Double click track resizer resets to default height

src/timeline2/view/qml/TrackHead.qml

@@ -516,9 +516,11 @@ Rectangle {
                 property double startY
                 property double originalY
                 drag.smoothed: false
+                property bool dragStarted: false
 
                 onPressed: {
                     root.autoScrolling = false
+                    dragStarted = false
                     startY = mapToItem(null, x, y).y
                     originalY = trackHeadRoot.height // reusing originalX to accumulate delta for bubble help
                 }
@@ -527,15 +529,21 @@ Rectangle {
                     if (!trimInMouseArea.containsMouse) {
                         parent.opacity = 0
                     }
-                    if (mouse.modifiers & Qt.ShiftModifier) {
+                    if (mouse.modifiers & Qt.ShiftModifier && dragStarted) {
                         timeline.adjustAllTrackHeight(trackHeadRoot.trackId, trackHeadRoot.myTrackHeight)
                     }
                 }
                 onEntered: parent.opacity = 0.3
                 onExited: parent.opacity = 0
+                onDoubleClicked: {
+                    timeline.defaultTrackHeight(mouse.modifiers & Qt.ShiftModifier ? -1 : trackHeadRoot.trackId)
+                }
                 onPositionChanged: {
                     if (mouse.buttons === Qt.LeftButton) {
                         parent.opacity = 0.5
+                        if (!dragStarted && Math.abs(mapToItem(null, x, y).y - startY) > 2) {
+                            dragStarted = true
+                        }
                         var newHeight = originalY + (mapToItem(null, x, y).y - startY)
                         newHeight =  Math.max(root.collapsedHeight, newHeight)
                         trackHeadRoot.myTrackHeight = newHeight

src/timeline2/view/timelinecontroller.cpp

@@ -1034,6 +1034,26 @@ void TimelineController::adjustAllTrackHeight(int trackId, int height)
     m_model->dataChanged(modelStart, modelEnd, {TimelineModel::HeightRole});
 }
 
+void TimelineController::defaultTrackHeight(int trackId)
+{
+    if (trackId > -1) {
+        m_model->getTrackById(trackId)->setProperty(QStringLiteral("kdenlive:trackheight"), QString::number(KdenliveSettings::trackheight()));
+        QModelIndex modelStart = m_model->makeTrackIndexFromID(trackId);
+        m_model->dataChanged(modelStart, modelStart, {TimelineModel::HeightRole});
+        return;
+    }
+    auto it = m_model->m_allTracks.cbegin();
+    while (it != m_model->m_allTracks.cend()) {
+        int target_track = (*it)->getId();
+        m_model->getTrackById(target_track)->setProperty(QStringLiteral("kdenlive:trackheight"), QString::number(KdenliveSettings::trackheight()));
+        ++it;
+    }
+    int tracksCount = m_model->getTracksCount();
+    QModelIndex modelStart = m_model->makeTrackIndexFromID(m_model->getTrackIndexFromPosition(0));
+    QModelIndex modelEnd = m_model->makeTrackIndexFromID(m_model->getTrackIndexFromPosition(tracksCount - 1));
+    m_model->dataChanged(modelStart, modelEnd, {TimelineModel::HeightRole});
+}
+
 void TimelineController::setPosition(int position)
 {
     // Process seek request

src/timeline2/view/timelinecontroller.h

@@ -295,6 +295,10 @@ public:
     */
     Q_INVOKABLE void adjustAllTrackHeight(int trackId, int height);
 
+    /** @brief Reset track @trackId height to default track height. Adjusts all tracks if @trackId == -1
+    */
+    Q_INVOKABLE void defaultTrackHeight(int trackId);
+
     Q_INVOKABLE bool exists(int itemId);
 
     Q_INVOKABLE int headerWidth() const;