feat: scroll the thread list smoothlyHEADmaster

The list scrolled per ITEM, Qt's default, so a wheel notch jumped
several whole cards at once and a touchpad's small deltas were
quantised into card-sized jumps. The eye lost track of how far the
list had moved.

The view now scrolls per pixel, so a touchpad moves it continuously,
and ThreadListView::wheelEvent turns each wheel notch into a 160ms
eased glide of exactly one card. Notches arriving mid-glide add to its
target rather than restarting from where it has got to. Pixel deltas
and modified wheels pass through to Qt unchanged. The cost of per-pixel
scrolling is that a card can rest half above the top edge.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/src/threadlistview.cpp b/src/threadlistview.cpp
index 019d7c9..b5176bf 100644
--- a/src/threadlistview.cpp
+++ b/src/threadlistview.cpp
@@ -22,6 +22,9 @@
 #include "threadlistmodel.h"
 
 #include <QMouseEvent>
+#include <QPropertyAnimation>
+#include <QScrollBar>
+#include <QWheelEvent>
 
 void ThreadListView::mousePressEvent(QMouseEvent *event)
 {
@@ -53,3 +56,33 @@ void ThreadListView::mousePressEvent(QMouseEvent *event)
 
     QTreeView::mousePressEvent(event);
 }
+
+void ThreadListView::wheelEvent(QWheelEvent *event)
+{
+    const int notches = event->angleDelta().y() / QWheelEvent::DefaultDeltasPerStep;
+    if (!event->pixelDelta().isNull() || event->modifiers() != Qt::NoModifier
+        || notches == 0) {
+        // ponytail: a high-resolution wheel sending less than one notch per
+        // event falls through to the plain per-pixel scroll, unanimated.
+        QTreeView::wheelEvent(event);
+        return;
+    }
+
+    QScrollBar *bar = verticalScrollBar();
+    if (!m_glide) {
+        m_glide = new QPropertyAnimation(bar, "value", this);
+        m_glide->setDuration(160);
+        m_glide->setEasingCurve(QEasingCurve::OutCubic);
+    }
+
+    const bool gliding = m_glide->state() == QAbstractAnimation::Running;
+    const int from = gliding ? m_glide->endValue().toInt() : bar->value();
+    const int to = qBound(bar->minimum(), from - notches * bar->singleStep(),
+                          bar->maximum());
+
+    m_glide->stop();
+    m_glide->setStartValue(bar->value());
+    m_glide->setEndValue(to);
+    m_glide->start();
+    event->accept();
+}