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view docs/html/sdljoystickgetaxis.html @ 1542:a8bf1aa21020
Fixed bug #15
SDL_blit_A.mmx-speed.patch.txt --
Speed improvements and a bugfix for the current GCC inline mmx
asm code:
- Changed some ops and removed some resulting useless ones.
- Added some instruction parallelism (some gain)
The resulting speed on my Xeon improved upto 35% depending on
the function (measured in fps).
- Fixed a bug where BlitRGBtoRGBSurfaceAlphaMMX() was
setting the alpha component on the destination surfaces (to
opaque-alpha) even when the surface had none.
SDL_blit_A.mmx-msvc.patch.txt --
MSVC mmx intrinsics version of the same GCC asm code.
MSVC compiler tries to parallelize the code and to avoid
register stalls, but does not always do a very good job.
Per-surface blending MSVC functions run quite a bit faster
than their pure-asm counterparts (upto 55% faster for 16bit
ones), but the per-pixel blending runs somewhat slower than asm.
- BlitRGBtoRGBSurfaceAlphaMMX and BlitRGBtoRGBPixelAlphaMMX (and all
variants) can now also handle formats other than (A)RGB8888. Formats
like RGBA8888 and some quite exotic ones are allowed -- like
RAGB8888, or actually anything having channels aligned on 8bit
boundary and full 8bit alpha (for per-pixel alpha blending).
The performance cost of this change is virtually 0 for per-surface
alpha blending (no extra ops inside the loop) and a single non-MMX
op inside the loop for per-pixel blending. In testing, the per-pixel
alpha blending takes a ~2% performance hit, but it still runs much
faster than the current code in CVS. If necessary, a separate function
with this functionality can be made.
This code requires Processor Pack for VC6.
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Wed, 15 Mar 2006 15:39:29 +0000 |
parents | 355632dca928 |
children |
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<HTML ><HEAD ><TITLE >SDL_JoystickGetAxis</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Joystick" HREF="joystick.html"><LINK REL="PREVIOUS" TITLE="SDL_JoystickUpdate" HREF="sdljoystickupdate.html"><LINK REL="NEXT" TITLE="SDL_JoystickGetHat" HREF="sdljoystickgethat.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation 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="sdljoystickupdate.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdljoystickgethat.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLJOYSTICKGETAXIS" ></A >SDL_JoystickGetAxis</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN6320" ></A ><H2 >Name</H2 >SDL_JoystickGetAxis -- Get the current state of an axis</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN6323" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN6324" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >Sint16 <B CLASS="FSFUNC" >SDL_JoystickGetAxis</B ></CODE >(SDL_Joystick *joystick, int axis);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6330" ></A ><H2 >Description</H2 ><P ><TT CLASS="FUNCTION" >SDL_JoystickGetAxis</TT > returns the current state of the given <TT CLASS="PARAMETER" ><I >axis</I ></TT > on the given <TT CLASS="PARAMETER" ><I >joystick</I ></TT >.</P ><P >On most modern joysticks the X axis is usually represented by <TT CLASS="PARAMETER" ><I >axis</I ></TT > 0 and the Y axis by <TT CLASS="PARAMETER" ><I >axis</I ></TT > 1. The value returned by <TT CLASS="FUNCTION" >SDL_JoystickGetAxis</TT > is a signed integer (-32768 to 32768) representing the current position of the <TT CLASS="PARAMETER" ><I >axis</I ></TT >, it maybe necessary to impose certain tolerances on these values to account for jitter. It is worth noting that some joysticks use axes 2 and 3 for extra buttons.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6341" ></A ><H2 >Return Value</H2 ><P >Returns a 16-bit signed integer representing the current position of the <TT CLASS="PARAMETER" ><I >axis</I ></TT >.</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6345" ></A ><H2 >Examples</H2 ><P ><PRE CLASS="PROGRAMLISTING" >Sint16 x_move, y_move; SDL_Joystick *joy1; . . x_move=SDL_JoystickGetAxis(joy1, 0); y_move=SDL_JoystickGetAxis(joy1, 1);</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN6349" ></A ><H2 >See Also</H2 ><P ><A HREF="sdljoysticknumaxes.html" ><TT CLASS="FUNCTION" >SDL_JoystickNumAxes</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdljoystickupdate.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="sdljoystickgethat.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_JoystickUpdate</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="joystick.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_JoystickGetHat</TD ></TR ></TABLE ></DIV ></BODY ></HTML >