Rrd4j Chart unreadable by fontsize too big

Dear community,

my charts are showing data in a completely unreadable way, since the font size on the axis and in the legend is far too big, see attachment. Problem occurs
-on iPad, iPhone and on Mac mini,
-in a browser on Basic UI, and in the openHAB app.

In addition, the charts show some funny triangular forms. Any clue for the reason?

Current system is
-openHAB 2.4.0
-running on Synology Diskstation DS218

Does anyone has a clue, how I can solve this issue?

Thank you in advance for your hints,
Doc MC

Can’t reproduce such behaviour on my android devices ( app and chrome browser).
On which kind of devices did you have those? A browser could be on anything, windows PC, android phone,…

Confirm you are using the chart elements on the sitemap and not a webview.

I have the same appearance on
-Safari on Mac mini (OSX Catalina)
-Safari on iPad Pro (iOS 13.4)
-Safari on iPhone XR (iOS 13.4.1)
-openHAB app (latest version) on iPad and iPhone.
For me it looks like as the charts are stored as pixel-graphics by the rrd4j persistence…

What do you mean by “Confirm you are using the chart elements on the sitemap and not a webview.”?

I coded it by copying and pasting from other authors in this community:

       Switch item=Chart_Zeitraum_D_W_M_Y label="" mappings=[0="Tag", 1="Woche", 2="Monat", 3="Jahr"]
        Frame label="Temperatur Innen" {
				Chart item=gChartTemperature period=D refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==0, Chart_Zeitraum_D_W_M_Y=="Uninitialized"]
				Chart item=gChartTemperature period=W refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==1]
				Chart item=gChartTemperature period=M refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==2]
				Chart item=gChartTemperature period=Y refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==3]
       Frame label="Luftfeuchtigkeit Innen" {

// Switch item=Chart_Zeitraum_D_W_M_Y label="" mappings=[0=“Tag”, 1=“Woche”, 2=“Monat”, 3=“Jahr”]
Chart item=gChartHumidity period=D refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==0, Chart_Zeitraum_D_W_M_Y==“Uninitialized”]
Chart item=gChartHumidity period=W refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==1]
Chart item=gChartHumidity period=M refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==2]
Chart item=gChartHumidity period=Y refresh=60000 visibility=[Chart_Zeitraum_D_W_M_Y==3]

rrd4j does store the data only.
For testing try the webview like:


in a browser.
Additionally, please post your used Java version, because the problem sounds like this old Thread

1 Like

Interesting. Here are now two actual screenshots, the first one from basic UI on safari (OS X Catalina), the 2nd one from the web view (@opus: I had to change the period to D, since I just today started with persistence). Seems that the (readable) webview chart is somehow changed. Hence, there seems to be a bug causing some triangular shape.

(fig 1: basic UI)

(fig 2: webview)

@opus: Thank you for the link, I was searching the forum before, but did not detect it. Problems looks identical to mine. On my Synology I have Java 8 running. Will check if I can find a newer version. When I get better results, I’ll share with the forum.

I would not comment on the differences of both charts without knowing if they were build for the same period. rrd4j would show differences when selecting another duration.
You could check each and every data point using the REST API.
But that would be looking into direction of faulty data, you were asking for the font size, the thread posted above was talking about such problem. The last entries showed a solution by changing/updating the java version, although no Mac nor IPone user seemed to be part of these thread.

Thank you for your comment. Both charts were generated within 1 min, so the data is expected to be the same. Since (except for the different scale on the y-axis) the charts look similar, I don’t think that there’s a problem with the data persistence. The main problem I see is the “unreadability” of the legends and axis description. (The “triangles” I only regard as minor bug…).

Seems that updating Java on Synology is my next task… since this package is not downloadable automatically by the Synology DSM (… and I’m not so firm in LINUX to install updates manually…).

Best regards,
Doc MC.

All understood, regarding the different charts, both should use the SAME period ( which I can’t verify without reading the scale).
Sorry, but can’t help on your Java/Synology problem. However, I’d check the used version before changing anything!

Just upgraded Java on my Synology to the latest version I could find, i.e. Java HotSpot™ 64-Bit Server VM (build 25.241-b07, mixed mode). I also tested the 32-Bit version since in some discussions there were problems with the 64-Bit version noted. But both without success. Charts still look the same. So I probably have to look for some alternative charts… or install everything on a RaspPi and go directly to influxDB with Grafana…

Can’t really say if that Java version (HotSpot?) is the needed one.
Mine looks like:

[17:47:38] openhabian@opuspi3:/etc/openhab2/rules$ java -version
openjdk version "1.8.0_222"
OpenJDK Runtime Environment (Zulu8.40.0.178-CA-linux_aarch32hf) (build 1.8.0_222-b178)
OpenJDK Client VM (Zulu8.40.0.178-CA-linux_aarch32hf) (build 25.222-b178, mixed mode, Evaluation)
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Seems that my version is even newer (sorry that I din’t copy the first line previously…). Here is the complete echo.

admin@Synology : / $ java -version

java version “1.8.0_241”

Java™ SE Runtime Environment (build 1.8.0_241-b07)

Java HotSpot™ 64-Bit Server VM (build 25.241-b07, mixed mode)

In this case I am out of ideas.

Don’t worry, @opus, at least I updated my Java version :wink: . As I see more and more obstacles running OH on my Synology (e.g. docker can’t be installed…), it’s just a question of time till I convert to a RaspPi.

Wish you a nice and long weekend and thank you for your effort,
Doc MC