Proposal: add SelectionStart and SelectionEnd to TrackBar

You can set the TBS_ENABLESELRANGE on TrackBar and send the TBM_SETSELSTART and TBM_SETSELSTART to set the selection range See docs

• https://docs.microsoft.com/en-us/windows/win32/controls/tbm-setselstart
• https://docs.microsoft.com/en-us/windows/win32/controls/tbm-setselend

Example:

We could add the following APIs to TrackBar:

public class TrackBar
{
    ...
    public bool ShowSelectionRange { get; set; }
    public int SelectionStart { get; set; }
    public int SelectionEnd { get; set; }
    ...
}

Discussion

• What should the default values of SelectionStart and SelectionEnd be if we haven't enabled selections? In my experiments I set them to 0 which worked nicely.
• In my prototype implementation, I set ShowSelectionRange to true if the user sets SelectionStart/SelectionEnd. One option could be to remove ShowSelectionRange and set SelectionStart/SelectionEnd to minus one or have some logic that sets the TrackBar style to TBS_ENABLESELRANGE if it is set to a custom value. However, this is negative as it leaves us with no way of removing the selection indicators once they've been created.
• Do we want SelectionStart and SelectionEnd or SelectionStart and SelectionLength or some sort of SelectionRange struct that encapsulates this? (e.g MonthCalendar.SelectionRange)