RFR: 5080391: ArrayIndexOutOfBounds during "undo" of Right-to-Left text insert [v2]

[Prasanta Sadhukhan]

On Fri, 7 Oct 2022 09:00:32 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

>> javax.swing.text.AbstractDocument$BranchElement.replace(...) method throws an `ArrayIndexOutOfBoundsException: arraycopy: length -1 is negative` when using an UndoManager on the default document of a JTextArea and you try to undo the insertion of a LEFT-TO-RIGHT language (e.g. Arabic) that is immediately followed by setting the component orientation on the JTextArea.
>> 
>> This is because System.arrayCopy() is called with -ve length because of the calculation done in AbstractDocment.replace where `src` is of 2bytes because of unicode text causing `nmove` to become -ve if `nchildren` is 1 (an unicode character is inserted)
>> 
>> System.arrayCopy throws `IndexOutOfBoundsException if:
>> 
>>     The srcPos argument is negative.
>>     The destPos argument is negative.
>>     The length argument is negative
>> 
>> 
>> so the fix is made to make  nmove, src, dest +ve
>> Also, Element.getElement() can return null which is not checked, causing NPE, if deletion of text is done which results in no element, which is also fixed in the PR
>> 
>> All jtreg testsuite tests are run without any regression.
>
> Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Test fix

test/jdk/javax/swing/text/AbstractDocument/TestUndoInsertArabicText.java line 38:

> 36: import javax.swing.undo.UndoManager;
> 37: 
> 38: public class TestUndoInsertArabicText {

Updated test to test insertion and undoing at beginning and middle, in addition to end of text

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PR: https://git.openjdk.org/jdk/pull/10446