RFR: 8322135: javax/swing/JTable/JTableScrollPrintTest.java & javax/swing/JTable/PrintAllPagesTest.java throws java.lang.InternalError: HTHEME is null

[Rajat Mahajan]

On Wed, 10 Apr 2024 04:32:53 GMT, Tejesh R <tr at openjdk.org> wrote:

> Getting a theme for particular dpi failed in windows L&F during print test. Before [JDK-8294427](https://bugs.openjdk.org/browse/JDK-8294427) fix, theme was independent of DPI. After the fix (https://github.com/openjdk/jdk/commit/a63afa4aa62863d1a199a0fb7d2f56ff8fcd04fd) getting a theme in Windows L&F became dependent on DPI. Now it works fine in paint to a frame or window but for printing the DPI is computed with scaling factor which might not be w.r.t set of connected monitors and hence error is returned according to [this from windows document](https://learn.microsoft.com/en-us/windows/win32/api/uxtheme/nf-uxtheme-openthemedatafordpi). 
> The suggested fix is to handle printer cases with default dpi since in error condition 0 is returned with `openThemeImpl(widget, dpi)`. The fix seems to be working fine without causing any regression (Tested in CI systems and also the affected tests).

Changes requested by rmahajan (Author).

src/java.desktop/windows/classes/sun/awt/windows/ThemeReader.java line 120:

> 118:     // this should be called only with writeLock held
> 119:     private static Long getThemeImpl(String widget, int dpi) {
> 120:         if (openThemeImpl(widget, dpi) == null || openThemeImpl(widget, dpi) == 0) {

I think it would be cleaner and better if this is handled in `openThemeImpl()` itself. We can put a check for NULL `theme `being returned and return the one based on `defaultDPI`, if that is the case.

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PR Review: https://git.openjdk.org/jdk/pull/18706#pullrequestreview-2012203269
PR Review Comment: https://git.openjdk.org/jdk/pull/18706#discussion_r1572824439