When resizing windows of clients that respond very slowly to resize
requests, the window's size sometimes snapped back to its original size
immediately after finishing the drag operation.
The problem was caused by the interplay of the layout rules (obtained
via the 'rules' ROM, generated by the 'rules' report) and the
temporary interactive state that occurs during drag operations.
The rules are updated only at the time of releasing the button to keep
the overhead while dragging the window low. However, when releasing the
mouse, the (now outdated) rules kicked back into effect, triggering
resize requests for the window to its old size.
The patch solves this problem by decoupling the dragged state of a
window from the physical release of the button. The button release
triggers a transition from a DRAGGING to a SETTLING state and programs
a timer. In the SETTLING state, the windows behave as in DRAGGING state,
giving the interactive geometry precedence over the rules-dictated
geometry. During this state, further responses of window-resize requests
may come in and are handled like dragging was still in progress. After a
timeout, however, the current window layout is conserved as a new rules
report and the state goes back to IDLE.
For clients that takes a very long time (in particular, VirtualBox when
resizing the desktop, which takes sometimes multiple seconds), the
snap-back artifact can still occur, but the effect is reduced.
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