Differential D27840 Diff 78698 src/qmlcontrols/kcmcontrols/settingstatebindingprivate.cpp

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src/qmlcontrols/kcmcontrols/settingstatebindingprivate.cpp

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1		/*
2		* Copyright 2020 Kevin Ottens <kevin.ottens@enioka.com>
3		*
4		* This library is free software; you can redistribute it and/or
5		* modify it under the terms of the GNU Library General Public
6		* License as published by the Free Software Foundation; either
7		* version 2 of the License, or (at your option) any later version.
8		*
9		* This library is distributed in the hope that it will be useful,
10		* but WITHOUT ANY WARRANTY; without even the implied warranty of
11		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12		* Library General Public License for more details.
13		*
14		* You should have received a copy of the GNU Library General Public License
15		* along with this library; see the file COPYING.LIB. If not, write to
16		* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
17		* Boston, MA 02110-1301, USA.
18		*/
19
20		#include "settingstatebindingprivate.h"
21
22		#include <QGuiApplication>
23		#include <QQmlContext>
24
25		namespace {
26		constexpr const char *bindingProperty = "__SettingStateBindingPrivate_binding";
27		constexpr const char *hasBindingProperty = "__SettingStateBindingPrivate_hasBinding";
28
29		bool isLayout(QQuickItem *item)
30		{
31		// Split since some exported types will be of the form: Foo_QMLTYPE_XX
	broulikUnsubmitted Done Odd. Wouldn't we just get `QQuickRowLayout` et al? Or is that if you do a custom item with a `Layout` as a base? broulik: Odd. Wouldn't we just get `QQuickRowLayout` et al? Or is that if you do a custom item with a…
	ervinAuthorUnsubmitted Not Done Or if you make something like Kirigami.FormLayout which has Item as base... obviously it's mostly an heuristic so can't be 100% perfect. ervin: Or if you make something like Kirigami.FormLayout which has Item as base... obviously it's…
32		const auto className = QByteArray(item->metaObject()->className()).split('_').first();
33		return className.endsWith("Layout")
34		\|\| className.endsWith("Column")
35		\|\| className.endsWith("Row")
36		\|\| className.endsWith("Grid");
37		}
38
39		QList<QQuickItem > findDescendantItems(QQuickItem item)
40		{
41		const auto children = item->childItems();
42		auto result = children;
43		for (auto child : children) {
44		result += findDescendantItems(child);
45		}
46		return result;
47		}
48
49		QQuickItem findOuterLayout(QQuickItem item)
50		{
51		if (!item->parentItem()) {
52		return item;
53		} else if (isLayout(item) && !isLayout(item->parentItem())) {
54		return item;
55		} else {
56		return findOuterLayout(item->parentItem());
57		}
58		}
59
60		}
61
62		QQuickItem *SettingStateBindingPrivate::target() const
63		{
64		return m_target;
65		}
66
67		void SettingStateBindingPrivate::setTarget(QQuickItem *target)
68		{
69		if (m_target == target) {
70		return;
71		}
72
73		if (m_target) {
74		m_target->setProperty(hasBindingProperty, QVariant());
75		m_target->setProperty(bindingProperty, QVariant());
76		disconnect(m_target);
77		}
78
79		m_target = target;
80		if (m_target) {
81		m_target->setProperty(hasBindingProperty, true);
82		m_target->setProperty(bindingProperty, QVariant::fromValue(this));
83		connect(m_target, &QQuickItem::parentChanged, this, &SettingStateBindingPrivate::triggerCoordChanges);
	broulikUnsubmitted Done Too bad `QQuickItemChangeListener` is private. Also, does any of this need event compression? broulik: Too bad `QQuickItemChangeListener` is private. Also, does any of this need event compression?
	ervinAuthorUnsubmitted Not Done That really didn't feel like it required event compression to be honest at least I couldn't perceive any visible impact. ervin: That really didn't feel like it required event compression to be honest at least I couldn't…
84		connect(m_target, &QQuickItem::widthChanged, this, &SettingStateBindingPrivate::triggerCoordChanges);
85		connect(m_target, &QQuickItem::heightChanged, this, &SettingStateBindingPrivate::triggerCoordChanges);
86		connect(m_target, &QQuickItem::xChanged, this, &SettingStateBindingPrivate::triggerCoordChanges);
87		connect(m_target, &QQuickItem::yChanged, this, &SettingStateBindingPrivate::triggerCoordChanges);
88		}
89
90		emit targetChanged();
91		emit leftCoordChanged();
	broulikUnsubmitted Done Check if it actually changed before emitting broulik: Check if it actually changed before emitting
	ervinAuthorUnsubmitted Not Done Well it will have changed in 90% of the cases and checking means doing the computation anyway, which will happen when the getter is called. We'd pay the price twice. An option is of course to cache the result of the getter to the price of higher complexity. Again I didn't perceive any visible impact on use. Should I go for it anyway? Note I'm not at all denying this implementation is in some way inefficient, I'm just pointing out the trade off in term of readability and maintainability of the system. ervin: Well it will have changed in 90% of the cases and checking means doing the computation anyway…
92		}
93
94		QQuickItem *SettingStateBindingPrivate::indicator() const
95		{
96		return m_indicator;
97		}
98
99		void SettingStateBindingPrivate::setIndicator(QQuickItem *indicator)
100		{
101		if (m_indicator == indicator) {
102		return;
103		}
104
105		m_indicator = indicator;
106
107		emit indicatorChanged();
108		emit leftCoordChanged();
	broulikUnsubmitted Done Check if it actually changed before emitting broulik: Check if it actually changed before emitting
	ervinAuthorUnsubmitted Not Done Same answer than the previous such case. ervin: Same answer than the previous such case.
109		}
110
111		qreal SettingStateBindingPrivate::leftCoord() const
112		{
113		if (!m_target \|\| !m_indicator) {
114		return 0.0f;
115		}
116
117		const auto parent = m_indicator->parentItem();
118		const auto outerLayout = findOuterLayout(m_target);
119
120		const auto siblings = [=] {
121		auto result = findDescendantItems(outerLayout);
122		result.erase(std::remove_if(result.begin(), result.end(),
123		[=](QQuickItem *item) {
124		return !item->property(hasBindingProperty).toBool();
125		}),
126		result.end());
127		return result;
128		}();
129
130		const auto leftToRight = QGuiApplication::layoutDirection() == Qt::LeftToRight;
131		const auto xValues = [=] {
132		auto result = QVector<qreal>();
133		result.reserve(siblings.size());
134		std::transform(siblings.cbegin(), siblings.cend(),
135		std::back_inserter(result),
136		[=](QQuickItem *item) {
137		const auto localX = leftToRight ? item->width() : -m_indicator->width();
138		return parent->mapFromItem(item, {localX, 0.0f}).x();
139		});
140		return result;
141		}();
142		if (leftToRight) {
143		return *std::max_element(xValues.cbegin(), xValues.cend());
144		} else {
145		return *std::min_element(xValues.cbegin(), xValues.cend());
146		}
147		}
148
149		void SettingStateBindingPrivate::triggerCoordChanges()
150		{
151		const auto outerLayout = findOuterLayout(m_target);
152		const auto items = findDescendantItems(outerLayout);
153
154		for (auto item : items) {
155		const auto binding = item->property(bindingProperty).value<SettingStateBindingPrivate *>();
156		if (binding) {
157		emit binding->leftCoordChanged();
158		}
159		}
160		}