GUI Messages
| Note This article needs a few screenshots |
On-screen GUI messages can be rendered in FlightGear using a simple property-based messaging system which is using property listeners and the PUI GUI system.
Internals
Whatever is written to /sim/messages/* at runtime is shown on-screen for a few seconds, then moved away. When the next message is written to that node, that is moved on-screen.
Behind the scenes, this works by using a property listener/callback that is triggered whenever the property tree branch is modified.
Features
This system is primarily used by the following features:
- Tutorials
- Multiplayer chat messages Chat Menu
- Howto:Define limits
- Failure management (limits.nas)
- Howto:Implement copilot announcements
- ATC
None of those are hard-coded, those are all going through the property tree and gui.nas, so you can "disable" things there. The higher-level features are limits.nas (or the failure manager) and the tutorial system.
To disable the system completely, set /sim/screen/nomap=true to prevent default message mapping - e.g. as a startup option --prop:/sim/screen/nomap=1 and/or by editing $FG_HOME/Preferences.xml
In addition, there's the tooltip system which is meanwhile using the Canvas 2D rendering API.