Fix bug #7361 (Assertion when a latex error occurs in the first (empty) paragraph)

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@37954 a592a061-630c-0410-9148-cb99ea01b6c8

src/BufferView.cpp

@@ -2364,6 +2364,42 @@ void BufferView::putSelectionAt(DocIterator const & cur,
 }
 
 
+bool BufferView::selectIfEmpty(DocIterator & cur)
+{
+	if (!cur.paragraph().empty())
+		return false;
+
+	pit_type const beg_pit = cur.pit();
+	if (beg_pit > 0) {
+		// The paragraph associated to this item isn't
+		// the first one, so it can be selected
+		cur.backwardPos();
+	} else {
+		// We have to resort to select the space between the
+		// end of this item and the begin of the next one
+		cur.forwardPos();
+	}
+	if (cur.empty()) {
+		// If it is the only item in the document,
+		// nothing can be selected
+		return false;
+	}
+	pit_type const end_pit = cur.pit();
+	pos_type const end_pos = cur.pos();
+	d->cursor_.clearSelection();
+	d->cursor_.reset();
+	d->cursor_.setCursor(cur);
+	d->cursor_.pit() = beg_pit;
+	d->cursor_.pos() = 0;
+	d->cursor_.setSelection(false);
+	d->cursor_.resetAnchor();
+	d->cursor_.pit() = end_pit;
+	d->cursor_.pos() = end_pos;
+	d->cursor_.setSelection();
+	return true;
+}
+
+
 Cursor & BufferView::cursor()
 {
 	return d->cursor_;

src/BufferView.h

@@ -247,6 +247,9 @@ public:
 	void putSelectionAt(DocIterator const & cur,
 		int length, bool backwards);
 
+	/// selects the item at cursor if its paragraph is empty.
+	bool selectIfEmpty(DocIterator & cur);
+
 	/// update the internal \c ViewMetricsInfo.
 	void updateMetrics();
 

src/frontends/qt4/GuiErrorList.cpp

@@ -172,11 +172,17 @@ bool GuiErrorList::goTo(int item)
 		return false;
 	}
 
-	// If this paragraph is empty, highlight the previous one
-	while (dit.paragraph().empty())
-		dit.backwardPos();
-
 	// Now make the selection.
+	BufferView * bv = const_cast<BufferView *>(bufferview());
+	if (bv->selectIfEmpty(dit)) {
+		// The paragraph is empty but can be selected
+		bv->processUpdateFlags(Update::Force | Update::FitCursor);
+		return true;
+	}
+	if (dit.empty()) {
+		// The paragraph is empty and cannot be selected
+		return false;
+	}
 	// if pos_end is 0, this means it is end-of-paragraph
 	pos_type const s = dit.paragraph().size();
 	pos_type const end = err.pos_end ? min(err.pos_end, s) : s;
@@ -184,7 +190,6 @@ bool GuiErrorList::goTo(int item)
 	pos_type const range = end == start ? s - start : end - start;
 	// end-of-paragraph cannot be highlighted, so highlight the last thing
 	dit.pos() = range ? start : end - 1;
-	BufferView * bv = const_cast<BufferView *>(bufferview());
 	// FIXME LFUN
 	// If we used an LFUN, we would not need these lines:
 	bv->putSelectionAt(dit, max(range, pos_type(1)), false);