Add some feedback if an insert operation fails.

CCBUG: 413661

src/kdenlivesettings.kcfg

@@ -123,17 +123,16 @@
       <label>Default OpenGL backend.</label>
       <default>0</default>
     </entry>
-    
+
     <entry name="showEffectSearchBar" type="Bool">
       <label>Show effect search bar by default.</label>
       <default>true</default>
     </entry>
-    
+
     <entry name="showCompoSearchBar" type="Bool">
       <label>Show composition search bar by default.</label>
       <default>true</default>
     </entry>
-    
 
   </group>
 

src/mainwindow.cpp

@@ -2485,6 +2485,7 @@ void MainWindow::slotInsertClipInsert()
     const QString &binId = m_clipMonitor->activeClipId();
     if (binId.isEmpty()) {
         // No clip in monitor
+        pCore->displayMessage(i18n("No clip selected in project bin"), InformationMessage);
         return;
     }
     int pos = getMainTimeline()->controller()->insertZone(binId, m_clipMonitor->getZoneInfo(), false);

src/timeline2/model/timelinefunctions.cpp

@@ -353,6 +353,7 @@ bool TimelineFunctions::insertZone(const std::shared_ptr<TimelineItemModel> &tim
         }
     }
     if (affectedTracks.isEmpty()) {
+        pCore->displayMessage(i18n("Please activate a track by clicking on a track's label"), InformationMessage);
         return false;
     }
     result = breakAffectedGroups(timeline, affectedTracks, QPoint(insertFrame, insertFrame + (zone.y() - zone.x())), undo, redo);

src/timeline2/view/timelinecontroller.cpp

@@ -1677,6 +1677,9 @@ void TimelineController::extractZone(QPoint zone, bool liftOnly)
         }
         ++it;
     }
+    if (tracks.isEmpty()) {
+        pCore->displayMessage(i18n("Please activate a track for this operation by clicking on its label"), InformationMessage);
+    }
     if (m_zone == QPoint()) {
         // Use current timeline position and clip zone length
         zone.setY(timelinePosition() + zone.y() - zone.x());
@@ -1740,6 +1743,7 @@ bool TimelineController::insertClipZone(const QString &binId, int tid, int posit
     if (aTrack > -1) {
         target_tracks << aTrack;
     }
+
     return TimelineFunctions::insertZone(m_model, target_tracks, binId, position, QPoint(in, out + 1), m_model->m_editMode == TimelineMode::OverwriteEdit, false);
 }
 
@@ -1782,6 +1786,10 @@ int TimelineController::insertZone(const QString &binId, QPoint zone, bool overw
     if (aTrack > -1) {
         target_tracks << aTrack;
     }
+    if (target_tracks.isEmpty()) {
+        pCore->displayMessage(i18n("Please select a target track by clicking on a track's target zone"), InformationMessage);
+        return -1;
+    }
     return TimelineFunctions::insertZone(m_model, target_tracks, binId, insertPoint, sourceZone, overwrite) ? insertPoint + (sourceZone.y() - sourceZone.x())
                                                                                                             : -1;
 }

[Eugen Mohr]

Could you put this commit into 19.08.3 branch as well?