Blend modes (#252)

* Add backend for selecting layer blend mode

* Change dropdown input to support callback on change

* Add debug messages

* Fix canvas update for blend-modes

* Finish up and polish blend modes implementations

* Add changes from code review

Co-authored-by: Keavon Chambers <keavon@keavon.com>
Co-authored-by: Dennis Kobert <dennis@kobert.dev>

core/editor/src/document/document_file.rs

@@ -38,11 +38,17 @@ fn layer_data<'a>(layer_data: &'a mut HashMap<Vec<LayerId>, LayerData>, path: &[
 	layer_data.get_mut(path).unwrap()
 }
 
-pub fn layer_panel_entry(layer_data: &mut LayerData, layer: &Layer, path: Vec<LayerId>) -> LayerPanelEntry {
+pub fn layer_panel_entry(layer_data: &mut LayerData, layer: &mut Layer, path: Vec<LayerId>) -> LayerPanelEntry {
+	let blend_mode = layer.blend_mode.clone();
 	let layer_type: LayerType = (&layer.data).into();
 	let name = layer.name.clone().unwrap_or_else(|| format!("Unnamed {}", layer_type));
 	let arr = layer.current_bounding_box().unwrap_or([DVec2::ZERO, DVec2::ZERO]);
 	let arr = arr.iter().map(|x| (*x).into()).collect::<Vec<(f64, f64)>>();
+
+	if layer.cache_dirty {
+		layer.render();
+	}
+
 	let thumbnail = if let [(x_min, y_min), (x_max, y_max)] = arr.as_slice() {
 		format!(
 			r#"<svg xmlns="http://www.w3.org/2000/svg" viewBox="{} {} {} {}">{}</svg>"#,
@@ -50,14 +56,16 @@ pub fn layer_panel_entry(layer_data: &mut LayerData, layer: &Layer, path: Vec<La
 			y_min,
 			x_max - x_min,
 			y_max - y_min,
-			layer.cache.clone()
+			layer.thumbnail_cache.clone()
 		)
 	} else {
 		String::new()
 	};
+
 	LayerPanelEntry {
 		name,
 		visible: layer.visible,
+		blend_mode,
 		layer_type,
 		layer_data: *layer_data,
 		path,
@@ -73,16 +81,17 @@ impl Document {
 	/// Returns a list of `LayerPanelEntry`s intended for display purposes. These don't contain
 	/// any actual data, but rather metadata such as visibility and names of the layers.
 	pub fn layer_panel(&mut self, path: &[LayerId]) -> Result<Vec<LayerPanelEntry>, EditorError> {
-		let folder = self.document.document_folder(path)?;
+		let folder = self.document.document_folder_mut(path)?;
+		let ids = folder.as_folder()?.layer_ids.clone();
 		let self_layer_data = &mut self.layer_data;
 		let entries = folder
-			.as_folder()?
-			.layers()
-			.iter()
-			.zip(folder.as_folder()?.layer_ids.iter())
+			.as_folder_mut()?
+			.layers_mut()
+			.iter_mut()
+			.zip(ids)
 			.rev()
 			.map(|(layer, id)| {
-				let path = [path, &[*id]].concat();
+				let path = [path, &[id]].concat();
 				layer_panel_entry(layer_data(self_layer_data, &path), layer, path)
 			})
 			.collect();

core/editor/src/document/document_message_handler.rs

@@ -3,6 +3,7 @@ use crate::{
 	consts::{MOUSE_ZOOM_RATE, VIEWPORT_SCROLL_RATE, VIEWPORT_ZOOM_SCALE_MAX, VIEWPORT_ZOOM_SCALE_MIN, WHEEL_ZOOM_RATE},
 	input::{mouse::ViewportPosition, InputPreprocessor},
 };
+use document_core::layers::BlendMode;
 use document_core::layers::Layer;
 use document_core::{DocumentResponse, LayerId, Operation as DocumentOperation};
 use glam::{DAffine2, DVec2};
@@ -24,6 +25,7 @@ pub enum DocumentMessage {
 	DeleteSelectedLayers,
 	DuplicateSelectedLayers,
 	CopySelectedLayers,
+	SetBlendModeForSelectedLayers(BlendMode),
 	PasteLayers,
 	AddFolder(Vec<LayerId>),
 	RenameLayer(Vec<LayerId>, String),
@@ -342,6 +344,13 @@ impl MessageHandler<DocumentMessage, &InputPreprocessor> for DocumentMessageHand
 				}
 				.into(),
 			),
+			SetBlendModeForSelectedLayers(blend_mode) => {
+				let active_document = self.active_document();
+
+				for path in active_document.layer_data.iter().filter_map(|(path, data)| data.selected.then(|| path)) {
+					responses.push_back(DocumentOperation::SetLayerBlendMode { path: path.clone(), blend_mode }.into());
+				}
+			}
 			ToggleLayerVisibility(path) => {
 				responses.push_back(DocumentOperation::ToggleVisibility { path }.into());
 			}

core/editor/src/frontend/layer_panel.rs

@@ -1,5 +1,8 @@
 use crate::document::LayerData;
-use document_core::{layers::LayerDataTypes, LayerId};
+use document_core::{
+	layers::{BlendMode, LayerDataTypes},
+	LayerId,
+};
 use serde::{Deserialize, Serialize};
 use std::fmt;
 
@@ -7,6 +10,7 @@ use std::fmt;
 pub struct LayerPanelEntry {
 	pub name: String,
 	pub visible: bool,
+	pub blend_mode: BlendMode,
 	pub layer_type: LayerType,
 	pub layer_data: LayerData,
 	pub path: Vec<LayerId>,

core/editor/src/tool/tool_options.rs

@@ -1,5 +1,6 @@
 use serde::{Deserialize, Serialize};
 
+// TODO: Rename this `ToolOption` to not be plural in a separate commit (together with `enum LayerDataTypes`)
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Serialize, Deserialize)]
 pub enum ToolOptions {
 	Select { append_mode: SelectAppendMode },