timelapse frame on stroke idle

src/canvas.cpp

@@ -741,6 +741,7 @@ void Canvas::stroke_commit()
 
     m_dirty = false;
     m_dirty_stroke = true; // new stroke ready for timelapse capture
+    m_disrty_stroke_time = std::chrono::steady_clock::now();
     App::I->redraw = true;
     
     // save viewport and clear color states