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/tools/shared/mod.rs

@@ -0,0 +1 @@
+pub mod resize;

editor/src/viewport_tools/tools/shared/resize.rs

@@ -0,0 +1,57 @@
+use crate::document::DocumentMessageHandler;
+use crate::input::keyboard::Key;
+use crate::input::mouse::ViewportPosition;
+use crate::input::InputPreprocessorMessageHandler;
+use crate::message_prelude::*;
+use crate::viewport_tools::snapping::SnapHandler;
+
+use graphene::Operation;
+
+use glam::{DAffine2, DVec2, Vec2Swizzles};
+
+#[derive(Clone, Debug, Default)]
+pub struct Resize {
+	pub drag_start: ViewportPosition,
+	pub path: Option<Vec<LayerId>>,
+	snap_handler: SnapHandler,
+}
+impl Resize {
+	/// Starts a resize, assigning the snap targets and snapping the starting position.
+	pub fn start(&mut self, document: &DocumentMessageHandler, mouse_position: DVec2) {
+		let layers = document.all_layers_sorted();
+		self.snap_handler.start_snap(document, layers, &[]);
+		self.drag_start = self.snap_handler.snap_position(document, mouse_position);
+	}
+
+	pub fn calculate_transform(&self, document: &DocumentMessageHandler, center: Key, lock_ratio: Key, ipp: &InputPreprocessorMessageHandler) -> Option<Message> {
+		if let Some(path) = &self.path {
+			let mut start = self.drag_start;
+
+			let stop = self.snap_handler.snap_position(document, ipp.mouse.position);
+
+			let mut size = stop - start;
+			if ipp.keyboard.get(lock_ratio as usize) {
+				size = size.abs().max(size.abs().yx()) * size.signum();
+			}
+			if ipp.keyboard.get(center as usize) {
+				start -= size;
+				size *= 2.;
+			}
+
+			Some(
+				Operation::SetLayerTransformInViewport {
+					path: path.to_vec(),
+					transform: DAffine2::from_scale_angle_translation(size, 0., start).to_cols_array(),
+				}
+				.into(),
+			)
+		} else {
+			None
+		}
+	}
+
+	pub fn cleanup(&mut self) {
+		self.snap_handler.cleanup();
+		self.path = None;
+	}
+}