Don't clear locator model immediately when a new search triggers

nyalldawson · nyalldawson · commit 1577a57a19ce · 2017-05-22T09:46:13.000+10:00
Instead delay the search until either a tiny timeout (100ms) or
the first new results come in, whichever happens first.

This avoids the list view clearing too frequently and giving
a distracting "flashing" appearance when users type quickly
into to locator bar.
diff --git a/src/gui/locator/qgslocatorwidget.cpp b/src/gui/locator/qgslocatorwidget.cpp
@@ -304,7 +304,7 @@ void QgsLocatorWidget::updateResults( const QString &text )
   else
   {
     mHasSelectedResult = false;
-    mLocatorModel->clear();
+    mLocatorModel->deferredClear();
     mLocator->fetchResults( text, createContext() );
   }
 }
@@ -350,16 +350,29 @@ QgsLocatorContext QgsLocatorWidget::createContext()
 
 QgsLocatorModel::QgsLocatorModel( QObject *parent )
   : QAbstractTableModel( parent )
-{}
+{
+  mDeferredClearTimer.setInterval( 100 );
+  mDeferredClearTimer.setSingleShot( true );
+  connect( &mDeferredClearTimer, &QTimer::timeout, this, &QgsLocatorModel::clear );
+}
 
 void QgsLocatorModel::clear()
 {
+  mDeferredClearTimer.stop();
+  mDeferredClear = false;
+
   beginResetModel();
   mResults.clear();
   mFoundResultsFromFilterNames.clear();
   endResetModel();
 }
 
+void QgsLocatorModel::deferredClear()
+{
+  mDeferredClear = true;
+  mDeferredClearTimer.start();
+}
+
 int QgsLocatorModel::rowCount( const QModelIndex & ) const
 {
   return mResults.size();
@@ -459,17 +472,29 @@ Qt::ItemFlags QgsLocatorModel::flags( const QModelIndex &index ) const
     flags = flags & ~( Qt::ItemIsSelectable | Qt::ItemIsEnabled );
   }
   return flags;
-
 }
 
 void QgsLocatorModel::addResult( const QgsLocatorResult &result )
 {
+  mDeferredClearTimer.stop();
+  if ( mDeferredClear )
+  {
+    mFoundResultsFromFilterNames.clear();
+  }
+
   int pos = mResults.size();
   bool addingFilter = !result.filter->displayName().isEmpty() && !mFoundResultsFromFilterNames.contains( result.filter->name() );
   if ( addingFilter )
     mFoundResultsFromFilterNames << result.filter->name();
 
-  beginInsertRows( QModelIndex(), pos, pos + ( addingFilter ? 1 : 0 ) );
+  if ( mDeferredClear )
+  {
+    beginResetModel();
+    mResults.clear();
+  }
+  else
+    beginInsertRows( QModelIndex(), pos, pos + ( addingFilter ? 1 : 0 ) );
+
   if ( addingFilter )
   {
     Entry entry;
@@ -480,7 +505,13 @@ void QgsLocatorModel::addResult( const QgsLocatorResult &result )
   Entry entry;
   entry.result = result;
   mResults << entry;
-  endInsertRows();
+
+  if ( mDeferredClear )
+    endResetModel();
+  else
+    endInsertRows();
+
+  mDeferredClear = false;
 }
 
 
diff --git a/src/gui/locator/qgslocatorwidget.h b/src/gui/locator/qgslocatorwidget.h
@@ -180,9 +180,18 @@ class QgsLocatorModel : public QAbstractTableModel
 
     /**
      * Resets the model and clears all existing results.
+     * \see deferredClear()
      */
     void clear();
 
+    /**
+     * Resets the model and clears all existing results after a short delay, or whenever the next result is added to the model
+     * (whichever occurs first). Using deferredClear() instead of clear() can avoid the visually distracting frequent clears
+     * which may occur if the model is being updated quickly multiple times as a result of users typing in a search query.
+     * \see deferredClear()
+     */
+    void deferredClear();
+
     int rowCount( const QModelIndex &parent = QModelIndex() ) const override;
     int columnCount( const QModelIndex &parent = QModelIndex() ) const override;
     QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const override;
@@ -206,6 +215,8 @@ class QgsLocatorModel : public QAbstractTableModel
 
     QList<Entry> mResults;
     QSet<QString> mFoundResultsFromFilterNames;
+    bool mDeferredClear = false;
+    QTimer mDeferredClearTimer;
 };
 
 class QgsLocatorProxyModel : public QSortFilterProxyModel
