[OpenJDK 2D-Dev] NPE in X11FontManager.getDefaultPlatformFont

[Jeremy Manson]

Hi Phil,

Thanks for the response.  You've actually caught me out: this was a bug I
found a while ago, and am only now just getting around to reporting.  I
made this change locally (inside Google), and lost my repro instructions.
 It was probably for a user issue, which means that I'm too chicken to back
it out and see what happens.  This fix looked obvious enough that I thought
I could get away with it, since it is clearly the case that X11FontManager
expects a non-null fontConfigFonts regardless of the value of
fontConfigFailed.

IIRC, the cause was either that the fontconfig library wasn't installed or
that the fontconfig file was obsolete / incorrect for the given system.  I
almost certainly did not fix any ULEs (I would have a record of that).  We
have some stripped down systems, and this may have been one of them.  It
was a headless configuration.  I did preserve my stack trace:

Exception in thread "main" java.lang.NullPointerException at
sun.awt.X11FontManager.getDefaultPlatformFont(X11FontManager.java:779) at
sun.font.SunFontManager$2.run(SunFontManager.java:428) at
java.security.AccessController.doPrivileged(Native Method) at
sun.font.SunFontManager.<init>(SunFontManager.java:371) at
sun.awt.X11FontManager.<init>(X11FontManager.java:32) at
sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:530) at
java.lang.Class.newInstance0(Class.java:372) at
java.lang.Class.newInstance(Class.java:325) at
sun.font.FontManagerFactory$1.run(FontManagerFactory.java:80) at
java.security.AccessController.doPrivileged(Native Method) at
sun.font.FontManagerFactory.getInstance(FontManagerFactory.java:71) at
sun.java2d.SunGraphicsEnvironment.getFontManagerForSGE(SunGraphicsEnvironment.java:185)
at
sun.java2d.SunGraphicsEnvironment.getAllFonts(SunGraphicsEnvironment.java:192)
at
sun.java2d.HeadlessGraphicsEnvironment.getAllFonts(HeadlessGraphicsEnvironment.java:91)

I'm sure that the line numbers are obsolete, but you get the general idea.
I don't seem to have what was beneath that in the stack, but I imagine it
was something that was relatively comfortable with getAllFonts returning
nothing (as appropriate).

Having said all that, it seems to me that if fontConfigFailed is not
allowed to be true unless you have a system configuration problem, then
that should be made clear at runtime, and that you should not get rather
mysterious NPEs at later points in the code.  You do have a fallback in
getDefaultPlatformFont that says "make something up so that we don't get
NPE", which made me think that the original author intended to prefer
avoiding NPEs.

Jeremy


On Tue, Jun 4, 2013 at 3:29 PM, Phil Race <philip.race at oracle.com> wrote:

> Jeremy,
>
> Why didn't it return any fonts ? Is this because the libfontconfig library
> isn't installed ?
>
> We've been runtime loading that lib but these days could potentially
> switch to linking against it at compile time, in which case you won't
> even get this far. So in other words this could be a system config issue.
> The most common thing I've seen is that 64 bit Linux doesn't have
> all the libs to run a 32 bit JRE. You probably found and fixed all of those
> because it was Unsatisfiedlinkerror or similar but the runtime linking
> is disguising that its really the same problem.
>
> If you really don't have any fonts installed, then that's also
> a missing package and we perhaps should have a better diagnostic,
> but there isn't really any point in continuing anyway without any fonts.
> Even headless applications may require fonts.
>
> -phil.
>
>
> On 6/4/2013 2:50 PM, Jeremy Manson wrote:
>
>> Hi folks,
>>
>> I encountered a NullPointerException in the above method, when fontconfig
>> doesn't return any fonts:
>>
>> http://hg.openjdk.java.net/**jdk8/jdk8/jdk/file/**
>> 7eae7c89dab4/src/solaris/**classes/sun/awt/**X11FontManager.java<http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/7eae7c89dab4/src/solaris/classes/sun/awt/X11FontManager.java>
>>
>> Line 779.  The issue is that FontConfigManager sets fontConfigFonts to
>> null when Fontconfig doesn't return any fonts:
>>
>> http://hg.openjdk.java.net/**jdk8/jdk8/jdk/file/**
>> 7eae7c89dab4/src/solaris/**classes/sun/font/**FontConfigManager.java<http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/7eae7c89dab4/src/solaris/classes/sun/font/FontConfigManager.java>
>>
>> Line 218.
>>
>> The solution I came up with is to initialize fontConfigFonts with a
>> zero-element array in this case:
>>
>> diff --git a/src/solaris/classes/sun/**font/FontConfigManager.java
>> b/src/solaris/classes/sun/**font/FontConfigManager.java
>> --- a/src/solaris/classes/sun/**font/FontConfigManager.java
>> +++ b/src/solaris/classes/sun/**font/FontConfigManager.java
>> @@ -216,6 +216,7 @@
>> logger.info <http://logger.info>("**Fontconfig returned no fonts at
>> all.");
>>
>>              }
>>              fontConfigFailed = true;
>> +            fontConfigFonts = new FcCompFont[0];
>>              return;
>>          } else if (fontConfigFailed) {
>>              for (int i = 0; i< fontArr.length; i++) {
>>
>> Thanks for your attention!
>>
>> Jeremy
>>
>
>
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