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change IME composing handling order to support implicitly confirming IME #2767

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change IME composing handling order to support implicitly confirming IME #2767

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31 changes: 19 additions & 12 deletions frontend/app/view/term/termwrap.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -616,31 +616,32 @@ export class TermWrap {
return;
}

// IME Composition Handling
// Block all data during composition - only send the final text after compositionend
// This prevents xterm.js from sending intermediate composition data (e.g., during compositionupdate)
if (this.isComposing) {
dlog("Blocked data during composition:", data);
return;
}

if (this.pasteActive) {
if (this.multiInputCallback) {
this.multiInputCallback(data);
}
}

// IME Deduplication (for Capslock input method switching)
// When switching input methods with Capslock during composition, some systems send the
// composed text twice. We allow the first send and block subsequent duplicates.
// IME handling: Check if this is confirmed text from a recent compositionend
// This must be checked BEFORE isComposing, because when implicitly confirming IME
// (e.g., typing next char), the event order is:
// compositionend → compositionstart (new) → xterm onData
// By the time onData fires, a new composition has started (isComposing=true),
// but we still need to send the confirmed text from the previous composition.
//
// We also handle deduplication here: when switching input methods with Capslock
// during composition, some systems send the composed text twice. We allow the
// first send and block subsequent duplicates within the dedup window.
const IMEDedupWindowMs = 50;
const now = Date.now();
const timeSinceCompositionEnd = now - this.lastCompositionEnd;
if (timeSinceCompositionEnd < IMEDedupWindowMs && data === this.lastComposedText && this.lastComposedText) {
if (!this.firstDataAfterCompositionSent) {
// First send after composition - allow it but mark as sent
// First send after composition - allow it even if isComposing is true
this.firstDataAfterCompositionSent = true;
dlog("First data after composition, allowing:", data);
this.sendDataHandler?.(data);
return;
} else {
// Second send of the same data - this is a duplicate from Capslock switching, block it
dlog("Blocked duplicate IME data:", data);
Expand All @@ -650,6 +651,12 @@ export class TermWrap {
}
}

// Block intermediate composition data (e.g., during compositionupdate)
if (this.isComposing) {
dlog("Blocked data during composition:", data);
return;
}

this.sendDataHandler?.(data);
}

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