I promise I haven't been working on this for 5 years. But I thought I'd come back with something new that I think is a bit better in some ways and a bit worst in others. This method works a bit better when it comes to encapsulation. I wrote a single Image Grid class that can be created, updated, and destroyed. When creating it you specify the Subpanel that it should be inserted into. This means that we can likely turn this into an XControl one day. The previous method of having parent/child windows floating around that needed to be resized and moved, complicated that encapsulation and likely never could have been in an XControl.
Resizing in my opinion is done better here too. Instead of generating a resize event, and then having to resize each window, we just let LabVIEW take care of it. LabVIEW is pretty good at resizing when using panes and having a single object fit to that pane. So when a resize occurs the only thing that is done is the optimal number of rows and columns are calculated and if there is no change then nothing else needs to happen in the G code.
Minimum pane sizes are used so that hopefully things don't get too small if the subpanel is set to fit to the pane.
Now the new limitations...this is limited to the number of subpanels I made and at the moment this is 20 rows, and 20 columns. It is possible I could have gotten creative and generated all the prime number of subpanels, and then used dynamic subpanel subpanel insertion to get an unlimited number but wow that sounded difficult. I figured how often will I need more than 20 rows or columns?
Another limitation is at the moment you cannot add or remove images without closing the session and opening a new one. The properties of each image can be manipulated quickly by providing the index, and the new Caption, Disabled Status, Image Path, or Background color (alpha layers supported BTW).
Also no way to modify the caption other than the text. I'd like to add a hide/show ability and a way to change font size.
Anyway source is 2015, uses OpenG and here is a video. It is slightly smoother to resize than it looks in the video.
https://www.screencast.com/t/qdZMxBuzprH
Image Grid Subpanels Of Subpanels.zip