List of Nasal extension functions: Difference between revisions

As such, the cmdarg() function is primarily used for listener callbacks declared in XML markup, cmdarg() returns the listened-to property as props.Node object, so you can use it with all its methods (see [[$FG_ROOT]]/Nasal/props.nas) for example:

The cmdarg() function avoids that you have to type the exact same path twice (once here and once in the setlistener() command) and it makes clear that this is the listened to property. Also, you can use all the nice props.Node methods on cmdarg() directly:

Use of cmdarg() outside of XML-bindings won't cause an error, but (still) return the last cmdarg() property. This just won't be the listened-to property anymore, but whatever the last legitimate cmdarg() user set. Most of the time it will be the property root of a joystick binding.

Concatenates an arbitrary number of arguments to one string, appends a new-line, and prints it to the terminal. Returns the number of printed characters.

=== <tt>logprint()</tt> ===

Returns the node value for a given path, or <tt>nil</tt> if the node doesn't exist or hasn't been initialized yet.  

Example:

Sets a property value for a given node path string. Always returns nil.

All arguments but the last are concatenated to a path string, with a slash (/) inserted between each element. The last value is written to the respective node. If the node isn't writable, then an error message is printed to the console.

Note: <tt>setprop()</tt> concatenates a list of input arguments by means of inserting a "/" in between. That is nice for properties, as this slash is part of the tree. However, when one wants to make use of indices, like [0], one has to concatenate by hand (using "~") ''inside'' one part of the string argument list. An example is:

This results in instrumentation/cdu/page[4]/title = 'MENU' (string)

Examples:

'''Erasing a property from the property tree''': a property that has been created, for example through <tt>setprop()</tt> can be erased via

=== <tt>interpolate()</tt> ===

Give the value from a value or a source node to a destination node in given time.

Examples:

=== <tt>settimer()</tt> ===

Runs a function after a given simulation time (default) or real time in seconds.

The first object is a function object (ie, "func { ... }").  Note that this is different from a function call (ie, "func ( ... )"). If you don't understand what this means, just remember to always enclose the first argument in any call to settimer with the word "func" and braces "{ }", and it will always work. For instance, if you want print the words "My result" in five seconds, use this code:

Inside the braces of the func object you can put any valid Nasal code, including a function call.  In fact, if you want to call a function with certain values as arguments, the way to do it is to turn it into a function object by enclosing it with a func{}, for example:

The third argument is optional and defaults to 0, which lets the time argument be interpreted as "seconds simulation time". In this case the timer doesn't run when FlightGear is paused. For user interaction purposes (measuring key press time, displaying popups, etc.) one usually prefers real time.

     var tmpl = props.Node.new({

             name : "PopTipSelf", modal : 0, layout : "hbox",

     });

     if (override != nil) tmpl.setValues(override);

     popdown(tipArgSelf);

     fgcommand("dialog-new", tmpl);

     fgcommand("dialog-show", tipArgSelf);

     currTimerSelf += 1;

     var thisTimerSelf = currTimerSelf;

     # Final argument 1 is a flag to use "real" time, not simulated time

     settimer(func { if(currTimerSelf == thisTimerSelf) { popdown(tipArgSelf) } }, delay, 1);

[[Nasal scripting language#settimer loops|More information about using the settimer function to create loops.]]

     m._hideTimer.singleShot = 1;

   },

   run: func

Returns information about geodetic coordinates. Takes two arguments: lat, lon (in degree) and returns a vector with two entries, or nil if no information could be obtained because the terrain tile wasn't loaded. The first entry is the elevation (in meters) for the given point, and the second is a hash with information about the assigned material, or nil if there was no material information available, because there is, for instance, an untextured building at that spot or the scenery tile is not loaded.

A full data set looks like this:

Note that geodinfo is a *very* CPU intensive operation, particularly in FG 2.4.0 and earlier, so use sparingly ([http://flightgear.org/forums/viewtopic.php?f=4&p=135044#p135044 forum discussion here]).

Usage:

The command debug.dump(airportinfo("KHAF")) outputs this:

   runways : { 12 : { stopway2 : 0, threshold1 : 232.5624,

   lon : -122.5010889999999, lat : 37.513831, stopway1 : 0, width : 45.72,

   threshold2 : 232.5624, heading : 138.1199999999999, length : 1523.0856 } },

   elevation : 20.42159999999999, id : "KHAF", name : "Half Moon Bay" }

That is: a hash with elements lat/lon/elev/id/name/has_metar for the airport, and a hash with runways, each of which consists of lat/lon/length/width/heading/threshold[12]/stopway[12]. Only one side of each runway is listed -- the other can easily be deduced.

Usage:

In advance of converting the Map and NavDisplay to use the [[Canvas]], James has improved the "flightplan()" extension function of the [[Nasal]] scripting interpreter to expose the full route-path vector for each flight plan leg as a vector on the leg.

Returns epoch time (time since 1972/01/01 00:00) in seconds as a floating point number with high resolution. This is useful for benchmarking purposes.

=== <tt>carttogeod()</tt> ===

Converts cartesian coordinates x/y/z to geodetic coordinates lat/lon/alt, which are returned as a vector. Units are degree and meter.

=== <tt>geodtocart()</tt> ===

Converts geodetic coordinates lat/lon/alt to cartesian coordinates x/y/z. Units are degree and meter.

=== <tt>parsexml()</tt> ===

This function is an interface to the built-in [http://expat.sourceforge.net/ Expat XML parser]. It takes up to five arguments. The first is a mandatory absolute path to an XML file, the remaining four are optional callback functions, each of which can be nil (which is also the default value).

Example:

<syntaxhighlight lang="php">

</syntaxhighlight>