Massively reorganize and clean up the whole Rust codebase (#478)

* Massively reorganize and clean up the whole Rust codebase

* Additional changes during code review

editor/src/viewport_tools/snapping.rs

@@ -0,0 +1,106 @@
+use crate::consts::SNAP_TOLERANCE;
+use crate::document::DocumentMessageHandler;
+
+use graphene::LayerId;
+
+use glam::DVec2;
+
+#[derive(Debug, Clone, Default)]
+pub struct SnapHandler {
+	snap_targets: Option<(Vec<f64>, Vec<f64>)>,
+}
+
+impl SnapHandler {
+	/// Gets a list of snap targets for the X and Y axes in Viewport coords for the target layers (usually all layers or all non-selected layers.)
+	/// This should be called at the start of a drag.
+	pub fn start_snap(&mut self, document_message_handler: &DocumentMessageHandler, target_layers: Vec<&[LayerId]>, ignore_layers: &[Vec<LayerId>]) {
+		if document_message_handler.snapping_enabled {
+			// Could be made into sorted Vec or a HashSet for more performant lookups.
+			self.snap_targets = Some(
+				target_layers
+					.iter()
+					.filter(|path| !ignore_layers.iter().any(|layer| layer.as_slice() == **path))
+					.filter_map(|path| document_message_handler.graphene_document.viewport_bounding_box(path).ok()?)
+					.flat_map(|[bound1, bound2]| [bound1, bound2, ((bound1 + bound2) / 2.)])
+					.map(|vec| vec.into())
+					.unzip(),
+			);
+		}
+	}
+
+	/// Finds the closest snap from an array of layers to the specified snap targets in viewport coords.
+	/// Returns 0 for each axis that there is no snap less than the snap tolerance.
+	pub fn snap_layers(&self, document_message_handler: &DocumentMessageHandler, selected_layers: &[Vec<LayerId>], mouse_delta: DVec2) -> DVec2 {
+		if document_message_handler.snapping_enabled {
+			if let Some((targets_x, targets_y)) = &self.snap_targets {
+				let (snap_x, snap_y): (Vec<f64>, Vec<f64>) = selected_layers
+					.iter()
+					.filter_map(|path| document_message_handler.graphene_document.viewport_bounding_box(path).ok()?)
+					.flat_map(|[bound1, bound2]| [bound1, bound2, (bound1 + bound2) / 2.])
+					.map(|vec| vec.into())
+					.unzip();
+
+				let closest_move = DVec2::new(
+					targets_x
+						.iter()
+						.flat_map(|target| snap_x.iter().map(move |snap| target - mouse_delta.x - snap))
+						.min_by(|a, b| a.abs().partial_cmp(&b.abs()).expect("Could not compare document bounds."))
+						.unwrap_or(0.),
+					targets_y
+						.iter()
+						.flat_map(|target| snap_y.iter().map(move |snap| target - mouse_delta.y - snap))
+						.min_by(|a, b| a.abs().partial_cmp(&b.abs()).expect("Could not compare document bounds."))
+						.unwrap_or(0.),
+				);
+
+				// Clamp, do not move if over snap tolerance
+				DVec2::new(
+					if closest_move.x.abs() > SNAP_TOLERANCE { 0. } else { closest_move.x },
+					if closest_move.y.abs() > SNAP_TOLERANCE { 0. } else { closest_move.y },
+				)
+			} else {
+				DVec2::ZERO
+			}
+		} else {
+			DVec2::ZERO
+		}
+	}
+
+	/// Handles snapping of a viewport position, returning another viewport position.
+	pub fn snap_position(&self, document_message_handler: &DocumentMessageHandler, position_viewport: DVec2) -> DVec2 {
+		if document_message_handler.snapping_enabled {
+			if let Some((targets_x, targets_y)) = &self.snap_targets {
+				// For each list of snap targets, find the shortest distance to move the point to that target.
+				let closest_move = DVec2::new(
+					targets_x
+						.iter()
+						.map(|x| (x - position_viewport.x))
+						.min_by(|a, b| a.abs().partial_cmp(&b.abs()).expect("Could not compare document bounds."))
+						.unwrap_or(0.),
+					targets_y
+						.iter()
+						.map(|y| (y - position_viewport.y))
+						.min_by(|a, b| a.abs().partial_cmp(&b.abs()).expect("Could not compare document bounds."))
+						.unwrap_or(0.),
+				);
+
+				// Do not move if over snap tolerance
+				let clamped_closest_move = DVec2::new(
+					if closest_move.x.abs() > SNAP_TOLERANCE { 0. } else { closest_move.x },
+					if closest_move.y.abs() > SNAP_TOLERANCE { 0. } else { closest_move.y },
+				);
+
+				position_viewport + clamped_closest_move
+			} else {
+				position_viewport
+			}
+		} else {
+			position_viewport
+		}
+	}
+
+	/// Removes snap target data. Call this when snapping is done.
+	pub fn cleanup(&mut self) {
+		self.snap_targets = None;
+	}
+}