From 786ef4b660266a861c5dbbfccc0ab132bbb92487 Mon Sep 17 00:00:00 2001
From: M66B <M66B@users.noreply.github.com>
Date: Mon, 23 Mar 2020 19:30:57 +0100
Subject: [PATCH] Download images parallel on faster connections

---
 .../java/eu/faircode/email/ImageHelper.java   | 31 +++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/app/src/main/java/eu/faircode/email/ImageHelper.java b/app/src/main/java/eu/faircode/email/ImageHelper.java
index cd2839f7d8..fe7f7fc289 100644
--- a/app/src/main/java/eu/faircode/email/ImageHelper.java
+++ b/app/src/main/java/eu/faircode/email/ImageHelper.java
@@ -37,6 +37,9 @@ import android.graphics.Typeface;
 import android.graphics.drawable.BitmapDrawable;
 import android.graphics.drawable.Drawable;
 import android.graphics.drawable.LevelListDrawable;
+import android.net.ConnectivityManager;
+import android.net.Network;
+import android.net.NetworkCapabilities;
 import android.os.Build;
 import android.os.Handler;
 import android.text.TextUtils;
@@ -69,13 +72,16 @@ import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
 
 class ImageHelper {
-    private static final ExecutorService executor =
-            Helper.getBackgroundExecutor(1, "image");
+    private static final ExecutorService executor_1 =
+            Helper.getBackgroundExecutor(1, "image_1");
+    private static final ExecutorService executor_n =
+            Helper.getBackgroundExecutor(0, "image_n");
 
     private static final int DOWNLOAD_TIMEOUT = 15 * 1000; // milliseconds
     private static final int MAX_REDIRECTS = 10;
     private static final long FIT_DRAWABLE_WARNING = 10 * 1000L; // milliseconds
     private static final long FIT_DRAWABLE_TIMEOUT = 20 * 1000L; // milliseconds
+    private static final int SLOW_CONNECTION = 2 * 1024; // Kbps
 
     static Bitmap generateIdenticon(@NonNull String email, int size, int pixels, Context context) {
         byte[] hash = getHash(email);
@@ -336,6 +342,27 @@ class ImageHelper {
             lld.setBounds(0, 0, px, px);
             lld.setLevel(1);
 
+            boolean slow = true;
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+                // 2G GSM ~14.4 Kbps
+                // G GPRS ~26.8 Kbps
+                // E EDGE ~108.8 Kbps
+                // 3G UMTS ~128 Kbps
+                // H HSPA ~3.6 Mbps
+                // H+ HSPA+ ~14.4 Mbps-23.0 Mbps
+                // 4G LTE ~50 Mbps
+                // 4G LTE-A ~500 Mbps
+                ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
+                Network active = (cm == null ? null : cm.getActiveNetwork());
+                NetworkCapabilities caps = (active == null ? null : cm.getNetworkCapabilities(active));
+                if (caps != null) {
+                    int kbps = caps.getLinkDownstreamBandwidthKbps();
+                    slow = (kbps < SLOW_CONNECTION);
+                }
+            }
+
+            ExecutorService executor = (slow ? executor_1 : executor_n);
+
             executor.submit(new Runnable() {
                 @Override
                 public void run() {