Enhance the Navigate Tool zoom behavior (#461)

* Snap zoom

* Navigate zoom from centre

* Ctrl to snap zoom in navigate

* Use ctrl for global snap rotate

* Fix the rotation input on snap rotate

* Update hint to use ctrl

* Fix mouse centre on drag

* Click to zoom in

* Clean up centre zoom

* Update user input hints; tweak some variable names for clarity and standardization

Co-authored-by: Keavon Chambers <[email protected]>

Author: 0HyperCube

editor/src/document/document_file.rs

@@ -859,9 +859,8 @@ impl MessageHandler<DocumentMessage, &InputPreprocessor> for DocumentMessageHand
 				);
 				responses.push_back(ArtboardMessage::RenderArtboards.into());
 
-				let document_transform = &self.movement_handler;
-
-				let scale = 0.5 + ASYMPTOTIC_EFFECT + document_transform.scale * SCALE_EFFECT;
+				let document_transform_scale = self.movement_handler.snapped_scale();
+				let scale = 0.5 + ASYMPTOTIC_EFFECT + document_transform_scale * SCALE_EFFECT;
 				let viewport_size = ipp.viewport_bounds.size();
 				let viewport_mid = ipp.viewport_bounds.center();
 				let [bounds1, bounds2] = self.graphene_document.visible_layers_bounding_box().unwrap_or([viewport_mid; 2]);
@@ -872,9 +871,9 @@ impl MessageHandler<DocumentMessage, &InputPreprocessor> for DocumentMessageHand
 				let scrollbar_multiplier = bounds_length - viewport_size;
 				let scrollbar_size = viewport_size / bounds_length;
 
-				let log = document_transform.scale.log2();
+				let log = document_transform_scale.log2();
 				let ruler_interval = if log < 0. { 100. * 2_f64.powf(-log.ceil()) } else { 100. / 2_f64.powf(log.ceil()) };
-				let ruler_spacing = ruler_interval * document_transform.scale;
+				let ruler_spacing = ruler_interval * document_transform_scale;
 
 				let ruler_origin = self.graphene_document.root.transform.transform_point2(DVec2::ZERO);