Preserve double/triple click mode when extending the selection

Summary:
When extending the selection using the mouse the double or triple click
mode that initiated the selection should be preserved.  If the user double
clicked to select a word, then extending the selection should extend
"word at a time" rather than "character at a time". Similarly if the user
triple clicked to select a whole line initially, then extending the selection
should extend "line at a time" rather than "character at a time".

BUG: 374454
FIXED-IN: 18.12

Reviewers: #konsole, hindenburg

Reviewed By: #konsole, hindenburg

Subscribers: konsole-devel

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D16660

src/TerminalDisplay.cpp

@@ -2309,8 +2309,10 @@ void TerminalDisplay::mousePressEvent(QMouseEvent* ev)
             }
         }
 
-        _lineSelectionMode = false;
-        _wordSelectionMode = false;
+        if (!ev->modifiers()) {
+            _lineSelectionMode = false;
+            _wordSelectionMode = false;
+        }
 
         // The user clicked inside selected text
         bool selected =  _screenWindow->isSelected(pos.x(), pos.y());