[LFC][IFC] Take grapheme clusters into account when keeping the first "character" on the line

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[zalan]

in preparation for enabling complex font codepath for IFC.

[zalan]

Created attachment 448115 [details]
Patch

[Antti Koivisto]

Comment on attachment 448115 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=448115&action=review

> Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp:296
> +    auto graphemeClustersIterator = NonSharedCharacterBreakIterator { textContent };
> +    auto nextPosition = ubrk_following(graphemeClustersIterator, inlineTextItem.start());
> +    if (nextPosition == UBRK_DONE)
> +        return inlineTextItem.length();
> +    return nextPosition - inlineTextItem.start();

Isn't it slow to make the iterator repeatedly? Maybe we should cache it or make it in the caller?

[Antti Koivisto]

Comment on attachment 448115 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=448115&action=review

>> Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp:296
>> +    auto graphemeClustersIterator = NonSharedCharacterBreakIterator { textContent };
>> +    auto nextPosition = ubrk_following(graphemeClustersIterator, inlineTextItem.start());
>> +    if (nextPosition == UBRK_DONE)
>> +        return inlineTextItem.length();
>> +    return nextPosition - inlineTextItem.start();
> 
> Isn't it slow to make the iterator repeatedly? Maybe we should cache it or make it in the caller?

I suppose it is always initialized with a different StringView so there is nothing to cache.

[zalan]

(In reply to Antti Koivisto from comment #3)
> Comment on attachment 448115 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=448115&action=review
> 
> >> Source/WebCore/layout/formattingContexts/inline/text/TextUtil.cpp:296
> >> +    auto graphemeClustersIterator = NonSharedCharacterBreakIterator { textContent };
> >> +    auto nextPosition = ubrk_following(graphemeClustersIterator, inlineTextItem.start());
> >> +    if (nextPosition == UBRK_DONE)
> >> +        return inlineTextItem.length();
> >> +    return nextPosition - inlineTextItem.start();
> > 
> > Isn't it slow to make the iterator repeatedly? Maybe we should cache it or make it in the caller?
> 
> I suppose it is always initialized with a different StringView so there is
> nothing to cache.
Yes. This codepath may be triggered once per line at most. It is also not a highly common case as regular web pages let their inline content fit the container. However it is very much used for testing content breaking (width: 0px).

[EWS]

Committed r287493 (245628@main): <https://commits.webkit.org/245628@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 448115 [details].

[Radar WebKit Bug Importer]

<rdar://problem/87028287>