Added new docs for SDL 1.2.1
--HG-- extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%4056
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Sam Lantinga
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371 changed files with 3272 additions and 2287 deletions
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@ -4,7 +4,7 @@
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>Handling the Keyboard</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.61
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CONTENT="Modular DocBook HTML Stylesheet Version 1.64
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"><LINK
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REL="HOME"
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TITLE="SDL Library Documentation"
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@ -78,7 +78,7 @@ CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN205"
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NAME="AEN271"
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>Keyboard Related Structures</A
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></H2
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><P
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@ -88,7 +88,7 @@ CLASS="SECT3"
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><H3
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CLASS="SECT3"
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><A
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NAME="AEN208"
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NAME="AEN274"
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>SDLKey</A
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></H3
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><P
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@ -114,7 +114,7 @@ CLASS="SECT3"
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><H3
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CLASS="SECT3"
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><A
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NAME="AEN216"
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NAME="AEN282"
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>SDLMod</A
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></H3
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><P
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@ -134,7 +134,7 @@ CLASS="SECT3"
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><H3
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CLASS="SECT3"
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><A
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NAME="AEN222"
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NAME="AEN288"
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>SDL_keysym</A
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></H3
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><PRE
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@ -215,7 +215,7 @@ CLASS="SECT3"
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><H3
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CLASS="SECT3"
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><A
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NAME="AEN241"
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NAME="AEN307"
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>SDL_KeyboardEvent</A
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></H3
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><PRE
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@ -283,7 +283,7 @@ CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN258"
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NAME="AEN324"
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>Reading Keyboard Events</A
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></H2
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><P
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@ -308,8 +308,17 @@ CLASS="LITERAL"
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> events using a <TT
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CLASS="LITERAL"
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>switch</TT
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> statement, like so:
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<PRE
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> statement, like so:</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN334"
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></A
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><P
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><B
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>Example 3-10. Reading Keyboard Events</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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> SDL_Event event;
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.
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@ -334,15 +343,16 @@ CLASS="PROGRAMLISTING"
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}
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.
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.</PRE
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>
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This is a very basic example. No information about the key press or release is interpreted. We will explore the other extreme out our first full example below - reporting all available information about a keyboard event.</P
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></DIV
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><P
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>This is a very basic example. No information about the key press or release is interpreted. We will explore the other extreme out our first full example below - reporting all available information about a keyboard event.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN269"
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NAME="AEN338"
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>A More Detailed Look</A
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></H2
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><P
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@ -384,11 +394,11 @@ CLASS="NOTE"
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN282"
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NAME="AEN351"
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></A
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><P
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><B
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>Example 3-1. keys.c - Key event information</B
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>Example 3-11. Interpreting Key Event Information</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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@ -405,7 +415,7 @@ CLASS="PROGRAMLISTING"
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int quit = 0;
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/* Initialise SDL */
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if( SDL_Init( SDL_INIT_VIDEO ) ){
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if( SDL_Init( SDL_INIT_VIDEO ) < 0){
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fprintf( stderr, "Could not initialise SDL: %s\n", SDL_GetError() );
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exit( -1 );
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}
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@ -518,13 +528,13 @@ CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN285"
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NAME="AEN354"
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>Game-type Input</A
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></H2
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><P
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>I have found that people using keyboard events for games and other interactive applications don't always understand one fundemental point.</P
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><A
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NAME="AEN288"
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NAME="AEN357"
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></A
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><BLOCKQUOTE
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CLASS="BLOCKQUOTE"
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@ -575,8 +585,17 @@ CLASS="PROGRAMLISTING"
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>
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At first glance you may think this is a perfectly reasonable piece of code for the task, but it isn't. Like I said keyboard events only occur when a key changes state, so the user would have to press and release the left cursor key 100 times to move the alien 100 pixels to the left.</P
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><P
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>To get around this problem we must not use the events to change the position of the alien, we use the events to set flags which are then used in a seperate section of code to move the alien. Something like this:
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<PRE
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>To get around this problem we must not use the events to change the position of the alien, we use the events to set flags which are then used in a seperate section of code to move the alien. Something like this:</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN363"
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></A
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><P
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><B
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>Example 3-12. Proper Game Movement</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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> /* Alien screen coordinates */
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int alien_x=0, alien_y=0;
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@ -649,8 +668,9 @@ CLASS="PROGRAMLISTING"
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/* Update the alien position */
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alien_x += alien_xvel;
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alien_y += alien_yvel;</PRE
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>
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As can be seen, we use two extra variables, alien_xvel and alien_yvel, which represent the motion of the ship, it is these variables that we update when we detect keypresses and releases.</P
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></DIV
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><P
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>As can be seen, we use two extra variables, alien_xvel and alien_yvel, which represent the motion of the ship, it is these variables that we update when we detect keypresses and releases.</P
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></DIV
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></DIV
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><DIV
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