(EDIT: this isn’t a whinge about Qubes. Its for anyone who tries to do the same and has trouble in future).
I installed sweethome3d in a debian qube, via apt. Gave it lots of memory (8000 max).
Sweet Home 3D runs, but has strange black-outs of panels at random moments. For example: draw a wall on the grid panel, and the other 3 panels go black, plus the menu blacks out.
Sometimes these missing elements can be recovered by clicking on the black bit where they should be, or mousing over the toolbar.
However, not always the case. For example, trying to set preferences (e.g imperial to metric), the menu dialog box flashes to black and refuses to come back, so you can’t use it.
The effect is the program is largely unusable.
I wonder if it has something to do graphics processing in Qubes? In contrast, I have used FreeCAD before (in a very basic fashion) and it worked.
There are apparently ways to get it running in Fedora, but they are too complex for me.
This machine is an lenovo x230 with 32G memory. EDIT: Qubes 4.1
EDIT: just installed on a backup machine I have (also x230, but less memory) running Lubuntu 22.4.04 and it seems to work just fine there.
You can try to increase the number of vCPU assigned to your qube. Since there is no GPU hardware acceleration and rendering is done using CPU then maybe the default 2 vCPUs is not enough.
That’s clearly not the issue: I do get this behaviour in a Debian13 VM when using the script lo launch it from the official deb, but if I just launch java -jar /usr/share/sweethome3d/sweethome3d.jar, the problem does not appear.
Digging from there, we can quickly see the faulty flag added by the script is -Dsun.java2d.opengl=true. Just copying the script and removing this or setting it to false allows to use the program.