Details view optimization

Constructing a KColorScheme object is very expensive because of a number
of tint computations. When scrolling a big list more than 30 % of the
time was spent here. Instead, we can precompute and store the inactive
text color. (see https://git.reviewboard.kde.org/r/100826/)

Thanks to Samuel Rødal for the patch!

2 files changed, 20 insertions, 3 deletions

diff --git a/src/views/dolphinfileitemdelegate.cpp b/src/views/dolphinfileitemdelegate.cpp
index 9fed95bca..4d66c73f1 100644
--- a/src/views/dolphinfileitemdelegate.cpp
+++ b/src/views/dolphinfileitemdelegate.cpp
@@ -22,6 +22,7 @@
 #include "dolphinmodel.h"
 #include <KColorScheme>
 #include <KFileItem>
+#include <KGlobalSettings>
 #include <KIcon>
 #include <KIconLoader>
 #include <KStringHandler>
@@ -37,9 +38,11 @@ DolphinFileItemDelegate::DolphinFileItemDelegate(QObject* parent) :
     KFileItemDelegate(parent),
     m_hasMinimizedNameColumn(false),
     m_cachedSize(),
-    m_cachedEmblems()
+    m_cachedEmblems(),
+    m_cachedInactiveTextColorDirty(true)
 {
     setJobTransfersVisible(true);
+    connect(KGlobalSettings::self(), SIGNAL(kdisplayPaletteChanged()), this, SLOT(handleDisplayPaletteChange()));
 }
 
 DolphinFileItemDelegate::~DolphinFileItemDelegate()
@@ -63,8 +66,11 @@ void DolphinFileItemDelegate::paint(QPainter* painter,
         // Use the inactive text color for all columns except the name column. This indicates for the user that
         // hovering other columns does not change the actions context.
         QPalette palette = opt.palette;
-        const QColor textColor = KColorScheme(QPalette::Active).foreground(KColorScheme::InactiveText).color();
-        palette.setColor(QPalette::Text, textColor);
+        if (m_cachedInactiveTextColorDirty) {
+            m_cachedInactiveTextColor = KColorScheme(QPalette::Active).foreground(KColorScheme::InactiveText).color();
+            m_cachedInactiveTextColorDirty = false;
+        }
+        palette.setColor(QPalette::Text, m_cachedInactiveTextColor);
         opt.palette = palette;
     }
 
@@ -102,6 +108,11 @@ int DolphinFileItemDelegate::nameColumnWidth(const QString& name, const QStyleOp
     return width;
 }
 
+void DolphinFileItemDelegate::handleDisplayPaletteChange()
+{
+    m_cachedInactiveTextColorDirty = true;
+}
+
 void DolphinFileItemDelegate::adjustOptionWidth(QStyleOptionViewItemV4& option,
                                                 const QAbstractProxyModel* proxyModel,
                                                 const DolphinModel* dolphinModel,
diff --git a/src/views/dolphinfileitemdelegate.h b/src/views/dolphinfileitemdelegate.h
index 5eb559a79..ab4a9fd20 100644
--- a/src/views/dolphinfileitemdelegate.h
+++ b/src/views/dolphinfileitemdelegate.h
@@ -37,6 +37,7 @@ class QAbstractProxyModel;
  */
 class DolphinFileItemDelegate : public KFileItemDelegate
 {
+    Q_OBJECT
 public:
     explicit DolphinFileItemDelegate(QObject* parent = 0);
     virtual ~DolphinFileItemDelegate();
@@ -60,6 +61,9 @@ public:
      */
     static int nameColumnWidth(const QString& name, const QStyleOptionViewItem& option);
 
+private slots:
+    void handleDisplayPaletteChange();
+
 private:
     static void adjustOptionWidth(QStyleOptionViewItemV4& option,
                                   const QAbstractProxyModel* proxyModel,
@@ -75,6 +79,8 @@ private:
     bool m_hasMinimizedNameColumn;
     mutable QSize m_cachedSize;
     mutable QPixmap m_cachedEmblems[KVersionControlPlugin::LocallyModifiedUnstagedVersion + 1];
+    mutable QColor m_cachedInactiveTextColor;
+    mutable bool m_cachedInactiveTextColorDirty;
 };
 
 inline void DolphinFileItemDelegate::setMinimizedNameColumn(bool minimized)