[vlc-commits] [Git][videolan/vlc][master] qt: use the old scrolling approach in flickables if Qt >= 6.6.0

[Steve Lhomme (@robUx4)]

Steve Lhomme pushed to branch master at VideoLAN / VLC


Commits:
0c21aa42 by Fatih Uzunoglu at 2025-06-17T10:37:59+00:00
qt: use the old scrolling approach in flickables if Qt >= 6.6.0

The new scrolling behavior has caused a lot of frustration, and
it completely broke scrolling when there are sections.

The old behavior with deceleration set to 10000 feels much better,
and fixes scrolling when there are view sections.

- - - - -


1 changed file:

- modules/gui/qt/maininterface/mainui.cpp


Changes:

=====================================
modules/gui/qt/maininterface/mainui.cpp
=====================================
@@ -93,6 +93,26 @@ MainUI::MainUI(qt_intf_t *p_intf, MainCtx *mainCtx, QWindow* interfaceWindow,  Q
     assert(m_interfaceWindow);
 
     registerQMLTypes();
+
+    // FIXME: Since Qt 6.6, Qt follows a different approach for scrolling. This new approach has
+    //        caused a lot of frustration (QTBUG-116388, QTBUG-129948, QTBUG-120038). However,
+    //        the previous scrolling behavior was not perfect either, so we have not been opting
+    //        in to use the previous behavior. That being said, the new approach broke scrolling
+    //        with views that has sections completely, so we don't have any option besides using
+    //        the previous scrolling implementation. The new approach (b1766d9), `Flickable:
+    //        Proportional wheel scrolling if deceleration is large` tells that the previous
+    //        deceleration value was 5000. In this case, we use 10000 instead to not make scrolling
+    //        as loose as it was before (which was apparently the main reason of coming up with the
+    //        new approach). Setting this environment variable to any value lower than 15000
+    //        reportedly (and evidently) brings back the old behavior, and does not continue
+    //        using the new approach with the deceleration set (which is what we want to fix
+    //        scrolling when there are sections).
+    if constexpr (QT_VERSION >= QT_VERSION_CHECK(6, 6, 0))
+    {
+        const auto envFlickableWheelDeceleration = "QT_QUICK_FLICKABLE_WHEEL_DECELERATION";
+        if (qEnvironmentVariableIsEmpty(envFlickableWheelDeceleration))
+            qputenv(envFlickableWheelDeceleration, QByteArrayLiteral("10000"));
+    }
 }
 
 MainUI::~MainUI()



View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/0c21aa42a39851c6015a4196e54c541b113dc06c

-- 
View it on GitLab: https://code.videolan.org/videolan/vlc/-/commit/0c21aa42a39851c6015a4196e54c541b113dc06c
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