Introduce the concept of global theme contexts

This commit adds the default theme context, which replaces
the need to manually check the project and the default theme
all the time; simplifies related code.

It also adds framework for custom theme contexts, to be used
by the editor. Custom contexts can be attached to any node,
and not necessarily a GUI/Window node. Contexts do no break
theme inheritance and only define which global themes a node
uses as a fallback.

Contexts propagate NOTIFICATION_THEME_CHANGED when one of their
global themes changes. This ensures that global themes act just
like themes assigned to individual nodes and can be previewed
live in the editor.

1 files changed, 3 insertions, 1 deletions

diff --git a/tests/test_main.cpp b/tests/test_main.cpp
index a4306db6f4..3a80fc8c00 100644
--- a/tests/test_main.cpp
+++ b/tests/test_main.cpp
@@ -238,7 +238,9 @@ struct GodotTestCaseListener : public doctest::IReporter {
 			RenderingServerDefault::get_singleton()->set_render_loop_enabled(false);
 
 			// ThemeDB requires RenderingServer to initialize the default theme.
-			// So we have to do this for each test case.
+			// So we have to do this for each test case. Also make sure there is
+			// no residual theme from something else.
+			ThemeDB::get_singleton()->finalize_theme();
 			ThemeDB::get_singleton()->initialize_theme_noproject();
 
 			physics_server_3d = PhysicsServer3DManager::get_singleton()->new_default_server();