RFR: 8344668: Unnecessary array allocations and copying in TextLine [v2]

[Harshitha Onkar]

On Thu, 5 Dec 2024 18:22:27 GMT, Daniel Gredler <dgredler at openjdk.org> wrote:

>> When `LineBreakMeasurer` is used to break text into lines, internally it uses `TextMeasurer` and `TextLine` to do the job. In the common case, `TextLine.getComponents(...)` allocates a `TextLineComponent[]` with room for a single array entry, and passes it to `TextLine.createComponentsOnRun(...)`, which fills the array and returns it, optionally resizing to a larger array if necessary, after which the array is resized back down to actual size (if necessary).
>> 
>> Unfortunately `TextLine.createComponentsOnRun(...)` is too eager in allocating larger arrays. In the most common case of a single component, this means that a single-element array is allocated, then a 9-element array is allocated (via `expandArray(...)`), and then another single-element array is allocated (to shrink the array back to actual size). Only one array allocation is necessary in this common case, and no array copying is needed.
>
> Daniel Gredler has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix second array expansion site

LGTM. Ran awt/font and java/awt/font/LineBreakMeasurer tests with fix and they work as expected.

@gredler Missed mentioning it earlier, copyright year needs to be updated for TextLine.java

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Marked as reviewed by honkar (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22288#pullrequestreview-2482750639