Avoid unnecessary coroutine context switch

app/src/main/java/com/hippo/ehviewer/EhApplication.kt

@@ -58,12 +58,10 @@ import com.hippo.yorozuya.FileUtils
 import com.hippo.yorozuya.IntIdGenerator
 import eu.kanade.tachiyomi.core.preference.AndroidPreferenceStore
 import eu.kanade.tachiyomi.ui.reader.setting.ReaderPreferences
+import eu.kanade.tachiyomi.util.lang.launchIO
 import kotlinx.coroutines.DelicateCoroutinesApi
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.GlobalScope
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
 import okhttp3.Cache
 import okhttp3.HttpUrl.Companion.toHttpUrl
 import okhttp3.OkHttpClient
@@ -118,36 +116,34 @@ class EhApplication : SceneApplication(), DefaultLifecycleObserver, ImageLoaderF
 
         AppCompatDelegate.setDefaultNightMode(Settings.getTheme())
 
-        GlobalScope.launch {
-            withContext(Dispatchers.IO) {
-                try {
-                    val downloadLocation = Settings.getDownloadLocation()
-                    if (Settings.getMediaScan()) {
-                        CommonOperations.removeNoMediaFile(downloadLocation)
-                    } else {
-                        CommonOperations.ensureNoMediaFile(downloadLocation)
-                    }
-                } catch (t: Throwable) {
-                    t.printStackTrace()
-                    ExceptionUtils.throwIfFatal(t)
+        launchIO {
+            try {
+                val downloadLocation = Settings.getDownloadLocation()
+                if (Settings.getMediaScan()) {
+                    CommonOperations.removeNoMediaFile(downloadLocation)
+                } else {
+                    CommonOperations.ensureNoMediaFile(downloadLocation)
                 }
+            } catch (t: Throwable) {
+                t.printStackTrace()
+                ExceptionUtils.throwIfFatal(t)
+            }
 
-                // Clear temp files
-                try {
-                    clearTempDir()
-                } catch (t: Throwable) {
-                    t.printStackTrace()
-                    ExceptionUtils.throwIfFatal(t)
-                }
+            // Clear temp files
+            try {
+                clearTempDir()
+            } catch (t: Throwable) {
+                t.printStackTrace()
+                ExceptionUtils.throwIfFatal(t)
             }
         }
-        GlobalScope.launch {
+        launchIO {
             theDawnOfNewDay()
         }
         mIdGenerator.setNextId(Settings.getInt(KEY_GLOBAL_STUFF_NEXT_ID, 0))
     }
 
-    private suspend fun theDawnOfNewDay() {
+    private fun theDawnOfNewDay() {
         if (!Settings.getRequestNews()) {
             return
         }
@@ -159,22 +155,20 @@ class EhApplication : SceneApplication(), DefaultLifecycleObserver, ImageLoaderF
                 EhCookieStore.KEY_IPD_PASS_HASH
             )
         ) {
-            withContext(Dispatchers.IO) {
-                val referer = EhUrl.REFERER_E
-                val request = EhRequestBuilder(EhUrl.HOST_E + "news.php", referer).build()
-                val call = okHttpClient.newCall(request)
-                try {
-                    call.execute().use { response ->
-                        val responseBody = response.body
-                        val body = responseBody.string()
-                        val html = EventPaneParser.parse(body)
-                        if (html != null) {
-                            showEventPane(html)
-                        }
+            val referer = EhUrl.REFERER_E
+            val request = EhRequestBuilder(EhUrl.HOST_E + "news.php", referer).build()
+            val call = okHttpClient.newCall(request)
+            try {
+                call.execute().use { response ->
+                    val responseBody = response.body
+                    val body = responseBody.string()
+                    val html = EventPaneParser.parse(body)
+                    if (html != null) {
+                        showEventPane(html)
                     }
-                } catch (e: Throwable) {
-                    e.printStackTrace()
                 }
+            } catch (e: Throwable) {
+                e.printStackTrace()
             }
         }
     }

app/src/main/java/com/hippo/ehviewer/client/EhTagDatabase.kt

@@ -24,12 +24,10 @@ import com.hippo.util.ExceptionUtils
 import com.hippo.util.HashCodeUtils
 import com.hippo.yorozuya.FileUtils
 import com.hippo.yorozuya.IOUtils
+import eu.kanade.tachiyomi.util.lang.launchIO
 import kotlinx.coroutines.DelicateCoroutinesApi
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.GlobalScope
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
-import kotlinx.coroutines.launch
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import okio.BufferedSource
@@ -193,7 +191,7 @@ object EhTagDatabase {
     @OptIn(DelicateCoroutinesApi::class)
     @JvmStatic
     fun update() {
-        GlobalScope.launch(Dispatchers.IO) {
+        launchIO {
             updateInternal()
         }
     }

app/src/main/java/com/hippo/ehviewer/ui/scene/SearchBarScene.kt

@@ -27,11 +27,10 @@ import com.hippo.ehviewer.Settings
 import com.hippo.ehviewer.client.EhTagDatabase
 import com.hippo.ehviewer.widget.SearchDatabase
 import com.hippo.scene.StageActivity
-import kotlinx.coroutines.Dispatchers
+import eu.kanade.tachiyomi.util.lang.withUIContext
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
 
 
 abstract class SearchBarScene : ToolbarScene() {
@@ -311,12 +310,12 @@ abstract class SearchBarScene : ToolbarScene() {
 
     @SuppressLint("NotifyDataSetChanged")
     private fun updateSuggestions(scrollToTop: Boolean = true) {
-        viewLifecycleOwner.lifecycleScope.launch(Dispatchers.Default) {
+        viewLifecycleOwner.lifecycleScope.launch {
             val suggestions = mutableListOf<Suggestion>()
             mergedSuggestionFlow().collect {
                 suggestions.add(it)
             }
-            withContext(Dispatchers.Main) {
+            withUIContext {
                 mSuggestionList = suggestions
                 mSuggestionAdapter?.notifyDataSetChanged()
             }

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -85,6 +85,8 @@ import eu.kanade.tachiyomi.ui.reader.setting.ReaderSettingsSheet
 import eu.kanade.tachiyomi.ui.reader.setting.ReadingModeType
 import eu.kanade.tachiyomi.ui.reader.viewer.BaseViewer
 import eu.kanade.tachiyomi.ui.reader.viewer.pager.R2LPagerViewer
+import eu.kanade.tachiyomi.util.lang.launchIO
+import eu.kanade.tachiyomi.util.lang.launchUI
 import eu.kanade.tachiyomi.util.preference.toggle
 import eu.kanade.tachiyomi.util.system.applySystemAnimatorScale
 import eu.kanade.tachiyomi.util.system.hasDisplayCutout
@@ -93,15 +95,12 @@ import eu.kanade.tachiyomi.util.view.copy
 import eu.kanade.tachiyomi.util.view.popupMenu
 import eu.kanade.tachiyomi.util.view.setTooltip
 import eu.kanade.tachiyomi.widget.listener.SimpleAnimationListener
-import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.FlowPreview
 import kotlinx.coroutines.cancel
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.merge
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.sample
-import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
 import java.io.File
 import java.io.FileInputStream
 import java.io.IOException
@@ -134,29 +133,27 @@ class ReaderActivity : EhActivity() {
                 AppConfig.getExternalTempDir().toString() + File.separator + mCacheFileName
             val cachefile = File(filepath)
             val resolver = contentResolver
-            lifecycleScope.launch {
-                withContext(Dispatchers.IO) {
-                    var `is`: InputStream? = null
-                    var os: OutputStream? = null
-                    try {
-                        `is` = FileInputStream(cachefile)
-                        os = resolver.openOutputStream(uri)
-                        IOUtils.copy(`is`, os)
-                    } catch (e: IOException) {
-                        e.printStackTrace()
-                    } finally {
-                        IOUtils.closeQuietly(`is`)
-                        IOUtils.closeQuietly(os)
-                        runOnUiThread {
-                            Toast.makeText(
-                                this@ReaderActivity,
-                                getString(R.string.image_saved, uri.path),
-                                Toast.LENGTH_SHORT
-                            ).show()
-                        }
+            lifecycleScope.launchIO {
+                var `is`: InputStream? = null
+                var os: OutputStream? = null
+                try {
+                    `is` = FileInputStream(cachefile)
+                    os = resolver.openOutputStream(uri)
+                    IOUtils.copy(`is`, os)
+                } catch (e: IOException) {
+                    e.printStackTrace()
+                } finally {
+                    IOUtils.closeQuietly(`is`)
+                    IOUtils.closeQuietly(os)
+                    runOnUiThread {
+                        Toast.makeText(
+                            this@ReaderActivity,
+                            getString(R.string.image_saved, uri.path),
+                            Toast.LENGTH_SHORT
+                        ).show()
                     }
-                    cachefile.delete()
                 }
+                cachefile.delete()
             }
         }
     }
@@ -253,7 +250,9 @@ class ReaderActivity : EhActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        window.colorMode = if (Image.isWideColorGamut && readerPreferences.wideColorGamut().get()) ActivityInfo.COLOR_MODE_WIDE_COLOR_GAMUT else ActivityInfo.COLOR_MODE_DEFAULT
+        window.colorMode = if (Image.isWideColorGamut && readerPreferences.wideColorGamut()
+                .get()
+        ) ActivityInfo.COLOR_MODE_WIDE_COLOR_GAMUT else ActivityInfo.COLOR_MODE_DEFAULT
         if (savedInstanceState == null) {
             onInit()
         } else {
@@ -279,7 +278,7 @@ class ReaderActivity : EhActivity() {
             mCurrentIndex = if (mPage >= 0) mPage else mGalleryProvider!!.startPage
         }
 
-        lifecycleScope.launch(Dispatchers.Main) {
+        lifecycleScope.launchUI {
             mGalleryProvider!!.state.collect {
                 if (it == PageLoader.STATE_READY) {
                     setGallery()

app/src/main/java/eu/kanade/tachiyomi/util/lang/CoroutinesExtensions.kt

@@ -0,0 +1,60 @@
+package eu.kanade.tachiyomi.util.lang
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.CoroutineStart
+import kotlinx.coroutines.DelicateCoroutinesApi
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.NonCancellable
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+
+/**
+ * Think twice before using this. This is a delicate API. It is easy to accidentally create resource or memory leaks when GlobalScope is used.
+ *
+ * **Possible replacements**
+ * - suspend function
+ * - custom scope like view or presenter scope
+ */
+@DelicateCoroutinesApi
+fun launchUI(block: suspend CoroutineScope.() -> Unit): Job =
+    GlobalScope.launch(Dispatchers.Main, CoroutineStart.DEFAULT, block)
+
+/**
+ * Think twice before using this. This is a delicate API. It is easy to accidentally create resource or memory leaks when GlobalScope is used.
+ *
+ * **Possible replacements**
+ * - suspend function
+ * - custom scope like view or presenter scope
+ */
+@DelicateCoroutinesApi
+fun launchIO(block: suspend CoroutineScope.() -> Unit): Job =
+    GlobalScope.launch(Dispatchers.IO, CoroutineStart.DEFAULT, block)
+
+/**
+ * Think twice before using this. This is a delicate API. It is easy to accidentally create resource or memory leaks when GlobalScope is used.
+ *
+ * **Possible replacements**
+ * - suspend function
+ * - custom scope like view or presenter scope
+ */
+@DelicateCoroutinesApi
+fun launchNow(block: suspend CoroutineScope.() -> Unit): Job =
+    GlobalScope.launch(Dispatchers.Main, CoroutineStart.UNDISPATCHED, block)
+
+fun CoroutineScope.launchUI(block: suspend CoroutineScope.() -> Unit): Job =
+    launch(Dispatchers.Main, block = block)
+
+fun CoroutineScope.launchIO(block: suspend CoroutineScope.() -> Unit): Job =
+    launch(Dispatchers.IO, block = block)
+
+fun CoroutineScope.launchNonCancellable(block: suspend CoroutineScope.() -> Unit): Job =
+    launchIO { withContext(NonCancellable, block) }
+
+suspend fun <T> withUIContext(block: suspend CoroutineScope.() -> T) = withContext(Dispatchers.Main, block)
+
+suspend fun <T> withIOContext(block: suspend CoroutineScope.() -> T) = withContext(Dispatchers.IO, block)
+
+suspend fun <T> withNonCancellableContext(block: suspend CoroutineScope.() -> T) =
+    withContext(NonCancellable, block)