Darkening the crop area impossible?

[Bart Coppens]

Looking at the GIMP yesterday, I noticed they had a cute little feature: when 
you are cropping an image, the part of the image that is not used will be 
darkened, so that it is quite clear what part will go away and what not.

I thought the big part of it would have been simple: make a region of the 
cropped parts, paint over them with half-transparent black, and done (minus 
some other things, updating the part that get un-darkened again and so). But 
I got stuck at the first part.

The current code (see bottom) has even different effects with OpenGL verus 
regular QPainter! OpenGL draws the entire thing in NotROP even though I 
create a _new_ painter, whereas the QPainter just makes it black...

So for archival purposes (and because somebody might now how to fix it for at 
least one KisCanvasPainter, that would really be enough to add it), here is 
the small patch that doesn't work;

Index: kis_tool_crop.cc
===================================================================
--- kis_tool_crop.cc    (revision 495477)
+++ kis_tool_crop.cc    (working copy)
@@ -396,6 +396,20 @@

         gc.setRasterOp(op);
         gc.setPen(old);
+
+        gc.end();
+
+        // Darken the area that will be cropped away
+        KisCanvas* canvas = controller -> kiscanvas();
+        KisCanvasPainter gc2(canvas);
+        QRegion toDraw(0, 0, canvas -> width(), canvas -> height());
+        toDraw = toDraw.subtract(QRegion(startx, starty, endx - startx, endy 
- starty));
+
+        rects = toDraw.rects();
+        QColor fillColor(qRgba(0,0,0, 125));
+        for (QMemArray <QRect>::ConstIterator it = rects.begin (); it != 
rects.end (); ++it) {
+            gc2.fillRect (*it, fillColor);
+        }
     }
 }

Bart Coppens