Wait for smooth scrolling animation to add new message (#2084)

Co-authored-by: Paweł <zneix@zneix.eu>
Co-authored-by: pajlada <rasmus.karlsson@pajlada.com>

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unversioned
 
+- Bugfix: Fixed visual glitch with smooth scrolling. (#2084)
+
 ## 2.3.0
 
 - Major: Added custom FrankerFaceZ VIP Badges. (#2628)

src/widgets/Scrollbar.cpp

@@ -188,6 +188,11 @@ qreal Scrollbar::getCurrentValue() const
     return this->currentValue_;
 }
 
+const QPropertyAnimation &Scrollbar::getCurrentValueAnimation() const
+{
+    return this->currentValueAnimation_;
+}
+
 void Scrollbar::offset(qreal value)
 {
     if (this->currentValueAnimation_.state() == QPropertyAnimation::Running)

src/widgets/Scrollbar.hpp

@@ -44,6 +44,8 @@ public:
     qreal getDesiredValue() const;
     qreal getCurrentValue() const;
 
+    const QPropertyAnimation &getCurrentValueAnimation() const;
+
     // offset the desired value without breaking smooth scolling
     void offset(qreal value);
     pajlada::Signals::NoArgSignal &getCurrentValueChanged();

src/widgets/helper/ChannelView.cpp

@@ -785,6 +785,18 @@ void ChannelView::messageAppended(MessagePtr &message,
     this->lastMessageHasAlternateBackground_ =
         !this->lastMessageHasAlternateBackground_;
 
+    if (!this->scrollBar_->isAtBottom() &&
+        this->scrollBar_->getCurrentValueAnimation().state() ==
+            QPropertyAnimation::Running)
+    {
+        QEventLoop loop;
+
+        connect(&this->scrollBar_->getCurrentValueAnimation(),
+                &QAbstractAnimation::stateChanged, &loop, &QEventLoop::quit);
+
+        loop.exec();
+    }
+
     if (this->messages_.pushBack(MessageLayoutPtr(messageRef), deleted))
     {
         if (this->paused())