[LyX/master] Do not change outliner tree depth when not appropriate

[Juergen Spitzmueller]

commit 4cd568d3126670503ffab49c87ba21b27a8bdc27
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Wed Feb 22 14:23:04 2023 +0100

    Do not change outliner tree depth when not appropriate
    
    This fixes expansion/collapsing on double-click (#12672)
---
 src/frontends/qt/TocWidget.cpp |   18 +++++++++++++-----
 src/frontends/qt/TocWidget.h   |    3 +++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/frontends/qt/TocWidget.cpp b/src/frontends/qt/TocWidget.cpp
index fcbd605..ef1a289 100644
--- a/src/frontends/qt/TocWidget.cpp
+++ b/src/frontends/qt/TocWidget.cpp
@@ -47,8 +47,8 @@ namespace lyx {
 namespace frontend {
 
 TocWidget::TocWidget(GuiView & gui_view, QWidget * parent)
-	: QWidget(parent), depth_(0), persistent_(false), gui_view_(gui_view),
-	  timer_(new QTimer(this))
+	: QWidget(parent), depth_(0), persistent_(false), keep_expanded_(false),
+	  gui_view_(gui_view), timer_(new QTimer(this))
 {
 	setupUi(this);
 
@@ -263,7 +263,8 @@ void TocWidget::on_tocTV_activated(QModelIndex const & index)
 
 void TocWidget::on_tocTV_pressed(QModelIndex const & index)
 {
-
+	DocIterator const & dit = gui_view_.documentBufferView()->cursor();
+	keep_expanded_ = gui_view_.tocModels().currentIndex(current_type_, dit) == index;
 	Qt::MouseButtons const button = QApplication::mouseButtons();
 	if (button & Qt::LeftButton) {
 		goTo(index);
@@ -273,6 +274,12 @@ void TocWidget::on_tocTV_pressed(QModelIndex const & index)
 }
 
 
+void TocWidget::on_tocTV_doubleClicked(QModelIndex const &)
+{
+	keep_expanded_ = true;
+}
+
+
 void TocWidget::goTo(QModelIndex const & index)
 {
 	LYXERR(Debug::GUI, "goto " << index.row()
@@ -492,7 +499,7 @@ void TocWidget::updateView()
 	// Expensive operations are on a timer.  We finish the update immediately
 	// for sparse edition actions, i.e. there was no edition/cursor movement
 	// recently, then every 300ms.
-	if (!timer_->isActive()) {
+	if (!timer_->isActive() && !keep_expanded_) {
 		finishUpdateView();
 		timer_->start(300);
 	}
@@ -512,8 +519,9 @@ void TocWidget::finishUpdateView()
 	// text and moving with arrows. For bigger operations, this is negligible,
 	// and outweighted by TocModels::reset() anyway.
 	if (canNavigate()) {
-		if (!persistent_)
+		if (!persistent_ && !keep_expanded_)
 			setTreeDepth(depth_);
+		keep_expanded_ = false;
 		persistentCB->setChecked(persistent_);
 		// select the item at current cursor location
 		if (gui_view_.documentBufferView()) {
diff --git a/src/frontends/qt/TocWidget.h b/src/frontends/qt/TocWidget.h
index 2838adb..079fd24 100644
--- a/src/frontends/qt/TocWidget.h
+++ b/src/frontends/qt/TocWidget.h
@@ -69,6 +69,7 @@ protected Q_SLOTS:
 
 	void on_tocTV_activated(QModelIndex const &);
 	void on_tocTV_pressed(QModelIndex const &);
+	void on_tocTV_doubleClicked(QModelIndex const &);
 	void on_updateTB_clicked();
 	void on_sortCB_stateChanged(int state);
 	void on_persistentCB_stateChanged(int state);
@@ -115,6 +116,8 @@ private:
 	int depth_;
 	/// persistence of uncollapsed nodes in toc view
 	bool persistent_;
+	/// keep uncollapsed nodes in this event
+	bool keep_expanded_;
 	///
 	GuiView & gui_view_;
 	// Timer for scheduling expensive update operations