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RandR screen change: collapse the notify burst onto the newest event, refresh screen data, realign windows from server truth - #251
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…align windows The server defers RRScreenChangeNotify per client until its next request, so the notify burst often starts with a stale duplicate: collapse it onto the last event. XRRGetScreenResources can serve cached state one transition old (RRSetScreenSize does not bump the config timestamp), so refresh the backend screen data from fresh sources before the gui rebuilds NSScreen, then realign mapped windows from the server truth and propagate the corrected origins to the gui, making the backend the single remapper for screen changes. Pairs with gnustep/libs-gui#1006 (gui-side guard against re-applying the old->new delta on an already-realigned frame).
fredkiefer
reviewed
Oct 13, 2026
fredkiefer
reviewed
Oct 13, 2026
fredkiefer
reviewed
Oct 13, 2026
| && (xEvent.xconfigure.window == RootWindow(dpy, defScreen))) | ||
| { | ||
| // Check if other RandR events are waiting in the queue. | ||
| // The server defers RRScreenChangeNotify per client until |
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Could you please advice your LLM to use less verbose comments?
…of fast enumeration, terser comments
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Thanks — fixed in the follow-up commit: braces everywhere, GS_FOR_IN, single-line comments. |
rfm
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Oct 14, 2026
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This looks good/reasonable to me
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Richard's approval is good enough for me and I like the idea behind this patch. |
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Follow-up to #249 and the analysis in that thread.
What this changes in the RRScreenChangeNotify branch
Collapse the notify burst onto the newest event. The server defers RRScreenChangeNotify per client until its next request, so a burst often starts with a stale duplicate of the previous state. The drain now assigns inside the loop: the branch always processes the last (newest) event, and
*eventstays untouched when nothing was drained.Refresh the backend screen data before the gui rebuilds NSScreen. XRRGetScreenResources can serve cached state one transition old (RRSetScreenSize does not bump the resources config timestamp), so resetScreens can derive the previous screen size. Calling
screenList(root geometry + per-CRTC info — the same fresh sources as x11: build single-monitor screen frame from root geometry, not the CRTC #249) before[NSScreen resetScreens]makes the gui see current data.Realign mapped windows from the server truth. After the screen update, each viewable window is re-read via XGetGeometry/XTranslateCoordinates, its os-frame recomputed and cached, and the corrected origin propagated to the gui via GSAppKitWindowMoved. The backend becomes the single remapper for screen changes.
Validation
Container harness (Xvfb + RANDR, WM-less, GSScaleFactor 1.3): a Terminal window's title bar across a 1280×800 → 1024×768 → 1280×800 cycle moves 271 → 270 → 270 px (a 1 px rounding difference), stable across repeated fresh runs and 4-cycle sequences. Without the change the window jumps ±32 px on every cycle.
Note: the full jump fix is two-layer — this PR pairs with the libs-gui guard in
applicationDidChangeScreenParameters:(gnustep/libs-gui#1006), which stops the gui from re-applying the old→new delta onto a frame the backend has already realigned.