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[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
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><TITLE
>SDL_PumpEvents</TITLE
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><H1
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>SDL_PumpEvents</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN5387"
></A
><H2
>Name</H2
>SDL_PumpEvents&nbsp;--&nbsp;Pumps the event loop, gathering events from the input devices.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN5390"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN5391"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void <B
CLASS="FSFUNC"
>SDL_PumpEvents</B
></CODE
>(void);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN5397"
></A
><H2
>Description</H2
><P
>Pumps the event loop, gathering events from the input devices.</P
><P
><TT
CLASS="FUNCTION"
>SDL_PumpEvents</TT
> gathers all the pending input information from devices and places it on the event queue. Without calls to <TT
CLASS="FUNCTION"
>SDL_PumpEvents</TT
> no events would ever be placed on the queue. Often calls the need for <TT
CLASS="FUNCTION"
>SDL_PumpEvents</TT
> is hidden from the user since <A
HREF="sdlpollevent.html"
><TT
CLASS="FUNCTION"
>SDL_PollEvent</TT
></A
> and <A
HREF="sdlwaitevent.html"
><TT
CLASS="FUNCTION"
>SDL_WaitEvent</TT
></A
> implicitly call <TT
CLASS="FUNCTION"
>SDL_PumpEvents</TT
>. However, if you are not polling or waiting for events (e.g. you are filtering them), then you must call <TT
CLASS="FUNCTION"
>SDL_PumpEvents</TT
> to force an event queue update.</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>You can only call this function in the thread that set the video mode.</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN5412"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlpollevent.html"
><TT
CLASS="FUNCTION"
>SDL_PollEvent</TT
></A
></P
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