Turns out, there's a lot of details to get right when implementing a floating window space. For example, dialog windows should always show above their parent window. Otherwise, it's easy to lose them under the (usually much bigger) parent.
The WIP floating branch in niri now handles this properly, even for xdg-desktop-portal dialogs (like file chooser) as long as the app correctly parents them via xdg-foreign.
Another piece of the floating puzzle: keeping windows on screen. When you change your monitor scale or resolution, you don't want your floating windows to suddenly go unreachable behind the monitor's new borders.
Here I'm resizing a nested niri with three windows, simulating resolution changes. No matter what I do, they always remain partially visible and reachable. Even for more unusual cases like trying to resize a window into out of bounds.
#niri