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view docs/man3/SDL_UserEvent.3 @ 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 | 546f7c1eb755 |
children | 1238da4a7112 |
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.TH "SDL_UserEvent" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" .SH "NAME" SDL_UserEvent \- A user-defined event type .SH "STRUCTURE DEFINITION" .PP .nf \f(CWtypedef struct{ Uint8 type; int code; void *data1; void *data2; } SDL_UserEvent;\fR .fi .PP .SH "STRUCTURE DATA" .TP 20 \fBtype\fR \fBSDL_USEREVENT\fP through to \fBSDL_NUMEVENTS-1\fP .TP 20 \fBcode\fR User defined event code .TP 20 \fBdata1\fR User defined data pointer .TP 20 \fBdata2\fR User defined data pointer .SH "DESCRIPTION" .PP \fBSDL_UserEvent\fR is in the \fBuser\fR member of the structure \fI\fBSDL_Event\fR\fR\&. This event is unique, it is never created by SDL but only by the user\&. The event can be pushed onto the event queue using \fI\fBSDL_PushEvent\fP\fR\&. The contents of the structure members or completely up to the programmer, the only requirement is that \fBtype\fR is a value from \fBSDL_USEREVENT\fP to \fBSDL_NUMEVENTS-1\fP (inclusive)\&. .SH "EXAMPLES" .PP .PP .nf \f(CWSDL_Event event; event\&.type = SDL_USEREVENT; event\&.user\&.code = my_event_code; event\&.user\&.data1 = significant_data; event\&.user\&.data2 = 0; SDL_PushEvent(&event);\fR .fi .PP .SH "SEE ALSO" .PP \fI\fBSDL_Event\fR\fR, \fI\fBSDL_PushEvent\fP\fR ...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00