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view docs/html/sdlkeysym.html @ 765:4c2ba6161939
Editors Note: The original patch was modified to use SDL_Delay() instead of
nanosleep because nanosleep may not be portable to all systems
using SDL with the ALSA backend. This may be a moot point with
the switch to blocking writes anyway...
Date: Sat, 27 Dec 2003 21:47:36 +0100
From: Michel Daenzer
To: Debian Bug Tracking System
Subject: [SDL] Bug#225252: [PATCH] ALSA fixes
Package: libsdl1.2debian-all
Version: 1.2.6-2
Severity: normal
Tags: patch
For SDL 1.2.6, the ALSA backend was changed to call snd_pcm_open() with
SND_PCM_NONBLOCK. That's a good idea per se, however, it causes high CPU
usage, interrupted sound and stuttering in some games here. Taking a nanosleep
whenever snd_pcm_writei() returns -EAGAIN fixes this, but I think it's more
efficient to use blocking mode for the actual sound playback. Feedback from the
SDL and ALSA lists appreciated.
The patch also fixes the default ALSA device to be used.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sun, 04 Jan 2004 15:40:50 +0000 |
parents | e5bc29de3f0a |
children | 355632dca928 |
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<HTML ><HEAD ><TITLE >SDL_keysym</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.64 "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="SDL Event Structures." HREF="eventstructures.html"><LINK REL="PREVIOUS" TITLE="SDL_QuitEvent" HREF="sdlquitevent.html"><LINK REL="NEXT" TITLE="SDLKey" HREF="sdlkey.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlquitevent.html" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdlkey.html" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLKEYSYM" >SDL_keysym</A ></H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN4275" ></A ><H2 >Name</H2 >SDL_keysym -- Keysym structure</DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4278" ></A ><H2 >Structure Definition</H2 ><PRE CLASS="PROGRAMLISTING" >typedef struct{ Uint8 scancode; SDLKey sym; SDLMod mod; Uint16 unicode; } SDL_keysym;</PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4281" ></A ><H2 >Structure Data</H2 ><DIV CLASS="INFORMALTABLE" ><A NAME="AEN4283" ></A ><P ></P ><TABLE BORDER="0" CLASS="CALSTABLE" ><TBODY ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >scancode</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Hardware specific scancode</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >sym</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >SDL virtual keysym</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >mod</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Current key modifiers</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >unicode</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Translated character</TD ></TR ></TBODY ></TABLE ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4302" ></A ><H2 >Description</H2 ><P >The <SPAN CLASS="STRUCTNAME" >SDL_keysym</SPAN > structure is used by reporting key presses and releases since it is a part of the <A HREF="sdlkeyboardevent.html" ><SPAN CLASS="STRUCTNAME" >SDL_KeyboardEvent</SPAN ></A >.</P ><P >The <TT CLASS="STRUCTFIELD" ><I >scancode</I ></TT > field should generally be left alone, it is the hardware dependent scancode returned by the keyboard. The <TT CLASS="STRUCTFIELD" ><I >sym</I ></TT > field is extremely useful. It is the SDL-defined value of the key (see <A HREF="sdlkey.html" >SDL Key Syms</A >. This field is very useful when you are checking for certain key presses, like so: <PRE CLASS="PROGRAMLISTING" >. . while(SDL_PollEvent(&event)){ switch(event.type){ case SDL_KEYDOWN: if(event.key.keysym.sym==SDLK_LEFT) move_left(); break; . . . } } . .</PRE > <TT CLASS="STRUCTFIELD" ><I >mod</I ></TT > stores the current state of the keyboard modifiers as explained in <A HREF="sdlgetmodstate.html" ><TT CLASS="FUNCTION" >SDL_GetModState</TT ></A >. The <TT CLASS="STRUCTFIELD" ><I >unicode</I ></TT > is only used when UNICODE translation is enabled with <A HREF="sdlenableunicode.html" ><TT CLASS="FUNCTION" >SDL_EnableUNICODE</TT ></A >. If <TT CLASS="STRUCTFIELD" ><I >unicode</I ></TT > is non-zero then this a the UNICODE character corresponding to the keypress. If the high 9 bits of the character are 0, then this maps to the equivalent ASCII character: <PRE CLASS="PROGRAMLISTING" >char ch; if ( (keysym.unicode & 0xFF80) == 0 ) { ch = keysym.unicode & 0x7F; } else { printf("An International Character.\n"); }</PRE > UNICODE translation does have a slight overhead so don't enable it unless its needed.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4321" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlkey.html" ><SPAN CLASS="STRUCTNAME" >SDLKey</SPAN ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlquitevent.html" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdlkey.html" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_QuitEvent</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="eventstructures.html" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDLKey</TD ></TR ></TABLE ></DIV ></BODY ></HTML >