Fix scroll area child widgets wheel event lock lasts too long after

scrolling stops in some circumstances Basically, if the user moves the mouse after scrolling the area with the wheel, we should release the time based lock we use to avoid unwanted widget changes mid-scroll immediately. Otherwise it's impossible to scroll wheel->move mouse onto widget->wheel to change widget value quickly.
qgis · Jan 18, 2022 · f4b7a93 · f4b7a93
1 parent 6c1fa05
commit f4b7a93
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Showing 3 changed files with 39 additions and 1 deletion.
diff --git a/python/gui/auto_generated/qgsscrollarea.sip.in b/python/gui/auto_generated/qgsscrollarea.sip.in
@@ -47,6 +47,7 @@ Returns ``True`` if a scroll recently occurred within
 the QScrollArea or its child :py:func:`~QgsScrollArea.viewport`
 %End
 
+
     void setVerticalOnly( bool verticalOnly );
 %Docstring
 Sets whether the scroll area only applies vertical.

diff --git a/src/gui/qgsscrollarea.cpp b/src/gui/qgsscrollarea.cpp
@@ -17,6 +17,7 @@
 #include <QMouseEvent>
 #include "qgsscrollarea.h"
 #include <QScrollBar>
+#include "qgslogger.h"
 
 // milliseconds to swallow child wheel events for after a scroll occurs
 #define TIMEOUT 1000
@@ -26,6 +27,7 @@ QgsScrollArea::QgsScrollArea( QWidget *parent )
   , mFilter( new ScrollAreaFilter( this, viewport() ) )
 {
   viewport()->installEventFilter( mFilter );
+  setMouseTracking( true );
 }
 
 void QgsScrollArea::wheelEvent( QWheelEvent *e )
@@ -53,6 +55,11 @@ bool QgsScrollArea::hasScrolled() const
   return mTimer.isActive();
 }
 
+void QgsScrollArea::resetHasScrolled()
+{
+  mTimer.stop();
+}
+
 void QgsScrollArea::setVerticalOnly( bool verticalOnly )
 {
   mVerticalOnly = verticalOnly;
@@ -69,7 +76,10 @@ ScrollAreaFilter::ScrollAreaFilter( QgsScrollArea *parent, QWidget *viewPort )
   : QObject( parent )
   , mScrollAreaWidget( parent )
   , mViewPort( viewPort )
-{}
+{
+  QFontMetrics fm( parent->font() );
+  mMoveDistanceThreshold = fm.horizontalAdvance( 'X' );
+}
 
 bool ScrollAreaFilter::eventFilter( QObject *obj, QEvent *event )
 {
@@ -90,6 +100,22 @@ bool ScrollAreaFilter::eventFilter( QObject *obj, QEvent *event )
       break;
     }
 
+    case QEvent::MouseMove:
+    {
+      if ( obj == mViewPort )
+      {
+        const QPoint mouseDelta = QCursor::pos() - mPreviousViewportCursorPos;
+        if ( mouseDelta.manhattanLength() > mMoveDistanceThreshold )
+        {
+          // release time based child widget constraint -- user moved the mouse over the viewport (and not just an accidental "wiggle")
+          // so we no longer are in the 'possible unwanted mouse wheel event going to child widget mid-scroll' state
+          mScrollAreaWidget->resetHasScrolled();
+        }
+        mPreviousViewportCursorPos = QCursor::pos();
+      }
+      break;
+    }
+
     case QEvent::Wheel:
     {
       if ( obj == mViewPort )
@@ -119,6 +145,8 @@ void ScrollAreaFilter::addChild( QObject *child )
   if ( child && child->isWidgetType() )
   {
     child->installEventFilter( this );
+    if ( QWidget *w = qobject_cast< QWidget * >( child ) )
+      w->setMouseTracking( true );
 
     // also install filter on existing children
     const auto constChildren = child->children();

diff --git a/src/gui/qgsscrollarea.h b/src/gui/qgsscrollarea.h
@@ -61,6 +61,13 @@ class GUI_EXPORT QgsScrollArea : public QScrollArea
      */
     bool hasScrolled() const;
 
+    /**
+     * Resets the hasScrolled() flag.
+     *
+     * \since QGIS 3.24
+     */
+    void resetHasScrolled() SIP_SKIP;
+
     /**
      * Sets whether the scroll area only applies vertical.
      *
@@ -105,6 +112,8 @@ class ScrollAreaFilter : public QObject
   private:
     QgsScrollArea *mScrollAreaWidget = nullptr;
     QWidget *mViewPort = nullptr;
+    QPoint mPreviousViewportCursorPos;
+    int mMoveDistanceThreshold = 0;
 
     void addChild( QObject *child );
     void removeChild( QObject *child );