Fix drawing VC background flickering in dark mode

Closes #199

Tusker/Screens/Compose/ComposeDrawingViewController.swift

@@ -14,6 +14,30 @@ protocol ComposeDrawingViewControllerDelegate: AnyObject {
     func composeDrawingViewController(_ drawingController: ComposeDrawingViewController, saveDrawing drawing: PKDrawing)
 }
 
+class ComposeDrawingNavigationController: UINavigationController {
+    override var preferredStatusBarStyle: UIStatusBarStyle {
+        .darkContent
+    }
+    
+    init(editing initialDrawing: PKDrawing, delegate: ComposeDrawingViewControllerDelegate) {
+        let vc = ComposeDrawingViewController(editing: initialDrawing)
+        vc.delegate = delegate
+        super.init(rootViewController: vc)
+        
+        modalPresentationStyle = .fullScreen
+    }
+    
+    required init?(coder aDecoder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+    
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        
+        overrideUserInterfaceStyle = .light
+    }
+}
+
 class ComposeDrawingViewController: UIViewController {
     
     weak var delegate: ComposeDrawingViewControllerDelegate?
@@ -63,7 +87,8 @@ class ComposeDrawingViewController: UIViewController {
         canvasView.drawingPolicy = .anyInput
         canvasView.minimumZoomScale = 0.5
         canvasView.maximumZoomScale = 2
-        canvasView.backgroundColor = .systemBackground
+        canvasView.backgroundColor = .white
+        canvasView.overrideUserInterfaceStyle = .light
         canvasView.translatesAutoresizingMaskIntoConstraints = false
         view.addSubview(canvasView)
         NSLayoutConstraint.activate([
@@ -74,6 +99,7 @@ class ComposeDrawingViewController: UIViewController {
         ])
         
         toolPicker = PKToolPicker()
+        toolPicker.overrideUserInterfaceStyle = .light
         toolPicker.setVisible(true, forFirstResponder: canvasView)
         toolPicker.addObserver(canvasView)
         toolPicker.addObserver(self)

Tusker/Screens/Compose/ComposeHostingController.swift

@@ -360,11 +360,7 @@ extension ComposeHostingController: ComposeUIStateDelegate {
             drawing = PKDrawing()
         }
         
-        let drawingVC = ComposeDrawingViewController(editing: drawing)
+        present(ComposeDrawingNavigationController(editing: drawing, delegate: self), animated: true)
-        drawingVC.delegate = self
-        let nav = UINavigationController(rootViewController: drawingVC)
-        nav.modalPresentationStyle = .fullScreen
-        present(nav, animated: true)
     }
 }