[OpenJDK 2D-Dev] NPE in X11FontManager.getDefaultPlatformFont
Jiri Vanek
jvanek at redhat.com
Tue Jun 11 10:59:20 UTC 2013
I'm quite curious why OpenJDK can not have its fall-back font.
Will "Oracle" JDK lost its headless advantage?
Throw out an NoFontsFound exception, log it later, and fall to default (even dummy) font. Still
better then die on nothing saying NPE
On 06/07/2013 09:19 PM, Phil Race wrote:
> "Oracle" JDK ships with fonts. And it has a default fontconfig.properties (not
> the same thing as libfontconfig) file that maps all the logical fonts to those fonts.
> So it fully meets the spec and can function just fine on a system that has no other fonts installed.
> So on reflection we wouldn't want to fail at this point without checking to see if we actually
> can continue.
> This doesn't help "Open" JDK as it is, since it doesn't have fonts, but there's nothing to stop
> an OpenJDK port doing the exact same, except that its kind of pointless for a distro to do
> that as it would be easier to make libfontconfig and some core fonts a pre-requisite package.
>
> I think I'll need to review everyone's "requirements" again to say
> exactly what should be the path forward.
This will be more then appreciated:) But I'm definitely not envying this responsibility to you.
Best regards, and thank you for this effort
J.
>
> For your "headless" situation, I'm not completely clear about what you intend to run,
> but it occurs to me that if you are even tickling this code, its reasonable to suppose
> that the app is likely to need fonts. Whereas someone running a back-end server app
> would never initialise the AWT toolkit, so shouldn't care less whether fonts are installed.
>
> -phil.
>
>
> On 6/5/2013 9:38 AM, Jeremy Manson wrote:
>> I don't have enough of an understanding of the issues to say that this configuration should
>> necessarily be supported. However, I am relatively sure that it shouldn't be supported just
>> enough to make the error and the code confusing. If it doesn't find any fonts, FontConfigManager
>> logs something to the platform logger and returns quietly.
>>
>> 213 if (anyFont == null) {
>> 214 if (FontUtilities.isLogging()) {
>> 215 PlatformLogger logger = FontUtilities.getLogger();
>> 216 logger.info <http://logger.info>("Fontconfig returned no fonts at all.");
>> 217 }
>> 218 fontConfigFailed = true;
>> 219 return;
>>
>> and then when the X11FontManager "believes" it doesn't find a default font, it does a fallback:
>>
>> 787 /* Absolute last ditch attempt in the face of fontconfig problems.
>> 788 * If we didn't match, pick the first, or just make something
>> 789 * up so we don't NPE.
>> 790 */
>> 791 if (info[0] == null) {
>> 792 if (fontConfigFonts.length > 0 &&
>> 793 fontConfigFonts[0].firstFont.fontFile != null) {
>> 794 info[0] = fontConfigFonts[0].firstFont.familyName;
>> 795 info[1] = fontConfigFonts[0].firstFont.fontFile;
>> 796 } else {
>> 797 info[0] = "Dialog";
>> 798 info[1] = "/dialog.ttf";
>> 799 }
>> 800 }
>>
>> That would make the casual reader believe that "no fonts" is a supported configuration (or, at
>> least, a configuration that isn't supposed to NPE). But the fallback doesn't get hit in this
>> case, because the X11FontManager believes that getFontConfigFonts can't return null.
>>
>> It seems reasonable to throw an exception, if that's what you want to do, but it seems to me that
>> the exception should have a relatively clear message about what happened, and the fact that that
>> configuration is unsupported. If you really want not to have code that deals with a lack of
>> fonts, it would make a certain amount of sense to take out the code that is there and tries to do
>> so. As it is, the code and its behavior occupy a very confusing middle ground, where the
>> developer has to trace through the library to figure out what happened and why it happened.
>>
>> (As for not linking with libfontconfig: we're trying to make a JDK that works regardless of
>> whether fontconfig is there. It should be able to work in headless, stripped down mode, and for a
>> developer who wants to use eclipse. I don't mind if devs need to catch exceptions on the headless
>> machines, but they like to know why they are catching them.)
>>
>> Jeremy
>>
>>
>>
>> On Wed, Jun 5, 2013 at 1:56 AM, Jiri Vanek <jvanek at redhat.com <mailto:jvanek at redhat.com>> wrote:
>>
>> Hi!
>>
>>
>> This is known issue - Openjdk fails when no fonts are installed.
>>
>> You can fix this by your own fontmanager (feel free to inspire at
>> https://bugzilla.redhat.com/show_bug.cgi?id=862355#c5 where I'm
>> creating an custom dummy fontmanager in case of failure)
>> You can set up similar manager class by -Dsun.font.fontmanager
>> property.
>>
>> Or you can support me and "force somebody" to review my patch
>> where I have tried to smuggle inside Openjdk default fallback font[1]
>>
>> On the contrary, if [1] will go in, then it can mask deeper
>> problems (as can be eg yours).
>>
>>
>>
>> [1]http://mail.openjdk.java.net/pipermail/2d-dev/2013-January/002999.html
>>
>>
>> Best regards
>> J.
>>
>>
>>
>> On 06/05/2013 01:32 AM, Jeremy Manson wrote:
>>
>> 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 <mailto:philip.race at oracle.com>
>> <mailto:philip.race at oracle.com <mailto: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> <http://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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