Allow ChannelViews without a Split (#4747)

src/widgets/helper/ChannelView.hpp

@@ -75,7 +75,23 @@ public:
         Search,
     };
 
-    explicit ChannelView(BaseWidget *parent = nullptr, Split *split = nullptr,
+    /// Creates a channel view without a split.
+    /// In such a view, usercards and reply-threads can't be opened.
+    ///
+    /// @param parent The parent of this widget. Can be `nullptr`.
+    /// @param context The context in which this view is shown (e.g. as a usercard).
+    /// @param messagesLimit The maximum amount of messages this view will display.
+    explicit ChannelView(QWidget *parent, Context context = Context::None,
+                         size_t messagesLimit = 1000);
+
+    /// Creates a channel view in a split.
+    ///
+    /// @param parent The parent of this widget.
+    /// @param split The split containing this widget.
+    ///              @a split must be in the widget tree of @a parent.
+    /// @param context The context in which this view is shown (e.g. as a usercard).
+    /// @param messagesLimit The maximum amount of messages this view will display.
+    explicit ChannelView(QWidget *parent, Split *split,
                          Context context = Context::None,
                          size_t messagesLimit = 1000);
 
@@ -192,6 +208,12 @@ protected:
                          QPoint &relativePos, int &index);
 
 private:
+    struct InternalCtor {
+    };
+
+    ChannelView(InternalCtor tag, QWidget *parent, Split *split,
+                Context context, size_t messagesLimit);
+
     void initializeLayout();
     void initializeScrollbar();
     void initializeSignals();
@@ -270,7 +292,7 @@ private:
     ChannelPtr channel_ = nullptr;
     ChannelPtr underlyingChannel_ = nullptr;
     ChannelPtr sourceChannel_ = nullptr;
-    Split *split_ = nullptr;
+    Split *split_;
 
     Scrollbar *scrollBar_;
     EffectLabel *goToBottom_{};