Error out when selecting unknown styles

internal/compiler/fileaccess.rs

@@ -22,6 +22,10 @@ impl<'a> VirtualFile<'a> {
     }
 }
 
+pub fn styles() -> Vec<&'static str> {
+    builtin_library::styles()
+}
+
 pub fn load_file<'a>(path: &'a std::path::Path) -> Option<VirtualFile<'static>> {
     match path.strip_prefix("builtin:/") {
         Ok(builtin_path) => builtin_library::load_builtin_file(builtin_path),
@@ -44,6 +48,20 @@ mod builtin_library {
 
     use super::VirtualFile;
 
+    pub(crate) fn styles() -> Vec<&'static str> {
+        widget_library()
+            .iter()
+            .filter_map(|d| {
+                let style = d.0;
+                if d.1.iter().any(|f| f.path == "sixtyfps_widgets.60") {
+                    Some(style)
+                } else {
+                    None
+                }
+            })
+            .collect()
+    }
+
     pub(crate) fn load_builtin_file(
         builtin_path: &std::path::Path,
     ) -> Option<VirtualFile<'static>> {