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.
85 lines
2.0 KiB
C++
85 lines
2.0 KiB
C++
/*
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* Copyright (C) 2012 Carl Hetherington <carl@carlh.net>
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* Copyright (C) 2014-2017 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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#include "canvas/container.h"
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using namespace ArdourCanvas;
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Container::Container (Canvas* canvas)
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: Item (canvas)
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, _render_with_alpha (-1)
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{
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}
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Container::Container (Item* parent)
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: Item (parent)
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, _render_with_alpha (-1)
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{
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}
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Container::Container (Item* parent, Duple const & p)
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: Item (parent, p)
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, _render_with_alpha (-1)
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{
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}
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void
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Container::prepare_for_render (Rect const & area) const
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{
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Item::prepare_for_render_children (area);
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}
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void
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Container::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
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{
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if (_render_with_alpha == 0) {
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return;
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} else if (_render_with_alpha > 0) {
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context->push_group ();
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}
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Item::render_children (area, context);
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if (_render_with_alpha >= 1.0) {
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context->pop_group ();
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} else if (_render_with_alpha > 0) {
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context->pop_group_to_source ();
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context->paint_with_alpha (_render_with_alpha);
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}
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}
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void
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Container::compute_bounding_box () const
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{
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_bounding_box = Rect ();
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/* nothing to do here; Item::bounding_box() will add all children for us */
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set_bbox_clean ();
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}
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void
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Container::set_render_with_alpha (double alpha)
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{
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if (_render_with_alpha == alpha) {
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return;
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}
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_render_with_alpha = alpha;
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redraw ();
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}
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