Mercurial > sdl-ios-xcode
annotate docs/html/sdlsemwait.html @ 615:7ec821f3cbd0
Date: Thu, 17 Apr 2003 23:27:34 -0400
From: Darrell Walisser
Subject: Yet another OS X cursor bug
The synopsis:
1. Call SDL_ShowCursor(0);
2. Call SDL_SetVideoMode();
3. Call SDL_GetEvent();
3. Call SDL_ShowCursor(1);
The result: Sometimes the cursor doesn't come back! Ack! Oddly enough,
it does come back when mousing over the dock or clicking in the menu
bar. But that's besides the point.
The reason why this is happening is a flaw in the handling of
activation/deactivation events. The short explanation is that the
HideCursor() and ShowCursor() calls must be balanced, but if the cursor
was initially hidden, HideCursor() was called again on the activate
event - so now the next ShowCursor() fails (as does the next, and the
next, for some reason).
So, here's the patch. All it does is keep track of the
HideCursor()/ShowCursor() calls so that they will always be balanced.
author | Sam Lantinga <slouken@libsdl.org> |
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date | Sun, 20 Apr 2003 05:41:16 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
rev | line source |
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0 | 1 <HTML |
2 ><HEAD | |
3 ><TITLE | |
4 >SDL_SemWait</TITLE | |
5 ><META | |
6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
0 | 8 "><LINK |
9 REL="HOME" | |
10 TITLE="SDL Library Documentation" | |
11 HREF="index.html"><LINK | |
12 REL="UP" | |
13 TITLE="Multi-threaded Programming" | |
14 HREF="thread.html"><LINK | |
15 REL="PREVIOUS" | |
16 TITLE="SDL_DestroySemaphore" | |
17 HREF="sdldestroysemaphore.html"><LINK | |
18 REL="NEXT" | |
19 TITLE="SDL_SemTryWait" | |
20 HREF="sdlsemtrywait.html"></HEAD | |
21 ><BODY | |
22 CLASS="REFENTRY" | |
23 BGCOLOR="#FFF8DC" | |
24 TEXT="#000000" | |
25 LINK="#0000ee" | |
26 VLINK="#551a8b" | |
27 ALINK="#ff0000" | |
28 ><DIV | |
29 CLASS="NAVHEADER" | |
30 ><TABLE | |
31 WIDTH="100%" | |
32 BORDER="0" | |
33 CELLPADDING="0" | |
34 CELLSPACING="0" | |
35 ><TR | |
36 ><TH | |
37 COLSPAN="3" | |
38 ALIGN="center" | |
39 >SDL Library Documentation</TH | |
40 ></TR | |
41 ><TR | |
42 ><TD | |
43 WIDTH="10%" | |
44 ALIGN="left" | |
45 VALIGN="bottom" | |
46 ><A | |
47 HREF="sdldestroysemaphore.html" | |
48 >Prev</A | |
49 ></TD | |
50 ><TD | |
51 WIDTH="80%" | |
52 ALIGN="center" | |
53 VALIGN="bottom" | |
54 ></TD | |
55 ><TD | |
56 WIDTH="10%" | |
57 ALIGN="right" | |
58 VALIGN="bottom" | |
59 ><A | |
60 HREF="sdlsemtrywait.html" | |
61 >Next</A | |
62 ></TD | |
63 ></TR | |
64 ></TABLE | |
65 ><HR | |
66 ALIGN="LEFT" | |
67 WIDTH="100%"></DIV | |
68 ><H1 | |
69 ><A | |
70 NAME="SDLSEMWAIT" | |
71 >SDL_SemWait</A | |
72 ></H1 | |
73 ><DIV | |
74 CLASS="REFNAMEDIV" | |
75 ><A | |
181
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76 NAME="AEN7635" |
0 | 77 ></A |
78 ><H2 | |
79 >Name</H2 | |
80 >SDL_SemWait -- Lock a semaphore and suspend the thread if the semaphore value is zero.</DIV | |
81 ><DIV | |
82 CLASS="REFSYNOPSISDIV" | |
83 ><A | |
181
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84 NAME="AEN7638" |
0 | 85 ></A |
86 ><H2 | |
87 >Synopsis</H2 | |
88 ><DIV | |
89 CLASS="FUNCSYNOPSIS" | |
90 ><A | |
181
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91 NAME="AEN7639" |
0 | 92 ></A |
93 ><P | |
94 ></P | |
95 ><PRE | |
96 CLASS="FUNCSYNOPSISINFO" | |
97 >#include "SDL.h" | |
98 #include "SDL_thread.h"</PRE | |
99 ><P | |
100 ><CODE | |
101 ><CODE | |
102 CLASS="FUNCDEF" | |
103 >int <B | |
104 CLASS="FSFUNC" | |
105 >SDL_SemWait</B | |
106 ></CODE | |
107 >(SDL_sem *sem);</CODE | |
108 ></P | |
109 ><P | |
110 ></P | |
111 ></DIV | |
112 ></DIV | |
113 ><DIV | |
114 CLASS="REFSECT1" | |
115 ><A | |
181
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116 NAME="AEN7645" |
0 | 117 ></A |
118 ><H2 | |
119 >Description</H2 | |
120 ><P | |
121 ><TT | |
122 CLASS="FUNCTION" | |
123 >SDL_SemWait()</TT | |
124 > suspends the calling thread until either | |
125 the semaphore pointed to by <TT | |
126 CLASS="PARAMETER" | |
127 ><I | |
128 >sem</I | |
129 ></TT | |
130 > has a positive value, | |
131 the call is interrupted by a signal or error. If the call is successful it | |
132 will atomically decrement the semaphore value.</P | |
133 ><P | |
134 >After <TT | |
135 CLASS="FUNCTION" | |
136 >SDL_SemWait()</TT | |
137 > is successful, the semaphore | |
138 can be released and its count atomically incremented by a successful call to | |
139 <A | |
140 HREF="sdlsempost.html" | |
141 >SDL_SemPost</A | |
142 >.</P | |
143 ></DIV | |
144 ><DIV | |
145 CLASS="REFSECT1" | |
146 ><A | |
181
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147 NAME="AEN7653" |
0 | 148 ></A |
149 ><H2 | |
150 >Return Value</H2 | |
151 ><P | |
152 >Returns <SPAN | |
153 CLASS="RETURNVALUE" | |
154 >0</SPAN | |
155 > if successful or | |
156 <SPAN | |
157 CLASS="RETURNVALUE" | |
158 >-1</SPAN | |
159 > if there was an error (leaving the semaphore unchanged).</P | |
160 ></DIV | |
161 ><DIV | |
162 CLASS="REFSECT1" | |
163 ><A | |
181
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164 NAME="AEN7658" |
0 | 165 ></A |
166 ><H2 | |
167 >Examples</H2 | |
168 ><P | |
169 ><PRE | |
170 CLASS="PROGRAMLISTING" | |
171 >if (SDL_SemWait(my_sem) == -1) { | |
172 return WAIT_FAILED; | |
173 } | |
174 | |
175 ... | |
176 | |
177 SDL_SemPost(my_sem);</PRE | |
178 ></P | |
179 ></DIV | |
180 ><DIV | |
181 CLASS="REFSECT1" | |
182 ><A | |
181
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183 NAME="AEN7662" |
0 | 184 ></A |
185 ><H2 | |
186 >See Also</H2 | |
187 ><P | |
188 ><A | |
189 HREF="sdlcreatesemaphore.html" | |
190 ><TT | |
191 CLASS="FUNCTION" | |
192 >SDL_CreateSemaphore</TT | |
193 ></A | |
194 >, | |
195 <A | |
196 HREF="sdldestroysemaphore.html" | |
197 ><TT | |
198 CLASS="FUNCTION" | |
199 >SDL_DestroySemaphore</TT | |
200 ></A | |
201 >, | |
202 <A | |
203 HREF="sdlsemtrywait.html" | |
204 ><TT | |
205 CLASS="FUNCTION" | |
206 >SDL_SemTryWait</TT | |
207 ></A | |
208 >, | |
209 <A | |
210 HREF="sdlsemwaittimeout.html" | |
211 ><TT | |
212 CLASS="FUNCTION" | |
213 >SDL_SemWaitTimeout</TT | |
214 ></A | |
215 >, | |
216 <A | |
217 HREF="sdlsempost.html" | |
218 ><TT | |
219 CLASS="FUNCTION" | |
220 >SDL_SemPost</TT | |
221 ></A | |
222 >, | |
223 <A | |
224 HREF="sdlsemvalue.html" | |
225 ><TT | |
226 CLASS="FUNCTION" | |
227 >SDL_SemValue</TT | |
228 ></A | |
229 ></P | |
230 ></DIV | |
231 ><DIV | |
232 CLASS="NAVFOOTER" | |
233 ><HR | |
234 ALIGN="LEFT" | |
235 WIDTH="100%"><TABLE | |
236 WIDTH="100%" | |
237 BORDER="0" | |
238 CELLPADDING="0" | |
239 CELLSPACING="0" | |
240 ><TR | |
241 ><TD | |
242 WIDTH="33%" | |
243 ALIGN="left" | |
244 VALIGN="top" | |
245 ><A | |
246 HREF="sdldestroysemaphore.html" | |
247 >Prev</A | |
248 ></TD | |
249 ><TD | |
250 WIDTH="34%" | |
251 ALIGN="center" | |
252 VALIGN="top" | |
253 ><A | |
254 HREF="index.html" | |
255 >Home</A | |
256 ></TD | |
257 ><TD | |
258 WIDTH="33%" | |
259 ALIGN="right" | |
260 VALIGN="top" | |
261 ><A | |
262 HREF="sdlsemtrywait.html" | |
263 >Next</A | |
264 ></TD | |
265 ></TR | |
266 ><TR | |
267 ><TD | |
268 WIDTH="33%" | |
269 ALIGN="left" | |
270 VALIGN="top" | |
271 >SDL_DestroySemaphore</TD | |
272 ><TD | |
273 WIDTH="34%" | |
274 ALIGN="center" | |
275 VALIGN="top" | |
276 ><A | |
277 HREF="thread.html" | |
278 >Up</A | |
279 ></TD | |
280 ><TD | |
281 WIDTH="33%" | |
282 ALIGN="right" | |
283 VALIGN="top" | |
284 >SDL_SemTryWait</TD | |
285 ></TR | |
286 ></TABLE | |
287 ></DIV | |
288 ></BODY | |
289 ></HTML | |
290 > |