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ScrollCalculator.qml
/*
* Copyright (C) 2014 Canonical Ltd.
*
* 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; version 3.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import QtQuick 2.15
import Lomiri.Components 1.3
Item {
id: scrollArea
readonly property bool areaActive: lateralPosition >= 0
property real stopScrollThreshold: units.gu(2)
property real progressThreshold: units.dp(4)
property int direction: Qt.LeftToRight
property real baseScrollAmount: units.dp(3)
property real maximumScrollAmount: units.dp(8)
property real lateralPosition: -1
property real forceScrollingPercentage: 0.4
signal scroll(real scrollAmount)
width: units.gu(5)
rotation: direction === Qt.LeftToRight ? 0 : 180
onAreaActiveChanged: areaActive ? handleEnter() : handleExit()
function handleEnter() {
d.thresholdAreaX = -scrollArea.stopScrollThreshold;
scrollTimer.restart();
d.init = true;
d.passedProgressThreshold = false;
d.progression = 0;
d.startingProgression = 0;
}
function handleExit() {
d.thresholdAreaX = -scrollArea.stopScrollThreshold;
scrollTimer.stop();
}
onLateralPositionChanged: {
if (scrollArea.areaActive) {
if (lateralPosition > width * (1 - forceScrollingPercentage)) {
d.thresholdAreaX = width * (1 - forceScrollingPercentage);
if (!scrollTimer.running) scrollTimer.restart();
} else if (lateralPosition > d.thresholdAreaX + scrollArea.stopScrollThreshold) {
d.thresholdAreaX = lateralPosition - scrollArea.stopScrollThreshold;
if (!scrollTimer.running) scrollTimer.restart();
} else if (lateralPosition < d.thresholdAreaX) {
d.thresholdAreaX = lateralPosition;
scrollTimer.stop();
}
d.progression = lateralPosition / width;
if (d.init) {
d.startingProgression = d.progression;
d.init = false;
}
}
}
Timer {
id: scrollTimer
interval: 16
repeat: true
onTriggered: {
if (d.passedProgressThreshold ||
Math.abs(d.progression - d.startingProgression) * scrollArea.width > scrollArea.progressThreshold) {
d.passedProgressThreshold = true;
var scrollAmount = scrollArea.baseScrollAmount + scrollArea.maximumScrollAmount * d.progression;
scrollArea.scroll(scrollAmount);
}
}
}
QtObject {
id: d
property real startingProgression: 0
property bool init: true
property real progression: 0
property real thresholdAreaX: -scrollArea.stopScrollThreshold
property bool passedProgressThreshold: false
}
}