open presets from the brush preview, fix scrollbar redraw

src/node_scroll.cpp

@@ -34,7 +34,10 @@ void NodeScroll::on_tick(float dt)
     float sz = m_size.y - (pad[0] + pad[2]);
     float new_pad = rect.w == 0 || rect.w <= sz ? 5 : 35;
     if (pad[1] != new_pad)
+    {
         YGNodeStyleSetPadding(y_node, YGEdgeRight, new_pad);
+        app_redraw();
+    }
 }
 
 void NodeScroll::draw()