Fix smooth scrolling when ChannelView is full (#4501)

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

src/widgets/helper/ChannelView.cpp

@@ -328,8 +328,10 @@ void ChannelView::updatePauses()
         this->pauseEnd_ = boost::none;
         this->pauseTimer_.stop();
 
-        this->scrollBar_->offset(this->pauseScrollOffset_);
-        this->pauseScrollOffset_ = 0;
+        this->scrollBar_->offsetMaximum(this->pauseScrollMaximumOffset_);
+        this->scrollBar_->offsetMinimum(this->pauseScrollMinimumOffset_);
+        this->pauseScrollMinimumOffset_ = 0;
+        this->pauseScrollMaximumOffset_ = 0;
 
         this->queueLayout();
     }
@@ -453,7 +455,7 @@ void ChannelView::performLayout(bool causedByScrollbar)
 void ChannelView::layoutVisibleMessages(
     const LimitedQueueSnapshot<MessageLayoutPtr> &messages)
 {
-    const auto start = size_t(this->scrollBar_->getCurrentValue());
+    const auto start = size_t(this->scrollBar_->getRelativeCurrentValue());
     const auto layoutWidth = this->getLayoutWidth();
     const auto flags = this->getFlags();
     auto redrawRequired = false;
@@ -461,7 +463,7 @@ void ChannelView::layoutVisibleMessages(
     if (messages.size() > start)
     {
         auto y = int(-(messages[start]->getHeight() *
-                       (fmod(this->scrollBar_->getCurrentValue(), 1))));
+                       (fmod(this->scrollBar_->getRelativeCurrentValue(), 1))));
 
         for (auto i = start; i < messages.size() && y <= this->height(); i++)
         {
@@ -521,21 +523,17 @@ void ChannelView::updateScrollbar(
 
     if (!showScrollbar && !causedByScrollbar)
     {
-        this->scrollBar_->setDesiredValue(0);
+        this->scrollBar_->scrollToTop();
     }
     this->showScrollBar_ = showScrollbar;
 
-    this->scrollBar_->setMaximum(messages.size());
-
     // If we were showing the latest messages and the scrollbar now wants to be
     // rendered, scroll to bottom
     if (this->enableScrollingToBottom_ && this->showingLatestMessages_ &&
-        showScrollbar)
+        showScrollbar && !causedByScrollbar)
     {
         this->scrollBar_->scrollToBottom(
-            // this->messageWasAdded &&
             getSettings()->enableSmoothScrollingNewMessages.getValue());
-        this->messageWasAdded_ = false;
     }
 }
 
@@ -544,6 +542,9 @@ void ChannelView::clearMessages()
     // Clear all stored messages in this chat widget
     this->messages_.clear();
     this->scrollBar_->clearHighlights();
+    this->scrollBar_->resetMaximum();
+    this->scrollBar_->setMaximum(0);
+    this->scrollBar_->setMinimum(0);
     this->queueLayout();
 
     this->lastMessageHasAlternateBackground_ = false;
@@ -750,12 +751,6 @@ void ChannelView::setChannel(ChannelPtr underlyingChannel)
             this->messageAddedAtStart(messages);
         });
 
-    // on message removed
-    this->channelConnections_.managedConnect(
-        this->channel_->messageRemovedFromStart, [this](MessagePtr &message) {
-            this->messageRemoveFromStart(message);
-        });
-
     // on message replaced
     this->channelConnections_.managedConnect(
         this->channel_->messageReplaced,
@@ -771,6 +766,8 @@ void ChannelView::setChannel(ChannelPtr underlyingChannel)
 
     auto snapshot = underlyingChannel->getMessageSnapshot();
 
+    this->scrollBar_->setMaximum(qreal(snapshot.size()));
+
     for (const auto &msg : snapshot)
     {
         auto messageLayout = std::make_shared<MessageLayout>(msg);
@@ -881,31 +878,26 @@ void ChannelView::messageAppended(MessagePtr &message,
     this->lastMessageHasAlternateBackground_ =
         !this->lastMessageHasAlternateBackground_;
 
-    if (!this->scrollBar_->isAtBottom() &&
-        this->scrollBar_->getCurrentValueAnimation().state() ==
-            QPropertyAnimation::Running)
+    if (this->paused())
     {
-        QEventLoop loop;
-
-        connect(&this->scrollBar_->getCurrentValueAnimation(),
-                &QAbstractAnimation::stateChanged, &loop, &QEventLoop::quit);
-
-        loop.exec();
+        this->pauseScrollMaximumOffset_++;
+    }
+    else
+    {
+        this->scrollBar_->offsetMaximum(1);
     }
 
     if (this->messages_.pushBack(messageRef))
     {
         if (this->paused())
         {
-            if (!this->scrollBar_->isAtBottom())
-                this->pauseScrollOffset_--;
+            this->pauseScrollMinimumOffset_++;
+            this->pauseSelectionOffset_++;
         }
         else
         {
-            if (this->scrollBar_->isAtBottom())
-                this->scrollBar_->scrollToBottom();
-            else
-                this->scrollBar_->offset(-1);
+            this->scrollBar_->offsetMinimum(1);
+            this->selection_.shiftMessageIndex(1);
         }
     }
 
@@ -931,7 +923,6 @@ void ChannelView::messageAppended(MessagePtr &message,
         this->scrollBar_->addHighlight(message->getScrollBarHighlight());
     }
 
-    this->messageWasAdded_ = true;
     this->queueLayout();
 }
 
@@ -956,12 +947,14 @@ void ChannelView::messageAddedAtStart(std::vector<MessagePtr> &messages)
     }
 
     /// Add the messages at the start
-    if (this->messages_.pushFront(messageRefs).size() > 0)
+    auto addedMessages = this->messages_.pushFront(messageRefs);
+    if (!addedMessages.empty())
     {
         if (this->scrollBar_->isAtBottom())
             this->scrollBar_->scrollToBottom();
         else
-            this->scrollBar_->offset(qreal(messages.size()));
+            this->scrollBar_->offset(qreal(addedMessages.size()));
+        this->scrollBar_->offsetMaximum(qreal(addedMessages.size()));
     }
 
     if (this->showScrollbarHighlights())
@@ -976,21 +969,6 @@ void ChannelView::messageAddedAtStart(std::vector<MessagePtr> &messages)
         this->scrollBar_->addHighlightsAtStart(highlights);
     }
 
-    this->messageWasAdded_ = true;
-    this->queueLayout();
-}
-
-void ChannelView::messageRemoveFromStart(MessagePtr &message)
-{
-    if (this->paused())
-    {
-        this->pauseSelectionOffset_ += 1;
-    }
-    else
-    {
-        this->selection_.shiftMessageIndex(1);
-    }
-
     this->queueLayout();
 }
 
@@ -1024,6 +1002,9 @@ void ChannelView::messagesUpdated()
 
     this->messages_.clear();
     this->scrollBar_->clearHighlights();
+    this->scrollBar_->resetMaximum();
+    this->scrollBar_->setMaximum(qreal(snapshot.size()));
+    this->scrollBar_->setMinimum(0);
     this->lastMessageHasAlternateBackground_ = false;
     this->lastMessageHasAlternateBackgroundReverse_ = true;
 
@@ -1227,7 +1208,8 @@ void ChannelView::scrollToMessageLayout(MessageLayout *layout,
 
     if (this->showScrollBar_)
     {
-        this->getScrollBar().setDesiredValue(messageIdx);
+        this->getScrollBar().setDesiredValue(this->scrollBar_->getMinimum() +
+                                             qreal(messageIdx));
     }
 }
 
@@ -1258,7 +1240,7 @@ void ChannelView::drawMessages(QPainter &painter)
 {
     auto &messagesSnapshot = this->getMessagesSnapshot();
 
-    size_t start = size_t(this->scrollBar_->getCurrentValue());
+    const auto start = size_t(this->scrollBar_->getRelativeCurrentValue());
 
     if (start >= messagesSnapshot.size())
     {
@@ -1266,7 +1248,7 @@ void ChannelView::drawMessages(QPainter &painter)
     }
 
     int y = int(-(messagesSnapshot[start].get()->getHeight() *
-                  (fmod(this->scrollBar_->getCurrentValue(), 1))));
+                  (fmod(this->scrollBar_->getRelativeCurrentValue(), 1))));
 
     MessageLayout *end = nullptr;
     bool windowFocused = this->window() == QApplication::activeWindow();
@@ -1368,7 +1350,8 @@ void ChannelView::wheelEvent(QWheelEvent *event)
 
         auto &snapshot = this->getMessagesSnapshot();
         int snapshotLength = int(snapshot.size());
-        int i = std::min<int>(int(desired), snapshotLength);
+        int i = std::min<int>(int(desired - this->scrollBar_->getMinimum()),
+                              snapshotLength - 1);
 
         if (delta > 0)
         {
@@ -2779,7 +2762,7 @@ bool ChannelView::tryGetMessageAt(QPoint p,
 {
     auto &messagesSnapshot = this->getMessagesSnapshot();
 
-    size_t start = this->scrollBar_->getCurrentValue();
+    const auto start = size_t(this->scrollBar_->getRelativeCurrentValue());
 
     if (start >= messagesSnapshot.size())
     {
@@ -2787,7 +2770,7 @@ bool ChannelView::tryGetMessageAt(QPoint p,
     }
 
     int y = -(messagesSnapshot[start]->getHeight() *
-              (fmod(this->scrollBar_->getCurrentValue(), 1)));
+              (fmod(this->scrollBar_->getRelativeCurrentValue(), 1)));
 
     for (size_t i = start; i < messagesSnapshot.size(); ++i)
     {