Render new trace server connection status bar item

[marco-miller]

Add a contextual (secondary, right-side) VS Code status bar item, that renders the current trace server status. Have the extension context pass this status service to each active web-view provider, for them to update the rendered status upon every related message from the view.

Have TraceExplorerOpenedTracesViewProvider pass its status service to the TraceViewerPanel upon using it, in turn. Without this, there are instances where the latest server status isn't shown as expected. Keep this undefined in trace-tree.ts where that is not required.

This makes the server status listener-based. Add this connection listener through the TspClientProvider constructor, thus consistently use the latter across. This means also using it in the TraceViewerContainer constructor, instead of TspClient's directly prior.

Properly stringify (thus parse) the boolean status value, as passing it straight would break the JSON message otherwise.

Explicitly defer showing the item to only once Trace Viewer gets selected for the first time. Like open trace-explorer views which remain shown if unselecting Trace Viewer, keep showing the status item from there on. The VS Code API, anyway, doesn't hold an event that could selectively hide anything upon solely exiting Trace Viewer.

Prefer a standard VS Code status bar item to the side widget approach of theia-trace-extension. This should be more standard for such a connection status display, from a VS Code UI (and UX) perspective. This also allows not having to implement a custom widget that differs from the Trace Viewer panels. -The latter being meant to render real views.

Base this simple design of the status bar item on [1] below. Now, use the warning background for a found server, for such a positive status to be highlighted, thus noticeable. Use the usual red background for a trace server that is not found, highlighting that as an error. No other color can or should be used anyway for status bar items, per [1]. The latter reference also includes [2]'s, used to come up with this change.

[1]https://code.visualstudio.com/api/ux-guidelines/status-bar
[2]https://github.com/microsoft/vscode-extension-samples/blob/main/statusbar-sample/src/extension.ts

Use a short (thus usable) enough statusBarItem.text, along with a tooltip to complement the trace server status narrative.

Overall, with this approach, defer the introduction of the inversify module, used in theia-trace-extension. This would be to inject instances such as objects involved in this change and likely other ones; some being potential singletons.

Slightly refactor a few surrounding blank lines while editing some of these files.

Fixes #33.

Signed-off-by: Marco Miller marco.miller@ericsson.com

[bhufmann]

I going to review this today.

[bhufmann]

I noticed that when TSP queries in the trace panel fail due to non-connected server, the status in s not updated.

With this current approach by polling in the provider only certain events will trigger that code path and the server status is not updated.

I think you should be able to use the RestClient.addConnectionStatusListener. Each webview has an instance of the tspclient and also access the static connection listener. When sending a tsp message then it the listener implementation can notify via a message it's vscode extension counterpart and update the status line. I think if you add it to the common class TspClientProvider then you can share the code. Note that the class TraceViewerContainer doesn't use the TspClientProvider class, but you can change that at the same time to be able to use the connection listener implementation.

[marco-miller]

This PR is ready for review again; thanks.

[bhufmann]

Thanks for the updates. A few more small things.

[bhufmann]

LGTM. Thanks for the contribution.