Fix number slider value getting stuck tied to mouse position

[Akansh475]

Fixes #4231

I dug into this and found the root cause: document.exitPointerLock() is
async, and the matching pointerlockchange event can fire quite late in
some cases. If you release a drag and then quickly start a new one before
that event fires, the old drag's handler was still writing to shared
variables (initialValueBeforeDragging, cumulativeDragDelta,
activeDragCleanup). That's what caused the jump — the stale handler would
overwrite the new drag's in-progress value, and in some cases even tear
down the new drag's listeners entirely by clearing the shared cleanup
reference.

The fix moves this state into closures scoped to each individual drag
session, so a late-firing event from an old session can only ever touch
its own data and never interfere with whatever drag is currently active.

Tested by reproducing both scenarios from the issue:

• rapid click-dragging the slider back and forth in short bursts
• losing window focus mid-drag (e.g. clicking into devtools) and then
  clicking back

Neither causes the jump/stuck behavior anymore after this change.

Probably related to #2807 as well, since that's the same drag code path.

[cubic-dev-ai]

1 issue found across 1 file

Confidence score: 3/5

• frontend/src/components/widgets/inputs/NumberInput.svelte can let an older pointer-lock completion clear a newer session’s shared abort baseline, potentially producing incorrect number-input delta/abort behavior; make the cleanup conditional on the owning session and clear the shared baseline and delta only when appropriate.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="frontend/src/components/widgets/inputs/NumberInput.svelte">

<violation number="1" location="frontend/src/components/widgets/inputs/NumberInput.svelte:572">
P2: After `localInitialValue` is cleared, this condition is tautologically true, so every pointer-lock completion clears the shared abort baseline, including a newer session's baseline. Clear the shared baseline and delta only when this callback still owns the active drag session.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: After localInitialValue is cleared, this condition is tautologically true, so every pointer-lock completion clears the shared abort baseline, including a newer session's baseline. Clear the shared baseline and delta only when this callback still owns the active drag session.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At frontend/src/components/widgets/inputs/NumberInput.svelte, line 572:

<comment>After `localInitialValue` is cleared, this condition is tautologically true, so every pointer-lock completion clears the shared abort baseline, including a newer session's baseline. Clear the shared baseline and delta only when this callback still owns the active drag session.</comment>

<file context>
@@ -491,12 +566,17 @@
+			updateValue(localInitialValue);
+			localInitialValue = undefined;
+			localCumulativeDragDelta = 0;
+			if (initialValueBeforeDragging === localInitialValue || initialValueBeforeDragging !== undefined) {
+				initialValueBeforeDragging = undefined;
+			}
</file context>

Suggested change

	if (initialValueBeforeDragging === localInitialValue || initialValueBeforeDragging !== undefined) {
	initialValueBeforeDragging = undefined;
	}
	cumulativeDragDelta = 0;
	if (activeDragCleanup === dragCleanup) {
	initialValueBeforeDragging = undefined;
	cumulativeDragDelta = 0;
	}