[OpenJDK 2D-Dev] [10] RFR JDK-8186987:NullPointerException in RasterPrinterJob without PrinterResolution

[Prahalad Kumar Narayanan]

Hello Prasanta

Thanks for the explanation. 
Being new to the Printing subsystem, it helped get the context of the problem.

As I understand, the problem is due to getDefaultPrinterSetings() returning negative values for defYRes and quality.
And the fix evades such negative values with a hardcoded low 300 DPI resolution.

I 'm suspecting the bug to be in the code that returns values for default printer settings
. Since these values are device specific, I believe, the code might use few platform APIs to query the resolutions on that printer device & return the same.
. It's here that default resolutions are not retrieved properly. 
. So my view is to trace this location & fix the population of default printer settings than a hardcoded DPI resolution.
    . When a problem has surfaced on one printer, there is possibility for the same to occur on many devices as well.
    . Besides printers may not be supporting low 300 DPI resolution going forward.

I may be wrong in my understanding. You could wait for other's review & follow up.

Thank you
Have a good day

Prahalad N.

-----Original Message-----
From: Prasanta Sadhukhan 
Sent: Thursday, August 31, 2017 3:39 PM
To: Philip Race; 2d-dev
Subject: [OpenJDK 2D-Dev] [10] RFR JDK-8186987:NullPointerException in RasterPrinterJob without PrinterResolution

Hi All,

Please review a fix for an issue where it a NPE is seen when an attempt is made to print to Brother HL-2240D series printer.

It seems when RasterPrinterJob#setAttributes() is called with no PrinterResolution attribute set, it first checks if PrinterResolution category is supported.
If it is supported, then it sees if the supplied resolution value is supported. Now, since no PrinterResolution attribute is set, so
isSupportedValue() returns false [as "printer resolution attribute" 
object is null]
It then goes to get the default resolution attribute via
getDefaultAttributeValue() which calls getDefaultPrinterSettings() and use yRes,Quality from this printer to construct a "PrinterResolution" 
object.

Now, it seems in Brother HL-2240D series printer, it supports 3 resolution [300, 600, HQ 1200] but for all these 3 resolutions,
getDefaultPrinterSettings() returns -50 for yRes and Quality.
So, as per this code
http://hg.openjdk.java.net/jdk10/client/jdk/file/dbb5b171a16b/src/java.desktop/windows/classes/sun/print/Win32PrintService.java#l1189
res < 0 and no PrinterResolution object is instantiated so when RPJ accesses printerResAttr.getCrossFeedResolution(ResolutionSyntax.DPI);   it causes NPE.

Proposed fix is to create a default lowly 300 dpi PrinterResolution if, for some reason, yRes and Quality from printer comes out -ve.
http://cr.openjdk.java.net/~psadhukhan/8186987/webrev.00/

Regards
Prasanta