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

[Alexey Ivanov]

On Fri, 19 Apr 2024 19:19:26 GMT, Rajat Mahajan <rmahajan 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).
>
> 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.

I agree. The current approach calls `openThemeImpl` three times: once or twice with the passed `dpi` and then once with `defaultDPI` as the fallback. Moreover, it *leaks theme handles* if `openThemeImpl` returns non-zero value and it does so repeatedly even when there's a cached theme handle.

Handling the failure inside `openThemeImpl` seems a better option. Even though it results in a higher memory usage.

I believe `openTheme` returns 0 because the DPI of a printer is higher than that of screens, and Windows doesn't support such DPIs. The problem is likely reproducible when you print other components such as buttons.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18706#discussion_r1572847417