Added setting to send format=flowed

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

@@ -51,6 +51,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
     private SwitchCompat swExtendedReply;
     private SwitchCompat swQuoteReply;
     private SwitchCompat swPlainOnly;
+    private SwitchCompat swFormatFlowed;
     private Spinner spSignatureLocation;
     private SwitchCompat swUsenetSignature;
     private SwitchCompat swRemoveSignatures;
@@ -67,7 +68,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
     private final static String[] RESET_OPTIONS = new String[]{
             "keyboard", "suggest_sent", "suggested_received",
             "prefix_once", "extended_reply", "quote_reply",
-            "plain_only", "signature_location", "usenet_signature", "remove_signatures",
+            "plain_only", "format_flowed", "signature_location", "usenet_signature", "remove_signatures",
             "resize_images", "resize_attachments", "resize",
             "send_reminders", "receipt_default", "receipt_type", "lookup_mx", "send_delayed"
     };
@@ -90,6 +91,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
         swExtendedReply = view.findViewById(R.id.swExtendedReply);
         swQuoteReply = view.findViewById(R.id.swQuoteReply);
         swPlainOnly = view.findViewById(R.id.swPlainOnly);
+        swFormatFlowed = view.findViewById(R.id.swFormatFlowed);
         spSignatureLocation = view.findViewById(R.id.spSignatureLocation);
         swUsenetSignature = view.findViewById(R.id.swUsenetSignature);
         swRemoveSignatures = view.findViewById(R.id.swRemoveSignatures);
@@ -166,6 +168,13 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
             }
         });
 
+        swFormatFlowed.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton compoundButton, boolean checked) {
+                prefs.edit().putBoolean("format_flowed", checked).apply();
+            }
+        });
+
         spSignatureLocation.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> adapterView, View view, int position, long id) {
@@ -321,6 +330,7 @@ public class FragmentOptionsSend extends FragmentBase implements SharedPreferenc
         swExtendedReply.setChecked(prefs.getBoolean("extended_reply", false));
         swQuoteReply.setChecked(prefs.getBoolean("quote_reply", true));
         swPlainOnly.setChecked(prefs.getBoolean("plain_only", false));
+        swFormatFlowed.setChecked(prefs.getBoolean("format_flowed", false));
 
         int signature_location = prefs.getInt("signature_location", 1);
         spSignatureLocation.setSelection(signature_location);

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

@@ -103,6 +103,7 @@ public class MessageHelper {
     static final int MAX_MESSAGE_SIZE = 10 * 1024 * 1024; // bytes
     static final int DEFAULT_ATTACHMENT_DOWNLOAD_SIZE = 256 * 1024; // bytes
     static final long ATTACHMENT_PROGRESS_UPDATE = 1500L; // milliseconds
+    static final int FORMAT_FLOWED_LINE_LENGTH = 72;
 
     // https://tools.ietf.org/html/rfc4021
 
@@ -569,6 +570,9 @@ public class MessageHelper {
             }
         }
 
+        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
+        boolean format_flowed = prefs.getBoolean("format_flowed", false);
+
         // multipart/mixed
         //   multipart/related
         //     multipart/alternative
@@ -578,13 +582,40 @@ public class MessageHelper {
         //  attachments
 
         String htmlContent = document.html();
+        String htmlContentType = "text/html; charset=" + Charset.defaultCharset().name();
+
         String plainContent = HtmlHelper.getText(htmlContent);
+        String plainContentType = "text/plain; charset=" + Charset.defaultCharset().name();
+
+        if (format_flowed) {
+            List<String> flowed = new ArrayList<>();
+            for (String line : plainContent.split("\\r?\\n")) {
+                if (line.contains(" ")) {
+                    StringBuffer sb = new StringBuffer();
+                    for (String word : line.split(" ")) {
+                        if (sb.length() + word.length() > FORMAT_FLOWED_LINE_LENGTH) {
+                            sb.append(' ');
+                            flowed.add(sb.toString());
+                            sb = new StringBuffer();
+                        }
+                        if (sb.length() > 0)
+                            sb.append(' ');
+                        sb.append(word);
+                    }
+                    if (sb.length() > 0)
+                        flowed.add(sb.toString());
+                } else
+                    flowed.add(line);
+            }
+            plainContent = TextUtils.join("\r\n", flowed);
+            plainContentType += "; format=flowed";
+        }
 
         BodyPart plainPart = new MimeBodyPart();
-        plainPart.setContent(plainContent, "text/plain; charset=" + Charset.defaultCharset().name());
+        plainPart.setContent(plainContent, plainContentType);
 
         BodyPart htmlPart = new MimeBodyPart();
-        htmlPart.setContent(htmlContent, "text/html; charset=" + Charset.defaultCharset().name());
+        htmlPart.setContent(htmlContent, htmlContentType);
 
         Multipart altMultiPart = new MimeMultipart("alternative");
         altMultiPart.addBodyPart(plainPart);
@@ -601,7 +632,7 @@ public class MessageHelper {
 
         if (availableAttachments == 0)
             if (message.plain_only != null && message.plain_only)
-                imessage.setContent(plainContent, "text/plain; charset=" + Charset.defaultCharset().name());
+                imessage.setContent(plainContent, plainContentType);
             else
                 imessage.setContent(altMultiPart);
         else {

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

@@ -134,6 +134,17 @@
             app:layout_constraintTop_toBottomOf="@id/swQuoteReply"
             app:switchPadding="12dp" />
 
+        <androidx.appcompat.widget.SwitchCompat
+            android:id="@+id/swFormatFlowed"
+            android:layout_width="0dp"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="12dp"
+            android:text="@string/title_advanced_flow"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toBottomOf="@id/swPlainOnly"
+            app:switchPadding="12dp" />
+
         <eu.faircode.email.FixedTextView
             android:id="@+id/tvSignatureLocation"
             android:layout_width="0dp"
@@ -145,7 +156,7 @@
             android:textColor="?android:attr/textColorPrimary"
             app:layout_constraintEnd_toEndOf="parent"
             app:layout_constraintStart_toStartOf="parent"
-            app:layout_constraintTop_toBottomOf="@id/swPlainOnly" />
+            app:layout_constraintTop_toBottomOf="@id/swFormatFlowed" />
 
         <Spinner
             android:id="@+id/spSignatureLocation"

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

@@ -277,6 +277,7 @@
     <string name="title_advanced_signature_location">Signature position</string>
     <string name="title_advanced_signature_end">Add signature after quoted/forwarded message</string>
     <string name="title_advanced_plain_only">Send plain text only by default</string>
+    <string name="title_advanced_flow">\'format flowed\' for plain text</string>
     <string name="title_advanced_receipt">When requesting a receipt</string>
     <string name="title_advanced_usenet_signature">Usenet signature convention</string>
     <string name="title_advanced_remove_signatures">Remove recognized signatures</string>