QS60Style: Color calculation should be optimized

Currently, QS60Style calculates some palette colors (tooltip base and
button). Since native side does not have a color for these, but a
nine-part theme graphic, the style tries to estimate the color of the
bitmap by taking a small sample of the QPixmap and calculate the
RGB colors of 32*32 pixels. This is rather slow, it takes around
110 msecs for each QApplication, when the application is started.
Note that color is cached to member variable of style, but it is very
rarely asked again (as the color is polished to all widgets/apps)
and the cache is not shared across processes.

As a fix, style now calculates the button color (tooltip color
is no longer calculated, as no other QStyle does that, and
tooltips do not anyway work in the Qt/Symbian) and stores the
calculated value to Global QSettings together with active theme
ID. Now, when a second Qt application is launched, the stored
theme ID value is matched with currently active theme. If it
matches, then the stored Button color is used. Otherwise, color
is again calculated and stored. If theme is unchanged, the
application launch is ~95msecs faster.

Task-number: QTBUG-14860
Reviewed-by: Jani Hautakangas

3 files changed, 130 insertions, 59 deletions

diff --git a/src/gui/styles/qs60style.cpp b/src/gui/styles/qs60style.cpp
index f3fb2f5..5e5adab 100644
--- a/src/gui/styles/qs60style.cpp
+++ b/src/gui/styles/qs60style.cpp
@@ -405,13 +405,14 @@ void QS60StylePrivate::clearCaches(CacheClearReason reason)
         QPixmapCache::clear();
         break;
     case CC_ThemeChange:
-        m_colorCache.clear();
         QPixmapCache::clear();
+#ifdef Q_WS_S60
+        deleteStoredSettings();
+#endif
         deleteBackground();
         break;
     case CC_UndefinedChange:
     default:
-        m_colorCache.clear();
         m_mappedFontsCache.clear();
         QPixmapCache::clear();
         deleteBackground();
@@ -419,64 +420,53 @@ void QS60StylePrivate::clearCaches(CacheClearReason reason)
     }
 }
 
-// Since S60Style has 'button' and 'tooltip' as a graphic, we don't have any native color which to use
-// for QPalette::Button and QPalette::ToolTipBase. Therefore S60Style needs to guesstimate
-// palette colors by calculating average rgb values for button pixels.
-// Returns Qt::black if there is an issue with the graphics (image is NULL, or no bits() found).
-QColor QS60StylePrivate::colorFromFrameGraphics(SkinFrameElements frame) const
+QColor QS60StylePrivate::calculatedColor(SkinFrameElements frame) const
 {
-    const bool cachedColorExists = m_colorCache.contains(frame);
-    if (!cachedColorExists) {
-        const int frameCornerWidth = pixelMetric(PM_FrameCornerWidth);
-        const int frameCornerHeight = pixelMetric(PM_FrameCornerHeight);
-        Q_ASSERT(2 * frameCornerWidth < 32);
-        Q_ASSERT(2 * frameCornerHeight < 32);
-
-        const QImage frameImage = QS60StylePrivate::frame(frame, QSize(32, 32)).toImage();
-        Q_ASSERT(frameImage.bytesPerLine() > 0);
-        if (frameImage.isNull())
-            return Qt::black;
-
-        const QRgb *pixelRgb = (const QRgb*)frameImage.bits();
-        const int pixels = frameImage.byteCount()/sizeof(QRgb);
-
-        int estimatedRed = 0;
-        int estimatedGreen = 0;
-        int estimatedBlue = 0;
-
-        int skips = 0;
-        int estimations = 0;
-
-        const int topBorderLastPixel = frameCornerHeight*frameImage.width() - 1;
-        const int bottomBorderFirstPixel = frameImage.width() * frameImage.height() - frameCornerHeight*frameImage.width() - 1;
-        const int rightBorderFirstPixel = frameImage.width() - frameCornerWidth;
-        const int leftBorderLastPixel = frameCornerWidth;
-
-        while ((skips + estimations) < pixels) {
-            if ((skips + estimations) > topBorderLastPixel &&
-                (skips + estimations) < bottomBorderFirstPixel) {
-                for (int rowIndex = 0; rowIndex < frameImage.width(); rowIndex++) {
-                    if (rowIndex > leftBorderLastPixel &&
-                        rowIndex < rightBorderFirstPixel) {
-                        estimatedRed += qRed(*pixelRgb);
-                        estimatedGreen += qGreen(*pixelRgb);
-                        estimatedBlue += qBlue(*pixelRgb);
-                    }
-                    pixelRgb++;
-                    estimations++;
+    const int frameCornerWidth = pixelMetric(PM_FrameCornerWidth);
+    const int frameCornerHeight = pixelMetric(PM_FrameCornerHeight);
+    Q_ASSERT(2 * frameCornerWidth < 32);
+    Q_ASSERT(2 * frameCornerHeight < 32);
+
+    const QImage frameImage = QS60StylePrivate::frame(frame, QSize(32, 32)).toImage();
+    Q_ASSERT(frameImage.bytesPerLine() > 0);
+    if (frameImage.isNull())
+        return Qt::black;
+
+    const QRgb *pixelRgb = (const QRgb*)frameImage.constBits();
+    const int pixels = frameImage.byteCount() / sizeof(QRgb);
+
+    int estimatedRed = 0;
+    int estimatedGreen = 0;
+    int estimatedBlue = 0;
+
+    int skips = 0;
+    int estimations = 0;
+
+    const int topBorderLastPixel = frameCornerHeight * frameImage.width() - 1;
+    const int bottomBorderFirstPixel = frameImage.width() * frameImage.height() - topBorderLastPixel;
+    const int rightBorderFirstPixel = frameImage.width() - frameCornerWidth;
+    const int leftBorderLastPixel = frameCornerWidth;
+
+    while ((skips + estimations) < pixels) {
+        if ((skips + estimations) > topBorderLastPixel &&
+            (skips + estimations) < bottomBorderFirstPixel) {
+            for (int rowIndex = 0; rowIndex < frameImage.width(); rowIndex++) {
+                if (rowIndex > leftBorderLastPixel &&
+                    rowIndex < rightBorderFirstPixel) {
+                    estimatedRed += qRed(*pixelRgb);
+                    estimatedGreen += qGreen(*pixelRgb);
+                    estimatedBlue += qBlue(*pixelRgb);
                 }
-            } else {
                 pixelRgb++;
-                skips++;
+                estimations++;
             }
+        } else {
+            pixelRgb++;
+            skips++;
         }
-        QColor frameColor(estimatedRed/estimations, estimatedGreen/estimations, estimatedBlue/estimations);
-        m_colorCache.insert(frame, frameColor);
-        return !estimations ? Qt::black : frameColor;
-    } else {
-        return m_colorCache.value(frame);
     }
-
+    QColor frameColor(estimatedRed/estimations, estimatedGreen/estimations, estimatedBlue/estimations);
+    return !estimations ? Qt::black : frameColor;
 }
 
 void QS60StylePrivate::setThemePalette(QApplication *app) const
@@ -731,11 +721,14 @@ void QS60StylePrivate::setThemePalette(QPalette *palette) const
     palette->setBrush(QPalette::Window, backgroundTexture());
     // set as transparent so that styled full screen theme background is visible
     palette->setBrush(QPalette::Base, Qt::transparent);
-    // set button and tooltipbase based on pixel colors
+    // set button color based on pixel colors
+#ifndef Q_WS_S60
+    //For emulated style, just calculate the color everytime
+    const QColor buttonColor = calculatedColor(SF_ButtonNormal);
+#else
     const QColor buttonColor = colorFromFrameGraphics(SF_ButtonNormal);
+#endif
     palette->setColor(QPalette::Button, buttonColor);
-    const QColor toolTipColor = colorFromFrameGraphics(SF_ToolTip);
-    palette->setColor(QPalette::ToolTipBase, toolTipColor);
     palette->setColor(QPalette::Light, palette->color(QPalette::Button).lighter());
     palette->setColor(QPalette::Dark, palette->color(QPalette::Button).darker());
     palette->setColor(QPalette::Midlight, palette->color(QPalette::Button).lighter(125));
diff --git a/src/gui/styles/qs60style_p.h b/src/gui/styles/qs60style_p.h
index b46f75e..7a7991a 100644
--- a/src/gui/styles/qs60style_p.h
+++ b/src/gui/styles/qs60style_p.h
@@ -523,8 +523,12 @@ public:
     static bool isSingleClickUi();
     static bool isWidgetPressed(const QWidget *widget);
 
-    // calculates average color based on button skin graphics (minus borders).
+#ifdef Q_WS_S60
+    static void deleteStoredSettings();
+    // calculates average color based on theme graphics (minus borders).
     QColor colorFromFrameGraphics(SkinFrameElements frame) const;
+#endif    
+    QColor calculatedColor(SkinFrameElements frame) const;
 
     //set theme palette for application
     void setThemePalette(QApplication *application) const;
@@ -542,7 +546,6 @@ public:
     static const int m_numberOfLayouts;
 
     mutable QHash<QPair<QS60StyleEnums::FontCategories , int>, QFont> m_mappedFontsCache;
-    mutable QHash<SkinFrameElements, QColor> m_colorCache;
 
     // Has one entry per SkinFrameElements
     static const struct frameElementCenter {
diff --git a/src/gui/styles/qs60style_s60.cpp b/src/gui/styles/qs60style_s60.cpp
index a1ea308..204699d 100644
--- a/src/gui/styles/qs60style_s60.cpp
+++ b/src/gui/styles/qs60style_s60.cpp
@@ -48,6 +48,7 @@
 #include "private/qpixmap_s60_p.h"
 #include "private/qcore_symbian_p.h"
 #include "qapplication.h"
+#include "qsettings.h"
 
 #include "qpluginloader.h"
 #include "qlibraryinfo.h"
@@ -69,6 +70,8 @@
 #include <gulicon.h>
 #include <AknBitmapAnimation.h>
 
+#include <centralrepository.h>
+
 #if !defined(QT_NO_STYLE_S60) || defined(QT_PLUGIN)
 
 QT_BEGIN_NAMESPACE
@@ -81,6 +84,8 @@ enum TDrawType {
     ENoDraw
 };
 
+const TUid personalisationUID = { 0x101F876F };
+
 enum TSupportRelease {
     ES60_None     = 0x0000, //indicates that the commonstyle should draw the graphics
     ES60_3_1      = 0x0001,
@@ -689,6 +694,76 @@ bool QS60StylePrivate::isSingleClickUi()
     return (QSysInfo::s60Version() > QSysInfo::SV_S60_5_0);
 }
 
+void QS60StylePrivate::deleteStoredSettings()
+{
+    QSettings settings(QSettings::UserScope, QLatin1String("Trolltech"));
+    settings.beginGroup(QLatin1String("QS60Style"));
+    settings.remove("");
+    settings.endGroup();
+}
+
+// Since S60Style has 'button' as a graphic, we don't have any native color which to use
+// for QPalette::Button. Therefore S60Style needs to guesstimate palette color by calculating
+// average rgb values for button pixels.
+// Returns Qt::black if there is an issue with the graphics (image is NULL, or no constBits() found).
+QColor QS60StylePrivate::colorFromFrameGraphics(SkinFrameElements frame) const
+{
+#ifndef QT_NO_SETTINGS
+    TInt themeID = 0;    
+    //First we need to fetch active theme ID. We need to store the themeID at the same time
+    //as color, so that we can later check if the stored color is still from the same theme.
+    //Native side stores active theme UID/Timestamp into central repository.
+    int error = 0;
+    QT_TRAP_THROWING(
+        CRepository *themeRepository = CRepository::NewLC(personalisationUID);
+        if (themeRepository) {
+            static const TInt KThemePkgIDDesSize = 23; //size of the stored theme package ID
+            TBuf<32> value; //themeID is currently max of 8 + 1 + 8 characters, but lets have some extra space 
+            const TUint32 key = 0x00000002; //active theme key in the repository
+            error = themeRepository->Get(key, value);
+            if (error == KErrNone) {
+                TLex lex(value);                
+                TPtrC numberToken(lex.NextToken());
+                if(numberToken.Length())
+                    error = TLex(numberToken).Val(themeID);
+                else
+                    error = KErrArgument;
+            }
+        }
+        CleanupStack::PopAndDestroy(themeRepository);
+    );
+
+    QSettings settings(QSettings::UserScope, QLatin1String("Trolltech"));
+    settings.beginGroup(QLatin1String("QS60Style"));
+    if (themeID != 0) {
+        QVariant buttonColor = settings.value(QLatin1String("ButtonColor"));
+        if (!buttonColor.isNull()) {
+            //there is a stored color value, lets see if the theme ID matches
+            if (error == KErrNone) {
+                QVariant themeUID = settings.value(QLatin1String("ThemeUID"));
+                if (!themeUID.isNull() && themeUID.toInt() == themeID) {
+                    QColor storedColor(buttonColor.value<QColor>());
+                    if (storedColor.isValid())
+                        return storedColor;
+                }
+            }
+            settings.remove(""); //if color was invalid, or theme has been changed, just delete all stored settings
+        }
+    }
+#endif
+
+    QColor color = calculatedColor(frame);
+
+#ifndef QT_NO_SETTINGS
+    settings.setValue(QLatin1String("ThemeUID"), QVariant(themeID));
+    if (frame == SF_ButtonNormal) //other colors are not currently calculated from graphics
+        settings.setValue(QLatin1String("ButtonColor"), QVariant(color));
+    settings.endGroup();
+#endif
+
+    return color;
+}
+
 QPoint qt_s60_fill_background_offset(const QWidget *targetWidget)
 {
     CCoeControl *control = targetWidget->effectiveWinId();