Log Rust crash error output to Crashlytics

Gifski/Gifski.swift

@@ -1,4 +1,5 @@
 import Cocoa
+import FirebaseCrashlytics
 
 final class Gifski {
 	enum Loop {
@@ -49,6 +50,10 @@ final class Gifski {
 
 		self.wrapper = wrapper
 
+		wrapper.setErrorMessageCallback {
+			Crashlytics.crashlytics().log($0)
+		}
+
 		wrapper.setProgressCallback { [weak self] in
 			guard let self else {
 				return 0

Gifski/GifskiWrapper.swift

@@ -8,12 +8,14 @@ final class GifskiWrapper {
 		case rgb
 	}
 
+	typealias ErrorMessageCallback = (String) -> Void
 	typealias ProgressCallback = () -> Int
 	typealias WriteCallback = (Int, UnsafePointer<UInt8>) -> Int
 
 	private let pointer: OpaquePointer
 	private var unmanagedSelf: Unmanaged<GifskiWrapper>!
 	private var hasFinished = false
+	private var errorMessageCallback: ErrorMessageCallback!
 	private var progressCallback: ProgressCallback!
 	private var writeCallback: WriteCallback!
 
@@ -38,6 +40,30 @@ final class GifskiWrapper {
 		}
 	}
 
+	func setErrorMessageCallback(_ callback: @escaping ErrorMessageCallback) {
+		guard !hasFinished else {
+			return
+		}
+
+		errorMessageCallback = callback
+
+		gifski_set_error_message_callback(
+			pointer,
+			{ message, context in // swiftlint:disable:this opening_brace
+				guard
+					let message,
+					let context
+				else {
+					return
+				}
+
+				let this = Unmanaged<GifskiWrapper>.fromOpaque(context).takeUnretainedValue()
+				this.errorMessageCallback(String(cString: message))
+			},
+			unmanagedSelf.toOpaque()
+		)
+	}
+
 	func setProgressCallback(_ callback: @escaping ProgressCallback) {
 		guard !hasFinished else {
 			return