RFR: 8246348: Crash in libpango on Ubuntu 20.04 with some unicode chars

[Kevin Rushforth]

On Thu, 11 Jun 2020 00:14:23 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> This addresses https://bugs.openjdk.java.net/browse/JDK-8246348
>
> modules/javafx.graphics/src/main/java/com/sun/javafx/font/freetype/PangoGlyphLayout.java line 90:
> 
>> 89:         for (char c: text) {
>> 90:             if (c == 0) c = '\f';
>> 91:         }
> 
> This won't actually do anything (it just sets a local variable that immediately goes out of scope). I don't think that
> we want to modify the array itself, so you will probably want to make a copy of the array in the case there is a '0'
> character.  As for what to replace the '0' char with, maybe a space? @prrace can probably suggest something.

Interestingly enough, I don't see a crash due to the 0 character, but I am seeing some new assertion warnings expecting
`length >= 0` even in cases where there isn't a 0 character.

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PR: https://git.openjdk.java.net/jfx/pull/249