POV-Ray

Basic conflict with 3.7 multi-threaded approach: you cannot know the status of the current threads (at the beginning, middle or end of their bloc)
If you count the number of finished blocs / total, you would have a slow start and quick finish.

Moreover, rendering has never been a linear process, so predicting the end of the computation is going to be always wrong.

Last: a progress bar/icon/whatever is stealing precious cycles from the renderer.

If you want to know the progress, open the rendering window and look by your self. Otherwise, leave it alone.

"Basic conflict with 3.7 multi-threaded approach: you cannot know the status of the current threads (at the beginning, middle or end of their bloc)
If you count the number of finished blocs / total, you would have a slow start and quick finish."

Not sure what you're saying here...

"Moreover, rendering has never been a linear process, so predicting the end of the computation is going to be always wrong."

Just want to know how much of the image there is left to render, nothing else!

"Last: a progress bar/icon/whatever is stealing precious cycles from the renderer."

Really? How many cycles could updating a 16x16px image possibly take? I've got three icons in the system tray already (network activity, CPU temp, CPU usage) that are set to update every second. Plus, I have any number of other things updating, like icons in the taskbar, icon docks, sidebars (not right now tho), the clock, etc. ...

"If you want to know the progress, open the rendering window and look by your self. Otherwise, leave it alone."

Repeatedly opening and closing the render window probably uses more CPU cycles over time than simply updating the tray icon...

Further, in Windows 7 you can show program progress in the taskbar icon itself. You can see this when copying files between folders, maybe elsewhere...

I was saying:

1. the status of the rendering threads is unavailable; Using the number of blocks already rendered (or the number of block already dispatched) is inaccurate.
In the first case, assuming a linear rendering time (which is not usual), the progress indicator is wrong at the beginning by being late on the progress (there are already more pixel rendered than advertised by a 0% value) and speed of the indicator raises at the end where it reaches 100% when the last block has been completed (but image is not yet saved). Even with a linear speed of render, it is impossible to provide a linear progress of the indicator (and the curve is unpredictable, so cannot be corrected). progress of 50% or 75% does not actually provide any accuracy about the remaining time, even if linear.

On the second case, also with an assumed linear rendering, the progress indicator is far too in advance and will reach 100% before the render is actually finished.

Further: The indicator of windows about file operation always leaves me more than adamant.
Estimation

Nevertheless, I can see on Windows 3.7beta39 that there is now a progress indicator, so that should make the issue closed.

As this has been requested again in  FS#332 , I think this issue deserves a status update:

- The functionality to display progress in the taskbar icon is part of the Taskbar Extensions introduced with Windows 7. I'm not an expert at Windows programming, but I guess using it might limit compatibility with older versions, most notably Windows Vista, for which Microsoft is committed to provide support until 2017-04-11. Up to that day we can still expect some machines to run pre-7 versions of Windows, especially those boxes tucked away somewhere in a corner to do nothing but run POV-Ray, so I think we shouldn't cease to support Vista until that day.

- I'm not sure whether it is worth investing much more time into the old Windows UI, as we need a new one anyway.

Therefore, I think the time to re-open this issue hasn't come yet.