CSS compatibility issues with AtlantaFX - docking indicators invisible due to ClassCastException: String cannot be cast to Paint

[SandeepaInduwaraSamaranayake]

When using SnapFX 0.8.0 in a JavaFX 25 application that applies the AtlantaFX theme (Application.setUserAgentStylesheet(...)), the docking drag‑and‑drop visual indicators (ghost overlays, drop zone highlights) do not appear. The console shows repeated CSS warnings:

Jul 14, 2026 12:42:42 PM javafx.scene.CssStyleHelper calculateValue WARNING: Caught 'java.lang.ClassCastException: class java.lang.String cannot be cast to class javafx.scene.paint.Paint (java.lang.String is in module java.base of loader 'bootstrap'; javafx.scene.paint.Paint is in module javafx.graphics@25 of loader 'app')' while converting value for '-fx-background-color' from rule '*.dock-split-pane' in stylesheet jar:file:///C:/Users/Hp/.m2/repository/org/snapfx/snapfx-core/0.8.0/snapfx-core-0.8.0.jar!/snapfx.css

These originate from snapfx.css and occur when JavaFX attempts to resolve Modena‑specific CSS variables (e.g., -fx-text-base-color, -fx-background, -fx-base) that are not defined in AtlantaFX.

The issue does not occur when using the default Modena stylesheet; in that case the warnings vanish and docking indicators function as expected.

Steps to Reproduce

1. Create a new JavaFX 25 project.
2. Add the AtlantaFX dependency (e.g., io.github.typhon0:AtlantaFX:...).
3. Apply the AtlantaFX theme at application startup:
4. Application.setUserAgentStylesheet("path/theme.css");
5. Initialize SnapFX, register some DockNodes, and build a layout.
6. Attempt to drag a dockable panel.
7. Observe that no drop zone preview (blue overlay, ghost, or target highlighting) appears, and the CSS warning is printed to the console.

Environment

SnapFX version: 0.8.0
Java version: 26
JavaFX version: 25
OS: Windows 10
Theme: AtlantaFX (2.0.1)