Add scaling by nudging with the Alt key (#990)

* update current progress working on issue#930

* Issue#930: features other than local scaling implemented

* runs cargo fmt

* issue930: implemented features(local scaling disregraded) update: merged master branch and solved coflicts

* combined scaling and nudge feature

* combined scaling and nudge feature

* resolved issues when trying to scale below 1. pixel and other comments

* reduce code complexity

* reduce complexity

* Improve code readability/idiomaticness

* Add hints

---------

Co-authored-by: Shiro <shiro@damedane.local>
Co-authored-by: Keavon Chambers <keavon@keavon.com>

editor/src/messages/portfolio/document/document_message.rs

@@ -1,4 +1,5 @@
 use crate::messages::frontend::utility_types::{ExportBounds, FileType};
+use crate::messages::input_mapper::utility_types::input_keyboard::Key;
 use crate::messages::portfolio::document::utility_types::layer_panel::LayerMetadata;
 use crate::messages::portfolio::document::utility_types::misc::{AlignAggregate, AlignAxis, FlipAxis};
 use crate::messages::prelude::*;
@@ -114,6 +115,8 @@ pub enum DocumentMessage {
 	NudgeSelectedLayers {
 		delta_x: f64,
 		delta_y: f64,
+		resize: Key,
+		resize_opposite_corner: Key,
 	},
 	PasteImage {
 		image: Image,

editor/src/messages/portfolio/document/document_message_handler.rs

@@ -551,14 +551,45 @@ impl MessageHandler<DocumentMessage, (u64, &InputPreprocessorMessageHandler, &Pe
 					.into(),
 				);
 			}
-			NudgeSelectedLayers { delta_x, delta_y } => {
+			NudgeSelectedLayers {
+				delta_x,
+				delta_y,
+				resize,
+				resize_opposite_corner,
+			} => {
 				self.backup(responses);
+
+				let opposite_corner = ipp.keyboard.key(resize_opposite_corner);
+				let sign = if opposite_corner { -1. } else { 1. };
+
 				for path in self.selected_layers().map(|path| path.to_vec()) {
-					let operation = DocumentOperation::TransformLayerInViewport {
-						path,
-						transform: DAffine2::from_translation((delta_x, delta_y).into()).to_cols_array(),
+					// Nudge translation
+					let transform = if !ipp.keyboard.key(resize) {
+						Some(DAffine2::from_translation((delta_x, delta_y).into()).to_cols_array())
+					}
+					// Nudge resize
+					else {
+						self.document_legacy
+							.viewport_bounding_box(&path, &render_data)
+							.ok()
+							.flatten()
+							.map(|[existing_top_left, existing_bottom_right]| {
+								let width = existing_bottom_right.x - existing_top_left.x;
+								let height = existing_bottom_right.y - existing_top_left.y;
+
+								let new_width = (width + delta_x * sign).max(1.);
+								let new_height = (height + delta_y * sign).max(1.);
+
+								let offset = DAffine2::from_translation(if opposite_corner { -existing_bottom_right } else { -existing_top_left });
+								let scale = DAffine2::from_scale((new_width / width, new_height / height).into());
+
+								(offset.inverse() * scale * offset).to_cols_array()
+							})
 					};
-					responses.push_back(operation.into());
+
+					if let Some(transform) = transform {
+						responses.push_back(DocumentOperation::TransformLayerInViewport { path, transform }.into());
+					}
 				}
 				responses.push_back(BroadcastEvent::DocumentIsDirty.into());
 			}