RFR: 6364: Improvements to the Thread Graph

[Alex Macdonald]

On Mon, 28 Sep 2020 21:07:35 GMT, Suchita Chaturvedi <schaturvedi at openjdk.org> wrote:

> "Edit Thread Lanes" at top right corner and "Thread State Selection" button, both are opening the same pop up.
> 
> Just a suggestion, Should we keep one and skip the other?

I still think it'd be useful to keep the text on that button, otherwise the only way to reach that functionality is via
the context menu or by using the icon in the top right corner (which you would only know of the functionality from
prior knowledge, or by hovering and displaying the tooltip). The idea here is that the functionality is upfront and
readable, and doesn't require legacy knowledge to access.

The idea was to have a dropdown combobox that would allow for quickly toggling lane events and allowing for instant
chart redraws. Unfortunately after implementing this I found out that it wasn't working as intended on Windows & Mac
because of the way SWT was handling the actions of checking the combobox. In Linux, selecting a SWT combobox is enough
to trigger the action, however in Windows & Mac the behaviour is different and the action only triggers if both the
item is highlighted and checked. As a preventative measure there's a check that uses the dropdown lane filter if the OS
is Linux, but the regular dialog if it's Windows or Mac. If this functionality should be reverted to make it the same
across OS's that's okay, but personally I think it's a neat feature for now.

> I have tried to use the new improved version of threads page. But for many JFRs I am getting "Too much content" issue
> and the page is not loading properly.

This one is tricky, because the chart needs a certain amount of space to properly display all the lanes otherwise the
"Too much content" overlay appears. For example, here are a couple of screenshots of the "plain_recording.jfr" provided
for uitests. There are a lot of threads displayed, and the screenshots show the threshold of displaying the threads or
not.

This is the smallest I can make the chart without displaying the overlay,
![01-just-right](https://user-images.githubusercontent.com/10425301/96511328-f00a4d00-122c-11eb-9880-8f7748d7de2b.png)

and here's what it looks like when I drag the sash just a bit more. At this point there just isn't enough space to
display all of the threads on the screen, and I'd need to adjust my selection to suit the screen real estate.
![02-too-much](https://user-images.githubusercontent.com/10425301/96511332-f0a2e380-122c-11eb-9984-d11b54daf70f.png)

-------------

PR: https://git.openjdk.java.net/jmc/pull/27