fix(cursor): no view write without its nudge during a held click (#381)

docs/architecture/07-cursor.md

@@ -123,6 +123,10 @@ slightly during zoom ramps, nearest keeps it pixelated and steady. Pure rules:
   cursor event back on DWM's (a 5-10 px shift at ~5x that snapped back when the zoom stopped). While
   DWM centres, every level write is followed by a pixel-and-back nudge, so DWM re-centres by its own
   rule in the same frame (`NudgeAfterLevelWrite`). Field-verified: shift gone, pans steady.
+- **No write without its nudge (#381).** The nudge is skipped while a mouse button is held (it made
+  some clicks fail), so a pan write during a held click would leave Wind's centre on screen until the
+  next cursor event: drag-selects and held clicks shook. Pan-only writes are held for the click
+  window instead (`HoldWriteForClick`); level changes and forced writes still go out.
 - `txDwmCentre=0` keeps the native pointer but lets Wind write the view itself (kill switch; pans
   then wobble by speed x tick x zoom).
 - **DWM's learned offset.** DWM learns the gap between `GetCursorPos` and its own cursor point and

src/native_cursor.h

@@ -96,4 +96,16 @@ inline bool NudgeAfterWrite(bool dwmCentring, bool wrote) {
     return dwmCentring && wrote;
 }
 
+// NO WRITE WITHOUT ITS NUDGE (issue #381, field report 2026-10-08: zoomed, holding the left button
+// for a drag-select or a held click made the view shake; plain panning was fine). The nudge is
+// skipped while a click is in progress (it made some clicks fail), but the write it belongs to
+// still went out, so during a hold every changed tick put Wind's centre on screen and the next
+// cursor event put DWM's back: the view alternated between the two. While DWM centres, a pan-only
+// write is held for the click instead; DWM keeps centring on every cursor event, and the first tick
+// after the click window writes and nudges as usual. Level changes and forced writes still go out
+// (a zoom during a drag must not freeze, and a centring switch needs its write).
+inline bool HoldWriteForClick(bool dwmCentring, bool clickInProgress, bool levelMoved, bool forced) {
+    return dwmCentring && clickInProgress && !levelMoved && !forced;
+}
+
 }  // namespace wind

src/transform_model.cpp

@@ -815,7 +815,10 @@ void TransformModel::present(const MapResult& r, double level, const Config& cfg
     ci.minOffsetPx      = cfg.txMinOffsetPx;
     ci.settleMs         = kSettleMs;
     const bool forceWrite = forceWrite_;
-    const bool writeNow = ShouldWriteTransform(ci) || forceWrite;
+    // A pan write while DWM centres must be followed by its nudge, which a click in progress
+    // forbids: hold it until the click window ends (HoldWriteForClick, issue #381).
+    const bool clickHold = HoldWriteForClick(dwmCentreOn_, ClickInProgress(), ci.levelMoved, forceWrite);
+    const bool writeNow = (ShouldWriteTransform(ci) || forceWrite) && !clickHold;
 
     if (writeNow) {
         lastOffX_ = m.offX; lastOffY_ = m.offY; lastTxX_ = m.txX; lastTxY_ = m.txY;

tests/test_native_cursor.cpp

@@ -64,6 +64,14 @@ TEST_CASE("while DWM centres, every write is followed by a cursor event (one cen
     CHECK(NudgeAfterWrite(true, false) == false);   // nothing written
 }
 
+TEST_CASE("A pan write is held while a click forbids its nudge (#381)") {
+    CHECK(HoldWriteForClick(true, true, false, false) == true);    // held button, DWM centres: hold
+    CHECK(HoldWriteForClick(true, false, false, false) == false);  // no click: write and nudge
+    CHECK(HoldWriteForClick(false, true, false, false) == false);  // Wind owns the view: write
+    CHECK(HoldWriteForClick(true, true, true, false) == false);    // a zoom during a drag still writes
+    CHECK(HoldWriteForClick(true, true, false, true) == false);    // a forced write (centring switch)
+}
+
 TEST_CASE("DWM centring yields only near an armed wall, not everywhere it is reachable") {
     // 12x: wall at 32000/12 = 2666.7 source px.
     CHECK(NearWall(true, 1000.0, 500.0, 12.0, 32000.0, 64.0) == false);   // middle of the screen