#2793 controls.nas throttleAxis() does not allow (invert:1)

[Huntley Palmer]

Investigating a query on the forum, set the following simple settings for a two-throttle ( AV8R) joystick:

    <!-- Analog axis 2. Throttle 1 -->
    <axis>
        <number>
            <unix>2</unix>
            <mac>3</mac>
            <windows>3</windows>
        </number>
        <desc>Throttles</desc>
        <binding>
        <command>nasal</command>
        <script>
        controls.propellerAxis(invert:1);
    </script>
      </binding>
    </axis>

    <!-- Analog axis 4. Throttle 2 -->
    <axis n="4">
        <desc>Prop Pitch; +Trg Mode0: Mixture;  </desc>
        <binding>
            <command>nasal</command>
            <script>
                controls.throttleAxis(invert:1);
        </script>
      </binding>
    </axis>

moitoring property tree at
/controls/engines/engine/propellor-pitch
and
/controls/engines/engine/throttle

the propellor pitch value is properly inverted while the throttle value is not.

Exchanging the bindings to the alternate axes does not change the situation, while propellorAxis() honours (invert:1) the throttle axis remains unaffected.

Inserting print statements in controls.nas @ 108 ff :

# Joystick axis handlers (use cmdarg).  Shouldn't be called from
# other contexts.  A non-null argument reverses the axis direction.
var axisHandler = func(pre, post) {
    print("entr axisHandler");
    func(invert = 0) {
        print("entr innerFunc");
        var val = cmdarg().getNode("setting").getValue();
        if(invert) val = -val;
        foreach(var e; engines)
            if(e.selected.getValue())
                setprop(pre ~ e.index ~ post, (1 - val) / 2);
    }
}

results in console printouts only for the propellorAxis movement, not for the throttle axis.

The commentary for the above function sould read 'uses cmdarg', descriptive, not 'use cmdarg', imperative.

[Huntley Palmer]

ref joystick.nas @ 285. RJH' comments suggest that
controls.nas @ 72 setfor allenginesProperty() may be involved; this functio does not seem to honour 'invert'

The entire code path seems a little esoteric bearing in mind the skill level of a user simply attempting to get an input device working !

[Huntley Palmer]

Additionally the default model, c172p, has its own flavour of throttleAxis:
at fgdata/Aircraft/c172p/Nasal/engine.nas @ 475

# backwards compatibility only - the controls.throttleAxis should not be overridden like this. The joystick binding Throttle (all) has
# been replaced and controls.throttleAxis will not be called from the controls binding - so this is to
# maintain compatibility with existing joystick xml files.
controls.throttleAxis = func {
    var value = (1 - cmdarg().getNode("setting").getValue()) / 2;
    var new_value = std.max(0.0, std.min(value, 1.0));
    setprop("/controls/engines/current-engine/throttle", new_value);
};

The commentary is unclear as to who should be obeying the 'should not be overridden like this'

In any case, if the forum user is attempting to configure a device using the default model it looks as if completely different behaviour to that noted in controls.nas will be experienced.

[Richard Harrison]

The problem is that the c172 overrides throttleAxis without implementing all of the parameters that are defined in controls.nas.

I have previously recommended that aircraft models should never do this; and instead use a listener on the engine property to perform any special functions.

This is why there is no output for throttle by adding print into controls.nas

[xDraconian]

@lightwork, Nice analysis work. I agree with your conclusions. This will need to be addressed by the aircraft maintainers.

[Proteus Four]

Someone have submitted this analyse to the aircraft maintainers ? I have the same problem see the ticket 1849

[Gijs]

I have now: https://github.com/c172p-team/c172p/issues/1524, so closing it here (as invalid, because c172p bugs are not tracked here).

[Wayne Bragg]

I have a possible fix for this, but I need someone to test it.
See https://github.com/c172p-team/c172p/issues/1524#issuecomment-2465630634

[Proteus Four]

Hello, I'm interested to test it but let me the week for that. 

I will try it this weekend. 

Thanks for the work.

Le 8 nov. 2024 20:48, Wayne Bragg <wlbragg@users.sourceforge.net> a écrit :

I have a possible fix for this, but I need someone to test it.
See https://github.com/c172p-team/c172p/issues/1524#issuecomment-2465630634

---

[codetickets:#2793] controls.nas throttleAxis() does not allow (invert:1)

Status: Invalid
Milestone: 2020.3
Labels: Joystick Aircraft
Created: Tue Feb 07, 2023 12:45 PM UTC by Huntley Palmer
Last Updated: Thu Nov 07, 2024 06:25 PM UTC
Owner: nobody

Investigating a query on the forum, set the following simple settings for a two-throttle ( AV8R) joystick:

    <!-- Analog axis 2. Throttle 1 -->
    <axis>
        <number>
            <unix>2</unix>
            <mac>3</mac>
            <windows>3</windows>
        </number>
        <desc>Throttles</desc>
        <binding>
        <command>nasal</command>
        <script>
        controls.propellerAxis(invert:1);
    </script>
      </binding>
    </axis>

    <!-- Analog axis 4. Throttle 2 -->
    <axis n="4">
        <desc>Prop Pitch; +Trg Mode0: Mixture;  </desc>
        <binding>
            <command>nasal</command>
            <script>
                controls.throttleAxis(invert:1);
        </script>
      </binding>
    </axis>

moitoring property tree at
/controls/engines/engine/propellor-pitch
and
/controls/engines/engine/throttle

the propellor pitch value is properly inverted while the throttle value is not.

Exchanging the bindings to the alternate axes does not change the situation, while propellorAxis() honours (invert:1) the throttle axis remains unaffected.

Inserting print statements in controls.nas @ 108 ff :

# Joystick axis handlers (use cmdarg).  Shouldn't be called from
# other contexts.  A non-null argument reverses the axis direction.
var axisHandler = func(pre, post) {
    print("entr axisHandler");
    func(invert = 0) {
        print("entr innerFunc");
        var val = cmdarg().getNode("setting").getValue();
        if(invert) val = -val;
        foreach(var e; engines)
            if(e.selected.getValue())
                setprop(pre ~ e.index ~ post, (1 - val) / 2);
    }
}

results in console printouts only for the propellorAxis movement, not for the throttle axis.

The commentary for the above function sould read 'uses cmdarg', descriptive, not 'use cmdarg', imperative.

---

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