First commit. Version 0.1.0

src/theme/surface.rs

@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: LGPL-2.1-only
+// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
+
+//! Composite surfaces: fill + outer shadows + inset shadows.
+//!
+//! A [`Surface`] is the richest kind of theme slot. It packages together a
+//! fill (possibly a gradient), an elevation stack, and inset shadows with
+//! their own blend modes. Widgets that only need a flat colour or a plain
+//! gradient do not construct [`Surface`] values directly; slot promotion
+//! (in `theme::slots`) hands them a [`Surface`] with empty decorations when
+//! they ask for one against a simpler slot.
+
+use super::paint::Paint;
+use super::shadow::{ InsetShadow, ShadowsRef };
+use crate::types::Color;
+
+// ─── Surface ─────────────────────────────────────────────────────────────────
+
+/// A composite theme surface: fill, elevation, insets.
+///
+/// All decorations are optional. A surface with `fill: Paint::Solid(...)`,
+/// no shadows and no insets behaves exactly like a flat-colour fill, which
+/// is why the promotion path from a `color` slot to a [`Surface`] is trivial.
+#[ derive( Debug, Clone, PartialEq ) ]
+pub struct Surface
+{
+	/// What the surface is filled with.
+	pub fill:          Paint,
+	/// Outer shadow stack. When `Some`, can reference another slot by name
+	/// or inline the full list.
+	pub shadows:       Option<ShadowsRef>,
+	/// Inset shadows, in back-to-front order. Each entry carries its own
+	/// [`crate::theme::BlendMode`].
+	pub inset_shadows: Vec<InsetShadow>,
+}
+
+impl Surface
+{
+	/// Build a surface from just a [`Paint`], with no shadows or insets.
+	pub fn from_paint( paint: Paint ) -> Self
+	{
+		Self
+		{
+			fill:          paint,
+			shadows:       None,
+			inset_shadows: Vec::new(),
+		}
+	}
+}
+
+impl From<Paint> for Surface
+{
+	fn from( p: Paint ) -> Self { Surface::from_paint( p ) }
+}
+
+impl From<Color> for Surface
+{
+	fn from( c: Color ) -> Self { Surface::from_paint( Paint::Solid( c ) ) }
+}
+
+// ─── Tests ───────────────────────────────────────────────────────────────────
+
+#[ cfg( test ) ]
+mod tests
+{
+	use super::*;
+	use crate::types::Color;
+	use crate::theme::shadow::{ BlendMode, InsetShadow, Shadow, ShadowsRef };
+
+	#[ test ]
+	fn surface_promotes_from_color()
+	{
+		let s: Surface = Color::hex( 0x04, 0xD9, 0xFE ).into();
+		assert_eq!( s.fill, Paint::Solid( Color::hex( 0x04, 0xD9, 0xFE ) ) );
+		assert!( s.shadows.is_none() );
+		assert!( s.inset_shadows.is_empty() );
+	}
+
+	#[ test ]
+	fn glass_accent_shape_composes()
+	{
+		let s = Surface
+		{
+			fill:    Paint::Solid( Color::hex( 0x04, 0xD9, 0xFE ) ),
+			shadows: Some( ShadowsRef::Named( "shadows-glass".to_string() ) ),
+			inset_shadows: vec!
+			[
+				InsetShadow { offset: [ -3.6, -3.6 ], blur: 13.5, spread: 0.0, color: Color::hex( 0x55, 0x55, 0x55 ), blend: BlendMode::PlusLighter },
+				InsetShadow { offset: [  1.8,  1.8 ], blur:  1.8, spread: 0.0, color: Color::hex( 0x55, 0x55, 0x55 ), blend: BlendMode::PlusLighter },
+				InsetShadow { offset: [  0.45, 0.45 ], blur: 0.9, spread: 0.0, color: Color::BLACK,                   blend: BlendMode::Overlay     },
+				InsetShadow { offset: [  1.8,  1.8 ], blur:  7.2, spread: 0.0, color: Color::rgba( 0.0, 0.0, 0.0, 0.15 ), blend: BlendMode::Normal },
+			],
+		};
+		assert_eq!( s.inset_shadows.len(), 4 );
+		assert_eq!( s.inset_shadows[0].blend, BlendMode::PlusLighter );
+		assert_eq!( s.inset_shadows[2].blend, BlendMode::Overlay );
+
+		let _ = Shadow
+		{
+			offset: [ 0.0, 0.0 ],
+			blur:   9.0,
+			spread: 0.0,
+			color:  Color::rgba( 33.0 / 255.0, 33.0 / 255.0, 33.0 / 255.0, 0.25 ),
+			blend:  BlendMode::Normal,
+		};
+	}
+}