Add mousewheel support in canvas windows. Thanks to Yue Shi Lai.

git-svn-id: http://svn.voria.com/code@231 1f10aa63-cdf2-0310-b900-c93c546f37ac

diff --git a/synfig-studio/trunk/src/gtkmm/workarea.cpp b/synfig-studio/trunk/src/gtkmm/workarea.cpp
index 1340f2a..e22108a 100644 (file)
--- a/synfig-studio/trunk/src/gtkmm/workarea.cpp
+++ b/synfig-studio/trunk/src/gtkmm/workarea.cpp
@@ -6,6 +6,7 @@
 **
 **     \legal
 **     Copyright (c) 2002-2005 Robert B. Quattlebaum Jr., Adrian Bentley
+**     Copyright 2006 Yue Shi Lai
 **
 **     This package is free software; you can redistribute it and/or
 **     modify it under the terms of the GNU General Public License as
@@ -1242,7 +1243,17 @@ WorkArea::on_drawing_area_event(GdkEvent *event)
                        //      button_pressed=0;                               
                }
        }
+       // GDK mouse scrolling events
+       else if(event->any.type==GDK_SCROLL)
+       {
+               // GDK information needed to properly interprete mouse
+               // scrolling events are: scroll.state, scroll.x/scroll.y, and
+               // scroll.direction. The value of scroll.direction will be
+               // obtained later.
 
+               modifier=Gdk::ModifierType(event->scroll.state);
+               mouse_pos=synfig::Point(screen_to_comp_coords(synfig::Point(event->scroll.x,event->scroll.y)));
+       }
 
        // Handle the renderables
        {
@@ -1644,6 +1655,97 @@ WorkArea::on_drawing_area_event(GdkEvent *event)
                return ret;
        }
                break;
+       case GDK_SCROLL:
+       {
+               // Handle a mouse scrolling event like Xara Xtreme and
+               // Inkscape:
+
+               // Scroll up/down: scroll up/down
+               // Shift + scroll up/down: scroll left/right
+               // Control + scroll up/down: zoom in/out
+
+               if(modifier&GDK_CONTROL_MASK)
+               {
+                       
+                       // The zoom is performed while preserving the pointer
+                       // position as a fixed point (similarly to Xara Xtreme and
+                       // Inkscape).
+
+                       // The strategy used below is to scroll to the updated
+                       // position, then zoom. This is easy to implement within
+                       // the present architecture, but has the disadvantage of
+                       // triggering multiple visible refreshes. Note: 1.25 is
+                       // the hard wired ratio in zoom_in()/zoom_out(). The
+                       // variable "drift" compensates additional inaccuracies in
+                       // the zoom. There is also an additional minus sign for
+                       // the inverted y coordinates.
+
+                       // FIXME: One might want to figure out where in the code
+                       // this empirical drift is been introduced.
+
+                       const synfig::Point scroll_point(get_scrollx_adjustment()->get_value(),get_scrolly_adjustment()->get_value());
+                       const double drift = 0.052;
+
+                       switch(event->scroll.direction)
+                       {
+                               case GDK_SCROLL_UP:
+                                       get_scrollx_adjustment()->set_value(scroll_point[0]+(mouse_pos[0]-scroll_point[0])*(1.25-(1+drift)));
+                                       get_scrolly_adjustment()->set_value(scroll_point[1]-(mouse_pos[1]+scroll_point[1])*(1.25-(1+drift)));
+                                       zoom_in();
+                                       break;
+                               case GDK_SCROLL_DOWN:
+                                       get_scrollx_adjustment()->set_value(scroll_point[0]+(mouse_pos[0]-scroll_point[0])*(1/1.25-(1+drift)));
+                                       get_scrolly_adjustment()->set_value(scroll_point[1]-(mouse_pos[1]+scroll_point[1])*(1/1.25-(1+drift)));
+                                       zoom_out();
+                                       break;
+                               default:
+                                       break;
+                       }
+               }
+               else if(modifier&GDK_SHIFT_MASK)
+               {
+                       // Scroll in either direction by 20 pixels. Ideally, the
+                       // amount of pixels per scrolling event should be
+                       // configurable. Xara Xtreme currently uses an (hard
+                       // wired) amount 20 pixel, Inkscape defaults to 40 pixels.
+
+                       const int scroll_pixel = 20;
+
+                       switch(event->scroll.direction)
+                       {
+                               case GDK_SCROLL_UP:
+                                       get_scrollx_adjustment()->set_value(get_scrollx_adjustment()->get_value()-scroll_pixel*pw);
+                                       break;
+                               case GDK_SCROLL_DOWN:
+                                       get_scrollx_adjustment()->set_value(get_scrollx_adjustment()->get_value()+scroll_pixel*pw);
+                                       break;
+                               default:
+                                       break;
+                       }
+               }
+               else
+               {       
+                       // Scroll in either direction by 20 pixels. Ideally, the
+                       // amount of pixels per scrolling event should be
+                       // configurable. Xara Xtreme currently uses an (hard
+                       // wired) amount 20 pixel, Inkscape defaults to 40 pixels.
+
+                       const int scroll_pixel = 20;
+
+                       switch(event->scroll.direction)
+                       {
+                               case GDK_SCROLL_UP:
+                                       get_scrolly_adjustment()->set_value(get_scrolly_adjustment()->get_value()+scroll_pixel*ph);
+                                       break;
+                               case GDK_SCROLL_DOWN:
+                                       get_scrolly_adjustment()->set_value(get_scrolly_adjustment()->get_value()-scroll_pixel*ph);
+                                       break;
+                               default:
+                                       break;
+                       }
+               }
+       }
+               break;
        default:
                break;
        }