restore hint-apply-color-scheme support

make hint-apply-color-scheme work (kiconeffect based coloring),
and make sure the kcolorschemes are reloaded when app palette changes
and the theme follows system colors

BUG:343389
Change-Id: I0a7a7eb0f89ed0948e618f1d608521f235aa1959

src/plasma/CMakeLists.txt

@@ -125,6 +125,7 @@ PRIVATE
     KF5::XmlGui   #KActionCollection
     KF5::GlobalAccel #Applet::setGlobalShortcut
     KF5::Notifications
+    KF5::IconThemes
     ${PLASMA_EXTRA_LIBS}
 )
 

src/plasma/private/theme_p.cpp

@@ -346,6 +346,11 @@ void ThemePrivate::scheduledCacheUpdate()
 
 void ThemePrivate::colorsChanged()
 {
+    // in the case the theme follows the desktop settings, refetch the colorschemes
+    // and discard the svg pixmap cache
+    if (!colors) {
+        KSharedConfig::openConfig()->reparseConfiguration();
+    }
     colorScheme = KColorScheme(QPalette::Active, KColorScheme::Window, colors);
     buttonColorScheme = KColorScheme(QPalette::Active, KColorScheme::Button, colors);
     viewColorScheme = KColorScheme(QPalette::Active, KColorScheme::View, colors);

src/plasma/svg.cpp

@@ -35,6 +35,7 @@
 #include <kconfiggroup.h>
 #include <QDebug>
 #include <kfilterdev.h>
+#include <kiconeffect.h>
 
 #include "applet.h"
 #include "package.h"
@@ -382,6 +383,13 @@ QPixmap SvgPrivate::findInCache(const QString &elementId, const QSizeF &s)
 
     renderPainter.end();
 
+    // Apply current color scheme if the svg asks for it
+    if (applyColors) {
+        QImage itmp = p.toImage();
+        KIconEffect::colorize(itmp, cacheAndColorsTheme()->color(Theme::BackgroundColor), 1.0);
+        p = p.fromImage(itmp);
+    }
+
     if (cacheRendering) {
         cacheAndColorsTheme()->insertIntoCache(id, p, QString::number((qint64)q, 16) % QLSEP % actualElementId);
     }
@@ -550,7 +558,10 @@ QMatrix SvgPrivate::matrixForElement(const QString &elementId)
 
 void SvgPrivate::checkColorHints()
 {
-    if (elementRect("current-color-scheme").isValid()) {
+    if (elementRect("hint-apply-color-scheme").isValid()) {
+        applyColors = true;
+        usesColors = true;
+    } else if (elementRect("current-color-scheme").isValid()) {
         applyColors = false;
         usesColors = true;
     } else {