QWebView scrolling doesn't clear old elements before painting again

Author: Petri <petri.ojala@digia.com>
Date:   Wed Feb 10 12:27:19 2010 +0200

        Patch to QTBUG-7286

        QWebView scrolling doesn't clear old elements before painting on top of them.

        The bug exists only if web page does not set its backgroung color.
        Solution is to set White color as a default color for web page backgrounds.
        White color was causing some visibility problem (at least with lineedit) and
        it was solved by editing  ::canDrawThemeBackground

Task-number: QTBUG-7286
Reviewed-by: Sami Merila

2 files changed, 18 insertions, 8 deletions

diff --git a/src/gui/styles/qs60style.cpp b/src/gui/styles/qs60style.cpp
index ea7399f..74707af 100644
--- a/src/gui/styles/qs60style.cpp
+++ b/src/gui/styles/qs60style.cpp
@@ -120,6 +120,8 @@ QPixmap *QS60StylePrivate::m_background = 0;
 // theme palette
 QPalette *QS60StylePrivate::m_themePalette = 0;
 
+qint64 QS60StylePrivate::m_webPaletteKey = 0;
+
 const struct QS60StylePrivate::frameElementCenter QS60StylePrivate::m_frameElementsData[] = {
     {SE_ButtonNormal,           QS60StyleEnums::SP_QsnFrButtonTbCenter},
     {SE_ButtonPressed,          QS60StyleEnums::SP_QsnFrButtonTbCenterPressed},
@@ -807,8 +809,12 @@ void QS60StylePrivate::setThemePaletteHash(QPalette *palette) const
     QPalette webPalette = *palette;
     webPalette.setColor(QPalette::WindowText, Qt::black);
     webPalette.setColor(QPalette::Text, Qt::black);
+    webPalette.setBrush(QPalette::Base, Qt::white);
+
     QApplication::setPalette(webPalette, "QWebView");
     QApplication::setPalette(webPalette, "QGraphicsWebView");
+
+    m_webPaletteKey = webPalette.cacheKey();
 }
 
 QSize QS60StylePrivate::partSize(QS60StyleEnums::SkinParts part, SkinElementFlags flags)
@@ -896,8 +902,11 @@ QSize QS60StylePrivate::partSize(QS60StyleEnums::SkinParts part, SkinElementFlag
     return result;
 }
 
-bool QS60StylePrivate::canDrawThemeBackground(const QBrush &backgroundBrush)
+bool QS60StylePrivate::canDrawThemeBackground(const QBrush &backgroundBrush, const QWidget *widget)
 {
+    // Always return true for web pages.
+    if (widget && m_webPaletteKey == QApplication::palette(widget).cacheKey())
+        return true;
     //If brush is not changed from style's default values, draw theme graphics.
     return (backgroundBrush.color() == Qt::transparent ||
             backgroundBrush.style() == Qt::NoBrush) ? true : false;
@@ -1901,7 +1910,7 @@ void QS60Style::drawControl(ControlElement element, const QStyleOption *option,
     case CE_ShapedFrame:
         if (const QTextEdit *textEdit = qobject_cast<const QTextEdit *>(widget)) {
             const QStyleOptionFrame *frame = qstyleoption_cast<const QStyleOptionFrame *>(option);
-            if (QS60StylePrivate::canDrawThemeBackground(frame->palette.base()))
+            if (QS60StylePrivate::canDrawThemeBackground(frame->palette.base(), widget))
                 QS60StylePrivate::drawSkinElement(QS60StylePrivate::SE_Editor, painter, option->rect, flags);
             else
                 QCommonStyle::drawControl(element, option, painter, widget);
@@ -2013,7 +2022,7 @@ void QS60Style::drawPrimitive(PrimitiveElement element, const QStyleOption *opti
             if (widget && qobject_cast<const QComboBox *>(widget->parentWidget()))
                 break;
 #endif
-            if (QS60StylePrivate::canDrawThemeBackground(option->palette.base()))
+            if (QS60StylePrivate::canDrawThemeBackground(option->palette.base(), widget))
                 QS60StylePrivate::drawSkinElement(QS60StylePrivate::SE_FrameLineEdit, painter, option->rect, flags);
             else
                 commonStyleDraws = true;
@@ -2093,7 +2102,7 @@ void QS60Style::drawPrimitive(PrimitiveElement element, const QStyleOption *opti
     case PE_PanelButtonTool:
     case PE_PanelButtonBevel:
     case PE_FrameButtonBevel:
-        if (QS60StylePrivate::canDrawThemeBackground(option->palette.base())) {
+        if (QS60StylePrivate::canDrawThemeBackground(option->palette.base(), widget)) {
             const bool isPressed = option->state & State_Sunken;
             const QS60StylePrivate::SkinElements skinElement =
                 isPressed ? QS60StylePrivate::SE_ButtonPressed : QS60StylePrivate::SE_ButtonNormal;
@@ -2125,7 +2134,7 @@ void QS60Style::drawPrimitive(PrimitiveElement element, const QStyleOption *opti
     case PE_IndicatorSpinDown:
     case PE_IndicatorSpinUp:
         if (const QStyleOptionSpinBox *spinBox = qstyleoption_cast<const QStyleOptionSpinBox *>(option)) {
-            if (QS60StylePrivate::canDrawThemeBackground(spinBox->palette.base())) {
+            if (QS60StylePrivate::canDrawThemeBackground(spinBox->palette.base(), widget)) {
                 QStyleOptionSpinBox optionSpinBox = *spinBox;
                 const QS60StyleEnums::SkinParts part = (element == PE_IndicatorSpinUp) ?
                     QS60StyleEnums::SP_QgnGrafScrollArrowUp :
@@ -2140,7 +2149,7 @@ void QS60Style::drawPrimitive(PrimitiveElement element, const QStyleOption *opti
 #endif //QT_NO_SPINBOX
 #ifndef QT_NO_COMBOBOX
         if (const QStyleOptionFrame *cmb = qstyleoption_cast<const QStyleOptionFrame *>(option)) {
-            if (QS60StylePrivate::canDrawThemeBackground( option->palette.base())) {
+            if (QS60StylePrivate::canDrawThemeBackground( option->palette.base(), widget)) {
                 // We want to draw down arrow here for comboboxes as well.
                 QStyleOptionFrame optionsComboBox = *cmb;
                 const QS60StyleEnums::SkinParts part = QS60StyleEnums::SP_QgnGrafScrollArrowDown;
@@ -2179,7 +2188,7 @@ void QS60Style::drawPrimitive(PrimitiveElement element, const QStyleOption *opti
 #endif //QT_NO_MENU
             ) {
             //Need extra check since dialogs have their own theme background
-            if (QS60StylePrivate::canDrawThemeBackground(option->palette.base()) &&
+            if (QS60StylePrivate::canDrawThemeBackground(option->palette.base(), widget) &&
                 option->palette.window().texture().cacheKey() ==
                     QS60StylePrivate::m_themePalette->window().texture().cacheKey())
                 QS60StylePrivate::drawSkinElement(QS60StylePrivate::SE_OptionsMenu, painter, option->rect, flags);
diff --git a/src/gui/styles/qs60style_p.h b/src/gui/styles/qs60style_p.h
index ea30b81..16d82e7 100644
--- a/src/gui/styles/qs60style_p.h
+++ b/src/gui/styles/qs60style_p.h
@@ -542,7 +542,7 @@ public:
 
     //Checks that the current brush is transparent or has BrushStyle NoBrush,
     //so that theme graphic background can be drawn.
-    static bool canDrawThemeBackground(const QBrush &backgroundBrush);
+    static bool canDrawThemeBackground(const QBrush &backgroundBrush, const QWidget *widget);
 
     static int currentAnimationFrame(QS60StyleEnums::SkinParts part);
 #ifdef Q_WS_S60
@@ -596,6 +596,7 @@ private:
     QPalette m_originalPalette;
 
     QPointer<QFocusFrame> m_focusFrame;
+    static qint64 m_webPaletteKey;
 
 #ifdef Q_WS_S60
     //list of progress bars having animation running