Mercurial > sdl-ios-xcode
annotate docs/html/guideinput.html @ 173:83018110dce8
Added initial support for EPOC/Symbian OS (thanks Hannu!)
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Tue, 11 Sep 2001 20:38:49 +0000 |
| parents | 55f1f1b3e27d |
| children | e5bc29de3f0a |
| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >Input handling</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="SDL Guide" | |
| 14 HREF="guide.html"><LINK | |
| 15 REL="PREVIOUS" | |
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16 TITLE="Using OpenGL With SDL" |
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17 HREF="guidevideoopengl.html"><LINK |
| 0 | 18 REL="NEXT" |
| 19 TITLE="Handling the Keyboard" | |
| 20 HREF="guideinputkeyboard.html"></HEAD | |
| 21 ><BODY | |
| 22 CLASS="CHAPTER" | |
| 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 | |
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47 HREF="guidevideoopengl.html" |
| 0 | 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="guideinputkeyboard.html" | |
| 61 >Next</A | |
| 62 ></TD | |
| 63 ></TR | |
| 64 ></TABLE | |
| 65 ><HR | |
| 66 ALIGN="LEFT" | |
| 67 WIDTH="100%"></DIV | |
| 68 ><DIV | |
| 69 CLASS="CHAPTER" | |
| 70 ><H1 | |
| 71 ><A | |
| 72 NAME="GUIDEINPUT" | |
| 73 >Chapter 3. Input handling</A | |
| 74 ></H1 | |
| 75 ><DIV | |
| 76 CLASS="TOC" | |
| 77 ><DL | |
| 78 ><DT | |
| 79 ><B | |
| 80 >Table of Contents</B | |
| 81 ></DT | |
| 82 ><DT | |
| 83 ><A | |
| 84 HREF="guideinput.html#GUIDEINPUTJOYSTICK" | |
| 85 >Handling Joysticks</A | |
| 86 ></DT | |
| 87 ><DT | |
| 88 ><A | |
| 89 HREF="guideinputkeyboard.html" | |
| 90 >Handling the Keyboard</A | |
| 91 ></DT | |
| 92 ></DL | |
| 93 ></DIV | |
| 94 ><DIV | |
| 95 CLASS="SECT1" | |
| 96 ><H1 | |
| 97 CLASS="SECT1" | |
| 98 ><A | |
| 99 NAME="GUIDEINPUTJOYSTICK" | |
| 100 >Handling Joysticks</A | |
| 101 ></H1 | |
| 102 ><DIV | |
| 103 CLASS="SECT2" | |
| 104 ><H2 | |
| 105 CLASS="SECT2" | |
| 106 ><A | |
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107 NAME="AEN135" |
| 0 | 108 >Initialization</A |
| 109 ></H2 | |
| 110 ><P | |
| 111 >The first step in using a joystick in a SDL program is to initialize the Joystick subsystems of SDL. This done by passing the <TT | |
| 112 CLASS="LITERAL" | |
| 113 >SDL_INIT_JOYSTICK</TT | |
| 114 > flag to <A | |
| 115 HREF="sdlinit.html" | |
| 116 ><TT | |
| 117 CLASS="FUNCTION" | |
| 118 >SDL_Init</TT | |
| 119 ></A | |
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120 >. The joystick flag will usually be used in conjunction with other flags (like the video flag) because the joystick is usually used to control something.</P |
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121 ><DIV |
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122 CLASS="EXAMPLE" |
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123 ><A |
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124 NAME="AEN141" |
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125 ></A |
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126 ><P |
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127 ><B |
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128 >Example 3-1. Initializing SDL with Joystick Support</B |
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129 ></P |
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130 ><PRE |
| 0 | 131 CLASS="PROGRAMLISTING" |
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132 > if (SDL_Init( SDL_INIT_VIDEO | SDL_INIT_JOYSTICK ) < 0) |
| 0 | 133 { |
| 134 fprintf(stderr, "Couldn't initialize SDL: %s\n", SDL_GetError()); | |
| 135 exit(1); | |
| 136 }</PRE | |
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137 ></DIV |
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138 ><P |
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139 >This will attempt to start SDL with both the video and the joystick subsystems activated.</P |
| 0 | 140 ></DIV |
| 141 ><DIV | |
| 142 CLASS="SECT2" | |
| 143 ><H2 | |
| 144 CLASS="SECT2" | |
| 145 ><A | |
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146 NAME="AEN145" |
| 0 | 147 >Querying</A |
| 148 ></H2 | |
| 149 ><P | |
| 150 >If we have reached this point then we can safely assume that the SDL library has been initialized and that the Joystick subsystem is active. We can now call some video and/or sound functions to get things going before we need the joystick. Eventually we have to make sure that there is actually a joystick to work with. It's wise to always check even if you know a joystick will be present on the system because it can also help detect when the joystick is unplugged. The function used to check for joysticks is <A | |
| 151 HREF="sdlnumjoysticks.html" | |
| 152 ><TT | |
| 153 CLASS="FUNCTION" | |
| 154 >SDL_NumJoysticks</TT | |
| 155 ></A | |
| 156 >.</P | |
| 157 ><P | |
| 158 >This function simply returns the number of joysticks available on the system. If it is at least one then we are in good shape. The next step is to determine which joystick the user wants to use. If the number of joysticks available is only one then it is safe to assume that one joystick is the one the user wants to use. SDL has a function to get the name of the joysticks as assigned by the operations system and that function is <A | |
| 159 HREF="sdljoystickname.html" | |
| 160 ><TT | |
| 161 CLASS="FUNCTION" | |
| 162 >SDL_JoystickName</TT | |
| 163 ></A | |
| 164 >. The joystick is specified by an index where 0 is the first joystick and the last joystick is the number returned by <TT | |
| 165 CLASS="FUNCTION" | |
| 166 >SDL_NumJoysticks</TT | |
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167 > - 1. In the demonstration a list of all available joysticks is printed to stdout.</P |
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168 ><DIV |
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169 CLASS="EXAMPLE" |
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170 ><A |
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171 NAME="AEN154" |
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172 ></A |
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173 ><P |
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174 ><B |
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175 >Example 3-2. Querying the Number of Available Joysticks</B |
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176 ></P |
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177 ><PRE |
| 0 | 178 CLASS="PROGRAMLISTING" |
| 179 > printf("%i joysticks were found.\n\n", SDL_NumJoysticks() ); | |
| 180 printf("The names of the joysticks are:\n"); | |
| 181 | |
| 182 for( i=0; i < SDL_NumJoysticks(); i++ ) | |
| 183 { | |
| 184 printf(" %s\n", SDL_JoystickName(i)); | |
| 185 }</PRE | |
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186 ></DIV |
| 0 | 187 ></DIV |
| 188 ><DIV | |
| 189 CLASS="SECT2" | |
| 190 ><H2 | |
| 191 CLASS="SECT2" | |
| 192 ><A | |
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193 NAME="AEN157" |
| 0 | 194 >Opening a Joystick and Receiving Joystick Events</A |
| 195 ></H2 | |
| 196 ><P | |
| 197 >SDL's event driven architecture makes working with joysticks a snap. Joysticks can trigger 4 different types of events: | |
| 198 <P | |
| 199 ></P | |
| 200 ><TABLE | |
| 201 BORDER="0" | |
| 202 ><TBODY | |
| 203 ><TR | |
| 204 ><TD | |
| 205 ><A | |
| 206 HREF="sdljoyaxisevent.html" | |
| 207 ><SPAN | |
| 208 CLASS="STRUCTNAME" | |
| 209 >SDL_JoyAxisEvent</SPAN | |
| 210 ></A | |
| 211 ></TD | |
| 212 ><TD | |
| 213 >Occurs when an axis changes</TD | |
| 214 ></TR | |
| 215 ><TR | |
| 216 ><TD | |
| 217 ><A | |
| 218 HREF="sdljoyballevent.html" | |
| 219 ><SPAN | |
| 220 CLASS="STRUCTNAME" | |
| 221 >SDL_JoyBallEvent</SPAN | |
| 222 ></A | |
| 223 ></TD | |
| 224 ><TD | |
| 225 >Occurs when a joystick trackball's position changes</TD | |
| 226 ></TR | |
| 227 ><TR | |
| 228 ><TD | |
| 229 ><A | |
| 230 HREF="sdljoyhatevent.html" | |
| 231 ><SPAN | |
| 232 CLASS="STRUCTNAME" | |
| 233 >SDL_JoyHatEvent</SPAN | |
| 234 ></A | |
| 235 ></TD | |
| 236 ><TD | |
| 237 >Occurs when a hat's position changes</TD | |
| 238 ></TR | |
| 239 ><TR | |
| 240 ><TD | |
| 241 ><A | |
| 242 HREF="sdljoybuttonevent.html" | |
| 243 ><SPAN | |
| 244 CLASS="STRUCTNAME" | |
| 245 >SDL_JoyButtonEvent</SPAN | |
| 246 ></A | |
| 247 ></TD | |
| 248 ><TD | |
| 249 >Occurs when a button is pressed or released</TD | |
| 250 ></TR | |
| 251 ></TBODY | |
| 252 ></TABLE | |
| 253 ><P | |
| 254 ></P | |
| 255 ></P | |
| 256 ><P | |
| 257 >Events are received from all joysticks opened. The first thing that needs to be done in order to receive joystick events is to call <A | |
| 258 HREF="sdljoystickeventstate.html" | |
| 259 ><TT | |
| 260 CLASS="FUNCTION" | |
| 261 >SDL_JoystickEventState</TT | |
| 262 ></A | |
| 263 > with the <TT | |
| 264 CLASS="LITERAL" | |
| 265 >SDL_ENABLE</TT | |
| 266 > flag. Next you must open the joysticks that you want to receive envents from. This is done with the <A | |
| 267 HREF="sdljoystickopen.html" | |
| 268 ><TT | |
| 269 CLASS="FUNCTION" | |
| 270 >SDL_JoystickOpen</TT | |
| 271 ></A | |
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272 > function. For the example we are only interested in events from the first joystick on the system, regardless of what it may be. To receive events from it we would do this:</P |
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273 ><DIV |
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274 CLASS="EXAMPLE" |
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275 ><A |
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276 NAME="AEN183" |
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277 ></A |
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278 ><P |
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279 ><B |
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280 >Example 3-3. Opening a Joystick</B |
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281 ></P |
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282 ><PRE |
| 0 | 283 CLASS="PROGRAMLISTING" |
| 284 > SDL_Joystick *joystick; | |
| 285 | |
| 286 SDL_JoystickEventState(SDL_ENABLE); | |
| 287 joystick = SDL_JoystickOpen(0);</PRE | |
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288 ></DIV |
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289 ><P |
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290 >If we wanted to receive events for other joysticks we would open them with calls to <TT |
| 0 | 291 CLASS="FUNCTION" |
| 292 >SDL_JoystickOpen</TT | |
| 293 > just like we opened joystick 0, except we would store the <SPAN | |
| 294 CLASS="STRUCTNAME" | |
| 295 >SDL_Joystick</SPAN | |
| 296 > structure they return in a different pointer. We only need the joystick pointer when we are querying the joysticks or when we are closing the joystick.</P | |
| 297 ><P | |
| 298 >Up to this point all the code we have is used just to initialize the joysticks in order to read values at run time. All we need now is an event loop, which is something that all SDL programs should have anyway to receive the systems quit events. We must now add code to check the event loop for at least some of the above mentioned events. Let's assume our event loop looks like this: | |
| 299 <PRE | |
| 300 CLASS="PROGRAMLISTING" | |
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301 > SDL_Event event; |
| 0 | 302 /* Other initializtion code goes here */ |
| 303 | |
| 304 /* Start main game loop here */ | |
| 305 | |
| 306 while(SDL_PollEvent(&event)) | |
| 307 { | |
| 308 switch(event.type) | |
| 309 { | |
| 310 case SDL_KEYDOWN: | |
| 311 /* handle keyboard stuff here */ | |
| 312 break; | |
| 313 | |
| 314 case SDL_QUIT: | |
| 315 /* Set whatever flags are necessary to */ | |
| 316 /* end the main game loop here */ | |
| 317 break; | |
| 318 } | |
| 319 } | |
| 320 | |
| 321 /* End loop here */</PRE | |
| 322 > | |
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323 To handle Joystick events we merely add cases for them, first we'll add axis handling code. Axis checks can get kinda of tricky because alot of the joystick events received are junk. Joystick axis have a tendency to vary just a little between polling due to the way they are designed. To compensate for this you have to set a threshold for changes and ignore the events that have'nt exceeded the threshold. 10% is usually a good threshold value. This sounds a lot more complicated than it is. Here is the Axis event handler:</P |
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324 ><DIV |
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325 CLASS="EXAMPLE" |
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326 ><A |
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327 NAME="AEN191" |
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328 ></A |
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329 ><P |
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330 ><B |
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331 >Example 3-4. Joystick Axis Events</B |
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332 ></P |
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333 ><PRE |
| 0 | 334 CLASS="PROGRAMLISTING" |
| 335 > case SDL_JOYAXISMOTION: /* Handle Joystick Motion */ | |
| 336 if ( ( event.jaxis.value < -3200 ) || (event.jaxis.value > 3200 ) ) | |
| 337 { | |
| 338 /* code goes here */ | |
| 339 } | |
| 340 break;</PRE | |
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341 ></DIV |
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342 ><P |
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343 >Another trick with axis events is that up-down and left-right movement are two different sets of axes. The most important axis is axis 0 (left-right) and axis 1 (up-down). To handle them seperatly in the code we do the following:</P |
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344 ><DIV |
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345 CLASS="EXAMPLE" |
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346 ><A |
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347 NAME="AEN195" |
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348 ></A |
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349 ><P |
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350 ><B |
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351 >Example 3-5. More Joystick Axis Events</B |
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352 ></P |
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353 ><PRE |
| 0 | 354 CLASS="PROGRAMLISTING" |
| 355 > case SDL_JOYAXISMOTION: /* Handle Joystick Motion */ | |
| 356 if ( ( event.jaxis.value < -3200 ) || (event.jaxis.value > 3200 ) ) | |
| 357 { | |
| 358 if( event.jaxis.axis == 0) | |
| 359 { | |
| 360 /* Left-right movement code goes here */ | |
| 361 } | |
| 362 | |
| 363 if( event.jaxis.axis == 1) | |
| 364 { | |
| 365 /* Up-Down movement code goes here */ | |
| 366 } | |
| 367 } | |
| 368 break;</PRE | |
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369 ></DIV |
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370 ><P |
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371 >Ideally the code here should use <TT |
| 0 | 372 CLASS="STRUCTFIELD" |
| 373 ><I | |
| 374 >event.jaxis.value</I | |
| 375 ></TT | |
| 376 > to scale something. For example lets assume you are using the joystick to control the movement of a spaceship. If the user is using an analog joystick and they push the stick a little bit they expect to move less than if they pushed it a lot. Designing your code for this situation is preferred because it makes the experience for users of analog controls better and remains the same for users of digital controls.</P | |
| 377 ><P | |
| 378 >If your joystick has any additional axis then they may be used for other sticks or throttle controls and those axis return values too just with different <TT | |
| 379 CLASS="STRUCTFIELD" | |
| 380 ><I | |
| 381 >event.jaxis.axis</I | |
| 382 ></TT | |
| 383 > values.</P | |
| 384 ><P | |
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385 >Button handling is simple compared to the axis checking.</P |
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386 ><DIV |
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387 CLASS="EXAMPLE" |
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388 ><A |
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389 NAME="AEN203" |
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390 ></A |
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391 ><P |
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392 ><B |
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393 >Example 3-6. Joystick Button Events</B |
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394 ></P |
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395 ><PRE |
| 0 | 396 CLASS="PROGRAMLISTING" |
| 397 > case SDL_JOYBUTTONDOWN: /* Handle Joystick Button Presses */ | |
| 398 if ( event.jbutton.button == 0 ) | |
| 399 { | |
| 400 /* code goes here */ | |
| 401 } | |
| 402 break;</PRE | |
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403 ></DIV |
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404 ><P |
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405 >Button checks are simpler than axis checks because a button can only be pressed or not pressed. The <TT |
| 0 | 406 CLASS="LITERAL" |
| 407 >SDL_JOYBUTTONDOWN</TT | |
| 408 > event is triggered when a button is pressed and the <TT | |
| 409 CLASS="LITERAL" | |
| 410 >SDL_JOYBUTTONUP</TT | |
| 411 > event is fired when a button is released. We do have to know what button was pressed though, that is done by reading the <TT | |
| 412 CLASS="STRUCTFIELD" | |
| 413 ><I | |
| 414 >event.jbutton.button</I | |
| 415 ></TT | |
| 416 > field.</P | |
| 417 ><P | |
| 418 >Lastly when we are through using our joysticks we should close them with a call to <A | |
| 419 HREF="sdljoystickclose.html" | |
| 420 ><TT | |
| 421 CLASS="FUNCTION" | |
| 422 >SDL_JoystickClose</TT | |
| 423 ></A | |
| 424 >. To close our opened joystick 0 we would do this at the end of our program: | |
| 425 <PRE | |
| 426 CLASS="PROGRAMLISTING" | |
| 427 > SDL_JoystickClose(joystick);</PRE | |
| 428 ></P | |
| 429 ></DIV | |
| 430 ><DIV | |
| 431 CLASS="SECT2" | |
| 432 ><H2 | |
| 433 CLASS="SECT2" | |
| 434 ><A | |
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435 NAME="AEN214" |
| 0 | 436 >Advanced Joystick Functions</A |
| 437 ></H2 | |
| 438 ><P | |
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439 >That takes care of the controls that you can count on being on every joystick under the sun, but there are a few extra things that SDL can support. Joyballs are next on our list, they are alot like axis we a few minor differences. Joyballs store relative changes unlike the the absolute postion stored in a axis event. Also one trackball event contains both the change in x and they change in y. Our case for it is as follows:</P |
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440 ><DIV |
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441 CLASS="EXAMPLE" |
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442 ><A |
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443 NAME="AEN217" |
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444 ></A |
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445 ><P |
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446 ><B |
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447 >Example 3-7. Joystick Ball Events</B |
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448 ></P |
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449 ><PRE |
| 0 | 450 CLASS="PROGRAMLISTING" |
| 451 > case SDL_JOYBALLMOTION: /* Handle Joyball Motion */ | |
| 452 if( event.jball.ball == 0 ) | |
| 453 { | |
| 454 /* ball handling */ | |
| 455 } | |
| 456 break;</PRE | |
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457 ></DIV |
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458 ><P |
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459 >The above checks the first joyball on the joystick. The change in position will be stored in <TT |
| 0 | 460 CLASS="STRUCTFIELD" |
| 461 ><I | |
| 462 >event.jball.xrel</I | |
| 463 ></TT | |
| 464 > and <TT | |
| 465 CLASS="STRUCTFIELD" | |
| 466 ><I | |
| 467 >event.jball.yrel</I | |
| 468 ></TT | |
| 469 >.</P | |
| 470 ><P | |
| 471 >Finally we have the hat event. Hats report only the direction they are pushed in. We check hat's position with the bitmasks: | |
| 472 | |
| 473 <P | |
| 474 ></P | |
| 475 ><TABLE | |
| 476 BORDER="0" | |
| 477 ><TBODY | |
| 478 ><TR | |
| 479 ><TD | |
| 480 ><TT | |
| 481 CLASS="LITERAL" | |
| 482 >SDL_HAT_CENTERED</TT | |
| 483 ></TD | |
| 484 ></TR | |
| 485 ><TR | |
| 486 ><TD | |
| 487 ><TT | |
| 488 CLASS="LITERAL" | |
| 489 >SDL_HAT_UP</TT | |
| 490 ></TD | |
| 491 ></TR | |
| 492 ><TR | |
| 493 ><TD | |
| 494 ><TT | |
| 495 CLASS="LITERAL" | |
| 496 >SDL_HAT_RIGHT</TT | |
| 497 ></TD | |
| 498 ></TR | |
| 499 ><TR | |
| 500 ><TD | |
| 501 ><TT | |
| 502 CLASS="LITERAL" | |
| 503 >SDL_HAT_DOWN</TT | |
| 504 ></TD | |
| 505 ></TR | |
| 506 ><TR | |
| 507 ><TD | |
| 508 ><TT | |
| 509 CLASS="LITERAL" | |
| 510 >SDL_HAT_LEFT</TT | |
| 511 ></TD | |
| 512 ></TR | |
| 513 ></TBODY | |
| 514 ></TABLE | |
| 515 ><P | |
| 516 ></P | |
| 517 > | |
| 518 | |
| 519 Also there are some predefined combinations of the above: | |
| 520 <P | |
| 521 ></P | |
| 522 ><TABLE | |
| 523 BORDER="0" | |
| 524 ><TBODY | |
| 525 ><TR | |
| 526 ><TD | |
| 527 ><TT | |
| 528 CLASS="LITERAL" | |
| 529 >SDL_HAT_RIGHTUP</TT | |
| 530 ></TD | |
| 531 ></TR | |
| 532 ><TR | |
| 533 ><TD | |
| 534 ><TT | |
| 535 CLASS="LITERAL" | |
| 536 >SDL_HAT_RIGHTDOWN</TT | |
| 537 ></TD | |
| 538 ></TR | |
| 539 ><TR | |
| 540 ><TD | |
| 541 ><TT | |
| 542 CLASS="LITERAL" | |
| 543 >SDL_HAT_LEFTUP</TT | |
| 544 ></TD | |
| 545 ></TR | |
| 546 ><TR | |
| 547 ><TD | |
| 548 ><TT | |
| 549 CLASS="LITERAL" | |
| 550 >SDL_HAT_LEFTDOWN</TT | |
| 551 ></TD | |
| 552 ></TR | |
| 553 ></TBODY | |
| 554 ></TABLE | |
| 555 ><P | |
| 556 ></P | |
| 557 > | |
| 558 | |
|
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559 Our case for the hat may resemble the following:</P |
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560 ><DIV |
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561 CLASS="EXAMPLE" |
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562 ><A |
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563 NAME="AEN244" |
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564 ></A |
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565 ><P |
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566 ><B |
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567 >Example 3-8. Joystick Hat Events</B |
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568 ></P |
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569 ><PRE |
| 0 | 570 CLASS="PROGRAMLISTING" |
| 571 > case SDL_JOYHATMOTION: /* Handle Hat Motion */ | |
| 572 if ( event.jhat.hat | SDL_HAT_UP ) | |
| 573 { | |
| 574 /* Do up stuff here */ | |
| 575 } | |
| 576 | |
| 577 if ( event.jhat.hat | SDL_HAT_LEFT ) | |
| 578 { | |
| 579 /* Do left stuff here */ | |
| 580 } | |
| 581 | |
| 582 if ( event.jhat.hat | SDL_HAT_RIGHTDOWN ) | |
| 583 { | |
| 584 /* Do right and down together stuff here */ | |
| 585 } | |
| 586 break;</PRE | |
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587 ></DIV |
| 0 | 588 ><P |
| 589 >In addition to the queries for number of joysticks on the system and their names there are additional functions to query the capabilities of attached joysticks: | |
| 590 <P | |
| 591 ></P | |
| 592 ><TABLE | |
| 593 BORDER="0" | |
| 594 ><TBODY | |
| 595 ><TR | |
| 596 ><TD | |
| 597 ><A | |
| 598 HREF="sdljoysticknumaxes.html" | |
| 599 ><TT | |
| 600 CLASS="FUNCTION" | |
| 601 >SDL_JoystickNumAxes</TT | |
| 602 ></A | |
| 603 ></TD | |
| 604 ><TD | |
| 605 >Returns the number of joysitck axes</TD | |
| 606 ></TR | |
| 607 ><TR | |
| 608 ><TD | |
| 609 ><A | |
| 610 HREF="sdljoysticknumbuttons.html" | |
| 611 ><TT | |
| 612 CLASS="FUNCTION" | |
| 613 >SDL_JoystickNumButtons</TT | |
| 614 ></A | |
| 615 ></TD | |
| 616 ><TD | |
| 617 >Returns the number of joysitck buttons</TD | |
| 618 ></TR | |
| 619 ><TR | |
| 620 ><TD | |
| 621 ><A | |
| 622 HREF="sdljoysticknumballs.html" | |
| 623 ><TT | |
| 624 CLASS="FUNCTION" | |
| 625 >SDL_JoystickNumBalls</TT | |
| 626 ></A | |
| 627 ></TD | |
| 628 ><TD | |
| 629 >Returns the number of joysitck balls</TD | |
| 630 ></TR | |
| 631 ><TR | |
| 632 ><TD | |
| 633 ><A | |
| 634 HREF="sdljoysticknumhats.html" | |
| 635 ><TT | |
| 636 CLASS="FUNCTION" | |
| 637 >SDL_JoystickNumHats</TT | |
| 638 ></A | |
| 639 ></TD | |
| 640 ><TD | |
| 641 >Returns the number of joysitck hats</TD | |
| 642 ></TR | |
| 643 ></TBODY | |
| 644 ></TABLE | |
| 645 ><P | |
| 646 ></P | |
| 647 > | |
| 648 | |
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649 To use these functions we just have to pass in the joystick structure we got when we opened the joystick. For Example:</P |
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650 ><DIV |
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651 CLASS="EXAMPLE" |
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652 ><A |
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653 NAME="AEN265" |
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654 ></A |
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655 ><P |
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656 ><B |
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657 >Example 3-9. Querying Joystick Characteristics</B |
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658 ></P |
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659 ><PRE |
| 0 | 660 CLASS="PROGRAMLISTING" |
| 661 > int number_of_buttons; | |
| 662 SDL_Joystick *joystick; | |
| 663 | |
| 664 joystick = SDL_JoystickOpen(0); | |
| 665 number_of_buttons = SDL_JoystickNumButtons(joystick);</PRE | |
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666 ></DIV |
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667 ><P |
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668 >This block of code would get the number of buttons on the first joystick in the system. </P |
| 0 | 669 ></DIV |
| 670 ></DIV | |
| 671 ></DIV | |
| 672 ><DIV | |
| 673 CLASS="NAVFOOTER" | |
| 674 ><HR | |
| 675 ALIGN="LEFT" | |
| 676 WIDTH="100%"><TABLE | |
| 677 WIDTH="100%" | |
| 678 BORDER="0" | |
| 679 CELLPADDING="0" | |
| 680 CELLSPACING="0" | |
| 681 ><TR | |
| 682 ><TD | |
| 683 WIDTH="33%" | |
| 684 ALIGN="left" | |
| 685 VALIGN="top" | |
| 686 ><A | |
|
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687 HREF="guidevideoopengl.html" |
| 0 | 688 >Prev</A |
| 689 ></TD | |
| 690 ><TD | |
| 691 WIDTH="34%" | |
| 692 ALIGN="center" | |
| 693 VALIGN="top" | |
| 694 ><A | |
| 695 HREF="index.html" | |
| 696 >Home</A | |
| 697 ></TD | |
| 698 ><TD | |
| 699 WIDTH="33%" | |
| 700 ALIGN="right" | |
| 701 VALIGN="top" | |
| 702 ><A | |
| 703 HREF="guideinputkeyboard.html" | |
| 704 >Next</A | |
| 705 ></TD | |
| 706 ></TR | |
| 707 ><TR | |
| 708 ><TD | |
| 709 WIDTH="33%" | |
| 710 ALIGN="left" | |
| 711 VALIGN="top" | |
|
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712 >Using OpenGL With SDL</TD |
| 0 | 713 ><TD |
| 714 WIDTH="34%" | |
| 715 ALIGN="center" | |
| 716 VALIGN="top" | |
| 717 ><A | |
| 718 HREF="guide.html" | |
| 719 >Up</A | |
| 720 ></TD | |
| 721 ><TD | |
| 722 WIDTH="33%" | |
| 723 ALIGN="right" | |
| 724 VALIGN="top" | |
| 725 >Handling the Keyboard</TD | |
| 726 ></TR | |
| 727 ></TABLE | |
| 728 ></DIV | |
| 729 ></BODY | |
| 730 ></HTML | |
| 731 > |