e14743d1 |
1 | .TH "SDL_Event" "3" "Tue 11 Sep 2001, 22:59" "SDL" "SDL API Reference" |
2 | .SH "NAME" |
3 | SDL_Event \- General event structure |
4 | .SH "STRUCTURE DEFINITION" |
5 | .PP |
6 | .nf |
7 | \f(CWtypedef union{ |
8 | Uint8 type; |
9 | SDL_ActiveEvent active; |
10 | SDL_KeyboardEvent key; |
11 | SDL_MouseMotionEvent motion; |
12 | SDL_MouseButtonEvent button; |
13 | SDL_JoyAxisEvent jaxis; |
14 | SDL_JoyBallEvent jball; |
15 | SDL_JoyHatEvent jhat; |
16 | SDL_JoyButtonEvent jbutton; |
17 | SDL_ResizeEvent resize; |
18 | SDL_ExposeEvent expose; |
19 | SDL_QuitEvent quit; |
20 | SDL_UserEvent user; |
21 | SDL_SysWMEvent syswm; |
22 | } SDL_Event;\fR |
23 | .fi |
24 | .PP |
25 | .SH "STRUCTURE DATA" |
26 | .TP 20 |
27 | \fBtype\fR |
28 | The type of event |
29 | .TP 20 |
30 | \fBactive\fR |
31 | \fIActivation event\fR |
32 | .TP 20 |
33 | \fBkey\fR |
34 | \fIKeyboard event\fR |
35 | .TP 20 |
36 | \fBmotion\fR |
37 | \fIMouse motion event\fR |
38 | .TP 20 |
39 | \fBbutton\fR |
40 | \fIMouse button event\fR |
41 | .TP 20 |
42 | \fBjaxis\fR |
43 | \fIJoystick axis motion event\fR |
44 | .TP 20 |
45 | \fBjball\fR |
46 | \fIJoystick trackball motion event\fR |
47 | .TP 20 |
48 | \fBjhat\fR |
49 | \fIJoystick hat motion event\fR |
50 | .TP 20 |
51 | \fBjbutton\fR |
52 | \fIJoystick button event\fR |
53 | .TP 20 |
54 | \fBresize\fR |
55 | \fIApplication window resize event\fR |
56 | .TP 20 |
57 | \fBexpose\fR |
58 | \fIApplication window expose event\fR |
59 | .TP 20 |
60 | \fBquit\fR |
61 | \fIApplication quit request event\fR |
62 | .TP 20 |
63 | \fBuser\fR |
64 | \fIUser defined event\fR |
65 | .TP 20 |
66 | \fBsyswm\fR |
67 | \fIUndefined window manager event\fR |
68 | .SH "DESCRIPTION" |
69 | .PP |
70 | The \fBSDL_Event\fR union is the core to all event handling is SDL, its probably the most important structure after \fBSDL_Surface\fR\&. \fBSDL_Event\fR is a union of all event structures used in SDL, using it is a simple matter of knowing which union member relates to which event \fBtype\fR\&. |
71 | .PP |
72 | .TP 20 |
73 | \fBEvent \fBtype\fR\fR |
74 | \fBEvent Structure\fR |
75 | .TP 20 |
76 | \fBSDL_ACTIVEEVENT\fP |
77 | \fI\fBSDL_ActiveEvent\fR\fR |
78 | .TP 20 |
79 | \fBSDL_KEYDOWN/UP\fP |
80 | \fI\fBSDL_KeyboardEvent\fR\fR |
81 | .TP 20 |
82 | \fBSDL_MOUSEMOTION\fP |
83 | \fI\fBSDL_MouseMotionEvent\fR\fR |
84 | .TP 20 |
85 | \fBSDL_MOUSEBUTTONDOWN/UP\fP |
86 | \fI\fBSDL_MouseButtonEvent\fR\fR |
87 | .TP 20 |
88 | \fBSDL_JOYAXISMOTION\fP |
89 | \fI\fBSDL_JoyAxisEvent\fR\fR |
90 | .TP 20 |
91 | \fBSDL_JOYBALLMOTION\fP |
92 | \fI\fBSDL_JoyBallEvent\fR\fR |
93 | .TP 20 |
94 | \fBSDL_JOYHATMOTION\fP |
95 | \fI\fBSDL_JoyHatEvent\fR\fR |
96 | .TP 20 |
97 | \fBSDL_JOYBUTTONDOWN/UP\fP |
98 | \fI\fBSDL_JoyButtonEvent\fR\fR |
99 | .TP 20 |
100 | \fBSDL_QUIT\fP |
101 | \fI\fBSDL_QuitEvent\fR\fR |
102 | .TP 20 |
103 | \fBSDL_SYSWMEVENT\fP |
104 | \fI\fBSDL_SysWMEvent\fR\fR |
105 | .TP 20 |
106 | \fBSDL_VIDEORESIZE\fP |
107 | \fI\fBSDL_ResizeEvent\fR\fR |
108 | .TP 20 |
109 | \fBSDL_VIDEOEXPOSE\fP |
110 | \fI\fBSDL_ExposeEvent\fR\fR |
111 | .TP 20 |
112 | \fBSDL_USEREVENT\fP |
113 | \fI\fBSDL_UserEvent\fR\fR |
114 | .SH "USE" |
115 | .PP |
116 | The \fBSDL_Event\fR structure has two uses |
117 | .IP " \(bu" 6 |
118 | Reading events on the event queue |
119 | .IP " \(bu" 6 |
120 | Placing events on the event queue |
121 | .PP |
122 | Reading events from the event queue is done with either \fI\fBSDL_PollEvent\fP\fR or \fI\fBSDL_PeepEvents\fP\fR\&. We\&'ll use \fBSDL_PollEvent\fP and step through an example\&. |
123 | .PP |
124 | First off, we create an empty \fBSDL_Event\fR structure\&. |
125 | .PP |
126 | .nf |
127 | \f(CWSDL_Event test_event;\fR |
128 | .fi |
129 | .PP |
130 | \fBSDL_PollEvent\fP removes the next event from the event queue, if there are no events on the queue it returns \fB0\fR otherwise it returns \fB1\fR\&. We use a \fBwhile\fP loop to process each event in turn\&. |
131 | .PP |
132 | .nf |
133 | \f(CWwhile(SDL_PollEvent(&test_event)) {\fR |
134 | .fi |
135 | .PP |
136 | The \fBSDL_PollEvent\fP function take a pointer to an \fBSDL_Event\fR structure that is to be filled with event information\&. We know that if \fBSDL_PollEvent\fP removes an event from the queue then the event information will be placed in our \fBtest_event\fR structure, but we also know that the \fItype\fP of event will be placed in the \fBtype\fR member of \fBtest_event\fR\&. So to handle each event \fBtype\fR seperately we use a \fBswitch\fP statement\&. |
137 | .PP |
138 | .nf |
139 | \f(CW switch(test_event\&.type) {\fR |
140 | .fi |
141 | .PP |
142 | We need to know what kind of events we\&'re looking for \fIand\fP the event \fBtype\fR\&'s of those events\&. So lets assume we want to detect where the user is moving the mouse pointer within our application\&. We look through our event types and notice that \fBSDL_MOUSEMOTION\fP is, more than likely, the event we\&'re looking for\&. A little \fImore\fR research tells use that \fBSDL_MOUSEMOTION\fP events are handled within the \fI\fBSDL_MouseMotionEvent\fR\fR structure which is the \fBmotion\fR member of \fBSDL_Event\fR\&. We can check for the \fBSDL_MOUSEMOTION\fP event \fBtype\fR within our \fBswitch\fP statement like so: |
143 | .PP |
144 | .nf |
145 | \f(CW case SDL_MOUSEMOTION:\fR |
146 | .fi |
147 | .PP |
148 | All we need do now is read the information out of the \fBmotion\fR member of \fBtest_event\fR\&. |
149 | .PP |
150 | .nf |
151 | \f(CW printf("We got a motion event\&. |
152 | "); |
153 | printf("Current mouse position is: (%d, %d) |
154 | ", test_event\&.motion\&.x, test_event\&.motion\&.y); |
155 | break; |
156 | default: |
157 | printf("Unhandled Event! |
158 | "); |
159 | break; |
160 | } |
161 | } |
162 | printf("Event queue empty\&. |
163 | ");\fR |
164 | .fi |
165 | .PP |
166 | .PP |
167 | It is also possible to push events onto the event queue and so use it as a two-way communication path\&. Both \fI\fBSDL_PushEvent\fP\fR and \fI\fBSDL_PeepEvents\fP\fR allow you to place events onto the event queue\&. This is usually used to place a \fBSDL_USEREVENT\fP on the event queue, however you could use it to post fake input events if you wished\&. Creating your own events is a simple matter of choosing the event type you want, setting the \fBtype\fR member and filling the appropriate member structure with information\&. |
168 | .PP |
169 | .nf |
170 | \f(CWSDL_Event user_event; |
171 | |
172 | user_event\&.type=SDL_USEREVENT; |
173 | user_event\&.user\&.code=2; |
174 | user_event\&.user\&.data1=NULL; |
175 | user_event\&.user\&.data2=NULL; |
176 | SDL_PushEvent(&user_event);\fR |
177 | .fi |
178 | .PP |
179 | .SH "SEE ALSO" |
180 | .PP |
181 | \fI\fBSDL_PollEvent\fP\fR, \fI\fBSDL_PushEvent\fP\fR, \fI\fBSDL_PeepEvents\fP\fR |
182 | .\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:59 |