fix(wallpaper): keep the system wallpaper in step with the animation

the still behind the menu bar tint, Mission Control and the lock screen was
only re-rendered on a setting change, and always at time 0, so it never
matched the frame on screen. stills (desktop sync and export) now render
on the live clock, and the desktop sync re-runs once a minute while
animating, timed on the wall clock since macOS throttles the app timer.

Author: dappermint

src/app/delegate.swift

@@ -13,6 +13,7 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
     var syncWork: DispatchWorkItem?
     var lastSync = ""
     var ticks = 0
+    var lastStill = Date()
 
     func applicationDidFinishLaunching(_ n: Notification) {
         Pref.register()
@@ -43,6 +44,13 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
             // ponytail: polls both config files every 2s; a stat is cheaper than watching a symlink chain nix swaps
             ticks += 1
             if ticks % 40 == 0 { Config.poll() }
+            // ponytail: the system wallpaper (menu bar tint, Mission Control, lock screen) follows
+            // the animation once a minute; finer means a full-screen PNG write every few seconds.
+            // wall clock, not ticks: macOS throttles the timer when the app is napped
+            if live, Date().timeIntervalSince(lastStill) > 60 {
+                lastSync = ""
+                syncDesktop()
+            }
         }
         wall.setPaused(!Pref.d.bool(forKey: "animate"))
         wall.refresh()
@@ -235,7 +243,7 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
         var firstOut: URL?
         for (i, (r, v)) in zip(wall.renderers, wall.views).enumerated() {
             let w = Int(v.drawableSize.width), h = Int(v.drawableSize.height)
-            guard let px = r.render(makeUniforms(w: w, h: h, time: 0), w: w, h: h),
+            guard let px = r.render(makeUniforms(w: w, h: h, time: r.now), w: w, h: h),
                   let img = cgImage(px, w: w, h: h)
             else { continue }
             let out =
@@ -270,6 +278,7 @@ extension AppDelegate {
               .appendingPathComponent("Pixeldish")
         else { return }
         lastSync = key
+        lastStill = Date()
         try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
         // the wallpaper store ignores a URL it already shows, so alternate two names per display
         let slot = Pref.d.bool(forKey: "desktopSlot")
@@ -280,7 +289,7 @@ extension AppDelegate {
             let sh = Int(screen.frame.height * screen.backingScaleFactor)
             // the window is oversized past the screen edges, crop back to what is visible
             guard w >= sw, h >= sh,
-                  let px = r.render(makeUniforms(w: w, h: h, time: 0), w: w, h: h),
+                  let px = r.render(makeUniforms(w: w, h: h, time: r.now), w: w, h: h),
                   let img = cgImage(px, w: w, h: h)?
                   .cropping(to: CGRect(x: (w - sw) / 2, y: (h - sh) / 2, width: sw, height: sh))
             else { continue }

src/render/renderer.swift

@@ -166,6 +166,8 @@ final class DishRenderer: NSObject, MTKViewDelegate {
     // `just test-live` to prove the window path draws, since the display itself
     // cannot be screenshotted without screen-recording permission
     var probeFrames = 0
+    // the clock the live view draws at; stills use it too so they match the screen
+    var now: Float { paused ? 0 : Float(Date().timeIntervalSince(start)) * prefValue("speed") }
 
     init?(shader path: String) {
         guard let dev = MTLCreateSystemDefaultDevice(),
@@ -258,9 +260,8 @@ final class DishRenderer: NSObject, MTKViewDelegate {
         else { return }
         rp.colorAttachments[0].clearColor = MTLClearColor(red: 0, green: 0, blue: 0, alpha: 1)
 
-        let t = paused ? 0 : Float(Date().timeIntervalSince(start)) * prefValue("speed")
         let size = view.drawableSize
-        encode(enc, makeUniforms(w: Int(size.width), h: Int(size.height), time: t))
+        encode(enc, makeUniforms(w: Int(size.width), h: Int(size.height), time: now))
         if probeFrames > 0 {
             probeFrames -= 1
             cb.present(rt)