GUI Messages

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FlightGear is using a simple property-based messaging system which can render GUI messages using propoerty listenenrs and the PUI GUI system.

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.

This system is primarily used by the following features:

• Tutorials
• Multiplayer chat messages
• 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.

The corresponding code can be found in gui.nas and screen.nas

To change the font size

Set /sim/gui/style[1]/fonts/message-display/name — Csaba Halász  (Nov 23rd, 2008). Re: [Flightgear-devel] screen.window size of font. (powered by Instant-Cquotes)

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