Pre-warm default font manager, to reduce time cost of engine setup

flutter · May 18, 2020 · 0d297ba · 0d297ba
1 parent b776e21
commit 0d297ba
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diff --git a/shell/platform/android/flutter_main.cc b/shell/platform/android/flutter_main.cc
@@ -21,6 +21,7 @@
 #include "flutter/shell/common/shell.h"
 #include "flutter/shell/common/switches.h"
 #include "third_party/dart/runtime/include/dart_tools_api.h"
+#include "third_party/skia/include/core/SkFontMgr.h"
 
 namespace flutter {
 
@@ -155,6 +156,10 @@ void FlutterMain::SetupObservatoryUriCallback(JNIEnv* env) {
       });
 }
 
+static void CreateDefaultFontManager(JNIEnv* env, jclass jcaller) {
+  sk_sp<SkFontMgr> font_mgr(SkFontMgr::RefDefault());
+}
+
 bool FlutterMain::Register(JNIEnv* env) {
   static const JNINativeMethod methods[] = {
       {
@@ -163,6 +168,11 @@ bool FlutterMain::Register(JNIEnv* env) {
                        "lang/String;Ljava/lang/String;Ljava/lang/String;J)V",
           .fnPtr = reinterpret_cast<void*>(&Init),
       },
+      {
+          .name = "nativeCreateDefaultFontManager",
+          .signature = "()V",
+          .fnPtr = reinterpret_cast<void*>(&CreateDefaultFontManager),
+      },
   };
 
   jclass clazz = env->FindClass("io/flutter/embedding/engine/FlutterJNI");

diff --git a/shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java b/shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java
@@ -106,6 +106,13 @@ public static native void nativeInit(
       @NonNull String engineCachesPath,
       long initTimeMillis);
 
+  /**
+   * Create the default font manager provided by SkFontMgr::RefDefault() which is a process-wide
+   * singleton owned by Skia. Note that, the first call to SkFontMgr::RefDefault() will take
+   * noticeable time, but later calls will return a reference to the preexisting font manager.
+   */
+  public static native void nativeCreateDefaultFontManager();
+
   // TODO(mattcarroll): add javadocs
   @UiThread
   public native boolean nativeGetIsSoftwareRenderingEnabled();

diff --git a/shell/platform/android/io/flutter/embedding/engine/loader/FlutterLoader.java b/shell/platform/android/io/flutter/embedding/engine/loader/FlutterLoader.java
@@ -119,6 +119,17 @@ public void startInitialization(@NonNull Context applicationContext, @NonNull Se
 
     System.loadLibrary("flutter");
 
+    // Pre-warm the default font manager as soon as possible on a background thread.
+    // It helps to reduce time cost of engine setup that blocks the platform thread.
+    new Thread(
+            new Runnable() {
+              @Override
+              public void run() {
+                FlutterJNI.nativeCreateDefaultFontManager();
+              }
+            })
+        .start();
+
     VsyncWaiter.getInstance(
             (WindowManager) applicationContext.getSystemService(Context.WINDOW_SERVICE))
         .init();