vgui_clip.cpp

/*
vgui_clip.cpp - clip in 2D space
Copyright (C) 2011 Uncle Mike

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

In addition, as a special exception, the author gives permission
to link the code of this program with VGUI library developed by
Valve, L.L.C ("Valve"). You must obey the GNU General Public License
in all respects for all of the code used other than VGUI library.
If you modify this file, you may extend this exception to your
version of the file, but you are not obligated to do so. If
you do not wish to do so, delete this exception statement
from your version.

*/

#include "vgui_main.h"
#include "wrect.h"
	
//-----------------------------------------------------------------------------
// For simulated scissor tests...
//-----------------------------------------------------------------------------
static wrect_t g_ScissorRect;
static qboolean g_bScissor = false;
namespace vgui_support {
//-----------------------------------------------------------------------------
// Enable/disable scissoring...
//-----------------------------------------------------------------------------
void EnableScissor( qboolean enable )
{
	g_bScissor = enable;
}

void SetScissorRect( int left, int top, int right, int bottom )
{
	// Check for a valid rectangle...
	assert( left <= right );
	assert( top <= bottom );

	g_ScissorRect.left = left;
	g_ScissorRect.top = top;
	g_ScissorRect.right = right;
	g_ScissorRect.bottom = bottom;
}

//-----------------------------------------------------------------------------
// Purpose: Used for clipping, produces an interpolated texture coordinate
//-----------------------------------------------------------------------------
inline float InterpTCoord( float val, float mins, float maxs, float tMin, float tMax )
{
	float	flPercent;

	if( mins != maxs )
		flPercent = (float)(val - mins) / (maxs - mins);
	else flPercent = 0.5f;

	return tMin + (tMax - tMin) * flPercent;
}

//-----------------------------------------------------------------------------
// Purpose: Does a scissor clip of the input rectangle.  
// Returns false if it is completely clipped off.
//-----------------------------------------------------------------------------
qboolean ClipRect( const vpoint_t &inUL, const vpoint_t &inLR, vpoint_t *pOutUL, vpoint_t *pOutLR )
{
	if( g_bScissor )
	{
		// pick whichever left side is larger
		if( g_ScissorRect.left > inUL.point[0] )
			pOutUL->point[0] = g_ScissorRect.left;
		else
			pOutUL->point[0] = inUL.point[0];

		// pick whichever right side is smaller
		if( g_ScissorRect.right <= inLR.point[0] )
			pOutLR->point[0] = g_ScissorRect.right;
		else
			pOutLR->point[0] = inLR.point[0];

		// pick whichever top side is larger
		if( g_ScissorRect.top > inUL.point[1] )
			pOutUL->point[1] = g_ScissorRect.top;
		else
			pOutUL->point[1] = inUL.point[1];

		// pick whichever bottom side is smaller
		if( g_ScissorRect.bottom <= inLR.point[1] )
			pOutLR->point[1] = g_ScissorRect.bottom;
		else
			pOutLR->point[1] = inLR.point[1];

		// Check for non-intersecting
		if(( pOutUL->point[0] > pOutLR->point[0] ) || ( pOutUL->point[1] > pOutLR->point[1] ))
		{
			return false;
		}

		pOutUL->coord[0] = InterpTCoord(pOutUL->point[0], 
				inUL.point[0], inLR.point[0], inUL.coord[0], inLR.coord[0] );
			pOutLR->coord[0] = InterpTCoord(pOutLR->point[0],  
				inUL.point[0], inLR.point[0], inUL.coord[0], inLR.coord[0] );

			pOutUL->coord[1] = InterpTCoord(pOutUL->point[1], 
				inUL.point[1], inLR.point[1], inUL.coord[1], inLR.coord[1] );
			pOutLR->coord[1] = InterpTCoord(pOutLR->point[1],  
				inUL.point[1], inLR.point[1], inUL.coord[1], inLR.coord[1] );
	}
	else
	{
		*pOutUL = inUL;
		*pOutLR = inLR;
	}
	return true;
}
}