In the root element "Gauge", "Version" means version of the XML-gauge spec.
(always 1.0, in both fs8 & fs9)


G:Var variables only go from 1-9.


Read messageboard post that L: variables need to be unique
within the first few chars, but I've successfully used
normal, fairly long names which are not unique until
the 12th char.


Cannot use linebreaks in RPN blocks in fs8. (* comments *) seem to work.
Apparently in fs9 linebreaks work! The new planes are all created with
readable formatting and comments!
Update: RPN inside <sring> tags still cannot contain linebreaks. Probably
only <value> has been fixed.

A lot of new things in fs9: macros, vector drawing, namespaces..
Can now use decimal coordinates, i.e.: X="9.25" Y="1.125"
This does not work in fs8.


Only one "event i/o stack": don't pound on a key event (like
(&gt;K:SMOKE_ON) every tick because it prevents human-entered
multiple key strokes, such as (e)ngine-(2), (E)xit-(2), etc.


Axis (for images) moves the image so that the specified
point in the image is at the point specified by Position.
  Ex:
    <position X="5" Y="5" />
	<image foo...>
		<axis X="5" Y="5" />
This places the origin of the image at the origin
of the encompassing element (or the gauge).


Cannot scale images except via ImagesSizes (2002).
ImageSizes=<640rez_Width>,<640rez_Height>,<1024rez_Width>,<1024rez_Height>


In 2004 you don't need ImageSizes="64,65,0,0" anymore, doesn't work.
Bitmaps need the correct dimensions in relation to each other.


Clip uses gauge-space coords (not image-space)


I cannot get goto to work. 


store and load (i.e. s0 ... l0) are scoped within the <value>


What is <Container/>?


Update frequency sometimes seems to work, other times not.
This from Rob Barend on avsim forum:
The update frequency determines the interval at which the gauge is refreshed:
<Update Frequency="*"/>
Line absent, * = 0 or greater than 9: 0.055 sec
1: 1.00 sec
2: 0.50 sec
3: 0.33 sec
4: 0.22 sec
5: 0.17 sec
6: 0.17 sec
7: 0.11 sec
8: 0.11 sec
9: 0.11 sec



Failure actions:
	Action="NONE"
	Action="FREEZE"
	Action="ZERO"
	Action="DRAW"
	Action="COVER"
	Action="MAX"


Failures:
(These are in the DTD, but formatted here for readability)

FAIL_SYSTEM_ENGINE
FAIL_SYSTEM_PITOT_STATIC
FAIL_SYSTEM_VACUUM
FAIL_SYSTEM_ELECTRICAL_PANELS
FAIL_SYSTEM_ELECTRICAL_AVIONICS

FAIL_GAUGE_ADF
FAIL_GAUGE_AIRSPEED
FAIL_GAUGE_ALTIMETER
FAIL_GAUGE_ATTITUDE
FAIL_GAUGE_COMMUNICATIONS (* no nav *)
FAIL_GAUGE_FUEL_INDICATORS
FAIL_GAUGE_GYRO_HEADING
FAIL_GAUGE_MAGNETIC_COMPASS
FAIL_GAUGE_NAVIGATION
FAIL_GAUGE_NAVIGATION_VOR1
FAIL_GAUGE_NAVIGATION_VOR2
FAIL_GAUGE_NAVIGATION_BOTH
FAIL_GAUGE_TRANSPONDER
FAIL_GAUGE_TURN_COORDINATOR
FAIL_GAUGE_VERTICAL_SPEED