View source for Luup plugin icons

[[Category:Development]]

The [[Luup plugins: Static JSON file|Luup plugin static JSON file]] describes the icon that appears in the dashboard of the UI4 web interface.

=Icon format=

All of Vera's icons are 42x42 pixel PNGs with transparency.  Icons of other sizes will be resized to 42x42.

=Configuration=

The top-level key '''flashicon''' contains a string.  This string is the name of an image file.  The filename is either a relative path or a URL starting with "http".

==Relative paths==

If the filename is a relative path, it is relative to the directory '''/www/cmh/skins/default''' on the Vera.  If the filename ends in the string ".swf", this extension is changed to ".png".  (This is presumably a holdover from UI3, which was flash-based.  In UI4, there is no reason to maintain this ruse, so just use the ".png" extension.)

Files installed in the "icons" directory are:
* Binary_Light.png
* Binary_Light_0.png
* Binary_Light_100.png
* Dimmable_Light.png
* Dimmable_Light_0.png
* Dimmable_Light_100.png
* Dimmable_Light_25.png
* Dimmable_Light_50.png
* Dimmable_Light_75.png
* Door_Lock.png
* Door_Lock_0.png
* Door_Lock_100.png
* Generic_IO.png
* Humidity_Sensor.png
* IR_Transmitter.png
* Insteon.png
* Ip_Camera.png
* Light_Sensor.png
* Motion_Sensor.png
* Motion_Sensor_0.png
* Motion_Sensor_100.png
* Power_Meter.png
* Scenes.png
* Temperature_Sensor.png
* Thermostat.png
* USB_UIRT.png
* Window_Covering.png
* Zwave.png
* advanced.png
* default.png
* default_device.png
* default_panel.png
* default_plugins.png
* device.png
* devices.png
* energy.png
* findvera.png
* generic_icon.png
* generic_sensor.png
* intro.png
* location.png
* music_audio.png
* plugins.png
* users.png

== URLs ==

If the filename is a URL, it refers to a remote file on a web server.

=Constant icons=

For an icon that remains the same all the time, the '''flashicon''' key is all you need to provide.  Ensure that the static JSON file does not contain a '''DisplayStatus''' key, and you are done.

=Variable icons=

For an icon that varies based on the value of a variable, place a '''DisplayStatus''' key at the top level of the static JSON file.  Its value is a JSON object (associative array) with four keys:
; Service
: The Service ID of the variable that controls the icon.  This can be found in the matching device XML file, under the '''serviceId''' element.
; Variable
: The variable name of the variable that controls the icon.
; MinValue
: The value that this variable has when it is considered "off" or at "0%".  This can even be a string, if the variable is a string that takes two values.
; MaxValue
: The value that this variable has when it is considered "on" or at "100%".  This can even be a string, if the variable is a string that takes two values.

Example for a binary switch:

<pre><nowiki>
  "DisplayStatus": {
        "Service": "urn:upnp-org:serviceId:SwitchPower1",
        "Variable": "Status",
        "MinValue": "0",
        "MaxValue": "1"
  }
</nowiki></pre>

Example for a variable which takes on a range of values.

<pre><nowiki>
  "DisplayStatus": {
        "Service": "urn:upnp-org:serviceId:Dimming1",
        "Variable": "LoadLevelStatus",
        "MinValue": "0",
        "MaxValue": "100" 
  }
</nowiki></pre>

The filename in '''flashicon''' undergoes a special transformation for variable icons.  The extension ".png" is changed to "_0.png", "_25.png", "_50.png", "_75.png" or "_100.png" depending on the value of the service variable, linearly scaled from its range of 0:(MaxValue-MinValue) to 0:100.  Values round up; 1-25 produces the "_25" image; 26-50 produces the "_50" image, and so on.  For images which are not found (for instance, if the web server returns '''404 Not Found''') the default image is used.

Consequently, at least three images, and as many as six, should be present for variable-icon plugins.  For example, if '''flashicon''' contains '''<nowiki>http://example.com/image.png</nowiki>''', the web server must be able to serve:
* '''<nowiki>http://example.com/image.png</nowiki>''' (for when the plugin is loading in the Luup engine)
* '''<nowiki>http://example.com/image_0.png</nowiki>'''
* '''<nowiki>http://example.com/image_100.png</nowiki>'''
and it should be able to serve (if the variable is a sliding scale):
* '''<nowiki>http://example.com/image_25.png</nowiki>'''
* '''<nowiki>http://example.com/image_50.png</nowiki>'''
* '''<nowiki>http://example.com/image_75.png</nowiki>'''

==Cheating to get finer-grained variable icons==

The JavaScript code that inserts the strings "_0" to "_100" into the image filename does not check that the raw variable value is in the range '''MinValue''' to '''MaxValue'''.  By deliberately choosing a '''MaxValue''' less than the highest value that a variable can take, you can make the JavaScript load images with "_125", "_150", etc., effectively providing any number of images.  '''MinValue''' is similarly handled, though the results are odd with negative variables or MinValue not equal to zero: the string inserted into the filename is "_-25", "-50", etc.

That this trick works is probably accidental, and its behaviour probably should not be relied on.