Added option to enable inverting original message

FAQ.md

@@ -1391,7 +1391,9 @@ FairEmail already tries to workaround these bugs, but if this fail you'll need t
 ~~The original message is shown as the sender has sent it, including all colors.~~
 ~~Changing the background color would not only make the original view not original anymore, it can also result in unreadable messages.~~
 
-Recent versions of FairEmail will invert all colors of the original message when using a dark or black theme.
+Recent versions of FairEmail can invert all colors of the original message when using a dark or black theme.
+You can turn this on the advanced settings.
+Be aware that this can cause [crashes](https://bugs.chromium.org/p/chromium/issues/detail?id=578150) on some devices.
 
 <br />
 

app/src/main/java/eu/faircode/email/AdapterMessage.java

@@ -1400,16 +1400,13 @@ public class AdapterMessage extends RecyclerView.Adapter<AdapterMessage.ViewHold
                     }
                 };
 
-                if (dark) {
-                    float[] NEGATIVE = new float[]{
-                            -1, 0, 0, 0, 255, // red
-                            0, -1, 0, 0, 255, // green
-                            0, 0, -1, 0, 255, // blue
-                            0, 0, 0, 1, 0 // alpha
-                    };
+                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+                boolean invert = prefs.getBoolean("invert", false);
 
+                if (dark && invert) {
+                    // https://bugs.chromium.org/p/chromium/issues/detail?id=578150
                     Paint paint = new Paint();
-                    paint.setColorFilter(new ColorMatrixColorFilter(NEGATIVE));
+                    paint.setColorFilter(new ColorMatrixColorFilter(Helper.MATRIX_NEGATIVE));
                     webView.setLayerType(View.LAYER_TYPE_HARDWARE, paint);
                 }
 

app/src/main/java/eu/faircode/email/FragmentOptions.java

@@ -86,6 +86,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
     private SwitchCompat swMonospaced;
     private SwitchCompat swHtml;
     private SwitchCompat swImages;
+    private SwitchCompat swInvert;
     private SwitchCompat swActionbar;
 
     private SwitchCompat swPull;
@@ -120,7 +121,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
 
     static String[] OPTIONS_RESTART = new String[]{
             "startup", "date", "threading", "avatars", "identicons", "name_email", "subject_italic", "flags", "preview",
-            "addresses", "monospaced", "autohtml", "autoimages", "actionbar",
+            "addresses", "monospaced", "autohtml", "autoimages", "invert", "actionbar",
             "pull", "swipenav", "autoexpand", "autoclose", "autonext",
             "authentication", "debug"
     };
@@ -129,7 +130,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
             "enabled", "schedule_start", "schedule_end",
             "metered", "download", "roaming",
             "startup", "date", "threading", "avatars", "identicons", "name_email", "subject_italic", "flags", "preview",
-            "addresses", "monospaced", "autohtml", "autoimages", "actionbar",
+            "addresses", "monospaced", "autohtml", "autoimages", "invert", "actionbar",
             "pull", "swipenav", "autoexpand", "autoclose", "autonext", "collapse", "autoread", "automove",
             "autoresize", "resize", "prefix_once", "autosend",
             "notify_preview", "search_local", "light", "sound",
@@ -171,6 +172,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
         swMonospaced = view.findViewById(R.id.swMonospaced);
         swHtml = view.findViewById(R.id.swHtml);
         swImages = view.findViewById(R.id.swImages);
+        swInvert = view.findViewById(R.id.swInvert);
         swActionbar = view.findViewById(R.id.swActionbar);
 
         swPull = view.findViewById(R.id.swPull);
@@ -390,6 +392,13 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
             }
         });
 
+        swInvert.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("invert", checked).apply();
+            }
+        });
+
         swActionbar.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
             @Override
             public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
@@ -686,6 +695,7 @@ public class FragmentOptions extends FragmentBase implements SharedPreferences.O
         swMonospaced.setChecked(prefs.getBoolean("monospaced", false));
         swHtml.setChecked(prefs.getBoolean("autohtml", false));
         swImages.setChecked(prefs.getBoolean("autoimages", false));
+        swInvert.setChecked(prefs.getBoolean("invert", false));
         swActionbar.setChecked(prefs.getBoolean("actionbar", true));
 
         swPull.setChecked(prefs.getBoolean("pull", true));

app/src/main/java/eu/faircode/email/Helper.java

@@ -132,6 +132,13 @@ public class Helper {
 
     static final float LOW_LIGHT = 0.6f;
 
+    static final float[] MATRIX_NEGATIVE = new float[]{
+            -1, 0, 0, 0, 255, // red
+            0, -1, 0, 0, 255, // green
+            0, 0, -1, 0, 255, // blue
+            0, 0, 0, 1, 0 // alpha
+    };
+
     static final String FAQ_URI = "https://github.com/M66B/open-source-email/blob/master/FAQ.md";
 
     static ThreadFactory backgroundThreadFactory = new ThreadFactory() {

app/src/main/res/layout/fragment_options.xml

@@ -503,6 +503,18 @@
             app:layout_constraintStart_toStartOf="parent"
             app:layout_constraintTop_toBottomOf="@id/swImages" />
 
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/swInvert"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginStart="12dp"
+            android:layout_marginTop="12dp"
+            android:layout_marginEnd="12dp"
+            android:text="@string/title_advanced_invert"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/tvImagesHint"
+            app:switchPadding="12dp" />
+
         <androidx.appcompat.widget.SwitchCompat
             android:id="@+id/swActionbar"
             android:layout_width="match_parent"
@@ -512,7 +524,7 @@
             android:layout_marginEnd="12dp"
             android:text="@string/title_advanced_actionbar"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/tvImagesHint"
+            app:layout_constraintTop_toBottomOf="@id/swInvert"
             app:switchPadding="12dp" />
 
         <TextView

app/src/main/res/values/strings.xml

@@ -177,6 +177,7 @@
     <string name="title_advanced_monospaced">Use monospaced font for message text</string>
     <string name="title_advanced_html">Automatically show original message for known contacts</string>
     <string name="title_advanced_images">Automatically show images for known contacts</string>
+    <string name="title_advanced_invert">Invert colors of original message when using a dark theme</string>
     <string name="title_advanced_actionbar">Conversation action bar</string>
 
     <string name="title_advanced_pull_refresh">Pull down to refresh</string>