delegatesizehelper updates

Make `DelegateSizeHelper` take a `QQuickItem` rather than a width value and move `TimelineDelegate` to use it rather than duplicting the code.

This requires the creation of `LibNeoChat` so that both the main and timeline modules can get access to the class.

Note: ideally more stuff will go into `LibNeoChat` but it turns out our dependencies are kinda spaghetti like and so will take some untangling.

autotests/delegatesizehelpertest.cpp

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
 
 #include <QObject>
+#include <QQuickItem>
 #include <QTest>
 
 #include "delegatesizehelper.h"
@@ -30,7 +31,7 @@ void DelegateSizeHelperTest::risingPercentage_data()
     QTest::addColumn<int>("currentPercentageWidth");
     QTest::addColumn<qreal>("currentWidth");
 
-    QTest::newRow("zero") << qreal(0) << int(0) << qreal(0);
+    QTest::newRow("zero") << qreal(0) << int(100) << qreal(0);
     QTest::newRow("one hundred") << qreal(100) << int(0) << qreal(0);
     QTest::newRow("one fifty") << qreal(150) << int(50) << qreal(75);
     QTest::newRow("two hundred") << qreal(200) << int(100) << qreal(200);
@@ -43,16 +44,18 @@ void DelegateSizeHelperTest::risingPercentage()
     QFETCH(int, currentPercentageWidth);
     QFETCH(qreal, currentWidth);
 
+    auto item = QQuickItem();
+    item.setWidth(parentWidth);
+
     DelegateSizeHelper delegateSizeHelper;
+    delegateSizeHelper.setParentItem(&item);
     delegateSizeHelper.setStartBreakpoint(100);
     delegateSizeHelper.setEndBreakpoint(200);
     delegateSizeHelper.setStartPercentWidth(0);
     delegateSizeHelper.setEndPercentWidth(100);
 
-    delegateSizeHelper.setParentWidth(parentWidth);
+    QCOMPARE(delegateSizeHelper.availablePercentageWidth(), currentPercentageWidth);
-
+    QCOMPARE(delegateSizeHelper.availableWidth(), currentWidth);
-    QCOMPARE(delegateSizeHelper.currentPercentageWidth(), currentPercentageWidth);
-    QCOMPARE(delegateSizeHelper.currentWidth(), currentWidth);
 }
 
 void DelegateSizeHelperTest::fallingPercentage_data()
@@ -74,16 +77,18 @@ void DelegateSizeHelperTest::fallingPercentage()
     QFETCH(int, currentPercentageWidth);
     QFETCH(qreal, currentWidth);
 
+    auto item = QQuickItem();
+    item.setWidth(parentWidth);
+
     DelegateSizeHelper delegateSizeHelper;
+    delegateSizeHelper.setParentItem(&item);
     delegateSizeHelper.setStartBreakpoint(100);
     delegateSizeHelper.setEndBreakpoint(200);
     delegateSizeHelper.setStartPercentWidth(100);
     delegateSizeHelper.setEndPercentWidth(0);
 
-    delegateSizeHelper.setParentWidth(parentWidth);
+    QCOMPARE(delegateSizeHelper.availablePercentageWidth(), currentPercentageWidth);
-
+    QCOMPARE(delegateSizeHelper.availableWidth(), currentWidth);
-    QCOMPARE(delegateSizeHelper.currentPercentageWidth(), currentPercentageWidth);
-    QCOMPARE(delegateSizeHelper.currentWidth(), currentWidth);
 }
 
 void DelegateSizeHelperTest::equalPercentage_data()
@@ -105,16 +110,18 @@ void DelegateSizeHelperTest::equalPercentage()
     QFETCH(int, currentPercentageWidth);
     QFETCH(qreal, currentWidth);
 
+    auto item = QQuickItem();
+    item.setWidth(parentWidth);
+
     DelegateSizeHelper delegateSizeHelper;
+    delegateSizeHelper.setParentItem(&item);
     delegateSizeHelper.setStartBreakpoint(100);
     delegateSizeHelper.setEndBreakpoint(200);
     delegateSizeHelper.setStartPercentWidth(50);
     delegateSizeHelper.setEndPercentWidth(50);
 
-    delegateSizeHelper.setParentWidth(parentWidth);
+    QCOMPARE(delegateSizeHelper.availablePercentageWidth(), currentPercentageWidth);
-
+    QCOMPARE(delegateSizeHelper.availableWidth(), currentWidth);
-    QCOMPARE(delegateSizeHelper.currentPercentageWidth(), currentPercentageWidth);
-    QCOMPARE(delegateSizeHelper.currentWidth(), currentWidth);
 }
 
 void DelegateSizeHelperTest::equalBreakpoint_data()
@@ -124,9 +131,9 @@ void DelegateSizeHelperTest::equalBreakpoint_data()
     QTest::addColumn<int>("currentPercentageWidth");
     QTest::addColumn<qreal>("currentWidth");
 
-    QTest::newRow("start higher") << int(100) << int(0) << int(-1) << qreal(0);
+    QTest::newRow("start higher") << int(100) << int(0) << int(100) << qreal(1000);
     QTest::newRow("equal") << int(50) << int(50) << int(50) << qreal(500);
-    QTest::newRow("end higher") << int(0) << int(100) << int(-1) << qreal(0);
+    QTest::newRow("end higher") << int(0) << int(100) << int(100) << qreal(1000);
 }
 
 /**
@@ -140,16 +147,18 @@ void DelegateSizeHelperTest::equalBreakpoint()
     QFETCH(int, currentPercentageWidth);
     QFETCH(qreal, currentWidth);
 
+    auto item = QQuickItem();
+    item.setWidth(1000);
+
     DelegateSizeHelper delegateSizeHelper;
+    delegateSizeHelper.setParentItem(&item);
     delegateSizeHelper.setStartBreakpoint(100);
     delegateSizeHelper.setEndBreakpoint(100);
     delegateSizeHelper.setStartPercentWidth(startPercentageWidth);
     delegateSizeHelper.setEndPercentWidth(endPercentageWidth);
 
-    delegateSizeHelper.setParentWidth(1000);
+    QCOMPARE(delegateSizeHelper.availablePercentageWidth(), currentPercentageWidth);
-
+    QCOMPARE(delegateSizeHelper.availableWidth(), currentWidth);
-    QCOMPARE(delegateSizeHelper.currentPercentageWidth(), currentPercentageWidth);
-    QCOMPARE(delegateSizeHelper.currentWidth(), currentWidth);
 }
 
 QTEST_GUILESS_MAIN(DelegateSizeHelperTest)

src/CMakeLists.txt

@@ -7,6 +7,8 @@ if (NOT ANDROID AND NOT WIN32 AND NOT APPLE AND NOT NEOCHAT_FLATPAK AND NOT NEOC
     add_subdirectory(purpose)
 endif()
 
+add_subdirectory(libneochat)
+
 add_library(neochat STATIC
     controller.cpp
     controller.h
@@ -109,8 +111,6 @@ add_library(neochat STATIC
     events/imagepackevent.h
     models/reactionmodel.cpp
     models/reactionmodel.h
-    delegatesizehelper.cpp
-    delegatesizehelper.h
     models/livelocationsmodel.cpp
     models/livelocationsmodel.h
     models/locationsmodel.cpp
@@ -413,6 +413,7 @@ endif()
 target_include_directories(neochat PRIVATE ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/models ${CMAKE_CURRENT_SOURCE_DIR}/enums)
 target_link_libraries(neochat PRIVATE settingsplugin timelineplugin devtoolsplugin loginplugin chatbarplugin)
 target_link_libraries(neochat PUBLIC
+    LibNeoChat
     Qt::Core
     Qt::Quick
     Qt::Qml

src/chatbar/ChatBar.qml

@@ -8,7 +8,9 @@ import QtQuick.Controls as QQC2
 import QtQuick.Layouts
 
 import org.kde.kirigami as Kirigami
+
 import org.kde.neochat
+import org.kde.neochat.libneochat as LibNeoChat
 
 /**
  * @brief A component for typing and sending chat messages.
@@ -165,7 +167,7 @@ QQC2.Control {
     }
 
     leftPadding: rightPadding
-    rightPadding: (root.width - chatBarSizeHelper.currentWidth) / 2
+    rightPadding: (root.width - chatBarSizeHelper.availableWidth) / 2
     topPadding: 0
     bottomPadding: 0
 
@@ -353,15 +355,14 @@ QQC2.Control {
             }
         }
     }
-    DelegateSizeHelper {
+    LibNeoChat.DelegateSizeHelper {
         id: chatBarSizeHelper
+        parentItem: root
         startBreakpoint: Kirigami.Units.gridUnit * 46
         endBreakpoint: Kirigami.Units.gridUnit * 66
         startPercentWidth: 100
         endPercentWidth: NeoChatConfig.compactLayout ? 100 : 85
         maxWidth: NeoChatConfig.compactLayout ? -1 : Kirigami.Units.gridUnit * 60
-
-        parentWidth: root.width
     }
 
     Component {

src/libneochat/CMakeLists.txt

@@ -0,0 +1,19 @@
+# SPDX-FileCopyrightText: 2023 Tobias Fella <tobias.fella@kde.org>
+# SPDX-License-Identifier: BSD-3-Clause
+
+add_library(LibNeoChat STATIC)
+
+target_sources(LibNeoChat PRIVATE
+    delegatesizehelper.cpp
+)
+
+ecm_add_qml_module(LibNeoChat GENERATE_PLUGIN_SOURCE
+    URI org.kde.neochat.libneochat
+    OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/src/org/kde/neochat/libneochat
+)
+
+generate_export_header(LibNeoChat BASE_NAME LibNeoChat)
+target_link_libraries(LibNeoChat PUBLIC
+    Qt::Core
+    Qt::Quick
+)

src/libneochat/delegatesizehelper.cpp

@@ -12,20 +12,60 @@ DelegateSizeHelper::DelegateSizeHelper(QObject *parent)
 {
 }
 
-qreal DelegateSizeHelper::parentWidth() const
+QQuickItem *DelegateSizeHelper::parentItem() const
 {
-    return m_parentWidth;
+    return m_parentItem;
 }
 
-void DelegateSizeHelper::setParentWidth(qreal parentWidth)
+void DelegateSizeHelper::setParentItem(QQuickItem *parentItem)
 {
-    if (parentWidth == m_parentWidth) {
+    if (parentItem == m_parentItem) {
         return;
     }
-    m_parentWidth = parentWidth;
+    m_parentItem = parentItem;
-    Q_EMIT parentWidthChanged();
+
-    Q_EMIT currentPercentageWidthChanged();
+    if (m_parentItem) {
-    Q_EMIT currentWidthChanged();
+        connect(m_parentItem, &QQuickItem::widthChanged, this, [this]() {
+            Q_EMIT availablePercentageWidthChanged();
+            Q_EMIT availableWidthChanged();
+        });
+    }
+
+    Q_EMIT parentItemChanged();
+    Q_EMIT availablePercentageWidthChanged();
+    Q_EMIT availableWidthChanged();
+}
+
+qreal DelegateSizeHelper::leftPadding() const
+{
+    return m_leftPadding;
+}
+
+void DelegateSizeHelper::setLeftPadding(qreal leftPadding)
+{
+    if (qFuzzyCompare(leftPadding, m_leftPadding)) {
+        return;
+    }
+    m_leftPadding = leftPadding;
+    Q_EMIT leftPaddingChanged();
+    Q_EMIT availablePercentageWidthChanged();
+    Q_EMIT availableWidthChanged();
+}
+
+qreal DelegateSizeHelper::rightPadding() const
+{
+    return m_rightPadding;
+}
+
+void DelegateSizeHelper::setRightPadding(qreal rightPadding)
+{
+    if (qFuzzyCompare(rightPadding, m_rightPadding)) {
+        return;
+    }
+    m_rightPadding = rightPadding;
+    Q_EMIT rightPaddingChanged();
+    Q_EMIT availablePercentageWidthChanged();
+    Q_EMIT availableWidthChanged();
 }
 
 qreal DelegateSizeHelper::startBreakpoint() const
@@ -86,7 +126,14 @@ void DelegateSizeHelper::setEndPercentWidth(int endPercentWidth)
 
 qreal DelegateSizeHelper::maxWidth() const
 {
-    return m_maxWidth;
+    if (m_maxWidth == std::nullopt) {
+        if (m_parentItem) {
+            return m_parentItem->width();
+        }
+        return 0.0;
+    }
+
+    return *m_maxWidth;
 }
 
 void DelegateSizeHelper::setMaxWidth(qreal maxWidth)
@@ -98,21 +145,23 @@ void DelegateSizeHelper::setMaxWidth(qreal maxWidth)
     Q_EMIT maxWidthChanged();
 }
 
-int DelegateSizeHelper::calculateCurrentPercentageWidth() const
+qreal DelegateSizeHelper::maxAvailableWidth() const
 {
-    // Don't do anything if m_parentWidth hasn't been set yet.
+    if (!m_parentItem || qFuzzyCompare(m_parentItem->width(), 0)) {
-    if (m_parentWidth < 0) {
+        return 0;
-        return -1;
     }
+    return std::max(m_parentItem->width() - m_leftPadding - m_rightPadding, 0.0);
+}
+
+int DelegateSizeHelper::calculateAvailablePercentageWidth() const
+{
     // Don't bother with calculations for a horizontal line.
     if (m_startPercentWidth == m_endPercentWidth) {
         return m_startPercentWidth;
     }
     // Dividing by zero is a bad idea.
-    if (m_startBreakpoint == m_endBreakpoint) {
+    if (m_startBreakpoint == m_endBreakpoint || qFuzzyCompare(maxAvailableWidth(), 0)) {
-        qWarning() << "DelegateSizeHelper::calculateCurrentPercentageWidth() - m_startBreakpoint is equal to m_endBreakpoint this would lead to divide by "
+        return 100;
-                      "zero, aborting";
-        return -1;
     }
 
     // Fit to y = mx + c
@@ -124,32 +173,19 @@ int DelegateSizeHelper::calculateCurrentPercentageWidth() const
     int maxPercentWidth = endPercentBigger ? m_endPercentWidth : m_startPercentWidth;
     int minPercentWidth = endPercentBigger ? m_startPercentWidth : m_endPercentWidth;
 
-    int calcPercentWidth = std::round(m * m_parentWidth + c);
+    int calcPercentWidth = std::round(m * maxAvailableWidth() + c);
     return std::clamp(calcPercentWidth, minPercentWidth, maxPercentWidth);
 }
 
-int DelegateSizeHelper::currentPercentageWidth() const
+int DelegateSizeHelper::availablePercentageWidth() const
 {
-    return calculateCurrentPercentageWidth();
+    return calculateAvailablePercentageWidth();
 }
 
-qreal DelegateSizeHelper::currentWidth() const
+qreal DelegateSizeHelper::availableWidth() const
 {
-    if (m_parentWidth < 0) {
+    qreal absoluteWidth = maxAvailableWidth() * availablePercentageWidth() * 0.01;
-        return 0.0;
+    return std::round(std::min(absoluteWidth, maxWidth()));
-    }
-    int percentWidth = calculateCurrentPercentageWidth();
-    // - 1 means bad input values so don't try to calculate.
-    if (percentWidth == -1) {
-        return 0.0;
-    }
-
-    qreal absoluteWidth = m_parentWidth * percentWidth * 0.01;
-    if (m_maxWidth < 0.0) {
-        return std::round(absoluteWidth);
-    } else {
-        return std::round(std::min(absoluteWidth, m_maxWidth));
-    }
 }
 
 #include "moc_delegatesizehelper.cpp"

src/libneochat/delegatesizehelper.h

@@ -5,6 +5,7 @@
 
 #include <QObject>
 #include <QQmlEngine>
+#include <QQuickItem>
 
 /**
  * @class DelegateSizeHelper
@@ -27,9 +28,25 @@ class DelegateSizeHelper : public QObject
     QML_ELEMENT
 
     /**
-     * @brief The width of the component's parent.
+     * @brief The parent item that defines the available content area.
      */
-    Q_PROPERTY(qreal parentWidth READ parentWidth WRITE setParentWidth NOTIFY parentWidthChanged)
+    Q_PROPERTY(QQuickItem *parentItem READ parentItem WRITE setParentItem NOTIFY parentItemChanged)
+
+    /**
+     * @brief The amount of padding to be removed from the left of the available content area.
+     *
+     * The padding is removed before calculating the available width, i.e. max available width
+     * at 100% is equal to parent width minus padding.
+     */
+    Q_PROPERTY(qreal leftPadding READ leftPadding WRITE setLeftPadding NOTIFY leftPaddingChanged)
+
+    /**
+     * @brief The amount of padding to be removed from the right of the available content area.
+     *
+     * The padding is removed before calculating the available width, i.e. max available width
+     * at 100% is equal to parent width minus padding.
+     */
+    Q_PROPERTY(qreal rightPadding READ rightPadding WRITE setRightPadding NOTIFY rightPaddingChanged)
 
     /**
      * @brief The width (in px) when the width percentage should start to transition.
@@ -67,7 +84,7 @@ class DelegateSizeHelper : public QObject
      *
      * @sa parentWidth, startBreakpoint, endBreakpoint
      */
-    Q_PROPERTY(int currentPercentageWidth READ currentPercentageWidth NOTIFY currentPercentageWidthChanged)
+    Q_PROPERTY(int availablePercentageWidth READ availablePercentageWidth NOTIFY availablePercentageWidthChanged)
 
     /**
      * @brief The width (in px) of the component at the current parentWidth.
@@ -76,50 +93,60 @@ class DelegateSizeHelper : public QObject
      *
      * @sa parentWidth
      */
-    Q_PROPERTY(qreal currentWidth READ currentWidth NOTIFY currentWidthChanged)
+    Q_PROPERTY(qreal availableWidth READ availableWidth NOTIFY availableWidthChanged)
 
 public:
     explicit DelegateSizeHelper(QObject *parent = nullptr);
 
-    qreal parentWidth() const;
+    QQuickItem *parentItem() const;
-    void setParentWidth(qreal parentWidth);
+    void setParentItem(QQuickItem *parentItem);
+
+    qreal leftPadding() const;
+    void setLeftPadding(qreal leftPadding);
+    qreal rightPadding() const;
+    void setRightPadding(qreal rightPadding);
 
     qreal startBreakpoint() const;
     void setStartBreakpoint(qreal startBreakpoint);
-
     qreal endBreakpoint() const;
     void setEndBreakpoint(qreal endBreakpoint);
 
     int startPercentWidth() const;
     void setStartPercentWidth(int startPercentWidth);
-
     int endPercentWidth() const;
     void setEndPercentWidth(int endPercentWidth);
 
     qreal maxWidth() const;
     void setMaxWidth(qreal maxWidth);
 
-    int currentPercentageWidth() const;
+    qreal maxAvailableWidth() const;
 
-    qreal currentWidth() const;
+    int availablePercentageWidth() const;
+    qreal availableWidth() const;
 
 Q_SIGNALS:
-    void parentWidthChanged();
+    void parentItemChanged();
+    void leftPaddingChanged();
+    void rightPaddingChanged();
     void startBreakpointChanged();
     void endBreakpointChanged();
     void startPercentWidthChanged();
     void endPercentWidthChanged();
     void maxWidthChanged();
-    void currentPercentageWidthChanged();
+    void availablePercentageWidthChanged();
-    void currentWidthChanged();
+    void availableWidthChanged();
 
 private:
-    qreal m_parentWidth = -1.0;
+    QPointer<QQuickItem> m_parentItem;
-    qreal m_startBreakpoint;
-    qreal m_endBreakpoint;
-    int m_startPercentWidth;
-    int m_endPercentWidth;
-    qreal m_maxWidth = -1.0;
 
-    int calculateCurrentPercentageWidth() const;
+    qreal m_leftPadding = 0.0;
+    qreal m_rightPadding = 0.0;
+
+    qreal m_startBreakpoint = 0.0;
+    qreal m_endBreakpoint = 0.0;
+    int m_startPercentWidth = 100;
+    int m_endPercentWidth = 85;
+    std::optional<qreal> m_maxWidth = std::nullopt;
+
+    int calculateAvailablePercentageWidth() const;
 };

src/qml/SpaceHierarchyDelegate.qml

@@ -10,6 +10,7 @@ import org.kde.kirigamiaddons.delegates as Delegates
 import org.kde.kirigamiaddons.labs.components as Components
 
 import org.kde.neochat
+import org.kde.neochat.libneochat as LibNeoChat
 
 Item {
     id: root
@@ -44,7 +45,7 @@ Item {
 
         anchors.horizontalCenter: root.horizontalCenter
         anchors.verticalCenter: root.verticalCenter
-        width: sizeHelper.currentWidth
+        width: sizeHelper.availableWidth
 
         highlighted: dropArea.containsDrag
 
@@ -201,15 +202,14 @@ Item {
         }
     }
 
-    DelegateSizeHelper {
+    LibNeoChat.DelegateSizeHelper {
         id: sizeHelper
+        parentItem: root
         startBreakpoint: Kirigami.Units.gridUnit * 46
         endBreakpoint: Kirigami.Units.gridUnit * 66
         startPercentWidth: 100
         endPercentWidth: 85
         maxWidth: Kirigami.Units.gridUnit * 60
-
-        parentWidth: root.treeView ? root.treeView.width : 0
     }
 
     Component {

src/qml/SpaceHomePage.qml

@@ -8,6 +8,7 @@ import QtQuick.Layouts
 import org.kde.kirigami as Kirigami
 
 import org.kde.neochat
+import org.kde.neochat.libneochat as LibNeoChat
 import org.kde.neochat.settings
 
 ColumnLayout {
@@ -93,15 +94,14 @@ ColumnLayout {
                 onTextChanged: spaceChildSortFilterModel.filterText = text
             }
         }
-        DelegateSizeHelper {
+        LibNeoChat.DelegateSizeHelper {
             id: sizeHelper
+            parentItem: root
             startBreakpoint: Kirigami.Units.gridUnit * 46
             endBreakpoint: Kirigami.Units.gridUnit * 66
             startPercentWidth: 100
             endPercentWidth: 85
             maxWidth: Kirigami.Units.gridUnit * 60
-
-            parentWidth: root.width
         }
     }
     Kirigami.Separator {

src/timeline/CMakeLists.txt

@@ -90,4 +90,5 @@ ecm_add_qml_module(timeline GENERATE_PLUGIN_SOURCE
 target_link_libraries(timeline PRIVATE
     Qt::Quick
     KF6::Kirigami
+    LibNeoChat
 )

src/timeline/MessageDelegate.qml

@@ -10,6 +10,7 @@ import org.kde.kirigami as Kirigami
 import org.kde.kirigamiaddons.components as KirigamiComponents
 
 import org.kde.neochat
+import org.kde.neochat.libneochat as LibNeoChat
 
 /**
  * @brief The base delegate for all messages in the timeline.
@@ -185,7 +186,7 @@ TimelineDelegate {
     /**
      * @brief The width available to the bubble content.
      */
-    property real contentMaxWidth: (root.isThreaded ? bubbleSizeHelper.parentWidth : bubbleSizeHelper.currentWidth) - bubble.leftPadding - bubble.rightPadding
+    property real contentMaxWidth: (root.isThreaded ? bubbleSizeHelper.parentWidth : bubbleSizeHelper.availableWidth) - bubble.leftPadding - bubble.rightPadding
 
     Message.room: root.room
     Message.timeline: root.ListView.view
@@ -321,14 +322,14 @@ TimelineDelegate {
             model: root.readMarkers
         }
 
-        DelegateSizeHelper {
+        LibNeoChat.DelegateSizeHelper {
             id: bubbleSizeHelper
+            parentItem: mainContainer
+            leftPadding: avatar.anchors.leftMargin + (NeoChatConfig.showAvatarInTimeline ? avatar.width + bubble.anchors.leftMargin : 0)
             startBreakpoint: Kirigami.Units.gridUnit * 25
             endBreakpoint: Kirigami.Units.gridUnit * 40
             startPercentWidth: root.alwaysFillWidth ? 100 : 90
             endPercentWidth: root.alwaysFillWidth ? 100 : 60
-
-            parentWidth: mainContainer.availableWidth - (NeoChatConfig.showAvatarInTimeline ? avatar.width + bubble.anchors.leftMargin : 0)
         }
     }
 

src/timeline/timelinedelegate.cpp

@@ -6,6 +6,17 @@
 TimelineDelegate::TimelineDelegate(QQuickItem *parent)
     : QQuickItem(parent)
 {
+    m_sizeHelper.setParentItem(this);
+    connect(&m_sizeHelper, &DelegateSizeHelper::leftPaddingChanged, this, [this]() {
+        Q_EMIT leftPaddingChanged();
+        resizeContent();
+        updatePolish();
+    });
+    connect(&m_sizeHelper, &DelegateSizeHelper::rightPaddingChanged, this, [this]() {
+        Q_EMIT rightPaddingChanged();
+        resizeContent();
+        updatePolish();
+    });
 }
 
 QQuickItem *TimelineDelegate::contentItem()
@@ -56,38 +67,22 @@ void TimelineDelegate::setAlwaysFillWidth(bool alwaysFillWidth)
 
 qreal TimelineDelegate::leftPadding()
 {
-    return m_leftPadding;
+    return m_sizeHelper.leftPadding();
 }
 
 void TimelineDelegate::setLeftPadding(qreal leftPadding)
 {
-    if (qFuzzyCompare(leftPadding, m_leftPadding)) {
+    m_sizeHelper.setLeftPadding(leftPadding);
-        return;
-    }
-
-    m_leftPadding = leftPadding;
-    Q_EMIT leftPaddingChanged();
-
-    resizeContent();
-    updatePolish();
 }
 
 qreal TimelineDelegate::rightPadding()
 {
-    return m_rightPadding;
+    return m_sizeHelper.rightPadding();
 }
 
 void TimelineDelegate::setRightPadding(qreal rightPadding)
 {
-    if (qFuzzyCompare(rightPadding, m_rightPadding)) {
+    m_sizeHelper.setRightPadding(rightPadding);
-        return;
-    }
-
-    m_rightPadding = rightPadding;
-    Q_EMIT rightPaddingChanged();
-
-    resizeContent();
-    updatePolish();
 }
 
 void TimelineDelegate::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
@@ -114,68 +109,27 @@ void TimelineDelegate::componentComplete()
 
 void TimelineDelegate::setCurveValues()
 {
-    m_leftPadding = qreal(m_units->largeSpacing());
+    m_sizeHelper.setLeftPadding(qreal(m_units->largeSpacing()));
-    m_rightPadding = qreal(m_units->largeSpacing());
+    m_sizeHelper.setRightPadding(qreal(m_units->largeSpacing()));
 
-    m_startBreakpoint = qreal(m_units->gridUnit() * 46);
+    m_sizeHelper.setStartBreakpoint(qreal(m_units->gridUnit() * 46));
-    m_endBreakpoint = qreal(m_units->gridUnit() * 66);
+    m_sizeHelper.setEndBreakpoint(qreal(m_units->gridUnit() * 66));
-    m_maxWidth = qreal(m_units->gridUnit() * 60);
+    m_sizeHelper.setMaxWidth(qreal(m_units->gridUnit() * 60));
 
     resizeContent();
 }
 
-int TimelineDelegate::availablePercentageWidth() const
-{
-    // Don't bother with calculations for a horizontal line.
-    if (m_startPercentWidth == m_endPercentWidth) {
-        return m_startPercentWidth;
-    }
-    // Dividing by zero is a bad idea.
-    if (m_startBreakpoint == m_endBreakpoint || qFuzzyCompare(width(), 0)) {
-        return 100;
-    }
-
-    // Fit to y = mx + c
-    qreal m = (m_endPercentWidth - m_startPercentWidth) / (m_endBreakpoint - m_startBreakpoint);
-    qreal c = m_startPercentWidth - m * m_startBreakpoint;
-
-    // This allows us to clamp correctly if the start or end width is bigger.
-    bool endPercentBigger = m_endPercentWidth > m_startPercentWidth;
-    int maxPercentWidth = endPercentBigger ? m_endPercentWidth : m_startPercentWidth;
-    int minPercentWidth = endPercentBigger ? m_startPercentWidth : m_endPercentWidth;
-
-    int calcPercentWidth = std::round(m * maxAvailableWidth() + c);
-    return std::clamp(calcPercentWidth, minPercentWidth, maxPercentWidth);
-}
-
-qreal TimelineDelegate::maxAvailableWidth() const
-{
-    if (qFuzzyCompare(width(), 0)) {
-        return 0;
-    }
-
-    return std::max(width() - m_leftPadding - m_rightPadding, 0.0);
-}
-
-qreal TimelineDelegate::availableWidth() const
-{
-    if (m_alwaysFillWidth) {
-        return maxAvailableWidth();
-    }
-
-    qreal absoluteWidth = maxAvailableWidth() * availablePercentageWidth() * 0.01;
-    return std::round(std::min(absoluteWidth, m_maxWidth));
-}
-
 void TimelineDelegate::resizeContent()
 {
     if (m_contentItem == nullptr || !isComponentComplete()) {
         return;
     }
 
-    const auto leftPadding = m_leftPadding + (maxAvailableWidth() - availableWidth()) / 2;
+    auto availableWidth = m_alwaysFillWidth ? m_sizeHelper.maxAvailableWidth() : m_sizeHelper.availableWidth();
+
+    const auto leftPadding = m_sizeHelper.leftPadding() + (m_sizeHelper.maxAvailableWidth() - availableWidth) / 2;
     m_contentItem->setPosition(QPointF(leftPadding, 0));
-    m_contentItem->setSize(QSizeF(availableWidth(), m_contentItem->implicitHeight()));
+    m_contentItem->setSize(QSizeF(availableWidth, m_contentItem->implicitHeight()));
 }
 
 void TimelineDelegate::updateImplicitHeight()

src/timeline/timelinedelegate.h

@@ -8,6 +8,8 @@
 
 #include <Kirigami/Platform/Units>
 
+#include "delegatesizehelper.h"
+
 /**
  * @brief The base Item for all delegates in the timeline.
  *
@@ -77,17 +79,8 @@ private:
     Kirigami::Platform::Units *m_units = nullptr;
     void setCurveValues();
 
-    qreal m_leftPadding;
+    DelegateSizeHelper m_sizeHelper;
-    qreal m_rightPadding;
 
-    qreal m_startBreakpoint;
-    qreal m_endBreakpoint;
-    int m_startPercentWidth = 100;
-    int m_endPercentWidth = 85;
-    qreal m_maxWidth;
-    int availablePercentageWidth() const;
-    qreal maxAvailableWidth() const;
-    qreal availableWidth() const;
     bool m_alwaysFillWidth = false;
 
     void resizeContent();