Enable scrollbar on the room list for macOS (#174)

resources/styles/nheko-dark.qss

@@ -45,6 +45,7 @@ PopupItem {
 RoomList,
 RoomList > * {
     background-color: #2d3139;
+    border: none;
 }
 
 CommunitiesList,

resources/styles/nheko.qss

@@ -45,6 +45,7 @@ PopupItem {
 RoomList,
 RoomList > * {
     background-color: white;
+    border: none;
 }
 
 CommunitiesList,

resources/styles/system.qss

@@ -70,6 +70,11 @@ RegisterPage {
     background-color: palette(window);
 }
 
+RoomList,
+RoomList > * {
+    border: none;
+}
+
 RoomInfoListItem {
     qproperty-highlightedBackgroundColor: palette(highlight);
     qproperty-hoverBackgroundColor: palette(light);

src/RoomList.cpp

@@ -34,18 +34,22 @@ RoomList::RoomList(QSharedPointer<UserSettings> userSettings, QWidget *parent)
   : QWidget(parent)
   , userSettings_{userSettings}
 {
-        setStyleSheet("border: none;");
         topLayout_ = new QVBoxLayout(this);
         topLayout_->setSpacing(0);
         topLayout_->setMargin(0);
 
         scrollArea_ = new QScrollArea(this);
         scrollArea_->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
-        scrollArea_->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
         scrollArea_->setSizeAdjustPolicy(QAbstractScrollArea::AdjustToContents);
         scrollArea_->setWidgetResizable(true);
         scrollArea_->setAlignment(Qt::AlignLeading | Qt::AlignTop | Qt::AlignVCenter);
 
+        // The scrollbar on macOS will hide itself when not active so it won't interfere
+        // with the content.
+#if not defined(Q_OS_MAC)
+        scrollArea_->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+#endif
+
         scrollAreaContents_ = new QWidget(this);
 
         contentsLayout_ = new QVBoxLayout(scrollAreaContents_);