Fix themeing issues on mentions

resources/styles/nheko-dark.qss

@@ -24,6 +24,17 @@ TimelineView > * {
     border: none;
 }
 
+UserMentionsWidget,
+UserMentionsWidget > * {
+    background-color: #202228;
+    border: none;
+}
+
+UserMentionsWidget > TimelineItem {
+    qproperty-backgroundColor: #202228;
+    qproperty-hoverColor: rgba(45, 49, 57, 120);
+}
+
 #scroll_widget {
     background-color: #202228;
 }

resources/styles/nheko.qss

@@ -24,6 +24,17 @@ TimelineView > * {
     border: none;
 }
 
+UserMentionsWidget,
+UserMentionsWidget > * {
+    background-color: white;
+    border: none;
+}
+
+UserMentionsWidget > TimelineItem {
+    qproperty-backgroundColor: white;
+    qproperty-hoverColor: rgba(192, 193, 195, 120);
+}
+
 #scroll_widget {
     background-color: white;
 }

resources/styles/system.qss

@@ -12,6 +12,16 @@ TimelineView > * {
     border: none;
 }
 
+UserMentionsWidget,
+UserMentionsWidget > * {
+    border: none;
+}
+
+UserMentionsWidget > TimelineItem {
+    qproperty-backgroundColor: palette(window);
+    qproperty-hoverColor: palette(base);
+}
+
 TextInputWidget {
     border: none;
     border-top: 1px solid palette(mid);

src/popups/UserMentions.cpp

@@ -1,3 +1,5 @@
+#include <QPainter>
+#include <QStyleOption>
 #include <QTabWidget>
 #include <QTimer>
 
@@ -140,7 +142,6 @@ UserMentions::pushItem(const QString &event_id,
                                                                  local_scroll_widget_);
                 local_view_item->setEventId(event_id);
                 local_view_item->hide();
-
                 local_scroll_layout_->addWidget(local_view_item);
 
                 QTimer::singleShot(0, this, [local_view_item]() {
@@ -148,4 +149,13 @@ UserMentions::pushItem(const QString &event_id,
                         local_view_item->adjustSize();
                 });
         }
+}
+
+void
+UserMentions::paintEvent(QPaintEvent *)
+{
+        QStyleOption opt;
+        opt.init(this);
+        QPainter p(this);
+        style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }

src/popups/UserMentions.h

@@ -5,6 +5,7 @@
 #include <QApplication>
 #include <QEvent>
 #include <QMap>
+#include <QPaintEvent>
 #include <QScrollArea>
 #include <QScrollBar>
 #include <QString>
@@ -26,6 +27,9 @@ public:
         void initializeMentions(const QMap<QString, mtx::responses::Notifications> &notifs);
         void showPopup();
 
+protected:
+        void paintEvent(QPaintEvent *) override;
+
 private:
         void pushItem(const QString &event_id,
                       const QString &user_id,