Show a placeholder for encrypted messages

Tells the user that the message could not be decrypted because the key
was not shared with the device. At the moment, this is technically not
completely correct, but it will be when libQuotient supports reading
encrypted messages

imports/NeoChat/Component/Timeline/EncryptedDelegate.qml

@@ -0,0 +1,19 @@
+// SPDX-FileCopyrightText: 2021 Tobias Fella <fella@posteo.de>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+import QtQuick 2.15
+import QtQuick.Controls 2.15
+
+import org.kde.kirigami 2.15 as Kirigami
+import org.kde.neochat 1.0
+
+TextEdit {
+    text: i18n("This message is encrypted and the sender has not shared the key with this device.")
+    color: Kirigami.Theme.disabledTextColor
+    font.pointSize: Kirigami.Theme.defaultFont.pointSize
+    selectByMouse: !Kirigami.Settings.isMobile
+    readOnly: true
+    wrapMode: Text.WordWrap
+    textFormat: Text.RichText
+    width: messageContainer.bubbleMaxWidth
+}

imports/NeoChat/Component/Timeline/qmldir

@@ -8,3 +8,4 @@ FileDelegate 1.0 FileDelegate.qml
 VideoDelegate 1.0 VideoDelegate.qml
 ReactionDelegate 1.0 ReactionDelegate.qml
 AudioDelegate 1.0 AudioDelegate.qml
+EncryptedDelegate 1.0 EncryptedDelegate.qml

imports/NeoChat/Page/RoomPage.qml

@@ -557,6 +557,22 @@ Kirigami.ScrollablePage {
                 }
             }
 
+            DelegateChoice {
+                roleValue: "encrypted"
+                delegate: TimelineContainer {
+                    id: encryptedContainer
+                    width: messageListView.width
+                    isLoaded: timelineDelegateChooser.delegateLoaded
+
+                    innerObject: EncryptedDelegate {
+                        Layout.fillWidth: Config.compactLayout
+                        Layout.maximumWidth: encryptedContainer.bubbleMaxWidth
+                        Layout.rightMargin: Kirigami.Units.largeSpacing
+                        Layout.leftMargin: Config.showAvatarInTimeline ? Kirigami.Units.largeSpacing : 0
+                    }
+                }
+            }
+
             DelegateChoice {
                 roleValue: "readMarker"
                 delegate: QQC2.ItemDelegate {

res.qrc

@@ -40,6 +40,7 @@
         <file>imports/NeoChat/Component/Timeline/AudioDelegate.qml</file>
         <file>imports/NeoChat/Component/Timeline/FileDelegate.qml</file>
         <file>imports/NeoChat/Component/Timeline/ImageDelegate.qml</file>
+        <file>imports/NeoChat/Component/Timeline/EncryptedDelegate.qml</file>
         <file>imports/NeoChat/Component/Login/qmldir</file>
         <file>imports/NeoChat/Component/Login/LoginStep.qml</file>
         <file>imports/NeoChat/Component/Login/Login.qml</file>

src/messageeventmodel.cpp

@@ -490,6 +490,9 @@ QVariant MessageEventModel::data(const QModelIndex &idx, int role) const
         if (evt.isStateEvent()) {
             return "state";
         }
+        if (is<const EncryptedEvent>(evt)) {
+            return "encrypted";
+        }
 
         return "other";
     }