Robin Gareus
70b00f5201
> This group functionality can be convenient for performing > intermediate compositing. One common use of a group is to > render objects as opaque within the group, (so that they > occlude each other), and then blend the result with > translucence onto the destination. https://www.cairographics.org/manual/cairo-cairo-t.html#cairo-push-group The main use case where will be to render opaque layered [MIDI] regions transparently onto a grid.
86 lines
2.8 KiB
C++
86 lines
2.8 KiB
C++
/*
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* Copyright (C) 2012 Carl Hetherington <carl@carlh.net>
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* Copyright (C) 2014-2015 Paul Davis <paul@linuxaudiosystems.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef __CANVAS_CONTAINER_H__
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#define __CANVAS_CONTAINER_H__
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#include "canvas/item.h"
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namespace ArdourCanvas
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{
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/** a Container is an item which has no content of its own
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* but renders its children in some geometrical arrangement.
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*
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* Imagined examples of containers:
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*
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* Container: renders each child at the child's self-determined position
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* Box: renders each child along an axis (vertical or horizontal)
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* Table/Grid: renders each child within a two-dimensional grid
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*
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* Other?
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*/
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class LIBCANVAS_API Container : public Item
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{
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public:
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Container (Canvas *);
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Container (Item *);
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Container (Item *, Duple const & position);
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/** The compute_bounding_box() method is likely to be identical
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* in all containers (the union of the children's bounding boxes).
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* It can be overridden as necessary.
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*/
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void compute_bounding_box () const;
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/** The render() method is likely to be identical in all containers
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* (just call Item::render_children()). It can be overridden as necessary.
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*/
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void render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const;
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/** The prepare_for_render() method is likely to be identical in all
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* containers (just call Item::prepare_for_render_children()). It can be
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* overridden as necessary.
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*/
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void prepare_for_render (Rect const & area) const;
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/** Render all children of this container as group,
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* so that they occlude each other. Then blend the result
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* onto the destination with the given alpha level.
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*
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* @param alpha
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* - alpha < 0 render normally, do not group rendering. This is the default.
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* - alpha == 0 do not render at all. rendered items would be invisible.
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* - alpha < 1.0 use a group to render objects, blend flattened result with the given transparency.
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* - alpha >= 1.0 simply blit the result of the grouped render operation.
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*/
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void set_render_with_alpha (double alpha);
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double render_with_alpha () const {
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return _render_with_alpha;
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}
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private:
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double _render_with_alpha;
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};
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}
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#endif
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