination surface.</DIV |
| ><DIV |
| CLASS="REFSYNOPSISDIV" |
| ><A |
| NAME="AEN2302" |
| ></A |
| ><H2 |
| >Synopsis</H2 |
| ><DIV |
| CLASS="FUNCSYNOPSIS" |
| ><A |
| NAME="AEN2303" |
| ></A |
| ><P |
| ></P |
| ><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 |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN2309" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >This performs a fast blit from the source surface to the destination surface.</P |
| ><P |
| >The width and height in <TT |
| CLASS="PARAMETER" |
| ><I |
| >srcrect</I |
| ></TT |
| > determine the |
| size of the copied rectangle. Only the position is used in the |
| <TT |
| CLASS="PARAMETER" |
| ><I |
| >dstrect</I |
| ></TT |
| > (the width and height are ignored).</P |
| ><P |
| >If <TT |
| CLASS="PARAMETER" |
| ><I |
| >srcrect</I |
| ></TT |
| > is <TT |
| CLASS="LITERAL" |
| >NULL</TT |
| >, the |
| entire surface is copied. If <TT |
| CLASS="PARAMETER" |
| ><I |
| >dstrect</I |
| ></TT |
| > is |
| <TT |
| CLASS="LITERAL" |
| >NULL</TT |
| >, then the destination position (upper left |
| corner) is (0, 0).</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->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="AEN2328" |
| ></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 ) |
| SDL_Delay(10); |
| -- 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 |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN2336" |
| ></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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