Fix viewport culling with nested layers (#939)

* Fix viewport culling with nested layers

* Clean up naming

document-legacy/src/layers/folder_layer.rs

@@ -6,7 +6,6 @@ use crate::{DocumentError, LayerId};
 
 use glam::DVec2;
 use serde::{Deserialize, Serialize};
-use std::fmt::Write;
 
 /// A layer that encapsulates other layers, including potentially more folders.
 /// The contained layers are rendered in the same order they are
@@ -22,10 +21,14 @@ pub struct FolderLayer {
 }
 
 impl LayerData for FolderLayer {
-	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData) -> bool {
+		let mut any_child_requires_refresh = false;
 		for layer in &mut self.layers {
-			let _ = writeln!(svg, "{}", layer.render(transforms, svg_defs, render_data));
+			let (svg_value, requires_refresh) = layer.render(transforms, svg_defs, render_data);
+			*svg += svg_value;
+			any_child_requires_refresh = any_child_requires_refresh || requires_refresh;
 		}
+		!any_child_requires_refresh
 	}
 
 	fn intersects_quad(&self, quad: Quad, path: &mut Vec<LayerId>, intersections: &mut Vec<Vec<LayerId>>, font_cache: &FontCache) {

document-legacy/src/layers/image_layer.rs

@@ -23,13 +23,13 @@ pub struct ImageLayer {
 }
 
 impl LayerData for ImageLayer {
-	fn render(&mut self, svg: &mut String, _svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, _svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) -> bool {
 		let transform = self.transform(transforms, render_data.view_mode);
 		let inverse = transform.inverse();
 
 		if !inverse.is_finite() {
 			let _ = write!(svg, "<!-- SVG shape has an invalid transform -->");
-			return;
+			return false;
 		}
 
 		let _ = writeln!(svg, r#"<g transform="matrix("#);
@@ -53,6 +53,8 @@ impl LayerData for ImageLayer {
 			self.blob_url.as_ref().unwrap_or(&String::new())
 		);
 		let _ = svg.write_str("</g>");
+
+		false
 	}
 
 	fn bounding_box(&self, transform: glam::DAffine2, _font_cache: &FontCache) -> Option<[DVec2; 2]> {

document-legacy/src/layers/layer_info.rs

@@ -119,7 +119,7 @@ impl<'a> TryFrom<&'a Layer> for &'a Subpath {
 
 /// Defines shared behavior for every layer type.
 pub trait LayerData {
-	/// Render the layer as an SVG tag to a given string.
+	/// Render the layer as an SVG tag to a given string, returning a boolean to indicate if a redraw is required next frame.
 	///
 	/// # Example
 	/// ```
@@ -143,7 +143,7 @@ pub trait LayerData {
 	///     </g>"
 	/// );
 	/// ```
-	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData);
+	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData) -> bool;
 
 	/// Determine the layers within this layer that intersect a given quad.
 	/// # Example
@@ -190,7 +190,7 @@ pub trait LayerData {
 }
 
 impl LayerData for LayerDataType {
-	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<glam::DAffine2>, render_data: RenderData) -> bool {
 		self.inner_mut().render(svg, svg_defs, transforms, render_data)
 	}
 
@@ -304,12 +304,15 @@ impl Layer {
 		LayerIter { stack: vec![self] }
 	}
 
-	pub fn render(&mut self, transforms: &mut Vec<DAffine2>, svg_defs: &mut String, render_data: RenderData) -> &str {
+	/// Renders the layer, returning the result and if a redraw is required
+	pub fn render(&mut self, transforms: &mut Vec<DAffine2>, svg_defs: &mut String, render_data: RenderData) -> (&str, bool) {
 		if !self.visible {
-			return "";
+			return ("", false);
 		}
 
 		transforms.push(self.transform);
+
+		// Skip rendering if outside the viewport bounds
 		if let Some(viewport_bounds) = render_data.culling_bounds {
 			if let Some(bounding_box) = self
 				.data
@@ -321,15 +324,17 @@ impl Layer {
 					transforms.pop();
 					self.cache.clear();
 					self.cache_dirty = true;
-					return "";
+					return ("", true);
 				}
 			}
 		}
 
+		let mut requires_redraw = false;
+
 		if self.cache_dirty {
 			self.thumbnail_cache.clear();
 			self.svg_defs_cache.clear();
-			self.data.render(&mut self.thumbnail_cache, &mut self.svg_defs_cache, transforms, render_data);
+			requires_redraw = self.data.render(&mut self.thumbnail_cache, &mut self.svg_defs_cache, transforms, render_data);
 
 			self.cache.clear();
 			let _ = writeln!(self.cache, r#"<g transform="matrix("#);
@@ -346,10 +351,16 @@ impl Layer {
 
 			self.cache_dirty = false;
 		}
+
 		transforms.pop();
 		svg_defs.push_str(&self.svg_defs_cache);
 
-		self.cache.as_str()
+		// If a redraw is required then set the cache to dirty.
+		if requires_redraw {
+			self.cache_dirty = true;
+		}
+
+		(self.cache.as_str(), requires_redraw)
 	}
 
 	pub fn intersects_quad(&self, quad: Quad, path: &mut Vec<LayerId>, intersections: &mut Vec<Vec<LayerId>>, font_cache: &FontCache) {

document-legacy/src/layers/nodegraph_layer.rs

@@ -33,7 +33,7 @@ pub struct ImageData {
 }
 
 impl LayerData for NodeGraphFrameLayer {
-	fn render(&mut self, svg: &mut String, _svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, _svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) -> bool {
 		let transform = self.transform(transforms, render_data.view_mode);
 		let inverse = transform.inverse();
 
@@ -41,7 +41,7 @@ impl LayerData for NodeGraphFrameLayer {
 
 		if !inverse.is_finite() {
 			let _ = write!(svg, "<!-- SVG shape has an invalid transform -->");
-			return;
+			return false;
 		}
 
 		let _ = writeln!(svg, r#"<g transform="matrix("#);
@@ -75,6 +75,8 @@ impl LayerData for NodeGraphFrameLayer {
 		);
 
 		let _ = svg.write_str(r#"</g>"#);
+
+		false
 	}
 
 	fn bounding_box(&self, transform: glam::DAffine2, _font_cache: &FontCache) -> Option<[DVec2; 2]> {

document-legacy/src/layers/shape_layer.rs

@@ -27,7 +27,7 @@ pub struct ShapeLayer {
 }
 
 impl LayerData for ShapeLayer {
-	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) -> bool {
 		let mut subpath = self.shape.clone();
 
 		let layer_bounds = subpath.bounding_box().unwrap_or_default();
@@ -36,7 +36,7 @@ impl LayerData for ShapeLayer {
 		let inverse = transform.inverse();
 		if !inverse.is_finite() {
 			let _ = write!(svg, "<!-- SVG shape has an invalid transform -->");
-			return;
+			return false;
 		}
 		subpath.apply_affine(transform);
 
@@ -54,6 +54,8 @@ impl LayerData for ShapeLayer {
 			self.style.render(render_data.view_mode, svg_defs, transform, layer_bounds, transformed_bounds)
 		);
 		let _ = svg.write_str("</g>");
+
+		false
 	}
 
 	fn bounding_box(&self, transform: glam::DAffine2, _font_cache: &FontCache) -> Option<[DVec2; 2]> {

document-legacy/src/layers/text_layer.rs

@@ -34,13 +34,13 @@ pub struct TextLayer {
 }
 
 impl LayerData for TextLayer {
-	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) {
+	fn render(&mut self, svg: &mut String, svg_defs: &mut String, transforms: &mut Vec<DAffine2>, render_data: RenderData) -> bool {
 		let transform = self.transform(transforms, render_data.view_mode);
 		let inverse = transform.inverse();
 
 		if !inverse.is_finite() {
 			let _ = write!(svg, "<!-- SVG shape has an invalid transform -->");
-			return;
+			return false;
 		}
 
 		let _ = writeln!(svg, r#"<g transform="matrix("#);
@@ -85,6 +85,8 @@ impl LayerData for TextLayer {
 			);
 		}
 		let _ = svg.write_str("</g>");
+
+		false
 	}
 
 	fn bounding_box(&self, transform: glam::DAffine2, font_cache: &FontCache) -> Option<[DVec2; 2]> {