From b780eaf6a063a7efe03417cf6b7008a188e222a4 Mon Sep 17 00:00:00 2001
From: Volker Hilsheimer <volker.hilsheimer@qt.io>
Date: Tue, 5 Nov 2024 17:03:45 +0100
Subject: [PATCH] StyleSheet/QTreeView: draw empty area and background of
 semi-transparent items

After 3ca615d9735f7ddb8e2ae5c13e5effd419a56300, the style sheet style
will not draw rows unless the item has a border. Otherwise, it will
assume that the item drawing later on will fill the background anyway.
We also never painted the background for empty rows.

However, if the item's background is semi-transparent, then the row
needs to be drawn first, so that the correct background shows through.
And for empty rows, we need to draw just the background. This is
especially important for trees with alternate background colors.

Add baseline test case for this particular combination. This will result
in a minor change to the results of the existing
transparentBackgroundNoBorderForBranchIndicator test case, where now the
background is drawn behind the indicator area when the item's background
is semi-transparent. I don't think this is a bug though.

Pick-to: 6.8
Fixes: QTBUG-123632
Change-Id: I2cd4efb748aaefc03a3b576458b750ee47479e97
Reviewed-by: Santhosh Kumar <santhosh.kumar.selvaraj@qt.io>
---
 src/widgets/styles/qstylesheetstyle.cpp           | 15 ++++++++++-----
 .../transparentItemBackgroundOnAlternating.qss    | 11 +++++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)
 create mode 100644 tests/baseline/stylesheet/qss/qtreeview/transparentItemBackgroundOnAlternating.qss

diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 363662585d3..edce3f3eeb2 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -4870,11 +4870,15 @@ void QStyleSheetStyle::drawPrimitive(PrimitiveElement pe, const QStyleOption *op
         // only indirectly through the background of the item. To get the
         // same background for all parts drawn by QTreeView, we have to
         // use the background rule for the item here.
-        if (renderRule(w, opt, PseudoElement_ViewItem).hasBackground()) {
-            pseudoElement = PseudoElement_ViewItem;
-            // Skip border for the branch and draw only the brackground
-            if (const QStyleOptionViewItem *vopt = qstyleoption_cast<const QStyleOptionViewItem *>(opt)) {
-                QRenderRule rule = renderRule(w, opt, PseudoElement_ViewItem);
+        if (const QStyleOptionViewItem *vopt = qstyleoption_cast<const QStyleOptionViewItem *>(opt)) {
+            // default handling for drawing empty space
+            if (vopt->viewItemPosition == QStyleOptionViewItem::Invalid)
+                break;
+            if (QRenderRule rule = renderRule(w, opt, PseudoElement_ViewItem); rule.hasBackground()) {
+                // if the item background is not fully opaque, then we have to paint the row
+                if (rule.background()->brush.color().alpha() != 1.0)
+                    baseStyle()->drawPrimitive(pe, opt, p, w);
+                // Skip border for the branch and draw only the brackground
                 if (vopt->features & QStyleOptionViewItem::HasDecoration &&
                     (vopt->viewItemPosition == QStyleOptionViewItem::Beginning ||
                      vopt->viewItemPosition == QStyleOptionViewItem::OnlyOne) && rule.hasBorder()) {
@@ -4886,6 +4890,7 @@ void QStyleSheetStyle::drawPrimitive(PrimitiveElement pe, const QStyleOption *op
                     }
                     return;
                 }
+                pseudoElement = PseudoElement_ViewItem;
             }
         }
         break;
diff --git a/tests/baseline/stylesheet/qss/qtreeview/transparentItemBackgroundOnAlternating.qss b/tests/baseline/stylesheet/qss/qtreeview/transparentItemBackgroundOnAlternating.qss
new file mode 100644
index 00000000000..d78be3af800
--- /dev/null
+++ b/tests/baseline/stylesheet/qss/qtreeview/transparentItemBackgroundOnAlternating.qss
@@ -0,0 +1,11 @@
+QTreeView {
+  qproperty-alternatingRowColors: true;
+  alternate-background-color: fuchsia;
+  background-color: orange;
+}
+
+QTreeView::item {
+  background-color: "#A00000FF";
+  color: #3C3C3C;
+  padding: 2px;
+}