PyKDE4 provides an analog Meter object which has a textlabel. By default this textlabel uses the global color scheme's foreground color to display text on a fixed white background (the meter itself). For a white-on-black color scheme like "Obsidian Black" this leads to white text on a white background. The label should use a fixed foreground color (like Qt::black) to make sure it is readable on its fixed-white background.
After a bit of research this bug seems to originate from kdelibs' plasma/widgets/meter.cpp, not the kde-python binding.
Created attachment 86149 [details] Uses theme's foreground-color for label 0 and black for all others. A probably ugly patch to the widget forcing it to use the current theme's foreground color only for the first label and black for all subsequent labels. This fixed the problem for me at least with fanspeed plasmoid which has indeed two labels, temperature monitor uses only one but is at least not broken now.
Hello! This bug report was filed for KDE Plasma 4, which reached end-of-support status in August 2015. KDE Plasma 5's desktop shell has been almost completely rewritten for better performance and usability, so it is likely that this bug is already resolved in Plasma 5. Accordingly, we hope you understand why we must close this bug report. If the issue described here is still present in KDE Plasma 5.12 or later, please feel free to open a new ticket in the "plasmashell" product after reading https://community.kde.org/Get_Involved/Bug_Reporting If you would like to get involved in KDE's bug triaging effort so that future mass bug closes like this are less likely, please read https://community.kde.org/Get_Involved#Bug_Triaging Thanks for your understanding! Nate Graham