FOX GUI elements' initialization is delayed when using 3D view

[m-kro]

Elements of the FOX GUI are initialized with a noticeable delay of several seconds when an OSG 3D view is opened.

Example case:

• Load a config with a 3D view / open a 3D view. I used bs3DOSM.sumocfg
• Open view settings
• Open a color dialog, e.g. in the streets tab
• The sliders and numerical color model values look like in the screenshot below
• After approx. 20s the correct values appear
• If one of the sliders is moved before, the values are loaded immediately
• Happens also with 2D views as long as a 3D view is open at the same time

Other cases:

• tooltips below view-related buttons are also very slow to initialize
  • first show up in the upper left corner with placeholder text
  • seconds later the real text appears
  • even later the tooltip is moved to its meant position

SUMO-version: 1.12.0 extra + current dev. operating system: Win10

[m-kro]

Hypothesis: not enough time left for updating the FOX elements on idling. Background: When the user triggers changes, they happen without visible delays. The frame rate statistics integrated in OSG drops from 50-60 fps to 20-30fps when the GUI settings dialog is opened.