Feature Request: Taskbar progress indicator

[dim5]

Description of the new feature/enhancement

Add a taskbar progress indicator for displaying the status of the current long running process (when possible).

For example, this can be helpful to users unpacking files with 7z or running python scripts with tqdm.

ConEmu's documentation.

[zadjii-msft]

I could have sworn we had an internal issue for this feature, but it never got migrated to github it appears....

FOUND IT! MSFT:18258406. Here are the relevant notes:

sequence	description
ESC ] 9 ; 4 ; st ; pr ST	Set progress state on Windows 7 taskbar and ConEmu title. When st is 0: remove progress. When st is 1: set progress value to pr (number, 0-100). When st is 2: set error state in progress on Windows 7 taskbar

Also related documentation: ITaskbarList3::SetProgressValue

We should probably also make sure that we support the TBPF_INDETERMINATE state - for something like our own bcz.cmd, where we don't know how long the operation will take.

In conpty mode, we should just pass these sequences through. There's a good amount of precedent for such sequences in the code already.

EDIT:
We should probably also have a couple settings for controlling this behavior:

• showProgressInTaskbar (default true) to show the progress in the taskbar entry
• showProgressInTab (default true) to show the progress in the tab itself.

showProgressInTab can probably be a follow up once microsoft/microsoft-ui-xaml#1386 is complete