Add (invisible) resize handle to frameless usercards and reply threads (#4795)

* feat: add resize handle to usercards&reply threads

* Add changelog entry

---------

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/widgets/dialogs/ReplyThreadPopup.cpp

@@ -13,6 +13,7 @@
 #include "util/LayoutCreator.hpp"
 #include "widgets/helper/Button.hpp"
 #include "widgets/helper/ChannelView.hpp"
+#include "widgets/helper/InvisibleSizeGrip.hpp"
 #include "widgets/Scrollbar.hpp"
 #include "widgets/splits/Split.hpp"
 #include "widgets/splits/SplitInput.hpp"
@@ -120,8 +121,10 @@ ReplyThreadPopup::ReplyThreadPopup(bool closeAutomatically, QWidget *parent,
         }
     });
 
-    auto layout = LayoutCreator<QWidget>(this->getLayoutContainer())
-                      .setLayoutType<QVBoxLayout>();
+    auto layers = LayoutCreator<QWidget>(this->getLayoutContainer())
+                      .setLayoutType<QGridLayout>()
+                      .withoutMargin();
+    auto layout = layers.emplace<QVBoxLayout>();
 
     layout->setSpacing(0);
     // provide draggable margin if frameless
@@ -174,6 +177,13 @@ ReplyThreadPopup::ReplyThreadPopup(bool closeAutomatically, QWidget *parent,
 
     layout->addWidget(this->ui_.threadView, 1);
     layout->addWidget(this->ui_.replyInput);
+
+    // size grip
+    if (closeAutomatically)
+    {
+        layers->addWidget(new InvisibleSizeGrip(this), 0, 0,
+                          Qt::AlignRight | Qt::AlignBottom);
+    }
 }
 
 void ReplyThreadPopup::setThread(std::shared_ptr<MessageThread> thread)