Extract gsvg_renderer from gcore, remove gcore/vello feature (#2760)

Extract `gsvg_renderer` from `gcore`, remove `gcore/vello` feature

node-graph/gsvg-renderer/src/convert_usvg_path.rs

@@ -0,0 +1,47 @@
+use bezier_rs::{ManipulatorGroup, Subpath};
+use glam::DVec2;
+use graphene_core::vector::PointId;
+
+pub fn convert_usvg_path(path: &usvg::Path) -> Vec<Subpath<PointId>> {
+	let mut subpaths = Vec::new();
+	let mut groups = Vec::new();
+
+	let mut points = path.data().points().iter();
+	let to_vec = |p: &usvg::tiny_skia_path::Point| DVec2::new(p.x as f64, p.y as f64);
+
+	for verb in path.data().verbs() {
+		match verb {
+			usvg::tiny_skia_path::PathVerb::Move => {
+				subpaths.push(Subpath::new(std::mem::take(&mut groups), false));
+				let Some(start) = points.next().map(to_vec) else { continue };
+				groups.push(ManipulatorGroup::new(start, Some(start), Some(start)));
+			}
+			usvg::tiny_skia_path::PathVerb::Line => {
+				let Some(end) = points.next().map(to_vec) else { continue };
+				groups.push(ManipulatorGroup::new(end, Some(end), Some(end)));
+			}
+			usvg::tiny_skia_path::PathVerb::Quad => {
+				let Some(handle) = points.next().map(to_vec) else { continue };
+				let Some(end) = points.next().map(to_vec) else { continue };
+				if let Some(last) = groups.last_mut() {
+					last.out_handle = Some(last.anchor + (2. / 3.) * (handle - last.anchor));
+				}
+				groups.push(ManipulatorGroup::new(end, Some(end + (2. / 3.) * (handle - end)), Some(end)));
+			}
+			usvg::tiny_skia_path::PathVerb::Cubic => {
+				let Some(first_handle) = points.next().map(to_vec) else { continue };
+				let Some(second_handle) = points.next().map(to_vec) else { continue };
+				let Some(end) = points.next().map(to_vec) else { continue };
+				if let Some(last) = groups.last_mut() {
+					last.out_handle = Some(first_handle);
+				}
+				groups.push(ManipulatorGroup::new(end, Some(second_handle), Some(end)));
+			}
+			usvg::tiny_skia_path::PathVerb::Close => {
+				subpaths.push(Subpath::new(std::mem::take(&mut groups), true));
+			}
+		}
+	}
+	subpaths.push(Subpath::new(groups, false));
+	subpaths
+}