55 lines
1.5 KiB
C++
55 lines
1.5 KiB
C++
/*
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* \brief Clipping guard
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* \author Norman Feske
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* \date 2006-08-08
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*
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* When drawing views recursively, we need to successively shrink the clipping
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* area to the intersection of the existing clipping area and the area of the
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* current view. After each drawing operation, we want to restore the previous
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* clipping area. The clipping guard functions the same way as a lock guard.
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* The clipping area of the canvas that is specified at the constructor of the
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* clipping guard gets shrinked as long as the clip guard exists. When we leave
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* the drawing function, all local variables including the clipping guard gets
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* destroyed and the clipping guard's destructor resets the clipping area of
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* the canvas.
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*
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* This mechanism effectively replaces the explicit clipping stack of the
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* original Nitpicker version by folding the clipping stack into the normal
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* stack.
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*/
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/*
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* Copyright (C) 2006-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _CLIP_GUARD_H_
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#define _CLIP_GUARD_H_
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#include "canvas.h"
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class Clip_guard
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{
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private:
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Canvas_base &_canvas;
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Rect const _orig_clip_rect;
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public:
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Clip_guard(Canvas_base &canvas, Rect new_clip_rect)
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:
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_canvas(canvas),
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_orig_clip_rect(_canvas.clip())
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{
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_canvas.clip(Rect::intersect(_orig_clip_rect, new_clip_rect));
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}
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~Clip_guard() { _canvas.clip(_orig_clip_rect); }
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};
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#endif /* _CLIP_GUARD_H_ */
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