KItemListWidget: Use primitives instead of custom painting

We should avoid custom painting since that will cause issues with
Union and other styles. We however still use the old hardcoded painting
for Breeze style, which can be removed when Breeze 6.8 is released.

For other styles, we draw using the primitives the QStyle provides.

Also make the icon items less wider for better information density.

CCBUG: 508294
BUG: 508465

1 files changed, 46 insertions, 28 deletions

diff --git a/src/kitemviews/kitemlistwidget.cpp b/src/kitemviews/kitemlistwidget.cpp
index 089211716..7d43a0c14 100644
--- a/src/kitemviews/kitemlistwidget.cpp
+++ b/src/kitemviews/kitemlistwidget.cpp
@@ -617,25 +617,10 @@ void KItemListWidget::setPressed(bool enabled)
 
 void KItemListWidget::drawItemStyleOption(QPainter *painter, QWidget *widget, QStyle::State styleState)
 {
-    QStyleOptionViewItem viewItemOption;
-    constexpr int roundness = 5; // From Breeze style.
-    constexpr qreal penWidth = 1.25;
-    initStyleOption(&viewItemOption);
-    viewItemOption.state = styleState;
-    viewItemOption.viewItemPosition = QStyleOptionViewItem::OnlyOne;
-    viewItemOption.showDecorationSelected = true;
-    viewItemOption.rect = selectionRectFull().toRect();
-    QPainterPath path;
-    const qreal adjustment = 0.5 * penWidth; // Use same adjustments as Breeze strokedRect uses, to snap to pixelGrid.
-    path.addRoundedRect(selectionRectFull().adjusted(adjustment, adjustment, -adjustment, -adjustment), roundness, roundness);
-    QColor backgroundColor{widget->palette().color(QPalette::Accent)};
-    painter->setRenderHint(QPainter::Antialiasing);
-    bool current = m_current && styleState & QStyle::State_Active;
-
-    // Background item, alpha values are from
-    // https://invent.kde.org/plasma/libplasma/-/blob/master/src/desktoptheme/breeze/widgets/viewitem.svg
+    painter->save();
+    // Shared between both Breeze and other styles
+    QColor backgroundColor{widget->palette().color(QPalette::Highlight)};
     backgroundColor.setAlphaF(0.0);
-
     if (m_clickHighlighted) {
         backgroundColor.setAlphaF(1.0);
     } else {
@@ -648,19 +633,52 @@ void KItemListWidget::drawItemStyleOption(QPainter *painter, QWidget *widget, QS
             backgroundColor.setAlphaF(0.06);
         }
     }
+    QStyleOptionViewItem viewItemOption;
+    initStyleOption(&viewItemOption);
+    viewItemOption.state = styleState;
+    viewItemOption.viewItemPosition = QStyleOptionViewItem::OnlyOne;
+    viewItemOption.showDecorationSelected = true;
+    viewItemOption.rect = selectionRectFull().toRect();
+    const bool current = m_current && styleState & QStyle::State_Active;
 
-    painter->fillPath(path, backgroundColor);
+    // TODO: Remove this check after Plasma 6.8 release
+    // See: https://invent.kde.org/plasma/breeze/-/merge_requests/595
+    if (style()->name() == QStringLiteral("breeze")) {
+        painter->setRenderHint(QPainter::Antialiasing);
+        constexpr int roundness = 5; // From Breeze style.
+        constexpr qreal penWidth = 1.25;
+        QPainterPath path;
+        const qreal adjustment = 0.5 * penWidth; // Use same adjustments as Breeze strokedRect uses, to snap to pixelGrid.
+        path.addRoundedRect(selectionRectFull().adjusted(adjustment, adjustment, -adjustment, -adjustment), roundness, roundness);
+        painter->fillPath(path, backgroundColor);
 
-    // Focus decoration
-    if (current) {
-        QColor focusColor{widget->palette().color(QPalette::Accent)};
-        focusColor = m_styleOption.palette.color(QPalette::Base).lightnessF() > 0.5 ? focusColor.darker(110) : focusColor.lighter(110);
-        focusColor.setAlphaF(m_selected || m_hovered ? 1.0 : 0.8);
-        // Set the pen color lighter or darker depending on background color
-        QPen pen{focusColor, penWidth};
-        pen.setCosmetic(true);
-        painter->strokePath(path, pen);
+        // Focus decoration
+        if (current) {
+            QColor focusColor{widget->palette().color(QPalette::Highlight)};
+            // Set the pen color lighter or darker depending on background color
+            focusColor = m_styleOption.palette.color(QPalette::Base).lightnessF() > 0.5 ? focusColor.darker(110) : focusColor.lighter(110);
+            focusColor.setAlphaF(m_selected || m_hovered ? 1.0 : 0.8);
+            QPen pen{focusColor, penWidth};
+            pen.setCosmetic(true);
+            painter->strokePath(path, pen);
+        }
+    } else {
+        viewItemOption.backgroundBrush = backgroundColor;
+        style()->drawPrimitive(QStyle::PE_PanelItemViewItem, &viewItemOption, painter, widget);
+
+        // Focus decoration
+        if (current) {
+            QStyleOptionFocusRect focusRectOption;
+            initStyleOption(&focusRectOption);
+            focusRectOption.state = QStyle::State_HasFocus;
+            if (m_selected && widget->hasFocus()) {
+                focusRectOption.state = QStyle::State_HasFocus | QStyle::State_Selected;
+            }
+            focusRectOption.rect = viewItemOption.rect;
+            style()->drawPrimitive(QStyle::PE_FrameFocusRect, &focusRectOption, painter, widget);
+        }
     }
+    painter->restore();
 }
 
 #include "moc_kitemlistwidget.cpp"