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view docs/html/sdljoyhatevent.html @ 3333:b334b4f7dfa0
[SDL] Bad math in SDL_RenderCopy
Mason Wheeler to sdl
When I tried to render an image using something other than NULL for srcrect, it got horribly distorted. I traced it down to the fact that the math in the rectangle adjustments performed just before the call to renderer->RenderCopy is written inside out. It should look like this:
if (dstrect->w != real_dstrect.w) {
int deltax = (dstrect->x - real_dstrect.x);
int deltaw = (dstrect->w - real_dstrect.w);
real_srcrect.x += (deltax * real_srcrect.w) / dstrect->w;
real_srcrect.w += (deltaw * real_srcrect.w) / dstrect->w;
}
if (dstrect->h != real_dstrect.h) {
int deltay = (dstrect->y - real_dstrect.y);
int deltah = (dstrect->h - real_dstrect.h);
real_srcrect.y += (deltay * real_srcrect.h) / dstrect->h;
real_srcrect.h += (deltah * real_srcrect.h) / dstrect->h;
author | Sam Lantinga <slouken@libsdl.org> |
---|---|
date | Sat, 03 Oct 2009 16:23:16 +0000 |
parents | 355632dca928 |
children |
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<HTML ><HEAD ><TITLE >SDL_JoyHatEvent</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="SDL Event Structures." HREF="eventstructures.html"><LINK REL="PREVIOUS" TITLE="SDL_JoyButtonEvent" HREF="sdljoybuttonevent.html"><LINK REL="NEXT" TITLE="SDL_JoyBallEvent" HREF="sdljoyballevent.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="sdljoybuttonevent.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="sdljoyballevent.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLJOYHATEVENT" ></A >SDL_JoyHatEvent</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN4320" ></A ><H2 >Name</H2 >SDL_JoyHatEvent -- Joystick hat position change event structure</DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4323" ></A ><H2 >Structure Definition</H2 ><PRE CLASS="PROGRAMLISTING" >typedef struct{ Uint8 type; Uint8 which; Uint8 hat; Uint8 value; } SDL_JoyHatEvent;</PRE ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4326" ></A ><H2 >Structure Data</H2 ><DIV CLASS="INFORMALTABLE" ><A NAME="AEN4328" ></A ><P ></P ><TABLE BORDER="0" CLASS="CALSTABLE" ><TBODY ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >type</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="LITERAL" >SDL_JOY</TT ></TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >which</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Joystick device index</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >hat</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Joystick hat index</TD ></TR ><TR ><TD ALIGN="LEFT" VALIGN="TOP" ><TT CLASS="STRUCTFIELD" ><I >value</I ></TT ></TD ><TD ALIGN="LEFT" VALIGN="TOP" >Hat position</TD ></TR ></TBODY ></TABLE ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4348" ></A ><H2 >Description</H2 ><P ><SPAN CLASS="STRUCTNAME" >SDL_JoyHatEvent</SPAN > is a member of the <A HREF="sdlevent.html" ><SPAN CLASS="STRUCTNAME" >SDL_Event</SPAN ></A > union and is used when an event of type <TT CLASS="LITERAL" >SDL_JOYHATMOTION</TT > is reported.</P ><P >A <TT CLASS="LITERAL" >SDL_JOYHATMOTION</TT > event occurs when ever a user moves a hat on the joystick. The field <TT CLASS="STRUCTFIELD" ><I >which</I ></TT > is the index of the joystick that reported the event and <TT CLASS="STRUCTFIELD" ><I >hat</I ></TT > is the index of the hat (for a more detailed exlaination see the <A HREF="joystick.html" >Joystick section</A >). <TT CLASS="STRUCTFIELD" ><I >value</I ></TT > is the current position of the hat. It is a logically OR'd combination of the following values (whose meanings should be pretty obvious:) :</P ><P ></P ><TABLE BORDER="0" ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_CENTERED</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_UP</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_RIGHT</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_DOWN</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_LEFT</TT ></TD ></TR ></TBODY ></TABLE ><P ></P ><P >The following defines are also provided:</P ><P ></P ><TABLE BORDER="0" ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_RIGHTUP</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_RIGHTDOWN</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_LEFTUP</TT ></TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >SDL_HAT_LEFTDOWN</TT ></TD ></TR ></TBODY ></TABLE ><P ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN4382" ></A ><H2 >See Also</H2 ><P ><A HREF="sdlevent.html" ><SPAN CLASS="STRUCTNAME" >SDL_Event</SPAN ></A >, <A HREF="joystick.html" >Joystick Functions</A >, <A HREF="sdljoystickeventstate.html" ><TT CLASS="FUNCTION" >SDL_JoystickEventState</TT ></A >, <A HREF="sdljoystickgetball.html" ><TT CLASS="FUNCTION" >SDL_JoystickGetHat</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="sdljoybuttonevent.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="sdljoyballevent.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_JoyButtonEvent</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="eventstructures.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SDL_JoyBallEvent</TD ></TR ></TABLE ></DIV ></BODY ></HTML >