From c05c93c8a27703bcb515a10a3a45a0020e2d73d2 Mon Sep 17 00:00:00 2001
From: Linda Zheng <thelindazheng@gmail.com>
Date: Wed, 27 Jul 2022 22:27:50 -0400
Subject: [PATCH] Implement bounding box function for bezier-rs (#726)

* Implement bounding box function for bezier-rs

* Fix eslint errors

Co-authored-by: Linda Zheng <linda-zheng@users.noreply.github.com>

* Rename bbox to bounding_box

* Address Keavon's comments

* Fix eslint issue

Co-authored-by: Hannah Li <hannahli2010@gmail.com>
Co-authored-by: Linda Zheng <linda-zheng@users.noreply.github.com>
---
 bezier-rs/docs/interactive-docs/src/App.vue   | 13 ++++++++++++
 .../docs/interactive-docs/wasm/src/lib.rs     | 21 ++++++++++++-------
 bezier-rs/lib/src/lib.rs                      | 20 ++++++++++++++++++
 3 files changed, 46 insertions(+), 8 deletions(-)

diff --git a/bezier-rs/docs/interactive-docs/src/App.vue b/bezier-rs/docs/interactive-docs/src/App.vue
index 9340d028..9112b841 100644
--- a/bezier-rs/docs/interactive-docs/src/App.vue
+++ b/bezier-rs/docs/interactive-docs/src/App.vue
@@ -356,6 +356,19 @@ export default defineComponent({
 						});
 					},
 				},
+				{
+					name: "Bounding Box",
+					callback: (canvas: HTMLCanvasElement, bezier: WasmBezierInstance): void => {
+						const context = getContextFromCanvas(canvas);
+						const bboxPoints: Point[] = JSON.parse(bezier.bounding_box());
+						const minPoint = bboxPoints[0];
+						const maxPoint = bboxPoints[1];
+						drawLine(context, minPoint, { x: minPoint.x, y: maxPoint.y }, COLORS.NON_INTERACTIVE.STROKE_1);
+						drawLine(context, minPoint, { x: maxPoint.x, y: minPoint.y }, COLORS.NON_INTERACTIVE.STROKE_1);
+						drawLine(context, maxPoint, { x: minPoint.x, y: maxPoint.y }, COLORS.NON_INTERACTIVE.STROKE_1);
+						drawLine(context, maxPoint, { x: maxPoint.x, y: minPoint.y }, COLORS.NON_INTERACTIVE.STROKE_1);
+					},
+				},
 			],
 			subpathFeatures: [
 				{
diff --git a/bezier-rs/docs/interactive-docs/wasm/src/lib.rs b/bezier-rs/docs/interactive-docs/wasm/src/lib.rs
index 577a004c..acbc2862 100644
--- a/bezier-rs/docs/interactive-docs/wasm/src/lib.rs
+++ b/bezier-rs/docs/interactive-docs/wasm/src/lib.rs
@@ -128,6 +128,16 @@ impl WasmBezier {
 		to_js_value(local_extrema)
 	}
 
+	pub fn de_casteljau_points(&self, t: f64) -> JsValue {
+		let hull = self
+			.0
+			.de_casteljau_points(t)
+			.iter()
+			.map(|level| level.iter().map(|&point| Point { x: point.x, y: point.y }).collect::<Vec<Point>>())
+			.collect::<Vec<Vec<Point>>>();
+		to_js_value(hull)
+	}
+
 	pub fn rotate(&self, angle: f64) -> WasmBezier {
 		WasmBezier(self.0.rotate(angle))
 	}
@@ -142,13 +152,8 @@ impl WasmBezier {
 		to_js_value(bezier_points)
 	}
 
-	pub fn de_casteljau_points(&self, t: f64) -> JsValue {
-		let hull = self
-			.0
-			.de_casteljau_points(t)
-			.iter()
-			.map(|level| level.iter().map(|&point| Point { x: point.x, y: point.y }).collect::<Vec<Point>>())
-			.collect::<Vec<Vec<Point>>>();
-		to_js_value(hull)
+	pub fn bounding_box(&self) -> JsValue {
+		let bbox_points: [Point; 2] = self.0.bounding_box().map(|p| Point { x: p.x, y: p.y });
+		to_js_value(bbox_points)
 	}
 }
diff --git a/bezier-rs/lib/src/lib.rs b/bezier-rs/lib/src/lib.rs
index f4fdc67b..8a290204 100644
--- a/bezier-rs/lib/src/lib.rs
+++ b/bezier-rs/lib/src/lib.rs
@@ -773,6 +773,26 @@ impl Bezier {
 		});
 		result
 	}
+
+	/// Return the min and max corners that represent the bounding box of the curve.
+	pub fn bounding_box(&self) -> [DVec2; 2] {
+		// Start by taking min/max of endpoints.
+		let mut endpoints_min = self.start.min(self.end);
+		let mut endpoints_max = self.start.max(self.end);
+
+		// Iterate through extrema points.
+		let extrema = self.local_extrema();
+		for t_values in extrema {
+			for t in t_values {
+				let point = self.evaluate(t);
+				// Update bounding box if new min/max is found.
+				endpoints_min = endpoints_min.min(point);
+				endpoints_max = endpoints_max.max(point);
+			}
+		}
+
+		[endpoints_min, endpoints_max]
+	}
 }
 
 #[cfg(test)]