<AWT Dev> RFR: 8262470: Printed GlyphVector outline with low DPI has bad quality on Windows

Alexander Scherbatiy alexsch at openjdk.java.net
Fri Feb 26 19:45:57 UTC 2021

Printing text using GlyphVector outline has bad quality on printers with low DPI on Windows.
The GDI system used for text printing on Windows accepts only integer path coordinates.
Rounding GlyphVector outline coordinates leads to distorted printed text.

The issue had been reported as JDK-8256264 but was reverted because of the regression JDK-8259007 "This test printed a blank page".

The fix JDK-8256264 scaled coordinates in wPrinterJob.moveTo()/lineTo()  methods up and scaled transforms in wPrinterJob.beginPath()/endPath() down.

The regression was in the WPathGraphics.deviceDrawLine() method which uses wPrinterJob.moveTo()/lineTo() methods without surrounding them with wPrinterJob.beginPath()/endPath() so the line coordinates were only scaled up.

I tried to put wPrinterJob.beginPath()/endPath()  methods around wPrinterJob.moveTo()/lineTo()   in the method WPathGraphics.deviceDrawLine()  but the line was not drawn at all even without scaling coordinates up and transform down (without JDK-8256264 fix). It looks like GDI treats this case as an empty shape.

The proposed fix applies path coordinates and transform scaling only in WPathGraphics.convertToWPath() method.
The one more PathPrecisionScaleFactorShapeTest.java manual test is added which checks that all methods that draw paths in WPathGraphics are used: line in WPathGraphics.deviceDrawLine() and SEG_LINETO/SEG_QUADTO/SEG_CUBICTO in WPathGraphics.convertToWPath() .

The `java/awt/print` and `java/awt/PrintJob` automatic and manual tests were run on Windows 10 Pro with the fix.

There are two failed automated tests which fail without the fix as well:

The following manual tests have issues on my system:
- `java/awt/print/Dialog/PrintDlgPageable.java` java.lang.IllegalAccessException: class com.sun.javatest.regtest.agent.MainWrapper$MainThread cannot access a member of class PrintDlgPageable with modifiers "public static"

- `java/awt/print/PrinterJob/PrintAttributeUpdateTest.java` I select pages radio button, press the print button but the test does not finish and I do not see any other dialogs with pass/fail buttons.

- `java/awt/PrintJob/PrintCheckboxTest/PrintCheckboxManualTest.java` Tests that there is no ClassCastException thrown in printing checkbox and scrollbar with XAWT. Error. Can't find HTML file: test\jdk\java\awt\PrintJob\PrintCheckboxTest\PrintCheckboxManualTest.html

- `java/awt/print/PrinterJob/SecurityDialogTest.java` A windows with instructions is shown but it does not contain  print/pass/fail buttons and it is not possible to close the window.

- The tests below fail with "Error. Parse Exception: Arguments to `manual' option not supported: yesno" message:


Commit messages:
 - 8262470: Printed GlyphVector outline with low DPI has bad quality on Windows

Changes: https://git.openjdk.java.net/jdk/pull/2756/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2756&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262470
  Stats: 725 lines in 5 files changed: 722 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2756.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2756/head:pull/2756

PR: https://git.openjdk.java.net/jdk/pull/2756

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