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70 | WIDTH="100%"></DIV |
71 | ><H1 |
72 | ><A |
73 | NAME="SDLBLITSURFACE" |
74 | ></A |
75 | >SDL_BlitSurface</H1 |
76 | ><DIV |
77 | CLASS="REFNAMEDIV" |
78 | ><A |
79 | NAME="AEN2299" |
80 | ></A |
81 | ><H2 |
82 | >Name</H2 |
83 | >SDL_BlitSurface -- This performs a fast blit from the source surface to the destination surface.</DIV |
84 | ><DIV |
85 | CLASS="REFSYNOPSISDIV" |
86 | ><A |
87 | NAME="AEN2302" |
88 | ></A |
89 | ><H2 |
90 | >Synopsis</H2 |
91 | ><DIV |
92 | CLASS="FUNCSYNOPSIS" |
93 | ><A |
94 | NAME="AEN2303" |
95 | ></A |
96 | ><P |
97 | ></P |
98 | ><PRE |
99 | CLASS="FUNCSYNOPSISINFO" |
100 | >#include "SDL.h"</PRE |
101 | ><P |
102 | ><CODE |
103 | ><CODE |
104 | CLASS="FUNCDEF" |
105 | >int <B |
106 | CLASS="FSFUNC" |
107 | >SDL_BlitSurface</B |
108 | ></CODE |
109 | >(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);</CODE |
110 | ></P |
111 | ><P |
112 | ></P |
113 | ></DIV |
114 | ></DIV |
115 | ><DIV |
116 | CLASS="REFSECT1" |
117 | ><A |
118 | NAME="AEN2309" |
119 | ></A |
120 | ><H2 |
121 | >Description</H2 |
122 | ><P |
123 | >This performs a fast blit from the source surface to the destination surface.</P |
124 | ><P |
125 | >The width and height in <TT |
126 | CLASS="PARAMETER" |
127 | ><I |
128 | >srcrect</I |
129 | ></TT |
130 | > determine the |
131 | size of the copied rectangle. Only the position is used in the |
132 | <TT |
133 | CLASS="PARAMETER" |
134 | ><I |
135 | >dstrect</I |
136 | ></TT |
137 | > (the width and height are ignored).</P |
138 | ><P |
139 | >If <TT |
140 | CLASS="PARAMETER" |
141 | ><I |
142 | >srcrect</I |
143 | ></TT |
144 | > is <TT |
145 | CLASS="LITERAL" |
146 | >NULL</TT |
147 | >, the |
148 | entire surface is copied. If <TT |
149 | CLASS="PARAMETER" |
150 | ><I |
151 | >dstrect</I |
152 | ></TT |
153 | > is |
154 | <TT |
155 | CLASS="LITERAL" |
156 | >NULL</TT |
157 | >, then the destination position (upper left |
158 | corner) is (0, 0).</P |
159 | ><P |
160 | >The final blit rectangle is saved in |
161 | <TT |
162 | CLASS="PARAMETER" |
163 | ><I |
164 | >dstrect</I |
165 | ></TT |
166 | > after all clipping is performed |
167 | (<TT |
168 | CLASS="PARAMETER" |
169 | ><I |
170 | >srcrect</I |
171 | ></TT |
172 | > is not modified).</P |
173 | ><P |
174 | >The blit function should not be called on a locked surface.</P |
175 | ><P |
176 | >The results of blitting operations vary greatly depending on whether <TT |
177 | CLASS="LITERAL" |
178 | >SDL_SRCAPLHA</TT |
179 | > is set or not. See <A |
180 | HREF="sdlsetalpha.html" |
181 | >SDL_SetAlpha</A |
182 | > 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. |
183 | <PRE |
184 | CLASS="PROGRAMLISTING" |
185 | >if (source surface has SDL_SRCALPHA set) { |
186 | if (source surface has alpha channel (that is, format->Amask != 0)) |
187 | blit using per-pixel alpha, ignoring any colour key |
188 | else { |
189 | if (source surface has SDL_SRCCOLORKEY set) |
190 | blit using the colour key AND the per-surface alpha value |
191 | else |
192 | blit using the per-surface alpha value |
193 | } |
194 | } else { |
195 | if (source surface has SDL_SRCCOLORKEY set) |
196 | blit using the colour key |
197 | else |
198 | ordinary opaque rectangular blit |
199 | }</PRE |
200 | ></P |
201 | ></DIV |
202 | ><DIV |
203 | CLASS="REFSECT1" |
204 | ><A |
205 | NAME="AEN2328" |
206 | ></A |
207 | ><H2 |
208 | >Return Value</H2 |
209 | ><P |
210 | >If the blit is successful, it returns <SPAN |
211 | CLASS="RETURNVALUE" |
212 | >0</SPAN |
213 | >, |
214 | otherwise it returns <SPAN |
215 | CLASS="RETURNVALUE" |
216 | >-1</SPAN |
217 | >.</P |
218 | ><P |
219 | >If either of the surfaces were in video memory, and the blit returns |
220 | <SPAN |
221 | CLASS="RETURNVALUE" |
222 | >-2</SPAN |
223 | >, the video memory was lost, so it should be |
224 | reloaded with artwork and re-blitted: |
225 | <PRE |
226 | CLASS="PROGRAMLISTING" |
227 | > while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) { |
228 | while ( SDL_LockSurface(image)) < 0 ) |
229 | SDL_Delay(10); |
230 | -- Write image pixels to image->pixels -- |
231 | SDL_UnlockSurface(image); |
232 | }</PRE |
233 | > |
234 | This happens under DirectX 5.0 when the system switches away from your |
235 | fullscreen application. Locking the surface will also fail until you |
236 | have access to the video memory again.</P |
237 | ></DIV |
238 | ><DIV |
239 | CLASS="REFSECT1" |
240 | ><A |
241 | NAME="AEN2336" |
242 | ></A |
243 | ><H2 |
244 | >See Also</H2 |
245 | ><P |
246 | ><A |
247 | HREF="sdllocksurface.html" |
248 | ><TT |
249 | CLASS="FUNCTION" |
250 | >SDL_LockSurface</TT |
251 | ></A |
252 | >, |
253 | <A |
254 | HREF="sdlfillrect.html" |
255 | ><TT |
256 | CLASS="FUNCTION" |
257 | >SDL_FillRect</TT |
258 | ></A |
259 | >, |
260 | <A |
261 | HREF="sdlsurface.html" |
262 | ><SPAN |
263 | CLASS="STRUCTNAME" |
264 | >SDL_Surface</SPAN |
265 | ></A |
266 | >, |
267 | <A |
268 | HREF="sdlrect.html" |
269 | ><SPAN |
270 | CLASS="STRUCTNAME" |
271 | >SDL_Rect</SPAN |
272 | ></A |
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