Do some caching of window title and related UI

This should avoid performance problems related to the window update machinery.
Moreover this fixes a crash introduced by 82808fea when closing a file.

Note that GuiWorkArea::Private already had a read_only_ member, but it
was unused.

Also rename LyXVC::vcname() to LyXVC::vcstatus() since it now contains
directly the UI string to be shown.

src/LyXVC.cpp

@@ -41,9 +41,14 @@ LyXVC::LyXVC()
 }
 
 
-string LyXVC::vcname() const
+docstring LyXVC::vcstatus() const
 {
-	return vcs->vcname();
+	if (!vcs)
+		return docstring();
+		if (locking())
+			return bformat(_("%1$s lock"), from_ascii(vcs->vcname()));
+		else
+			return from_ascii(vcs->vcname());
 }
 
 

src/LyXVC.h

@@ -12,6 +12,7 @@
 #ifndef LYX_VC_H
 #define LYX_VC_H
 
+#include "support/docstring.h"
 #include "support/unique_ptr.h"
 
 #include <string>
@@ -48,8 +49,8 @@ public:
 	};
 	///
 	LyXVC();
-	/// Name of the underlying VCS
-	std::string vcname() const;
+	/// Status of the underlying VCS
+	docstring vcstatus() const;
 	/// Is \p fn under version control?
 	static bool fileInVC(support::FileName const & fn);
 	/** Not a good name perhaps. This function should be called whenever

src/frontends/qt4/GuiView.cpp

@@ -1182,12 +1182,7 @@ void GuiView::updateWindowTitle(GuiWorkArea * wa)
 
 	if (buf.lyxvc().inUse()) {
 		version_control_->show();
-		if (buf.lyxvc().locking())
-			version_control_->setText(
-				toqstr(bformat(_("%1$s lock"),
-				               from_ascii(buf.lyxvc().vcname()))));
-		else
-			version_control_->setText(toqstr(buf.lyxvc().vcname()));
+		version_control_->setText(toqstr(buf.lyxvc().vcstatus()));
 	} else
 		version_control_->hide();
 }

src/frontends/qt4/GuiWorkArea.cpp

@@ -47,7 +47,6 @@
 #include "support/convert.h"
 #include "support/debug.h"
 #include "support/gettext.h"
-#include "support/FileName.h"
 #include "support/lassert.h"
 #include "support/TempFile.h"
 
@@ -247,11 +246,12 @@ SyntheticMouseEvent::SyntheticMouseEvent()
 
 
 GuiWorkArea::Private::Private(GuiWorkArea * parent)
-: p(parent), screen_(0), buffer_view_(0), read_only_(false), lyx_view_(0),
-cursor_visible_(false), cursor_(0),
-need_resize_(false), schedule_redraw_(false), preedit_lines_(1),
-pixel_ratio_(1.0),
-completer_(new GuiCompleter(p, p)), dialog_mode_(false)
+: p(parent), screen_(0), buffer_view_(0), lyx_view_(0),
+  cursor_visible_(false), cursor_(0),
+  need_resize_(false), schedule_redraw_(false), preedit_lines_(1),
+  pixel_ratio_(1.0),
+  completer_(new GuiCompleter(p, p)), dialog_mode_(false),
+  read_only_(false), clean_(true)
 {
 }
 
@@ -1388,8 +1388,15 @@ QVariant GuiWorkArea::inputMethodQuery(Qt::InputMethodQuery query) const
 
 void GuiWorkArea::updateWindowTitle()
 {
-	d->lyx_view_->updateWindowTitle(this);
+	Buffer const & buf = bufferView().buffer();
+	if (buf.fileName() != d->file_name_ || buf.isReadonly() != d->read_only_
+	    || buf.lyxvc().vcstatus() != d->vc_status_ || buf.isClean() != d->clean_) {
+		d->file_name_ = buf.fileName();
+		d->read_only_ = buf.isReadonly();
+		d->vc_status_ = buf.lyxvc().vcstatus();
+		d->clean_ = buf.isClean();
 		titleChanged(this);
+	}
 }
 
 

src/frontends/qt4/GuiWorkArea_Private.h

@@ -15,6 +15,7 @@
 #include "FuncRequest.h"
 #include "LyXRC.h"
 
+#include "support/FileName.h"
 #include "support/Timeout.h"
 
 #include <QMouseEvent>
@@ -150,8 +151,6 @@ struct GuiWorkArea::Private
 	QPaintDevice * screen_;
 	///
 	BufferView * buffer_view_;
-	/// Read only Buffer status cache.
-	bool read_only_;
 	///
 	GuiView * lyx_view_;
 	/// is the cursor currently displayed
@@ -187,6 +186,17 @@ struct GuiWorkArea::Private
 	/// when the menu is actually shown (after releasing on Windows)
 	/// and after the DEPM has done its job.
 	std::string context_menu_name_;
+
+	/// stuff related to window title
+	///
+	support::FileName file_name_;
+	///
+	bool read_only_;
+	///
+	docstring vc_status_;
+	///
+	bool clean_;
+
 }; // GuiWorkArea
 
 } // namespace frontend