PCManFM-Qt patch for disabling smooth-scrolling to fix scrolling behavior on touchpad devices, until https://github.com/lxqt/libfm-qt/pull/875 lands in packages

pcmanfm-qt_disable_smooth_scrolling.patch

--- src/folderview.cpp.orig     2023-02-02 22:54:09.780036423 +0100
+++ src/folderview.cpp  2023-02-02 22:50:06.284034359 +0100
@@ -1592,9 +1592,6 @@
                     return true;
                 }
             }
-            // row-by-row scrolling when Shift is pressed
-            if((QApplication::keyboardModifiers() & Qt::ShiftModifier)
-                && (mode == CompactMode || mode == DetailedListMode)) // other modes have smooth scroling                                                                                              
             {
                 QScrollBar *sbar = (mode == CompactMode ? view->horizontalScrollBar()
                                                         : view->verticalScrollBar());
@@ -1629,54 +1626,6 @@
                     return true;
                 }
             }
-            // This is to fix #85: Scrolling doesn't work in compact view
-            // Actually, I think it's the bug of Qt, not ours.
-            // When in compact mode, only the horizontal scroll bar is used and the vertical one is hidden.                                                                                            
-            // So, when a user scroll his mouse wheel, it's reasonable to scroll the horizontal scollbar.                                                                                              
-            // Qt does not implement such a simple feature, unfortunately.
-            // We do it by forwarding the scroll event in the viewport to the horizontal scrollbar.
-            // FIXME: if someday Qt supports this, we have to disable the workaround.
-            else if(mode == CompactMode) {
-#if (QT_VERSION < QT_VERSION_CHECK(5,14,0))
-                QScrollBar* scroll = view->horizontalScrollBar();
-                if(scroll) {
-                    QApplication::sendEvent(scroll, event);
-                    return true;
-                }
-#else
-                return false; // the problem with horizontal wheel scrolling from inside view is fixed in Qt 5.14                                                                                      
-#endif
-            }
-            // Smooth Scrolling
-            // Some tricks are adapted from <https://github.com/zhou13/qsmoothscrollarea>.
-            else if(mode != DetailedListMode
-                    && event->spontaneous()
-                    && static_cast<QWheelEvent*>(event)->source() == Qt::MouseEventNotSynthesized
-                    && !(QApplication::keyboardModifiers() & Qt::AltModifier)) {
-                if(QScrollBar* vbar = view->verticalScrollBar()) {
-                    // keep track of the wheel event for smooth scrolling
-                    int delta = static_cast<QWheelEvent*>(event)->angleDelta().y();
-                    if(QApplication::keyboardModifiers() & Qt::ShiftModifier) {
-                        delta /= QApplication::wheelScrollLines(); // row-by-row scrolling
-                    }
-                    if((delta > 0 && vbar->value() == vbar->minimum()) || (delta < 0 && vbar->value() == vbar->maximum())) {                                                                           
-                        break; // the scrollbar can't move
-                    }
-
-                    if(!smoothScrollTimer_) {
-                        smoothScrollTimer_ = new QTimer();
-                        connect(smoothScrollTimer_, &QTimer::timeout, this, &FolderView::scrollSmoothly);                                                                                              
-                    }
-
-                    // set the data for smooth scrolling
-                    scrollData data;
-                    data.delta = delta;
-                    data.leftFrames = scrollAnimFrames;
-                    queuedScrollSteps_.append(data);
-                    smoothScrollTimer_->start(1000 / SCROLL_FRAMES_PER_SEC);
-                    return true;
-                }
-            }
             break;
         default:
             break;

Here's a quick rundown on how to apply this on Debian 11 for reference:

# download the source code package
# (this will also automatically extract it in a subfolder)
apt source libfm-qt

# install necessary packages to compile libfm-qt
sudo apt build-dep libfm-qt

# enter the extracted source code directory (version number may differ)
cd libfm-qt-0.16.0/

# create a file using any editor (e.g. nano) and paste the patch into it
nano pcmanfm-qt_disable_smooth_scrolling.patch

# apply the patch
patch -p0 < pcmanfm-qt_disable_smooth_scrolling.patch

# build the modified libfm-qt package
dpkg-buildpackage -rfakeroot -uc -b

# install the patched version (version numbers may differ)
sudo dpkg -i ../libfm-qt8_0.16.0-3_amd64.deb
sudo dpkg -i ../libfm-qt-l10n_0.16.0-3_all.deb