Bug 404590

SUMMARY

When using a smaller ksysguard window (or a window with many plots), sensor legends are collapsed by dropping sensor labels, which makes them hard to read unless one knows the color -> sensor association by heart.

For a sufficiently complex plot or a sufficiently small screen, there may be no ksysguard window size that fits in the screen for which the sensor legend is readable. This happens much before the plot itself is too small to be readable.

What makes this especially sad is that for many typical plots (e.g. stacked user/nice/system/iowait CPU load, read/write bandwidth of all drives / network interfaces), the legend is actually quite redundant and could be shortened by the user if given the ability to relabel sensors in a fashion that still makes sense in the context of a specific plot (e.g. in the context of a disk bandwidth plot "Read accesses device sda (8:0)" can be shortened to "sda reads").

I can think of several ways to resolve this:

- The configuration cop-out: Let users give sensors a shorter label in plot legends (would be particularly useful with I/O sensors, whose name is very long and can usually be shortened in the context of specific plot).
- The hard way: Review sensor names to make them shorter, without becoming ambiguous, or try to automatically shrink sensor names to adapt them to the context of a specific plot.
- The UI design trick: Redesign the legend display so that it can scale better to multiple sensors, e.g. by putting it inside of the graph or judiciously ellipsing-away a fraction of a sensor's label as the plot size shrinks.

STEPS TO REPRODUCE
1. Create a new ksysguard tab with room for a few plots (say, a 2x4 grid, which is otherwise pretty comfortable on a 24-inch screen).
2. Add several I/O sensors to a given plot (say, read/write bandwidth for two drives, which is a common configuration with SSDs + HDDs these days)

OBSERVED RESULT

The plot's legend is only displayed correctly if the window is maximized. Below a certain critical size, labels are immediately hidden without prior adaptation (e.g. putting an ellipsis in a middle). For sufficiently many traces, the legend may never be displayed correctly at any reasonable window size. It does not seem possible for the user to reconfigure sensor labels so that they fix on the screen.

EXPECTED RESULT

Plot legends should scale better with decreasing plot/window size.

SOFTWARE/OS VERSIONS

OS: openSUSE Tumbleweed, Linux kernel 4.20.7-1-default
KDE Plasma Version: N/A
KDE Frameworks Version: 5.55.0
Qt Version: 5.12.0