Mirror details view mode for right-to-left languages

This commit implements mirroring of the details view mode for right-to-
left languages. This is the last of the Dolphin view modes which did
not adapt to right-to-left languages correctly.

Implementation-wise this is mostly about adapting the math so all the
information is placed correctly no matter the view mode or layout
direction. While most of the view actually changes the painting code
for right-to-left languages, for the column header I decided to keep
the logic left-to-right and instead reverse the order of the role
columns.

To implement this mirroring I needed to rework quite a bit of logic, so
I used the opportunity to fix some bugs/behaviur quirks:
- Left and right padding is now saved and restored separately instead
  of only saving the left padding
- Changing the right padding no longer disables "automatic column
  resizing".
- The grip handles for column resizing can now be grabbed when near the
  grip handle instead of only allowing grabbing when slightly to the
  left of the grip.
- Role column headers now only show a hover highlight effect when the
  mouse cursor is actually above that role and not above the grip
  handle or the padding.
- There is now a soft-boarder when shrinking the right padding so
  shrinking the padding "below zero width" will no longer immediately
  clear automatic resize behaviour. So now it is possible to simply
  remove the right padding by resizing it to zero width.

BUG: 449211
BUG: 495942

# Acknowledgement

This work is part of a my project funded through the NGI0 Entrust Fund,
a fund established by NLnet with financial support from the European
Commission's Next Generation Internet programme, under the aegis of DG
Communications Networks, Content and Technology.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/kitemviews/kstandarditemlistwidget.h b/src/kitemviews/kstandarditemlistwidget.h
index 588ec3548..7ff97a126 100644
--- a/src/kitemviews/kstandarditemlistwidget.h
+++ b/src/kitemviews/kstandarditemlistwidget.h
@@ -176,7 +176,7 @@ protected:
     void dataChanged(const QHash<QByteArray, QVariant> &current, const QSet<QByteArray> &roles = QSet<QByteArray>()) override;
     void visibleRolesChanged(const QList<QByteArray> &current, const QList<QByteArray> &previous) override;
     void columnWidthChanged(const QByteArray &role, qreal current, qreal previous) override;
-    void sidePaddingChanged(qreal width) override;
+    void sidePaddingChanged(qreal leftPaddingWidth, qreal rightPaddingWidth) override;
     void styleOptionChanged(const KItemListStyleOption &current, const KItemListStyleOption &previous) override;
     void hoveredChanged(bool hovered) override;
     void selectedChanged(bool selected) override;
@@ -213,6 +213,7 @@ private:
     void updateDetailsLayoutTextCache();
 
     void drawPixmap(QPainter *painter, const QPixmap &pixmap);
+    /** Draw the lines and arrows that visualize the expanded state and level of this row. */
     void drawSiblingsInformation(QPainter *painter);
 
     QRectF roleEditingRect(const QByteArray &role) const;