fix(browser): hide spinner on main-frame load errors in BrowserClient (#68)

BrowserClient flips BrowserCallback.onLoadingStateChanged on
onPageStarted (true) and onPageFinished (false), but does not
override onReceivedError. On many failure modes (DNS, certificate,
offline, 4xx/5xx) onPageFinished does not always fire after the
error, so the toolbar / progress UI stays stuck on isLoading = true
even though the page never loaded.

Add a main-frame-only onReceivedError override that flips
isLoading = false too. isForMainFrame keeps a single blocked
sub-resource from flipping the spinner off while the main load is
still running.

Author: jim-daf

app/src/main/kotlin/io/github/landwarderer/futon/browser/BrowserClient.kt

@@ -3,6 +3,7 @@ package io.github.landwarderer.futon.browser
 import android.annotation.SuppressLint
 import android.graphics.Bitmap
 import android.os.Looper
+import android.webkit.WebResourceError
 import android.webkit.WebResourceRequest
 import android.webkit.WebResourceResponse
 import android.webkit.WebView
@@ -33,6 +34,21 @@ open class BrowserClient(
 		callback.onLoadingStateChanged(isLoading = true)
 	}
 
+	override fun onReceivedError(
+		view: WebView?,
+		request: WebResourceRequest?,
+		error: WebResourceError?,
+	) {
+		super.onReceivedError(view, request, error)
+		// Drop the spinner on main-frame failures (DNS, certificate, offline,
+		// 4xx/5xx) too, since onPageFinished does not always fire after an
+		// error and the BrowserCallback would otherwise stay stuck on
+		// isLoading = true.
+		if (request?.isForMainFrame == true) {
+			callback.onLoadingStateChanged(isLoading = false)
+		}
+	}
+
 	override fun onPageCommitVisible(view: WebView, url: String) {
 		super.onPageCommitVisible(view, url)
 		callback.onTitleChanged(view.title.orEmpty(), url)