StyleSheet: use item background rule when filling row backround

QTreeView draws the different sub-rects of an item's background over
multiple calls to drawPrimitive(PE_PanelItemViewRow). The item row is
not separately stylable, but the item might have a styled background
property. To get a consistent background, we must use the item's
background rule when filling the item's row background.

To fix that, delegate the filling of the branch background to
drawPrimitive(PE_PanelItemViewRow), and implement PE_PanelItemViewRow
handling to render the rule for the ViewItem pseudo element if there is
a background rule defined for it.

Add a baseline test stylesheet for this scenario. Note that the selection
in an item view is better styled via the selection-background-color
qss property.

Task-number: QTBUG-73251
Task-number: QTBUG-106227
Pick-to: 6.4 6.2
Change-Id: I5d0c170f78009fe5015dd749975e6df27485b3b8
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/baseline/stylesheet/qss/qtreeview/styledSelection.qss b/tests/baseline/stylesheet/qss/qtreeview/styledSelection.qss
new file mode 100644
index 0000000000..7d54a74fe5
--- /dev/null
+++ b/tests/baseline/stylesheet/qss/qtreeview/styledSelection.qss
@@ -0,0 +1,10 @@
+QTreeView {
+    alternate-background-color: yellow;
+    show-decoration-selected: 1;
+}
+QTreeView::item:selected:active {
+    background: qlineargradient(x1:0, y1:0 x2: 0, y2: 1, stop: 0 #fea1f1 stop: 1 #567dbc)
+}
+QTreeView::branch {
+    border: 2px
+}