On Tue, 15 Jul 2025 03:58:55 GMT, Sergey Bylokhov <[email protected]> wrote:
>> I modified Abhishek's test:
>>
>>
>> System.out.println(" i bef at aft");
>> for (int i : new int[] {0, 1, 2, 8, 9, 10}) {
>> System.out.printf("%2d%5s%5s%5s\n",
>> i,
>> at.getBeforeIndex(CHARACTER, i),
>> at.getAtIndex(CHARACTER, i),
>> at.getAfterIndex(CHARACTER, i));
>> }
>>
>>
>> This way, I created a table of returned values:
>>
>>
>> Text: "0123456789"
>> Text Length: 10
>> i bef at aft
>> 0 null 0 1
>> 1 0 1 2
>> 2 1 2 3
>> 8 7 8 9
>> 9 8 9 null
>> 10 null null null
>>
>>
>> I'd expect to see 9 as the return value of `getBeforeIndex` for the index of
>> 10. This would make the table symmetrical.
>>
>> Therefore, I'm in favour for Abhishek's proposed fix.
>>
>> ---
>>
>> The description of the methods in `AccessibleText` is vague. None of the
>> three methods specifies what the index means and what values are accepted
>> for it.
>>
>> According to the text model, index 10 is still valid, it's the index between
>> the last character and the implied line break, so
>> `tf.getDocument().getText(10, 1)` returns `\n`.
>>
>> Having this in mind, the specification of the `getBeforeIndex`,
>> `getAtIndex`, `getAfterIndex` methods should be updated to *explicitly
>> specify the valid values for the `index` parameter*.
>
>>I'd expect to see 9 as the return value of getBeforeIndex for the index of
>>10. This would make the table symmetrical.
>
> Why do you expect that? The spec states that the index should be "an index
> within the text." That index is also used in other methods, such as
> getCharacterBounds(), etc. If we fixed it only for text at the end, it would
> make the behavior even less symmetric, since for a negative value, the model
> will always throw an exception.
>
>>According to the text model, index 10 is still valid, it's the index between
>>the last character and the implied line break, so
>>tf.getDocument().getText(10, 1) returns \n.
>
> The last character is implementation detail, it is not part of the "users
> data" this is the reason why it is excluded from the Document.getLength(). So
> passing length as a last character might cause an exception for custom
> documents. We also have the getCharCount() methods which returns "the number
> of characters (valid indices)".
>
> Also, why are we only talking about JTextComponent? There are other same
> implementations of AccessibleText for example
> [JLabel](https://github.com/openjdk/jdk/blob/0acd065bf5a75090b84c28b28856a62d86c52791/src/java.desktop/share/classes/javax/swing/JLabel.java#L1287).
>
>>Here i disagree, the "within the text" does not imply that the position
>>behind the last character is not within the text. Otherwise with the caret is
>>at the end of the text it is impossible to request last word or character
>>before the caret position which is one of the valid use cases of this
>>accessibility method. I think the fix is valid.
>
> It means exactly that, and it is also impossible to request the first
> character after the caret position if it is at the start of the document. For
> both cases getAtIndex() should work.
I agree with @mrserb: there already is `getAtIndex` and the documentation is
clear about that the index should be within the text. From my side I'd add that
changing this behavior may break backward-compatibility with client's custom
AWT/Swing components.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/25941#issuecomment-3073048371
