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/gradient.h

@@ -42,12 +42,11 @@ public:
     void setDefaults    (const rtengine::procparams::ProcParams* defParams, const ParamsEdited* pedited = NULL);
     void setBatchMode   (bool batchMode);
 
-    void updateGeometry (int centerX_, int centerY_, double feather_, double degree_);
-
     void adjusterChanged (Adjuster* a, double newval);
     void enabledChanged  ();
     void setAdjusterBehavior (bool degreeadd, bool featheradd, bool strengthadd, bool centeradd);
     void trimValues          (rtengine::procparams::ProcParams* pp);
+    void updateGeometry  (const int centerX_, const int centerY_, const double feather_, const double degree_, const int fullWidth=-1, const int fullHeight=-1);
 
     void setEditProvider (EditDataProvider* provider);