Mutter 3.28 doesn't handle right and bottom resizes correctly when running Qt apps with "--platform wayland"
Dragging the right or bottom edge (or bottom-right corner) handle to resize the window of a Qt application started with "--platform wayland" behaves erratically. After the window has been resized, hovering the cursor over it in the exploded app view of GNOME Shell shows a rectangular highlight that corresponds to the former size of the window (as if mutter hadn't registered the new size). Attempting a subsequent resize operation will automatically reset the window to its previous size. When dragging the left or top edge (or any corner except the bottom-right one) handle, this issue does not occur. Mutter 3.26 did not exhibit this problem.
I've attached a minimal Qt application as a testcase. I've also experienced the same erratic resize behavior when running a barebone Wayland test client I wrote from scratch that used to operate correctly under mutter 3.26. It was based on the zxdg_toplevel_v6 (now xdg_toplevel) client interface. I can also provide the code for this second testcase if it can help.