Change flipping to use the joint bounding box of the selection (#323)

* Change flipping to use the joint bounding box

* Fix minor untested changes

* Replace unwrap with question mark

core/editor/src/document/document_message_handler.rs

@@ -58,7 +58,7 @@ pub enum DocumentMessage {
 	WheelCanvasZoom,
 	SetCanvasRotation(f64),
 	NudgeSelectedLayers(f64, f64),
-	FlipLayer(Vec<LayerId>, bool, bool),
+	FlipSelectedLayers(FlipAxis),
 	AlignSelectedLayers(AlignAxis, AlignAggregate),
 	DragLayer(Vec<LayerId>, DVec2),
 	MoveSelectedLayersTo { path: Vec<LayerId>, insert_index: isize },
@@ -66,6 +66,12 @@ pub enum DocumentMessage {
 	SetLayerTranslation(Vec<LayerId>, Option<f64>, Option<f64>),
 }
 
+#[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
+pub enum FlipAxis {
+	X,
+	Y,
+}
+
 #[derive(PartialEq, Clone, Debug, Serialize, Deserialize)]
 pub enum AlignAxis {
 	X,
@@ -652,13 +658,52 @@ impl MessageHandler<DocumentMessage, &InputPreprocessor> for DocumentMessageHand
 					}
 				}
 			}
-			FlipLayer(path, flip_horizontal, flip_vertical) => {
-				if let Ok(layer) = self.active_document_mut().document.layer_mut(&path) {
-					let scale = DVec2::new(if flip_horizontal { -1. } else { 1. }, if flip_vertical { -1. } else { 1. });
+			FlipSelectedLayers(axis) => {
+				// TODO: Handle folder nested transforms with the transforms API
+				let selected_paths = self.selected_layers_sorted();
+				if selected_paths.is_empty() {
+					return;
+				}
+
+				let selected_layers = selected_paths.iter().filter_map(|path| {
+					let layer = self.active_document().document.layer(path).ok()?;
+					// TODO: Refactor with `reduce` and `merge_bounding_boxes` once the latter is added
+					let (min, max) = {
+						let bounding_box = layer.bounding_box(layer.transform, layer.style)?;
+						match axis {
+							FlipAxis::X => (bounding_box[0].x, bounding_box[1].x),
+							FlipAxis::Y => (bounding_box[0].y, bounding_box[1].y),
+						}
+					};
+					Some((path.clone(), (min, max)))
+				});
+
+				let (min, max) = selected_layers
+					.clone()
+					.map(|(_, extrema)| extrema)
+					.reduce(|(min_a, max_a), (min_b, max_b)| (min_a.min(min_b), max_a.max(max_b)))
+					.unwrap();
+				let middle = (min + max) / 2.;
+
+				for (path, _) in selected_layers {
+					let layer = self.active_document().document.layer(&path).unwrap();
+					let mut transform = layer.transform;
+					let scale = match axis {
+						FlipAxis::X => DVec2::new(-1., 1.),
+						FlipAxis::Y => DVec2::new(1., -1.),
+					};
+					transform = transform * DAffine2::from_scale(scale);
+
+					let coord = match axis {
+						FlipAxis::X => &mut transform.translation.x,
+						FlipAxis::Y => &mut transform.translation.y,
+					};
+					*coord = *coord - 2. * (*coord - middle);
+
 					responses.push_back(
 						DocumentOperation::SetLayerTransform {
 							path,
-							transform: (layer.transform * DAffine2::from_scale(scale)).to_cols_array(),
+							transform: transform.to_cols_array(),
 						}
 						.into(),
 					);

core/editor/src/document/mod.rs

@@ -5,4 +5,4 @@ mod document_message_handler;
 pub use document_file::{Document, LayerData};
 
 #[doc(inline)]
-pub use document_message_handler::{AlignAggregate, AlignAxis, DocumentMessage, DocumentMessageDiscriminant, DocumentMessageHandler};
+pub use document_message_handler::{AlignAggregate, AlignAxis, DocumentMessage, DocumentMessageDiscriminant, DocumentMessageHandler, FlipAxis};

core/editor/src/tool/tools/select.rs

@@ -10,7 +10,7 @@ use crate::input::{mouse::ViewportPosition, InputPreprocessor};
 use crate::tool::{DocumentToolData, Fsm, ToolActionHandlerData};
 use crate::{
 	consts::SELECTION_TOLERANCE,
-	document::{AlignAggregate, AlignAxis, Document},
+	document::{AlignAggregate, AlignAxis, Document, FlipAxis},
 	message_prelude::*,
 };
 
@@ -173,18 +173,12 @@ impl Fsm for SelectToolFsmState {
 					self
 				}
 				(_, FlipHorizontal) => {
-					let selected_layers = document.layer_data.iter().filter_map(|(path, data)| data.selected.then(|| path.clone()));
-					for path in selected_layers {
-						responses.push_back(DocumentMessage::FlipLayer(path, true, false).into());
-					}
+					responses.push_back(DocumentMessage::FlipSelectedLayers(FlipAxis::X).into());
 
 					self
 				}
 				(_, FlipVertical) => {
-					let selected_layers = document.layer_data.iter().filter_map(|(path, data)| data.selected.then(|| path.clone()));
-					for path in selected_layers {
-						responses.push_back(DocumentMessage::FlipLayer(path, false, true).into());
-					}
+					responses.push_back(DocumentMessage::FlipSelectedLayers(FlipAxis::Y).into());
 
 					self
 				}