fdo#68877: Select "<?>" as Elements window do

Elements Dock needs to have the same behavior of Elements window. After insert some symbol, if
this symbol have some placeholder, select the first placehold to user put some data.

This increases usability of Elements Dock.

Change-Id: Idc57cc6817d94f698632eb938600a55c8f9afbd8
Reviewed-on: https://gerrit.libreoffice.org/5780Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>

starmath/source/edit.cxx

@@ -1025,11 +1025,31 @@ void SmEditWindow::InsertText(const OUString& rText)
 
         nEndIndex += aSelection.nEndPos;
 
+        // TODO: unify this function with the InsertCommand: The do the same thing for different
+        // callers
+        OUString string(rText);
+
         // put a space before a new command if not in the beginning of a line
         if (aSelection.nStartPos > 0 && aCurrentFormula[nStartIndex - 1] != ' ')
-            pEditView->InsertText(" " + rText);
+            string = " " + string;
+
+        pEditView->InsertText(string);
+
+        // Remember start of the selection and move the cursor there afterwards.
+        aSelection.nEndPara = aSelection.nStartPara;
+        if (HasMark(string))
+        {
+            aSelection.nEndPos = aSelection.nStartPos;
+            pEditView->SetSelection(aSelection);
+            SelNextMark();
+        }
         else
-            pEditView->InsertText(rText);
+        {   // set selection after inserted text
+            aSelection.nEndPos = aSelection.nStartPos + string.getLength();
+            aSelection.nStartPos = aSelection.nEndPos;
+            pEditView->SetSelection(aSelection);
+        }
+
         aModifyTimer.Start();
         StartCursorMove();
         GrabFocus();