feat: print elapsed time of methods

both within a method, and between two methods

Used to determine whether GZip makes sense

AnkiDroid/src/main/java/com/ichi2/anki/AbstractFlashcardViewer.kt

@@ -2360,6 +2360,7 @@ abstract class AbstractFlashcardViewer :
         private val onPageFinishedCallback: OnPageFinishedCallback? = null
     ) : WebViewClient() {
         private var pageFinishedFired = true
+        private val pageRenderStopwatch = Stopwatch.init("page render")
 
         @TargetApi(Build.VERSION_CODES.N)
         override fun shouldOverrideUrlLoading(view: WebView, request: WebResourceRequest): Boolean {
@@ -2378,6 +2379,7 @@ abstract class AbstractFlashcardViewer :
         }
 
         override fun onPageStarted(view: WebView?, url: String?, favicon: Bitmap?) {
+            pageRenderStopwatch.reset()
             pageFinishedFired = false
         }
 
@@ -2659,6 +2661,7 @@ abstract class AbstractFlashcardViewer :
                 return
             }
             pageFinishedFired = true
+            pageRenderStopwatch.logElapsed()
             Timber.d("Java onPageFinished triggered: %s", url)
             // onPageFinished will be called multiple times if the WebView redirects by setting window.location.href
             onPageFinishedCallback?.onPageFinished()

AnkiDroid/src/main/java/com/ichi2/utils/TimeUtil.kt

@@ -0,0 +1,81 @@
+/*
+ *  Copyright (c) 2023 David Allison <[email protected]>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.utils
+
+import androidx.annotation.CheckResult
+import com.ichi2.libanki.utils.TimeManager
+import timber.log.Timber
+
+/**
+ * Usage:
+ *
+ * ```kotlin
+ * val result = measureTime("operation") { operation() }
+ * ```
+ * -> `D/TimeUtilKt executed mHtmlGenerator in 23ms`
+ */
+fun <T> measureTime(functionName: String? = "", function: () -> T): T {
+    val startTime = TimeManager.time.intTimeMS()
+    val result = function()
+    val endTime = TimeManager.time.intTimeMS()
+    Timber.d(
+        "executed %sin %dms",
+        if (functionName.isNullOrEmpty()) "" else "$functionName ",
+        endTime - startTime
+    )
+    return result
+}
+
+/**
+ * Used to time an operation across two function calls
+ *
+ * ```kotlin
+ * private val renderStopwatch: Stopwatch = Stopwatch.init("page render")
+ *
+ * fun start() {
+ *     renderStopwatch.reset()
+ * }
+ *
+ * fun stop() {
+ *     renderStopwatch.logElapsed()
+ * }
+ * ```
+ *
+ * -> `D/Stopwatch executed page render in 67ms`
+ */
+class Stopwatch(private val executionName: String?) {
+    private var startTime = TimeManager.time.intTimeMS()
+
+    fun logElapsed() {
+        val endTime = TimeManager.time.intTimeMS()
+        Timber.d(
+            "executed %sin %dms",
+            if (executionName.isNullOrEmpty()) "" else "$executionName ",
+            endTime - startTime
+        )
+    }
+
+    fun reset() {
+        startTime = TimeManager.time.intTimeMS()
+    }
+    companion object {
+
+        /** initializes the stopwatch to ensure `stop()` before `start()` won't crash */
+        @CheckResult
+        fun init(executionName: String? = null) = Stopwatch(executionName)
+    }
+}