Minimum viewport scale cover when zooming (#1282)

* Minimum viewport scale cover

* Update const name

editor/src/consts.rs

@@ -5,6 +5,7 @@ pub const VIEWPORT_ZOOM_WHEEL_RATE: f64 = (1. / 600.) * 3.;
 pub const VIEWPORT_ZOOM_MOUSE_RATE: f64 = 1. / 400.;
 pub const VIEWPORT_ZOOM_SCALE_MIN: f64 = 0.000_000_1;
 pub const VIEWPORT_ZOOM_SCALE_MAX: f64 = 10_000.;
+pub const VIEWPORT_ZOOM_MIN_FRACTION_COVER: f64 = 0.01;
 pub const VIEWPORT_ZOOM_LEVELS: [f64; 74] = [
 	0.0001, 0.000125, 0.00016, 0.0002, 0.00025, 0.00032, 0.0004, 0.0005, 0.00064, 0.0008, 0.001, 0.0016, 0.002, 0.0025, 0.0032, 0.004, 0.005, 0.0064, 0.008, 0.01, 0.01125, 0.015, 0.02, 0.025, 0.03,
 	0.04, 0.05, 0.06, 0.08, 0.1, 0.125, 0.15, 0.2, 0.25, 0.33333333, 0.4, 0.5, 0.66666666, 0.8, 1., 1.25, 1.6, 2., 2.5, 3.2, 4., 5., 6.4, 8., 10., 12.5, 16., 20., 25., 32., 40., 50., 64., 80., 100.,

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

@@ -181,8 +181,12 @@ impl MessageHandler<DocumentMessage, (u64, &InputPreprocessorMessageHandler, &Pe
 			}
 			#[remain::unsorted]
 			Navigation(message) => {
-				self.navigation_handler
+				let document_bounds = self.document_bounds(&render_data);
-					.process_message(message, responses, (&self.document_legacy, ipp, self.selected_visible_layers_bounding_box(&render_data)));
+				self.navigation_handler.process_message(
+					message,
+					responses,
+					(&self.document_legacy, document_bounds, ipp, self.selected_visible_layers_bounding_box(&render_data)),
+				);
 			}
 			#[remain::unsorted]
 			Overlays(message) => {

editor/src/messages/portfolio/document/navigation/navigation_message_handler.rs

@@ -1,6 +1,6 @@
 use crate::consts::{
-	VIEWPORT_ROTATE_SNAP_INTERVAL, VIEWPORT_SCROLL_RATE, VIEWPORT_ZOOM_LEVELS, VIEWPORT_ZOOM_MOUSE_RATE, VIEWPORT_ZOOM_SCALE_MAX, VIEWPORT_ZOOM_SCALE_MIN, VIEWPORT_ZOOM_TO_FIT_PADDING_SCALE_FACTOR,
+	VIEWPORT_ROTATE_SNAP_INTERVAL, VIEWPORT_SCROLL_RATE, VIEWPORT_ZOOM_LEVELS, VIEWPORT_ZOOM_MIN_FRACTION_COVER, VIEWPORT_ZOOM_MOUSE_RATE, VIEWPORT_ZOOM_SCALE_MAX, VIEWPORT_ZOOM_SCALE_MIN,
-	VIEWPORT_ZOOM_WHEEL_RATE,
+	VIEWPORT_ZOOM_TO_FIT_PADDING_SCALE_FACTOR, VIEWPORT_ZOOM_WHEEL_RATE,
 };
 use crate::messages::frontend::utility_types::MouseCursorIcon;
 use crate::messages::input_mapper::utility_types::input_keyboard::{Key, KeysGroup};
@@ -51,11 +51,18 @@ impl Default for NavigationMessageHandler {
 	}
 }
 
-impl MessageHandler<NavigationMessage, (&Document, &InputPreprocessorMessageHandler, Option<[DVec2; 2]>)> for NavigationMessageHandler {
+impl MessageHandler<NavigationMessage, (&Document, Option<[DVec2; 2]>, &InputPreprocessorMessageHandler, Option<[DVec2; 2]>)> for NavigationMessageHandler {
 	#[remain::check]
-	fn process_message(&mut self, message: NavigationMessage, responses: &mut VecDeque<Message>, (document, ipp, selection_bounds): (&Document, &InputPreprocessorMessageHandler, Option<[DVec2; 2]>)) {
+	fn process_message(
+		&mut self,
+		message: NavigationMessage,
+		responses: &mut VecDeque<Message>,
+		(document, document_bounds, ipp, selection_bounds): (&Document, Option<[DVec2; 2]>, &InputPreprocessorMessageHandler, Option<[DVec2; 2]>),
+	) {
 		use NavigationMessage::*;
 
+		let old_zoom = self.zoom;
+
 		#[remain::sorted]
 		match message {
 			DecreaseCanvasZoom { center_on_mouse } => {
@@ -157,6 +164,8 @@ impl MessageHandler<NavigationMessage, (&Document, &InputPreprocessorMessageHand
 					let amount = 1. + difference * VIEWPORT_ZOOM_MOUSE_RATE;
 
 					self.zoom *= amount;
+					self.zoom *= Self::clamp_zoom(self.zoom, document_bounds, old_zoom, ipp);
+
 					if let Some(mouse) = zoom_from_viewport {
 						let zoom_factor = self.snapped_scale() / zoom_start;
 
@@ -192,6 +201,7 @@ impl MessageHandler<NavigationMessage, (&Document, &InputPreprocessorMessageHand
 			}
 			SetCanvasZoom { zoom_factor } => {
 				self.zoom = zoom_factor.clamp(VIEWPORT_ZOOM_SCALE_MIN, VIEWPORT_ZOOM_SCALE_MAX);
+				self.zoom *= Self::clamp_zoom(self.zoom, document_bounds, old_zoom, ipp);
 				responses.add(BroadcastEvent::DocumentIsDirty);
 				responses.add(DocumentMessage::DirtyRenderDocumentInOutlineView);
 				responses.add(PortfolioMessage::UpdateDocumentWidgets);
@@ -243,7 +253,8 @@ impl MessageHandler<NavigationMessage, (&Document, &InputPreprocessorMessageHand
 				let mut zoom_factor = 1. + scroll.abs() * VIEWPORT_ZOOM_WHEEL_RATE;
 				if ipp.mouse.scroll_delta.y > 0 {
 					zoom_factor = 1. / zoom_factor
-				};
+				}
+				zoom_factor *= Self::clamp_zoom(self.zoom * zoom_factor, document_bounds, old_zoom, ipp);
 
 				responses.add(self.center_zoom(ipp.viewport_bounds.size(), zoom_factor, ipp.mouse.position));
 				responses.add(SetCanvasZoom { zoom_factor: self.zoom * zoom_factor });
@@ -351,4 +362,15 @@ impl NavigationMessageHandler {
 
 		NavigationMessage::TranslateCanvas { delta }.into()
 	}
+
+	pub fn clamp_zoom(zoom: f64, document_bounds: Option<[DVec2; 2]>, old_zoom: f64, ipp: &InputPreprocessorMessageHandler) -> f64 {
+		let document_size = (document_bounds.map(|[min, max]| max - min).unwrap_or_default() / old_zoom) * zoom;
+		let scale_factor = (document_size / ipp.viewport_bounds.size()).max_element();
+
+		if scale_factor > f64::EPSILON * 100. && scale_factor.is_finite() && scale_factor < VIEWPORT_ZOOM_MIN_FRACTION_COVER {
+			VIEWPORT_ZOOM_MIN_FRACTION_COVER / scale_factor
+		} else {
+			1.
+		}
+	}
 }