KItemListView: add view position in scrollToItem()

An item, on being scrolled to, is always located at the nearest edge of
the view. This is not always convenient. Allow specifying where the item
should be positioned with respect to the view in scrollToItem().

BUG: 423884

4 files changed, 56 insertions, 16 deletions

diff --git a/src/kitemviews/kitemlistcontroller.cpp b/src/kitemviews/kitemlistcontroller.cpp
index be7a63e09..0016bb22a 100644
--- a/src/kitemviews/kitemlistcontroller.cpp
+++ b/src/kitemviews/kitemlistcontroller.cpp
@@ -539,7 +539,7 @@ void KItemListController::slotChangeCurrentItem(const QString &text, bool search
             m_selectionManager->beginAnchoredSelection(index);
         }
 
-        m_view->scrollToItem(index);
+        m_view->scrollToItem(index, KItemListView::ViewItemPosition::Beginning);
     }
 }
 
diff --git a/src/kitemviews/kitemlistview.cpp b/src/kitemviews/kitemlistview.cpp
index 457c02ec5..be22b91cc 100644
--- a/src/kitemviews/kitemlistview.cpp
+++ b/src/kitemviews/kitemlistview.cpp
@@ -537,7 +537,7 @@ bool KItemListView::isElided(int index) const
     return m_sizeHintResolver->isElided(index);
 }
 
-void KItemListView::scrollToItem(int index)
+void KItemListView::scrollToItem(int index, ViewItemPosition viewItemPosition)
 {
     QRectF viewGeometry = geometry();
     if (m_headerWidget->isVisible()) {
@@ -546,29 +546,65 @@ void KItemListView::scrollToItem(int index)
     }
     QRectF currentRect = itemRect(index);
 
-    // Fix for Bug 311099 - View the underscore when using Ctrl + PagDown
+    // Fix for Bug 311099 - View the underscore when using Ctrl + PageDown
     currentRect.adjust(-m_styleOption.horizontalMargin, -m_styleOption.verticalMargin, m_styleOption.horizontalMargin, m_styleOption.verticalMargin);
 
-    if (!viewGeometry.contains(currentRect)) {
-        qreal newOffset = scrollOffset();
-        if (scrollOrientation() == Qt::Vertical) {
+    qreal newOffset = scrollOffset();
+    if (scrollOrientation() == Qt::Vertical && (currentRect.top() < viewGeometry.top() || currentRect.bottom() > viewGeometry.bottom())) {
+        switch (viewItemPosition) {
+        case Beginning:
+            newOffset += currentRect.top() - viewGeometry.top();
+            break;
+        case Middle:
+            newOffset += 0.5 * (currentRect.top() + currentRect.bottom() - (viewGeometry.top() + viewGeometry.bottom()));
+            break;
+        case End:
+            newOffset += currentRect.bottom() - viewGeometry.bottom();
+            break;
+        case Nearest:
             if (currentRect.top() < viewGeometry.top()) {
                 newOffset += currentRect.top() - viewGeometry.top();
-            } else if (currentRect.bottom() > viewGeometry.bottom()) {
+            } else {
                 newOffset += currentRect.bottom() - viewGeometry.bottom();
             }
-        } else {
+            break;
+        default:
+            Q_UNREACHABLE();
+        }
+    } else if (scrollOrientation() == Qt::Horizontal && (currentRect.left() < viewGeometry.left() || currentRect.right() > viewGeometry.right())) {
+        switch (viewItemPosition) {
+        case Beginning:
+            if (layoutDirection() == Qt::RightToLeft) {
+                newOffset += currentRect.right() - viewGeometry.right();
+            } else {
+                newOffset += currentRect.left() - viewGeometry.left();
+            }
+            break;
+        case Middle:
+            newOffset += 0.5 * (currentRect.left() + currentRect.right() - (viewGeometry.left() + viewGeometry.right()));
+            break;
+        case End:
+            if (layoutDirection() == Qt::RightToLeft) {
+                newOffset += currentRect.left() - viewGeometry.left();
+            } else {
+                newOffset += currentRect.right() - viewGeometry.right();
+            }
+            break;
+        case Nearest:
             if (currentRect.left() < viewGeometry.left()) {
                 newOffset += currentRect.left() - viewGeometry.left();
-            } else if (currentRect.right() > viewGeometry.right()) {
+            } else {
                 newOffset += currentRect.right() - viewGeometry.right();
             }
+            break;
+        default:
+            Q_UNREACHABLE();
         }
+    }
 
-        if (newOffset != scrollOffset()) {
-            Q_EMIT scrollTo(newOffset);
-            return;
-        }
+    if (newOffset != scrollOffset()) {
+        Q_EMIT scrollTo(newOffset);
+        return;
     }
 
     Q_EMIT scrollingStopped();
diff --git a/src/kitemviews/kitemlistview.h b/src/kitemviews/kitemlistview.h
index 7bcaec704..8812eb8cc 100644
--- a/src/kitemviews/kitemlistview.h
+++ b/src/kitemviews/kitemlistview.h
@@ -59,6 +59,9 @@ class DOLPHIN_EXPORT KItemListView : public QGraphicsWidget
     Q_PROPERTY(qreal itemOffset READ itemOffset WRITE setItemOffset NOTIFY itemOffsetChanged)
 
 public:
+    /** The position in the view to which an item should be scrolled to. */
+    enum ViewItemPosition { Beginning, Middle, End, Nearest };
+
     explicit KItemListView(QGraphicsWidget *parent = nullptr);
     ~KItemListView() override;
 
@@ -251,9 +254,10 @@ public:
 
     /**
      * Scrolls to the item with the index \a index so that the item
-     * will be fully visible.
+     * will be fully visible. The item is positioned within the view
+     * as specified by \a viewItemPosition.
      */
-    void scrollToItem(int index);
+    void scrollToItem(int index, ViewItemPosition viewItemPosition = ViewItemPosition::Nearest);
 
     /**
      * If several properties of KItemListView are changed synchronously, it is
diff --git a/src/views/dolphinview.cpp b/src/views/dolphinview.cpp
index ace763b15..0a1d70bf1 100644
--- a/src/views/dolphinview.cpp
+++ b/src/views/dolphinview.cpp
@@ -1761,7 +1761,7 @@ void DolphinView::updateViewState()
 
                 // scroll to current item and reset the state
                 if (m_scrollToCurrentItem) {
-                    m_view->scrollToItem(currentIndex);
+                    m_view->scrollToItem(currentIndex, KItemListView::ViewItemPosition::Middle);
                     m_scrollToCurrentItem = false;
                 }
                 m_currentItemUrl = QUrl();