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docs(common/models): adds comments about bug in iOS insertText
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jahorton
parent
8516561081
commit
fc2a17890c
1 changed files with 89 additions and 79 deletions
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@ -407,94 +407,104 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
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textDocumentProxy.insertText(newText)
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}
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// Should never change throughout the next loop; right-deletions only!
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let oldLeftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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var pointsToDelete = numCharsToRightDelete
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while pointsToDelete > 0 {
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let oldContext = textDocumentProxy.documentContextAfterInput ?? ""
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self.swallowContextChangeCount += 1
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// Asynchronously triggers a context change.
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textDocumentProxy.adjustTextPosition(byCharacterOffset: 1)
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let newContext = textDocumentProxy.documentContextAfterInput ?? ""
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// NOTE: when a script uses character clusters, the code below fails to
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// produce the correct effects despite `textDocumentProxy` reporting that
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// the code correctly manipulates the text. There's either a bug in Apple's
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// code or something critical that we're missing here.
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//
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// The `textDidChange` call that occurs after this `insertText` will
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// report the final, 'incorrect' details, rather than what is reported
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// at the end of this method.
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if numCharsToRightDelete > 0 {
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// Should never change throughout the next loop; right-deletions only!
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let oldLeftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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var pointsToDelete = numCharsToRightDelete
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while pointsToDelete > 0 {
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let oldContext = textDocumentProxy.documentContextAfterInput ?? ""
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self.swallowContextChangeCount += 1
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// Asynchronously triggers a context change.
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textDocumentProxy.adjustTextPosition(byCharacterOffset: 1)
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let newContext = textDocumentProxy.documentContextAfterInput ?? ""
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var failsafeCount = 0
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while (textDocumentProxy.documentContextBeforeInput ?? "" != oldLeftContext)
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&& failsafeCount < numCharsToRightDelete { // mild breakage > locked kbd
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// While adjustTextPosition makes cluster-based jumps...
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// deleteBackward does not. So, we 'force' it.
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textDocumentProxy.deleteBackward()
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failsafeCount += 1
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}
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var failsafeCount = 0
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while (textDocumentProxy.documentContextBeforeInput ?? "" != oldLeftContext)
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&& failsafeCount < numCharsToRightDelete { // mild breakage > locked kbd
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// While adjustTextPosition makes cluster-based jumps...
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// deleteBackward does not. So, we 'force' it.
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textDocumentProxy.deleteBackward()
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failsafeCount += 1
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}
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// Determine the removed codepoint count. Also, find the index
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// of the first character that shouldn't be removed, if possible.
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let unitsDeleted = oldContext.utf16.count - newContext.utf16.count
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var pointsDeleted = 0
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// Determine the removed codepoint count. Also, find the index
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// of the first character that shouldn't be removed, if possible.
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let unitsDeleted = oldContext.utf16.count - newContext.utf16.count
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var pointsDeleted = 0
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// Our current index within the deleted context.
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var deletedIndex = oldContext.utf16.startIndex
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// Marks the first index we wish to NOT remove.
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var remnantIndex: String.Index? = nil
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// Marks the first index that was NOT removed by deleteBackward.
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let undeletedStartIndex = oldContext.utf16.index(deletedIndex, offsetBy: unitsDeleted)
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// Our current index within the deleted context.
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var deletedIndex = oldContext.utf16.startIndex
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// Marks the first index we wish to NOT remove.
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var remnantIndex: String.Index? = nil
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// Marks the first index that was NOT removed by deleteBackward.
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let undeletedStartIndex = oldContext.utf16.index(deletedIndex, offsetBy: unitsDeleted)
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while deletedIndex < undeletedStartIndex {
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if(InputViewController.isSurrogate(oldContext.utf16[deletedIndex])) {
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// Check - is it truly a surrogate pair?
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let pairedIndex = oldContext.utf16.index(after: deletedIndex)
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if(InputViewController.isSurrogate(oldContext.utf16[pairedIndex])) {
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// If so, pre-emptively increase the index - the pair will count
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// as a single character as a result.
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deletedIndex = pairedIndex
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while deletedIndex < undeletedStartIndex {
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if(InputViewController.isSurrogate(oldContext.utf16[deletedIndex])) {
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// Check - is it truly a surrogate pair?
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let pairedIndex = oldContext.utf16.index(after: deletedIndex)
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if(InputViewController.isSurrogate(oldContext.utf16[pairedIndex])) {
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// If so, pre-emptively increase the index - the pair will count
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// as a single character as a result.
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deletedIndex = pairedIndex
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}
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}
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pointsDeleted += 1
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deletedIndex = oldContext.utf16.index(after: deletedIndex)
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// Intended end of deletion found!
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if pointsDeleted == pointsToDelete {
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remnantIndex = deletedIndex
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break // There's nothing to be gained by further loop iterations.
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}
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}
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pointsDeleted += 1
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deletedIndex = oldContext.utf16.index(after: deletedIndex)
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// Intended end of deletion found!
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if pointsDeleted == pointsToDelete {
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remnantIndex = deletedIndex
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break // There's nothing to be gained by further loop iterations.
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if let remnantIndex = remnantIndex, remnantIndex < undeletedStartIndex {
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// We need to restore some of the deleted text!
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let remnant = String(oldContext.utf16[remnantIndex..<undeletedStartIndex]) ?? ""
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textDocumentProxy.insertText(remnant)
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// Must place the caret back in its correct position!
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// Unfortunately, Apple's adjustTextPosition is definitely cluster-based.
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var leftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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// Ideally, we want to stop at the exact position, but the lack of
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// granularity on adjustTextPosition may not cooperate with that goal.
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while(leftContext.count > oldLeftContext.count) {
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textDocumentProxy.adjustTextPosition(byCharacterOffset: -remnant.count)
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leftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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}
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// FAILSAFE, non-ideal behavior below.
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//
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// It's probably (?) better to keep the caret at the end of a cluster that
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// previously started before the caret, even if right-deletions add new
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// characters to the cluster. I think.
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//
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// Khmer example: if right-deletes leave a joeung-S that can attach
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// to a main consonant to the left of my cursor, it will 'snap' into
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// a cluster. It'd be more natural to have that cluster on the left,
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// so I can add more chars to the cluster if desired.
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//
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// It's also easier to immediately backspace the extra chars if needed
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// this way, rather than forcing a caret reposition.
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if(leftContext.count < oldLeftContext.count) {
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log.debug("Could not reposition caret perfectly after a right-delete!")
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textDocumentProxy.adjustTextPosition(byCharacterOffset: 1)
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}
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}
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// We've handled a set of code points; make sure we mark our progress!
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pointsToDelete -= pointsDeleted
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}
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if let remnantIndex = remnantIndex, remnantIndex < undeletedStartIndex {
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// We need to restore some of the deleted text!
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let remnant = String(oldContext.utf16[remnantIndex..<undeletedStartIndex]) ?? ""
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textDocumentProxy.insertText(remnant)
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// Must place the caret back in its correct position!
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// Unfortunately, Apple's adjustTextPosition is definitely cluster-based.
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var leftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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// Ideally, we want to stop at the exact position, but the lack of
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// granularity on adjustTextPosition may not cooperate with that goal.
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while(leftContext.count > oldLeftContext.count) {
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textDocumentProxy.adjustTextPosition(byCharacterOffset: -remnant.count)
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leftContext = textDocumentProxy.documentContextBeforeInput ?? ""
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}
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// FAILSAFE, non-ideal behavior below.
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//
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// It's probably (?) better to keep the caret at the end of a cluster that
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// previously started before the caret, even if right-deletions add new
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// characters to the cluster. I think.
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//
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// Khmer example: if right-deletes leave a joeung-S that can attach
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// to a main consonant to the left of my cursor, it will 'snap' into
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// a cluster. It'd be more natural to have that cluster on the left,
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// so I can add more chars to the cluster if desired.
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//
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// It's also easier to immediately backspace the extra chars if needed
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// this way, rather than forcing a caret reposition.
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if(leftContext.count < oldLeftContext.count) {
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log.debug("Could not reposition caret perfectly after a right-delete!")
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textDocumentProxy.adjustTextPosition(byCharacterOffset: 1)
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}
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}
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// We've handled a set of code points; make sure we mark our progress!
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pointsToDelete -= pointsDeleted
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}
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}
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