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fix(ios): better delete pattern

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This commit is contained in:
Joshua Horton 2024-04-12 10:50:06 +07:00
parent 1d9126d6cb
commit d6df7c29f4
1 changed files with 57 additions and 32 deletions
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89
ios/engine/KMEI/KeymanEngine/Classes/Keyboard/InputViewController.swift
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@ -333,6 +333,60 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
}
}
}
func deleteSelection() -> Bool {
if let selected = textDocumentProxy.selectedText, selected.count > 0 {
/*
Since we're doing some funky text manipulation, it's best to add
a "canary" check in case something does go awry with it in
the future.
*/
let beforeManipulation = textDocumentProxy.documentContextBeforeInput ?? ""
/*
Apple has some special nuances to its text deletion that our internal
Web engine does not emulate.
.deleteBackward() behaviors:
- If there is selected text immediately following a space (U+0020),
it will delete that space IN ADDITION to the selected text.
- If there is selected text that starts mid-word, it will NOT delete
the preceding character.
Compare to Web: Web states an exact number of characters to delete
before the start of the currently-selected range... and it does this
completely unaware of the nuances listed above for .deleteBackward().
Keyman keyboard rules are likewise unaware of Apple's nuances.
In order to maintain proper synchronization between app context and
internal Web-engine context, we need to force selected-text deletion
to NEVER delete preceding spaces. Any attempts to adjust and include
the aforementioned nuance will need considerable design work to "get
right" due to the risk for adverse affects with Keyman keyboard rules.
.insertText() is great for this... when the string isn't empty. If
it is, well, "sorry, out of luck." That said, we can just insert
something that won't combine, like a ZWNJ, and then delete it.
The silver lining: Apple makes it impossible for users to select text
in a way that splits character clusters. This implies that it's
impossible for an inserted ZWNJ to combine with existing context,
making this operation safe.
*/
textDocumentProxy.insertText("\u{200c}")
textDocumentProxy.deleteBackward()
let afterManipulation = textDocumentProxy.documentContextBeforeInput ?? ""
// And now to finish our 'canary' check.
if beforeManipulation != afterManipulation {
os_log(.error, log: KeymanEngineLogger.engine, "Could not cleanly execute backspace for selected text")
}
return true
}
return false
}
func insertText(_ keymanWeb: KeymanWebViewController, numCharsToDelete: Int, newText: String) {
if keymanWeb.isSubKeysMenuVisible {
@ -347,39 +401,10 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
perform(#selector(self.enableInputClickSound), with: nil, afterDelay: 0.1)
}
var deleteSelection = false
// `true` if there was selected text to be deleted
let deletedSelection = self.deleteSelection()
if let selected = textDocumentProxy.selectedText {
if selected.count > 0 {
deleteSelection = true
}
}
if deleteSelection && newText == "" {
/*
if deleteSelection && newText == "", we have a backspace on
selected text. Sadly, .insertText("")... does nothing. Why, Apple!?
The one silver lining: Apple makes it impossible for users to select text
in a way that splits character clusters.
So, we can just insert something that won't combine, like a ZWNJ, and then delete it.
*/
let beforeManipulation = textDocumentProxy.documentContextBeforeInput ?? ""
textDocumentProxy.insertText("\u{200c}")
textDocumentProxy.deleteBackward()
let afterManipulation = textDocumentProxy.documentContextBeforeInput ?? ""
// For good measure, a canary to signal if our selected-text backspace handling
// goes awry.
if beforeManipulation != afterManipulation {
os_log(.error, log: KeymanEngineLogger.engine, "Could not cleanly execute backspace for selected text")
}
sendContextUpdate()
return
} else if numCharsToDelete <= 0 || deleteSelection {
if numCharsToDelete <= 0 || deletedSelection {
textDocumentProxy.insertText(newText)
sendContextUpdate()
return