[OpenJDK 2D-Dev] [11] RFR: [JDK-5064835] TextMeasurer/deleteChar function fails when deleting more than one characters

Prahalad Kumar Narayanan prahalad.kumar.narayanan at oracle.com
Fri Dec 29 11:00:24 UTC 2017

Hello Everyone

Good day to you.

Request your time in reviewing the fix for the bug: 
JDK-5064835    TextMeasurer/deleteChar function fails when deleting more than one characters.

Root Cause:
. The spec clearly mentions that the concerned method is to be used to delete a single character.
. However, the spec does not mention the outcome when the method is used to delete multiple characters (as reported in the bug)

Solution Approaches:
. Since the spec does not mention the outcome when multiple characters are deleted, the result is left to the implementation.
. The solution can be approached in two perspectives-
      1. Update the spec to explicitly mention the exception that would be thrown in such cases or
      2. Re-initialize the TextMeasurer with the new text as present in the argument of the method.

. I inspected feasibility/ risk of both the approaches and I 'm of the opinion that approach 1. is better. 
. Reason is that, with the second approach- 
      . The re-initialization would reset all text attributes, and state variabes that were set on TextMeasurer (and internal StyledParagraph) object.
      . If re-initialization is required, one could create a new TextMeasurer using the modified text rather than invoking deleteChar method.
. Thus in the proposed solution- I 've added a throws clause that explicitly mentions that IllegalArgumentException will be thrown when attempted to delete multiple characters.

Other Info:
. The fix was tested with existing jtreg test cases- No regressions were seen.
. 2 JCK tests have been found to fail. They are- 
      . java_awt/Font/TextMeasurer/CharTest (TestCase5)
      . java_awt/Font/LineBreakMeasurer/CharTest (TestCase4)
. In both the failures, incorrect arguments are passed to deleteChar method- newParagraph (with multiple chars deleted) & beginIndex (-1)
. While the test case expects index out of bounds exception for -ve index, the code now throws IllegalArgumentsException.
. A minor correction to JCK test will fix the issue. I shall raise a JCK bug once the fix is approved & submitted.

Kindly review the changes at your convenience & share your feedback:

Note: I 've not raised a CSR for this bug yet.
Based on review, I will create the CSR for change to the specification.

Thank you for your time in review &
Happy New Year 

Prahalad N.

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