theme: build out the theme engine core with resolve pipeline

crates/theme/src/system.rs

@@ -0,0 +1,72 @@
+//! The normalized snapshot a platform adapter produces.
+
+use gpui::Hsla;
+
+use crate::ThemeVariant;
+
+/// Accessibility preferences read from the OS, forwarded into resolution.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct AccessibilityPreferences {
+    pub high_contrast: bool,
+    pub reduce_motion: bool,
+    pub reduce_transparency: bool,
+}
+
+/// Which adapter produced a [`SystemTheme`].
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub enum SourceKind {
+    #[default]
+    Fallback,
+    Macos,
+}
+
+impl SourceKind {
+    pub fn label(self) -> &'static str {
+        match self {
+            Self::Fallback => "neutral fallback",
+            Self::Macos => "macOS (NSColor)",
+        }
+    }
+}
+
+/// A partial palette with optional colors.
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct PartialPalette {
+    pub background: Option<Hsla>,
+    pub foreground: Option<Hsla>,
+    pub surface: Option<Hsla>,
+    pub surface_foreground: Option<Hsla>,
+    pub primary_foreground: Option<Hsla>,
+    pub accent_foreground: Option<Hsla>,
+    pub secondary: Option<Hsla>,
+    pub secondary_foreground: Option<Hsla>,
+    pub muted: Option<Hsla>,
+    pub muted_foreground: Option<Hsla>,
+    pub destructive: Option<Hsla>,
+    pub border: Option<Hsla>,
+    pub input: Option<Hsla>,
+    pub ring: Option<Hsla>,
+    pub selection: Option<Hsla>,
+}
+
+/// A normalized snapshot of the running system's theme.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct SystemTheme {
+    pub variant: ThemeVariant,
+    pub accent: Option<Hsla>,
+    pub palette: PartialPalette,
+    pub accessibility: AccessibilityPreferences,
+    pub source: SourceKind,
+}
+
+impl SystemTheme {
+    pub fn fallback(variant: ThemeVariant) -> Self {
+        Self {
+            variant,
+            accent: None,
+            palette: PartialPalette::default(),
+            accessibility: AccessibilityPreferences::default(),
+            source: SourceKind::Fallback,
+        }
+    }
+}