Fixes #6753: Lv2 help window issues (#6957)

This fixes at least three issues:

* Help window is not synched with window manager's `X`-button
* Help window is not being closed on track destruction or on closing the plugin window
* Trims help window strings and force-adds a newline, because `QLabel::sizeHint` sometimes computes too small values. Now, together with #6956, all help windows fit their strings. Some help windows are too large by one line, but this seems better than forcing the user to resize them if they are too small by one line.

plugins/Lv2Effect/Lv2FxControlDialog.cpp

@@ -72,4 +72,13 @@ void Lv2FxControlDialog::modelChanged()
 }
 
 
+
+
+void Lv2FxControlDialog::hideEvent(QHideEvent *event)
+{
+	closeHelpWindow();
+	QWidget::hideEvent(event);
+}
+
+
 } // namespace lmms::gui

plugins/Lv2Effect/Lv2FxControlDialog.h

@@ -46,6 +46,7 @@ public:
 private:
 	Lv2FxControls *lv2Controls();
 	void modelChanged() final;
+	void hideEvent(QHideEvent *event) override;
 };
 
 

plugins/Lv2Instrument/Lv2Instrument.cpp

@@ -295,6 +295,15 @@ void Lv2InsView::dropEvent(QDropEvent *_de)
 
 
 
+void Lv2InsView::hideEvent(QHideEvent *event)
+{
+	closeHelpWindow();
+	QWidget::hideEvent(event);
+}
+
+
+
+
 void Lv2InsView::modelChanged()
 {
 	Lv2ViewBase::modelChanged(castModel<Lv2Instrument>());

plugins/Lv2Instrument/Lv2Instrument.h

@@ -124,6 +124,7 @@ public:
 protected:
 	void dragEnterEvent(QDragEnterEvent *_dee) override;
 	void dropEvent(QDropEvent *_de) override;
+	void hideEvent(QHideEvent* event) override;
 
 private:
 	void modelChanged() override;