sdl-ios-xcode: docs/html/guideinput.html comparison

comparison docs/html/guideinput.html @ 55:55f1f1b3e27d

Added new docs for SDL 1.2.1

author	Sam Lantinga <slouken@lokigames.com>
date	Sun, 10 Jun 2001 19:31:57 +0000
parents	74212992fb08
children	e5bc29de3f0a

comparison

equal deleted inserted replaced

-:028447a8a758
+:55f1f1b3e27d
 ><HEAD
 ><TITLE
 >Input handling</TITLE
 ><META
 NAME="GENERATOR"
-CONTENT="Modular DocBook HTML Stylesheet Version 1.61
+CONTENT="Modular DocBook HTML Stylesheet Version 1.64
 "><LINK
 REL="HOME"
 TITLE="SDL Library Documentation"
 HREF="index.html"><LINK
 REL="UP"
 TITLE="SDL Guide"
 HREF="guide.html"><LINK
 REL="PREVIOUS"
-TITLE="Graphics and Video"
+TITLE="Using OpenGL With SDL"
-HREF="guidevideo.html"><LINK
+HREF="guidevideoopengl.html"><LINK
 REL="NEXT"
 TITLE="Handling the Keyboard"
 HREF="guideinputkeyboard.html"></HEAD
 ><BODY
 CLASS="CHAPTER"
 ><TD
 WIDTH="10%"
 ALIGN="left"
 VALIGN="bottom"
 ><A
-HREF="guidevideo.html"
+HREF="guidevideoopengl.html"
 >Prev</A
 ></TD
 ><TD
 WIDTH="80%"
 ALIGN="center"
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
-NAME="AEN94"
+NAME="AEN135"
 >Initialization</A
 ></H2
 ><P
 >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
 CLASS="LITERAL"
 HREF="sdlinit.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_Init</TT
 ></A
->.  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.
+>.  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
-<PRE
+><DIV
-CLASS="PROGRAMLISTING"
+CLASS="EXAMPLE"
->    if ( ! SDL_Init( SDL_INIT_VIDEO | SDL_INIT_JOYSTICK ) )
+><A
+NAME="AEN141"
+></A
+><P
+><B
+>Example 3-1. Initializing SDL with Joystick Support</B
+></P
+><PRE
+CLASS="PROGRAMLISTING"
+>    if (SDL_Init( SDL_INIT_VIDEO | SDL_INIT_JOYSTICK ) &#60; 0)
 {
 fprintf(stderr, "Couldn't initialize SDL: %s\n", SDL_GetError());
 exit(1);
 }</PRE
->
+></DIV
-This will attempt to start SDL with both the video and the joystick subsystems activated.</P
+><P
+>This will attempt to start SDL with both the video and the joystick subsystems activated.</P
 ></DIV
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
-NAME="AEN101"
+NAME="AEN145"
 >Querying</A
 ></H2
 ><P
 >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
 HREF="sdlnumjoysticks.html"
 >SDL_JoystickName</TT
 ></A
 >.  The joystick is specified by an index where 0 is the first joystick and the last joystick is the number returned by <TT
 CLASS="FUNCTION"
 >SDL_NumJoysticks</TT
-> - 1.  In the demonstration a list of all available joysticks is printed to stdout.
+> - 1.  In the demonstration a list of all available joysticks is printed to stdout.</P
-<PRE
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN154"
+></A
+><P
+><B
+>Example 3-2. Querying the Number of Available Joysticks</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    printf("%i joysticks were found.\n\n", SDL_NumJoysticks() );
 printf("The names of the joysticks are:\n");
 for( i=0; i &#60; SDL_NumJoysticks(); i++ )
 {
 printf("    %s\n", SDL_JoystickName(i));
 }</PRE
-></P
+></DIV
 ></DIV
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
-NAME="AEN111"
+NAME="AEN157"
 >Opening a Joystick and Receiving Joystick Events</A
 ></H2
 ><P
 >SDL's event driven architecture makes working with joysticks a snap.  Joysticks can trigger 4 different types of events:
 <P
 HREF="sdljoystickopen.html"
 ><TT
 CLASS="FUNCTION"
 >SDL_JoystickOpen</TT
 ></A
-> 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:
+> 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
-<PRE
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN183"
+></A
+><P
+><B
+>Example 3-3. Opening a Joystick</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    SDL_Joystick *joystick;
 SDL_JoystickEventState(SDL_ENABLE);
 joystick = SDL_JoystickOpen(0);</PRE
->
+></DIV
-If we wanted to receive events for other joysticks we would open them with calls to <TT
+><P
+>If we wanted to receive events for other joysticks we would open them with calls to <TT
 CLASS="FUNCTION"
 >SDL_JoystickOpen</TT
 > just like we opened joystick 0, except we would store the <SPAN
 CLASS="STRUCTNAME"
 >SDL_Joystick</SPAN
 > 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
 ><P
 >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:
 <PRE
 CLASS="PROGRAMLISTING"
->    SDL_Event *event;
+>    SDL_Event event;
 /* Other initializtion code goes here */
 /* Start main game loop here */
 while(SDL_PollEvent(&#38;event))
 }
 }
 /* End loop here */</PRE
 >
-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:
+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
-<PRE
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN191"
+></A
+><P
+><B
+>Example 3-4. Joystick Axis Events</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_JOYAXISMOTION:  /* Handle Joystick Motion */
 if ( ( event.jaxis.value &#60; -3200 ) || (event.jaxis.value &#62; 3200 ) )
 {
 /* code goes here */
 }
 break;</PRE
->
+></DIV
-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
-<PRE
+>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
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN195"
+></A
+><P
+><B
+>Example 3-5. More Joystick Axis Events</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_JOYAXISMOTION:  /* Handle Joystick Motion */
 if ( ( event.jaxis.value &#60; -3200 ) || (event.jaxis.value &#62; 3200 ) )
 {
 if( event.jaxis.axis == 0)
 {
 /* Up-Down movement code goes here */
 }
 }
 break;</PRE
->
+></DIV
-Ideally the code here should use <TT
+><P
+>Ideally the code here should use <TT
 CLASS="STRUCTFIELD"
 ><I
 >event.jaxis.value</I
 ></TT
 > 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
 ><I
 >event.jaxis.axis</I
 ></TT
 > values.</P
 ><P
->Button handling is simple compared to the axis checking.
+>Button handling is simple compared to the axis checking.</P
-<PRE
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN203"
+></A
+><P
+><B
+>Example 3-6. Joystick Button Events</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_JOYBUTTONDOWN:  /* Handle Joystick Button Presses */
 if ( event.jbutton.button == 0 )
 {
 /* code goes here */
 }
 break;</PRE
->
+></DIV
+><P
-Button checks are simpler than axis checks because a button can only be pressed or not pressed.  The <TT
+>Button checks are simpler than axis checks because a button can only be pressed or not pressed.  The <TT
 CLASS="LITERAL"
 >SDL_JOYBUTTONDOWN</TT
 > event is triggered when a button is pressed and the <TT
 CLASS="LITERAL"
 >SDL_JOYBUTTONUP</TT
 ><DIV
 CLASS="SECT2"
 ><H2
 CLASS="SECT2"
 ><A
-NAME="AEN156"
+NAME="AEN214"
 >Advanced Joystick Functions</A
 ></H2
 ><P
->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:
+>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
-<PRE
+><DIV
+CLASS="EXAMPLE"
+><A
+NAME="AEN217"
+></A
+><P
+><B
+>Example 3-7. Joystick Ball Events</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_JOYBALLMOTION:  /* Handle Joyball Motion */
 if( event.jball.ball == 0 )
 {
 /* ball handling */
 }
 break;</PRE
->
+></DIV
-The above checks the first joyball on the joystick. The change in position will be stored in <TT
+><P
+>The above checks the first joyball on the joystick. The change in position will be stored in <TT
 CLASS="STRUCTFIELD"
 ><I
 >event.jball.xrel</I
 ></TT
 > and <TT
 ></TABLE
 ><P
 ></P
 >
-Our case for the hat may resemble the following:
+Our case for the hat may resemble the following:</P
+><DIV
-<PRE
+CLASS="EXAMPLE"
+><A
+NAME="AEN244"
+></A
+><P
+><B
+>Example 3-8. Joystick Hat Events</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    case SDL_JOYHATMOTION:  /* Handle Hat Motion */
 if ( event.jhat.hat | SDL_HAT_UP )
 {
 /* Do up stuff here */
 if ( event.jhat.hat | SDL_HAT_RIGHTDOWN )
 {
 /* Do right and down together stuff here */
 }
 break;</PRE
-></P
+></DIV
 ><P
 >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:
 <P
 ></P
 ><TABLE
 ></TABLE
 ><P
 ></P
 >
-To use these functions we just have to pass in the joystick structure we got when we opened the joystick. For Example:
+To use these functions we just have to pass in the joystick structure we got when we opened the joystick. For Example:</P
+><DIV
-<PRE
+CLASS="EXAMPLE"
+><A
+NAME="AEN265"
+></A
+><P
+><B
+>Example 3-9. Querying Joystick Characteristics</B
+></P
+><PRE
 CLASS="PROGRAMLISTING"
 >    int number_of_buttons;
 SDL_Joystick *joystick;
 joystick = SDL_JoystickOpen(0);
 number_of_buttons = SDL_JoystickNumButtons(joystick);</PRE
->
+></DIV
+><P
-This block of code would get the number of buttons on the first joystick in the system.	</P
+>This block of code would get the number of buttons on the first joystick in the system.	</P
 ></DIV
 ></DIV
 ></DIV
 ><DIV
 CLASS="NAVFOOTER"
 ><TD
 WIDTH="33%"
 ALIGN="left"
 VALIGN="top"
 ><A
-HREF="guidevideo.html"
+HREF="guidevideoopengl.html"
 >Prev</A
 ></TD
 ><TD
 WIDTH="34%"
 ALIGN="center"
 ><TR
 ><TD
 WIDTH="33%"
 ALIGN="left"
 VALIGN="top"
->Graphics and Video</TD
+>Using OpenGL With SDL</TD
 ><TD
 WIDTH="34%"
 ALIGN="center"
 VALIGN="top"
 ><A

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comparison docs/html/guideinput.html @ 55:55f1f1b3e27d