Add colors in Rust (#78)

* 🎨 Add colors in Rust

* 🌿 Use an option for the properties and #[repr(C)]

* ❌ Remove WASM dependency on document.

* 😎 Wrap Fill and stroke in a style struct.

* 📦 Use crate::Color

* Merge Add transactions for temporary modifications to the document

* Run cargo fmt

* Color without a 'U'

core/document/src/layers/folder.rs

@@ -0,0 +1,87 @@
+use crate::{DocumentError, LayerId};
+
+use super::{Layer, LayerData, LayerDataTypes};
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Folder {
+	next_assignment_id: LayerId,
+	pub layer_ids: Vec<LayerId>,
+	layers: Vec<Layer>,
+}
+
+impl LayerData for Folder {
+	fn render(&self) -> String {
+		self.layers
+			.iter()
+			.filter(|layer| layer.visible)
+			.map(|layer| layer.data.render())
+			.fold(String::with_capacity(self.layers.len() * 30), |s, n| s + "\n" + &n)
+	}
+}
+impl Folder {
+	pub fn add_layer(&mut self, layer: Layer, insert_index: isize) -> Option<LayerId> {
+		let mut insert_index = insert_index as i128;
+		if insert_index < 0 {
+			insert_index = self.layers.len() as i128 + insert_index as i128 + 1;
+		}
+
+		if insert_index <= self.layers.len() as i128 && insert_index >= 0 {
+			self.layers.insert(insert_index as usize, layer);
+			self.layer_ids.insert(insert_index as usize, self.next_assignment_id);
+			self.next_assignment_id += 1;
+			Some(self.next_assignment_id - 1)
+		} else {
+			None
+		}
+	}
+
+	pub fn remove_layer(&mut self, id: LayerId) -> Result<(), DocumentError> {
+		let pos = self.layer_ids.iter().position(|x| *x == id).ok_or(DocumentError::LayerNotFound)?;
+		self.layers.remove(pos);
+		self.layer_ids.remove(pos);
+		Ok(())
+	}
+
+	/// Returns a list of layers in the folder
+	pub fn list_layers(&self) -> &[LayerId] {
+		self.layer_ids.as_slice()
+	}
+
+	pub fn layer(&self, id: LayerId) -> Option<&Layer> {
+		let pos = self.layer_ids.iter().position(|x| *x == id)?;
+		Some(&self.layers[pos])
+	}
+
+	pub fn layer_mut(&mut self, id: LayerId) -> Option<&mut Layer> {
+		let pos = self.layer_ids.iter().position(|x| *x == id)?;
+		Some(&mut self.layers[pos])
+	}
+
+	pub fn folder(&self, id: LayerId) -> Option<&Folder> {
+		match self.layer(id) {
+			Some(Layer {
+				data: LayerDataTypes::Folder(folder), ..
+			}) => Some(&folder),
+			_ => None,
+		}
+	}
+
+	pub fn folder_mut(&mut self, id: LayerId) -> Option<&mut Folder> {
+		match self.layer_mut(id) {
+			Some(Layer {
+				data: LayerDataTypes::Folder(folder), ..
+			}) => Some(folder),
+			_ => None,
+		}
+	}
+}
+
+impl Default for Folder {
+	fn default() -> Self {
+		Self {
+			layer_ids: vec![],
+			layers: vec![],
+			next_assignment_id: 0,
+		}
+	}
+}