Have a listener modify a waitbar when user calls waitbar(x,hwaitbar)

I recently cleaned up a piece of code I use modify the color of a waitbar's progress bar, ColorProgressBar.m.

If one creates a waitbar, h, the color can be controlled with that code.

h = waitbar(0.5,'my waitbar');
ColorProgressBar(h);
waitbar(0.75,h);
ColorProgressBar(h);

This was cobbled together from other Q&A around the internet. My only complaint with this code is that the user must still call ColorProgressBar after performing an update to a waitbar via waitbar(x,h).

Is there a way to add a listener somewhere to invoke this color change function automatically? Piecing through the hidden JavaWrapper and and JProgressBar used in the waitbar, I could not find any properties or events to listen for, preventing me from invoking this color change automatically.

Knowing how to do this would significantly cut back how users interact with my code, no longer requiring an explicit call to ColorProgressBar after the waitbar has been updated, as well as change other functions using similar concepts.

[Stephen23]

This seems like a very complex approach ... basically a waitbar/progress bar is just a patch. Why not just create a patch inside your function, and change it each time the function is called. This does not require waitbar at all, and only requires about five lines of code.

You will find plenty of submissions on FEX that do exactly this:

https://www.mathworks.com/matlabcentral/fileexchange?term=waitbar

[Walter Roberson]

Last time I looked, waitbar was at the Java level. At some point I posted code to change the color using Java methods. I seem to recall having hit some frustrating limit in working with them that I did not solve.

[Jake August]

The waitbar in R2017/18 uses the JProgressBar, not a patch. I know how to set the foreground of the JProgressBar to change colors, but would like that to be an automatic feature of waitbar(x,hwaitbar).

I realize that I could add a property to the waitbar figure, e.g. "ProcessCompleted", that has a postset listener to perform all waitbar updates and manage color, but again, I want it to behave as natural as the update waitbar command.

[Walter Roberson]

Additional technical information about waitbar is at https://www.mathworks.com/matlabcentral/answers/293374-waitbar-color-2016a-is-broken-red-how-to-set-to-older-continuous-green#answer_227433