In looking through the archive for topics related to using the gnome canvas, I
came accross an example submitted by Colin Fox back in Apr 2002. I updated
the syntax of the example to work under the more recent version of pygtk and
have appended it below. The example runs, but it doesn't seem to run
correctly. The canvas starts out responding to enter_notify and leave_notify
events, but then freezes after a few such events. The canvas also freezes if
the mouse is clicked over the object. Is this caused by a bug in the example
or is there a bug in the canvas?
--Doug Blanding
#!/usr/bin/env python
import gtk
import gnome.canvas
class WorldObject:
def __init__(self,canvas,x,y):
self.myobj = None
self.myline = None
self.mylinepoints = [x,y,x,y]
self.canvas = canvas
self.width = 20
self.height = 20
self.x = x
self.y = y
self.lmb_pressed = 0
self.build()
def set_line_endpoint(self,x,y):
self.mylinepoints[2] = x
self.mylinepoints[3] = y
self.myline.set(points=self.mylinepoints)
def item_event(self, widget, event=None):
if event.type == gtk.gdk.BUTTON_RELEASE:
if event.button == 1:
self.lmb_pressed = 0
self.myline.hide()
return gtk.TRUE
elif event.type == gtk.gdk.BUTTON_PRESS:
if event.button == 1:
self.lmb_pressed = 1
self.set_line_endpoint(event.x,event.y)
self.myline.show()
return gtk.TRUE
elif event.type == gtk.gdk.MOTION_NOTIFY:
if event.state & gtk.gdk.BUTTON1_MASK:
self.set_line_endpoint(event.x, event.y)
return gtk.TRUE
elif event.type == gtk.gdk.ENTER_NOTIFY:
# Make the outline wide, show the arrow
widget.set(width_units=3, fill_color="cyan")
self.myline.show()
return gtk.TRUE
elif event.type == gtk.gdk.LEAVE_NOTIFY:
# Make the outline thin, hide the arrow
widget.set(width_units=1, fill_color="blue")
if self.lmb_pressed == 0:
self.myline.hide()
return gtk.TRUE
return gtk.FALSE
def build(self):
self.myobj = self.canvas.root().add('GnomeCanvasEllipse',
x1=self.x-(self.width/2),
y1=self.y-(self.height/2),
x2=self.x+(self.width/2),
y2=self.y+(self.height/2),
fill_color='blue', outline_color='black',
width_units=1.0)
self.myline = self.canvas.root().add('GnomeCanvasLine',
points=self.mylinepoints,
width_units=1.0,
line_style='GDK_LINE_ON_OFF_DASH',
arrow_shape_a=10.0,
arrow_shape_b=15.0,
arrow_shape_c=5.0,
first_arrowhead=gtk.FALSE,
last_arrowhead=gtk.TRUE,
fill_color='black')
self.myline.hide()
self.myobj.show()
self.myobj.connect("event",self.item_event)
class SimpleTest:
def __init__(self):
self.width = 400
self.height = 400
self.canvas = None
def populate(self):
self.element = WorldObject(self.canvas,200,200)
def open_window(self):
win = gtk.Window()
win.connect('destroy', gtk.mainquit)
win.set_title('Simple Example')
self.canvas = gnome.canvas.Canvas()
self.canvas.set_size_request(self.width, self.height)
self.canvas.set_scroll_region(0,0, self.width, self.height)
win.add(self.canvas)
self.canvas.show()
win.show()
if __name__ == '__main__':
st = SimpleTest()
st.open_window()
st.populate()
gtk.mainloop()
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