Setting an items icon dynamically

[Jonathan Giles]

Hi all,

I would like to be able to dynamically alter the icon for some items in my sitemap. My specific case is that I have three items representing the state of my water tank. What I would really like to do is use the cistern images included with openhab (which include cistern-100.png through cistern-0.png) to provide a visual representation in the normal icon area of the sitemap (in the same way that dimmer and roller blind support this).

I could easily write a rule to determine which image to use (by rounding the current percentage full down to the nearest 10 percent), but that doesn't help with modifying the image in the sitemap itself. Is there a way to do this, or is it just not possible? I could create a Dimmer item to represent the image, but I don't think there is any way of saying to the other items to use the Dimmer items image as their image.

Thanks!
-- Jonathan

[Ben Jones]

What is the type of your item? Assuming it is a number, what is the range of values it can be? From what you have said about percentages it sounds like 0-100?

If so you should just be able to specify the base icon name - 'cistern' - and openHAB will pick the closest icon, rounding down I think.

So if you have 3 icons, cistern-0, cistern-50 and cistern-100, you would see the -0 icon for any value from 0-49, the -50 icon for values 50-99, and -100 for 100. 

You might need to test that as I am not certain which way the bias is. 

[Jonathan Giles]

I read at [1] that this doesn't apply to Numbers, just Dimmer and RollerShutter. My testing seems to back this up.

The other (probably bigger) issue is that I have three items that I want to have the same image. One is percent-based, but the other two are just numbers. Ideally I would use the percent-based item (or a Dimmer / RollerShutter derived from it if needs be) as the image for all three items. I have a feeling it isn't possible, but it would be cool if it was.

[1] https://groups.google.com/d/msg/openhab/0A7ii5MuvXk/3n4R68fqQa8J

Thanks,

-- Jonathan

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[Ben Jones]

Apologies - I thought this range matching worked for numbers as well. Switching that percentage item to a Dimmer item will resolve it as you noted.

If the number items have a distinct (known) set of values you can just copy the cistern icon a number of times, and rename to 'cistern-xx' for each value. openHAB should pick up the correct icon that way. 

Can you post your item definitions here for us to have a look?

[Jonathan Giles]

Here's the relevant section of my items file. The three items I am
displaying in my sitemap are the second, third, and fourth line. Ideally
I would base the cistern image for all three off of the fourth line (the
percentage full).

Number Water_Tank_Ultrasonic_cm "Ultrasonic reading [%.2f cm]" <cistern> (Water_Tank) { http="<[http://192.168.1.101:8081/homePi/waterTank/ultrasonic/reading/5:3600000:REGEX((.*?))]" }
Number Water_Tank_Water_Height "Water height [%.2f cm]" <cistern> (Water_Tank)
Number Water_Tank_Water_In_Tank "Water in tank [%.0f Litres]" <cistern> (Water_Tank)
Number Water_Tank_Percentage_Full "Percentage Full [%.0f Percent]" <cistern> (Water_Tank)
Switch Water_Tank_Fill "Water Tank Filling" (Water_Tank) { openSprinkler="1" }

-- Jonathan

[Ben Jones]

Don't think it is possible to link two items together on the one sitemap widget - as cool as that would be. I.e. the label from one and the icon from another. Maybe in v2.0....

[Jonathan Giles]

Yeah - I assumed as much. Nonetheless, it would definitely be a nice
thing to consider for a future release.

-- Jonathan