Restructure project directories (#333)

`/client/web` -> `/frontend`
`/client/cli` -> *delete for now*
`/client/native` -> *delete for now*
`/core/editor` -> `/editor`
`/core/document` -> `/graphene`
`/core/renderer` -> `/charcoal`
`/core/proc-macro` -> `/proc-macros` *(now plural)*

graphene/src/layers/style/mod.rs

@@ -0,0 +1,99 @@
+use crate::color::Color;
+use serde::{Deserialize, Serialize};
+const OPACITY_PRECISION: usize = 3;
+
+fn format_opacity(name: &str, opacity: f32) -> String {
+	if (opacity - 1.).abs() > 10f32.powi(-(OPACITY_PRECISION as i32)) {
+		format!(r#" {}-opacity="{:.precision$}""#, name, opacity, precision = OPACITY_PRECISION)
+	} else {
+		String::new()
+	}
+}
+
+#[repr(C)]
+#[derive(Debug, Clone, Copy, PartialEq, Default, Serialize, Deserialize)]
+pub struct Fill {
+	color: Option<Color>,
+}
+impl Fill {
+	pub fn new(color: Color) -> Self {
+		Self { color: Some(color) }
+	}
+	pub fn color(&self) -> Option<Color> {
+		self.color
+	}
+	pub fn none() -> Self {
+		Self { color: None }
+	}
+	pub fn render(&self) -> String {
+		match self.color {
+			Some(c) => format!(r##" fill="#{}"{}"##, c.rgb_hex(), format_opacity("fill", c.a())),
+			None => r#" fill="none""#.to_string(),
+		}
+	}
+}
+
+#[repr(C)]
+#[derive(Debug, Clone, Copy, PartialEq, Default, Serialize, Deserialize)]
+pub struct Stroke {
+	color: Color,
+	width: f32,
+}
+
+impl Stroke {
+	pub fn new(color: Color, width: f32) -> Self {
+		Self { color, width }
+	}
+	pub fn color(&self) -> Color {
+		self.color
+	}
+	pub fn width(&self) -> f32 {
+		self.width
+	}
+	pub fn render(&self) -> String {
+		format!(r##" stroke="#{}"{} stroke-width="{}""##, self.color.rgb_hex(), format_opacity("stroke", self.color.a()), self.width)
+	}
+}
+
+#[repr(C)]
+#[derive(Debug, Clone, Copy, PartialEq, Default, Serialize, Deserialize)]
+pub struct PathStyle {
+	stroke: Option<Stroke>,
+	fill: Option<Fill>,
+}
+impl PathStyle {
+	pub fn new(stroke: Option<Stroke>, fill: Option<Fill>) -> Self {
+		Self { stroke, fill }
+	}
+	pub fn fill(&self) -> Option<Fill> {
+		self.fill
+	}
+	pub fn stroke(&self) -> Option<Stroke> {
+		self.stroke
+	}
+	pub fn set_fill(&mut self, fill: Fill) {
+		self.fill = Some(fill);
+	}
+	pub fn set_stroke(&mut self, stroke: Stroke) {
+		self.stroke = Some(stroke);
+	}
+	pub fn clear_fill(&mut self) {
+		self.fill = None;
+	}
+	pub fn clear_stroke(&mut self) {
+		self.stroke = None;
+	}
+	pub fn render(&self) -> String {
+		format!(
+			"{}{}",
+			match self.fill {
+				Some(fill) => fill.render(),
+				None => String::new(),
+			},
+			match self.stroke {
+				Some(stroke) => stroke.render(),
+				None => String::new(),
+			},
+		)
+	}
+}