Make the background of the system tray icon with the overlayed number of unread messages transparent. Man, this was more difficult than I had anticipated.

svn path=/trunk/kdepim/; revision=253211

kmsystemtray.cpp

@@ -33,6 +33,7 @@
 #include <kdebug.h>
 
 #include <qpainter.h>
+#include <qbitmap.h>
 #include <qtooltip.h>
 #include <qwidgetlist.h>
 #include <qobjectlist.h>
@@ -65,8 +66,7 @@ KMSystemTray::KMSystemTray(QWidget *parent, const char *name)
   kdDebug(5006) << "Initting systray" << endl;
 
   mDefaultIcon = loadIcon( "kmail" );
-  mTransparentIcon = loadIcon( "kmail" );
-  KIconEffect::semiTransparent( mTransparentIcon );
+  mLightIconImage = loadIcon( "kmaillight" ).convertToImage();
 
   setPixmap(mDefaultIcon);
 
@@ -163,20 +163,42 @@ void KMSystemTray::updateCount()
       countFont.setPointSizeFloat( countFontSize );
     }
 
-    QPixmap bg(oldPixmapWidth, oldPixmapHeight);
-    bg.fill(this, 0, 0);
-
-    /** Overlay count on transparent icon */
-    QPainter p(&bg);
-    p.drawPixmap(0, 0, mTransparentIcon);
-    p.setFont(countFont);
-    p.setPen(Qt::blue);
-    p.drawText(pixmap()->rect(), Qt::AlignCenter, countString);
-
-    setPixmap(bg);
+    // Create an image which represents the number of unread messages
+    // and which has a transparent background.
+    // Unfortunately this required the following twisted code because for some
+    // reason text that is drawn on a transparent pixmap is invisible
+    // (apparently the alpha channel isn't changed when the text is drawn).
+    // Therefore I have to draw the text on a solid background and then remove
+    // the background by making it transparent with QPixmap::setMask. This
+    // involves the slow createHeuristicMask() function (from the API docs:
+    // "This function is slow because it involves transformation to a QImage,
+    // non-trivial computations and a transformation back to a QBitmap."). Then
+    // I have to convert the resulting QPixmap to a QImage in order to overlay
+    // the light KMail icon with the number (because KIconEffect::overlay only
+    // works with QImage). Finally the resulting QImage has to be converted
+    // back to a QPixmap.
+    // That's a lot of work for overlaying the KMail icon with the number of
+    // unread messages, but every other approach I tried failed miserably.
+    //                                                           IK, 2003-09-22
+    QPixmap numberPixmap( oldPixmapWidth, oldPixmapHeight );
+    numberPixmap.fill( Qt::white );
+    QPainter p( &numberPixmap );
+    p.setFont( countFont );
+    p.setPen( Qt::blue );
+    p.drawText( numberPixmap.rect(), Qt::AlignCenter, countString );
+    numberPixmap.setMask( numberPixmap.createHeuristicMask() );
+    QImage numberImage = numberPixmap.convertToImage();
+
+    // Overlay the light KMail icon with the number image
+    QImage iconWithNumberImage = mLightIconImage.copy();
+    KIconEffect::overlay( iconWithNumberImage, numberImage );
+
+    QPixmap iconWithNumber;
+    iconWithNumber.convertFromImage( iconWithNumberImage );
+    setPixmap( iconWithNumber );
   } else
   {
-    setPixmap(mDefaultIcon);
+    setPixmap( mDefaultIcon );
   }
 }
 

kmsystemtray.h

@@ -24,6 +24,7 @@
 #include <qguardedptr.h>
 #include <qptrvector.h>
 #include <qpixmap.h>
+#include <qimage.h>
 
 class KMFolder;
 class KMMainWidget;
@@ -79,7 +80,7 @@ private:
 
   KPopupMenu * mPopupMenu;
   QPixmap mDefaultIcon;
-  QPixmap mTransparentIcon;
+  QImage mLightIconImage;
 
   QPtrVector<KMFolder> mPopupFolders;
   QMap<QGuardedPtr<KMFolder>, int> mFoldersWithUnread;