Modified Preview Canvas

- Now the Preview can show free space around the image (the image's
corner will coincide with the center of the preview area)
- Editing objects can now be manipulated in this free space
- The editing mechanism has been split : it was completely handled in
rtengine before, now rtengine still handle the pipette's data provider,
but rtgui now handle the objects data provider.
- Bugfix: when using coarse rotate in the Editor panel, the Gradient
widgets are now correctly displayed

rtgui/imageareapanel.cc

@@ -84,9 +84,7 @@ void ImageAreaPanel::synchronize ()
         after->imageArea->getScrollPosition (x, y);
 
         if (imgw > 0 && imgh > 0) {
-            int bimgw, bimgh;
-            imageArea->getScrollImageSize (bimgw, bimgh);
-            imageArea->setScrollPosition (x * bimgw / imgw, y * bimgh / imgh);
+            imageArea->setScrollPosition (x, y);
             imageArea->queue_draw ();
         }
     } else if (before && this == after) {
@@ -95,9 +93,7 @@ void ImageAreaPanel::synchronize ()
         before->imageArea->getScrollPosition (x, y);
 
         if (imgw > 0 && imgh > 0) {
-            int bimgw, bimgh;
-            imageArea->getScrollImageSize (bimgw, bimgh);
-            imageArea->setScrollPosition (x * bimgw / imgw, y * bimgh / imgh);
+            imageArea->setScrollPosition (x, y);
             imageArea->queue_draw ();
         }
     }