Move all crates into a crates directory (#1940)

crates/epaint/src/shadow.rs

@@ -0,0 +1,82 @@
+use super::*;
+
+/// The color and fuzziness of a fuzzy shape.
+/// Can be used for a rectangular shadow with a soft penumbra.
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct Shadow {
+    /// The shadow extends this much outside the rect.
+    /// The size of the fuzzy penumbra.
+    pub extrusion: f32,
+
+    /// Color of the opaque center of the shadow.
+    pub color: Color32,
+}
+
+impl Shadow {
+    /// Tooltips, menus, …
+    pub fn small_dark() -> Self {
+        Self {
+            extrusion: 16.0,
+            color: Color32::from_black_alpha(96),
+        }
+    }
+
+    /// Tooltips, menus, …
+    pub fn small_light() -> Self {
+        Self {
+            extrusion: 16.0,
+            color: Color32::from_black_alpha(32),
+        }
+    }
+
+    /// Subtle and nice on dark backgrounds
+    pub fn big_dark() -> Self {
+        Self {
+            extrusion: 32.0,
+            color: Color32::from_black_alpha(96),
+        }
+    }
+
+    /// Subtle and nice on white backgrounds
+    pub fn big_light() -> Self {
+        Self {
+            extrusion: 32.0,
+            color: Color32::from_black_alpha(40),
+        }
+    }
+
+    pub fn tessellate(&self, rect: emath::Rect, rounding: impl Into<Rounding>) -> Mesh {
+        // tessellator.clip_rect = clip_rect; // TODO(emilk): culling
+
+        let Self { extrusion, color } = *self;
+
+        let rounding: Rounding = rounding.into();
+        let half_ext = 0.5 * extrusion;
+
+        let ext_rounding = Rounding {
+            nw: rounding.nw + half_ext,
+            ne: rounding.ne + half_ext,
+            sw: rounding.sw + half_ext,
+            se: rounding.se + half_ext,
+        };
+
+        use crate::tessellator::*;
+        let rect = RectShape::filled(rect.expand(half_ext), ext_rounding, color);
+        let pixels_per_point = 1.0; // doesn't matter here
+        let font_tex_size = [1; 2]; // unused size we are not tessellating text.
+        let mut tessellator = Tessellator::new(
+            pixels_per_point,
+            TessellationOptions {
+                feathering: true,
+                feathering_size_in_pixels: extrusion * pixels_per_point,
+                ..Default::default()
+            },
+            font_tex_size,
+            vec![],
+        );
+        let mut mesh = Mesh::default();
+        tessellator.tessellate_rect(&rect, &mut mesh);
+        mesh
+    }
+}