AppletPanel: drop hover-reveal, dim handle at rest with 500ms hold

ten9876 · claude · ten9876 · commit 94b67450dd83 · 2026-05-01T11:40:05.000-07:00
Maintainer feedback: the hover-reveal felt too abrupt and the
transparent track left a visible gap on the right edge of the panel
when the slider faded out.

Changes from the original PR:
- Track always visible at #0a0a14 (matches the rest of the app and
  fills the gap consistently — no transparent strip).
- Handle dim (#2a3a4a) at rest, bright (#4a6880) on hover or drag.
- 500ms delay before dimming back so quick scroll gestures don't
  flicker; re-entering during the hold cancels the timer.
- Implemented via dynamic property `active` plus an event filter on
  the QScrollBar (QSS doesn't support animated transitions).

`min-height: 20px` and the bright color are unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) &lt;noreply@anthropic.com&gt;
diff --git a/src/gui/AppletPanel.cpp b/src/gui/AppletPanel.cpp
@@ -39,6 +39,9 @@
 #include "core/AppSettings.h"
 #include <QPushButton>
 #include <QScrollArea>
+#include <QScrollBar>
+#include <QStyle>
+#include <QTimer>
 #include <QVBoxLayout>
 #include <QHBoxLayout>
 #include <QLabel>
@@ -368,13 +371,24 @@ AppletPanel::AppletPanel(QWidget* parent) : QWidget(parent)
     m_scrollArea->setFrameShape(QFrame::NoFrame);
     m_scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
     m_scrollArea->setWidgetResizable(true);
+    // Handle dims to #2a3a4a at rest, brightens to #4a6880 on hover/drag.
+    // 500 ms delay before dimming back so quick drags don't flicker.
     m_scrollArea->setStyleSheet(
-        "QScrollBar:vertical { background: transparent; width: 12px; }"
-        "QScrollBar:vertical:hover { background: #0a0a14; }"
-        "QScrollBar::handle:vertical { background: transparent; border-radius: 4px; min-height: 20px; }"
-        "QScrollBar::handle:vertical:hover, QScrollBar::handle:vertical:pressed { background: #4a6880; }"
+        "QScrollBar:vertical { background: #0a0a14; width: 12px; }"
+        "QScrollBar::handle:vertical { background: #2a3a4a; border-radius: 4px; min-height: 20px; }"
+        "QScrollBar::handle:vertical[active=\"true\"] { background: #4a6880; }"
         "QScrollBar::add-line:vertical, QScrollBar::sub-line:vertical { height: 0; }");
 
+    if (auto* sb = m_scrollArea->verticalScrollBar()) {
+        sb->setProperty("active", false);
+        sb->installEventFilter(this);
+    }
+    m_scrollDimTimer = new QTimer(this);
+    m_scrollDimTimer->setSingleShot(true);
+    m_scrollDimTimer->setInterval(500);
+    connect(m_scrollDimTimer, &QTimer::timeout, this,
+            [this]() { setScrollHandleActive(false); });
+
     auto* container = new QWidget;
     m_stack = new QVBoxLayout(container);
     m_stack->setContentsMargins(0, 0, 0, 0);
@@ -1104,5 +1118,35 @@ void AppletPanel::setTxDspChainOrder(
     }
 }
 
+bool AppletPanel::eventFilter(QObject* obj, QEvent* ev)
+{
+    if (m_scrollArea && obj == m_scrollArea->verticalScrollBar()) {
+        switch (ev->type()) {
+        case QEvent::Enter:
+        case QEvent::MouseButtonPress:
+            if (m_scrollDimTimer) m_scrollDimTimer->stop();
+            setScrollHandleActive(true);
+            break;
+        case QEvent::Leave:
+        case QEvent::MouseButtonRelease:
+            if (m_scrollDimTimer) m_scrollDimTimer->start();
+            break;
+        default:
+            break;
+        }
+    }
+    return QWidget::eventFilter(obj, ev);
+}
+
+void AppletPanel::setScrollHandleActive(bool active)
+{
+    if (!m_scrollArea) return;
+    auto* sb = m_scrollArea->verticalScrollBar();
+    if (!sb) return;
+    if (sb->property("active").toBool() == active) return;
+    sb->setProperty("active", active);
+    sb->style()->unpolish(sb);
+    sb->style()->polish(sb);
+}
 
 } // namespace AetherSDR
diff --git a/src/gui/AppletPanel.h b/src/gui/AppletPanel.h
@@ -10,6 +10,7 @@
 class QComboBox;
 class QPushButton;
 class QScrollArea;
+class QTimer;
 class QVBoxLayout;
 
 namespace AetherSDR {
@@ -175,10 +176,14 @@ class AppletPanel : public QWidget {
 
     friend class AppletDropArea;
 
+protected:
+    bool eventFilter(QObject* obj, QEvent* ev) override;
+
 private:
     void rebuildStackOrder();
     void saveOrder();
     int dropIndexFromY(int localY) const;
+    void setScrollHandleActive(bool active);
 
     ContainerManager* m_containerMgr{nullptr};
     ContainerWidget*  m_rootSidebar{nullptr};
@@ -228,6 +233,7 @@ class AppletPanel : public QWidget {
     QPushButton* m_ssBtn{nullptr};
     QVBoxLayout* m_stack{nullptr};
     QScrollArea* m_scrollArea{nullptr};
+    QTimer*      m_scrollDimTimer{nullptr};
     QWidget*     m_dropIndicator{nullptr};
     QPushButton* m_lockBtn{nullptr};   // controls-lock toggle (#745)
 
