fix "save" button in preference dialog not response

[springzfx]

I notice there is a dark theme in recent commit. So I tried it, and find out an issue that you can not save preference. "Save" button have no response. The issue starts from Provide access to dark theme in preferences (#4372).

The reason is that default value for key "fxTheme" is not set, thus cause a null exception when access this option. Solution is simple, just to set default value "Base.css" for key "fxTheme" in preference.

Finally, I have to say dark theme is a great job. thanks

[tobiasdiez]

Thanks for the PR. Although your solution works, it has the disadvantage that now the Base.css file is loaded twice every time (this was remarked in one of the recent PRs on this topic, not sure which one). It would be nice if you could also fix this in the progress. I'm not sure whether it is easier to modify the ThemeLoader to not load the base css file twice or leave the property value at null by default but prevent the NPE from happening by other means. I would leave this to you to decide.

Thanks also for the kind words regarding the dark theme. There might still be some visual problems with it. If you notice something, please open an issue (or even better a PR) for it!

[tobiasdiez]

Please don't use the Base.css constant here but instead reuse a corresponding constant in ThemeLoader.

[springzfx]

public void installBaseCss(Scene scene, JabRefPreferences preferences);
I track the theme loading process, but not find it loaded twice.
More information will help me to figure it out.

[tobiasdiez]

When jabRefPreferences.get(JabRefPreferences.FX_THEME) returns Base.css, then after

jabref/src/main/java/org/jabref/gui/util/ThemeLoader.java

Lines 48 to 51 in e8daf26

	String cssFileName = jabRefPreferences.get(JabRefPreferences.FX_THEME);
	if (cssFileName != null) {
	try {
	cssProperty = Paths.get(JabRefFrame.class.getResource(cssFileName).toURI()).toString();

cssProperty points to the base css file. Hence, it will be loaded twice in installBaseCss:

jabref/src/main/java/org/jabref/gui/util/ThemeLoader.java

Line 65 in e8daf26

addAndWatchForChanges(scene, DEFAULT_PATH_MAIN_CSS, 0);

and in

jabref/src/main/java/org/jabref/gui/util/ThemeLoader.java

Lines 68 to 71 in e8daf26

	final Path path = Paths.get(cssProperty);
	if (Files.isReadable(path)) {
	String cssUrl = path.toUri().toString();
	addAndWatchForChanges(scene, cssUrl, 1);

[springzfx]

The most simple fix is this:

jabref/src/main/java/org/jabref/gui/util/ThemeLoader.java

Lines 82 to 86 in 613db98

	private void addAndWatchForChanges(Scene scene, String cssUrl, int index) {
	// avoid repeat add
	if (scene.getStylesheets().contains(cssUrl)) return;
	scene.getStylesheets().add(index, cssUrl);

[springzfx]

It the issue(#4385 (comment)) mentioned this double loading problem.

[tobiasdiez]

That works. Thanks for the follow-up. Please fix the code style issues and then we can merge.