The thumbnail preview feature does not work on my windows 10. The preview comes up black. I've attached a screen shot. In the screen shot I made the preview thumbnail larger than normal to make it clear what you're seeing (I have it set to 300px). Previews work from the built-in taskbar.

This is a new computer, here are the stats:
12th Gen Intel(R) Core(TM) i9-12900K 3.19 GHz
Installed RAM 64.0 GB (63.8 GB usable)
DisplayFusion Pro 9.9
Windows 10 (20H2) (10.0.19044.0) 64-bit
NVidia 3090
I'll provide more details privately if you want them.

Oops, I accidentally logged in with an old username. This is my proper account, if it matters.

Owen, files attached, but things changed today after a shutdown and reboot. Some of the previews are working and others are black and yet others seem to have some parts of the window and not others. It's very strange. Debug file attached and a screen capture showing it partially functional.

Owen,

I just tried it again, but it looks identical (only smaller). It still quite random. I also tried closing and reopening DF, but nothing changed. I tried turning off the thumbnail display animation, but that had no noticeable effect. One thing that might not have shown on the video I sent is that it often shows a black preview for a second before filling it in with the actual screenshot. I don't know if this is intentional or part of the bug I'm seeing, but if it's intentional it's actually annoying to watch and I would remove it. Better to not show anything until the screenshot is captured, in my opinion.

Anything else you'd like me to try?

Owen,

I just tested about fifteen applications and out of them no single-window application worked properly (Word, Excel, Slack, Notepad++, NordVPN, and others). Of the three big multi-window applications Chrome, file explorer, and Directory Opus, the results were mixed (meaning that some windows in Chrome displayed correctly while no windows in either of the other two displayed correctly). I have yet to find an application that works consistently on this new computer, but I'll keep my eye out.

Not as far as I can tell. I've had Chrome and Directory Opus open since some time yesterday and out of the 23 open Chrome windows, 9 windows have a proper display, 3 windows change size from the initial smaller black window but two of those just show a larger black window and one of them shows a window that is only partially drawn. Now the really weird thing. While I was bring up windows checking the contents of the ones being shown, one of those three went from showing a partially drawn window to a black window.

So, I did some more testing and discovered that if the window has any part visible on the current monitor it comes up black. It doesn't matter if the window has focus even if it previously had a thumbnail. This was for any application. In the case of slack, as soon as I minimized the window the thumbnail came back and it was up to date (it wasn't pulling up an old thumbnail).

This just gets more and more interesting. Makes me want to write a program that tries to get thumbnails from every open window, just to see what happens.

Update: So, I wrote a program that pulls the image of every application on the computer and it works for all applications except for Chromium. I am using PrintWindow() to pull the current image of the applications.

Some of the issues I ran into:

• Windows that are minimized must be restored first. I then move the window off the active desktop before running PrintWindow, then moving it back (and resetting all styles and extended styles).
• For Chrome windows I can get them to work using CaptureWindow, but this requires that the window be on a valid portion of the desktop (which also means the window will flash its contents when I capture it). Needless to say this sucks.
• For Chrome I tried forcing the window to repaint in a number of ways, none of which worked (I really expected RedrawWindow(All Children) to work here). I also tried forcing the event queue to drain as well as pausing for 5 seconds to wait for the page to draw, thinking that maybe it was either a blocking or drawing delay issue, but neither made any difference at all.
• Photoshop won't paint the actual image, it only paints the chrome, menus, and toolbars. Not sure why this would be. In some of my tests it printed the contents of the image as a series of expanding windows. Weird stuff.

So, I'm not sure what DF's task bar is doing that it gets the Chromium window sometimes and not other times. I couldn't find a workable solution for Chromium at all. I also can't understand why having the application window on the current monitor makes a difference (I could not reproduce this failure at all, except for Chromium all application windows worked, except Photoshop).

I don't know if any of this is helpful, but figured I'd post it. Anyone who wants the test application I built is welcome to it, just let me know. It's interesting, if not terribly useful.

Owen,

Sorry for the delay, I completely missed this message. I brought up the Monitor Mirror dialog and it faithfully represents exactly what is being displayed on the monitor. If the preview is black on the monitor it's black in the mirror dialog. I assume that's what you were asking.

Also, if I have the monitor mirror application on a monitor with a DF taskbar, the preview thumbnail for the dialog follows the same rule as many windows, the thumbnail displays correctly only when the dialog is minimized. If the dialog is showing on the monitor, the thumbnail is black. (I tried this just in case this is what you were asking me to test, but I figure it was option A above

The black thumbnails, and some features I just can't bear to lose from 7TT, finally got too much for me and weeks ago I changed back to the Windows 10 taskbars. But I'm happy to try anything you would like me to try.

Scott