Async projection (#32)

* Offload projection to a detached task to not block main actor * Attempt to improve this * Refactor into `projectInParallel` helper * Update packages
maparoni · Oct 29, 2024 · 3985921 · 3985921
1 parent 699e5d9
commit 3985921
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Showing 5 changed files with 183 additions and 34 deletions.
diff --git a/Package.resolved b/Package.resolved
@@ -5,26 +5,44 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/maparoni/geojsonkit.git",
       "state" : {
-        "revision" : "8f1e5094a8ab8cbb020074cd4848a5804c17bab0",
-        "version" : "0.5.2"
+        "revision" : "a5aabe3a1edddbcf14b49b3fa5be1ddd48dff7c8",
+        "version" : "0.6.0"
       }
     },
     {
       "identity" : "geojsonkit-turf",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/maparoni/geojsonkit-turf",
       "state" : {
-        "revision" : "21452ac7ee183930325e786575d552129c21b165",
-        "version" : "0.2.0"
+        "revision" : "99c542f4c3c105caa9567c61fd8036e94e07df05",
+        "version" : "0.4.1"
+      }
+    },
+    {
+      "identity" : "swift-algorithms",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-algorithms.git",
+      "state" : {
+        "revision" : "f6919dfc309e7f1b56224378b11e28bab5bccc42",
+        "version" : "1.2.0"
       }
     },
     {
       "identity" : "swift-argument-parser",
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-argument-parser",
       "state" : {
-        "revision" : "8f4d2753f0e4778c76d5f05ad16c74f707390531",
-        "version" : "1.2.3"
+        "revision" : "41982a3656a71c768319979febd796c6fd111d5c",
+        "version" : "1.5.0"
+      }
+    },
+    {
+      "identity" : "swift-numerics",
+      "kind" : "remoteSourceControl",
+      "location" : "https://github.com/apple/swift-numerics.git",
+      "state" : {
+        "revision" : "0a5bc04095a675662cf24757cc0640aa2204253b",
+        "version" : "1.0.2"
       }
     }
   ],

diff --git a/Package.swift b/Package.swift
@@ -21,6 +21,7 @@ let package = Package(
     .package(url: "https://github.com/maparoni/geojsonkit.git", from: "0.5.0"),
     .package(url: "https://github.com/maparoni/geojsonkit-turf", from: "0.1.0"),
 //    .package(name: "geojsonkit-turf", path: "../GeoJSONKit-Turf"),
+    .package(url: "https://github.com/apple/swift-algorithms.git", from: "1.0.0"),
   ],
   targets: [
     .target(
@@ -38,6 +39,7 @@ let package = Package(
       name: "GeoDrawer",
       dependencies: [
         "GeoProjector",
+        .product(name: "Algorithms", package: "swift-algorithms"),
       ]),
   ]
 )
diff --git a/Sources/GeoDrawer/GeoDrawer.swift b/Sources/GeoDrawer/GeoDrawer.swift
@@ -12,6 +12,7 @@ import CoreGraphics
 #endif
 
 import GeoJSONKit
+import Algorithms
 
 @_exported import GeoProjector
 
@@ -227,6 +228,40 @@ extension GeoDrawer {
       return .circle(point, radius: radius, fill: fill, stroke: stroke, strokeWidth: strokeWidth)
     }
   }
+
+  struct OffsettedElement<Element: Equatable>: Comparable, Equatable {
+    let offset: Int
+    let element: Element
+
+    static func == (lhs: OffsettedElement, rhs: OffsettedElement) -> Bool {
+      lhs.offset == rhs.offset && lhs.element == rhs.element
+    }
+
+    static func < (lhs: OffsettedElement, rhs: OffsettedElement) -> Bool {
+      lhs.offset < rhs.offset
+    }
+  }
+
+  func projectInParallel(_ contents: [Content]) async throws -> [ProjectedContent] {
+    try await withThrowingTaskGroup(of: [OffsettedElement<ProjectedContent>].self) { group in
+      let chunks = Array(contents.enumerated()).chunks(ofCount: 25)
+      for chunk in chunks {
+        let added = group.addTaskUnlessCancelled {
+          await Task {
+            return chunk.compactMap { input in
+              project(input.element).flatMap { OffsettedElement(offset: input.offset, element: $0) }
+            }
+          }.value
+        }
+        if !added {
+          throw CancellationError()
+        }
+      }
+
+      let unsorted = try await group.reduce(into: []) { $0.append(contentsOf: $1) }
+      return unsorted.sorted(by: <).map(\.element)
+    }
+  }
 }
 
 // MARK: - Line helper

diff --git a/Sources/GeoDrawer/GeoMap+AppKit.swift b/Sources/GeoDrawer/GeoMap+AppKit.swift
@@ -16,26 +16,32 @@ import GeoJSONKit
 
 public class GeoMapView: NSView {
   public var contents: [GeoDrawer.Content] = [] {
-    didSet { setNeedsDisplay(bounds) }
+    didSet {
+      invalidateProjectedContents()
+      setNeedsDisplay(bounds)
+    }
   }
 
   public var projection: Projection = Projections.Equirectangular() {
     didSet {
       _drawer = nil
+      invalidateProjectedContents()
       setNeedsDisplay(bounds)
     }
   }
 
   public var zoomTo: GeoJSON.BoundingBox? = nil {
     didSet {
       _drawer = nil
+      invalidateProjectedContents()
       setNeedsDisplay(bounds)
     }
   }
 
   public var insets: GeoProjector.EdgeInsets = .zero {
     didSet {
       _drawer = nil
+      invalidateProjectedContents()
       setNeedsDisplay(bounds)
     }
   }
@@ -61,6 +67,7 @@ public class GeoMapView: NSView {
   public override var frame: NSRect {
     didSet {
       _drawer = nil
+      invalidateProjectedContents()
       setNeedsDisplay(bounds)
     }
   }
@@ -82,20 +89,67 @@ public class GeoMapView: NSView {
   }
 
   public override func draw(_ rect: NSRect) {
-    super.draw(rect)
+    // Don't draw if we're busy as this will flicker weirdly
+    let projected: [GeoDrawer.ProjectedContent]
+    switch projectProgress {
+    case .busy(_, .some(let previous)):
+      projected = previous
+    case .busy(_, .none), .idle:
+      return // Don't update drawing; will get called again instead when finished
+    case .finished(let finished):
+      projected = finished
+    }
 
+    super.draw(rect)
+
     // Get the current graphics context and cast it to a CGContext
     let context = NSGraphicsContext.current!.cgContext
 
     // Use Core Graphics functions to draw the content of your view
     drawer.draw(
-      contents,
+      projected,
       mapBackground: mapBackground.cgColor,
       mapOutline: mapOutline.cgColor,
       mapBackdrop: mapBackdrop.cgColor,
       in: context
     )
   }
+
+  // MARK: - Performance
+
+  enum ProjectionProgress {
+    case finished([GeoDrawer.ProjectedContent])
+    case busy(Task<Void, Never>, previously: [GeoDrawer.ProjectedContent]?)
+    case idle
+  }
+
+  private var projectProgress = ProjectionProgress.idle
+
+  private func invalidateProjectedContents() {
+    let previous: [GeoDrawer.ProjectedContent]?
+    switch projectProgress {
+    case .finished(let projected):
+      previous = projected
+    case .busy(let task, let previously):
+      task.cancel()
+      previous = previously
+    case .idle:
+      previous = nil
+    }
+
+    projectProgress = .busy(Task(priority: .high) { [weak self] in
+      guard let self else { return }
+      do {
+        let projected = try await drawer.projectInParallel(contents)
+        await MainActor.run {
+          self.projectProgress = .finished(projected)
+          self.setNeedsDisplay(self.bounds)
+        }
+      } catch {
+        assert(error is CancellationError)
+      }
+    }, previously: previous)
+  }
 }
 
 @available(macOS 10.15, *)

diff --git a/Sources/GeoDrawer/GeoMap+UIKit.swift b/Sources/GeoDrawer/GeoMap+UIKit.swift
@@ -17,65 +17,57 @@ import GeoJSONKit
 public class GeoMapView: UIView {
   public var contents: [GeoDrawer.Content] = [] {
     didSet {
-      _projected = nil
-      setNeedsDisplay(bounds)
+      if contents == oldValue { return }
+      invalidateProjectedContents()
+      setNeedsDisplay()
     }
   }
 
   public var projection: Projection = Projections.Equirectangular() {
     didSet {
       _drawer = nil
-      _projected = nil
-      setNeedsDisplay(bounds)
+      invalidateProjectedContents()
+      setNeedsDisplay()
     }
   }
 
   public var zoomTo: GeoJSON.BoundingBox? = nil {
     didSet {
+      if zoomTo == oldValue { return }
       _drawer = nil
-      _projected = nil
-      setNeedsDisplay(bounds)
+      invalidateProjectedContents()
+      setNeedsDisplay()
     }
   }
 
   public var insets: GeoProjector.EdgeInsets = .zero {
     didSet {
+      if insets == oldValue { return }
       _drawer = nil
-      _projected = nil
-      setNeedsDisplay(bounds)
+      invalidateProjectedContents()
+      setNeedsDisplay()
     }
   }
 
   public var mapBackground: UIColor = .systemTeal {
     didSet {
-      setNeedsDisplay(bounds)
+      setNeedsDisplay()
     }
   }
 
   public var mapOutline: UIColor = .black {
     didSet {
-      setNeedsDisplay(bounds)
+      setNeedsDisplay()
     }
   }
 
 
   public override var frame: CGRect {
     didSet {
+      if frame == oldValue { return }
       _drawer = nil
-      _projected = nil
-      setNeedsDisplay(bounds)
-    }
-  }
-
-
-  private var _projected: [GeoDrawer.ProjectedContent]!
-  private var projected: [GeoDrawer.ProjectedContent] {
-    if let _projected {
-      return _projected
-    } else {
-      let projected = contents.compactMap(drawer.project(_:))
-      _projected = projected
-      return projected
+      invalidateProjectedContents()
+      setNeedsDisplay()
     }
   }
 
@@ -96,7 +88,6 @@ public class GeoMapView: UIView {
   }
 
   public override func draw(_ rect: CGRect) {
-    super.draw(rect)
 
     // Get the current graphics context and cast it to a CGContext
     let context = UIGraphicsGetCurrentContext()!
@@ -110,6 +101,19 @@ public class GeoMapView: UIView {
       background = .white
     }
 
+    // Don't draw if we're busy as this will flicker weirdly
+    let projected: [GeoDrawer.ProjectedContent]
+    switch projectProgress {
+    case .busy(_, .some(let previous)):
+      projected = previous
+    case .busy(_, .none), .idle:
+      return // Don't update drawing; will get called again instead when finished
+    case .finished(let finished):
+      projected = finished
+    }
+
+    super.draw(rect)
+
     // Use Core Graphics functions to draw the content of your view
     drawer.draw(
       projected,
@@ -121,6 +125,42 @@ public class GeoMapView: UIView {
 
     context.flush()
   }
+
+  // MARK: - Performance
+
+  enum ProjectionProgress {
+    case finished([GeoDrawer.ProjectedContent])
+    case busy(Task<Void, Never>, previously: [GeoDrawer.ProjectedContent]?)
+    case idle
+  }
+
+  private var projectProgress = ProjectionProgress.idle
+
+  private func invalidateProjectedContents() {
+    let previous: [GeoDrawer.ProjectedContent]?
+    switch projectProgress {
+    case .finished(let projected):
+      previous = projected
+    case .busy(let task, let previously):
+      task.cancel()
+      previous = previously
+    case .idle:
+      previous = nil
+    }
+
+    projectProgress = .busy(Task.detached(priority: .high) { [weak self] in
+      guard let self else { return }
+      do {
+        let projected = try await drawer.projectInParallel(contents)
+        await MainActor.run {
+          self.projectProgress = .finished(projected)
+          self.setNeedsDisplay(self.bounds)
+        }
+      } catch {
+        assert(error is CancellationError)
+      }
+    }, previously: previous)
+  }
 }
 
 @available(iOS 13.0, visionOS 1.0, *)