Hi again,
Thanks everyone for the last tips. Here's another problem. I try to
check on the canvas if there is already an item or not (the item can be
a simple rectangle). I try to use :
item = self.canvas.get_item_at(event.x,event.y)
if item != None:
return TRUE
This brings a Segmentation Fault if there is nothing under
(event.x,event.y) ! Do you know why ?
(see the attached example which is a modified version of the
canvas-example.py by Jesper Skov)
Oh, by the way, how can I check wheter this is a rectangle or an ellipse
? Any item.type() or so ?
Best,
Sebastien
[EMAIL PROTECTED]
#!/usr/bin/env python
# Author: Jesper Skov <[EMAIL PROTECTED]>
# A rewite of the C canvas example in the GNOME Developer's Information
import GDK
from gtk import *
from gnome.ui import *
from whrandom import *
import GdkImlib
class CanvasExample:
def __init__(self):
self.generator = whrandom()
self.width = 400
self.height = 400
self.all = []
self.colors = ("red",
"yellow",
"green",
"cyan",
"blue",
"magenta")
def change_item_color(self, item):
# Pick a random color from the list.
n = int(self.generator.random() * len(self.colors)) - 1
item.set(fill_color = self.colors[n])
################ added part ##############################
def test_if_item(self,event):
item = self.canvas.get_item_at(event.x,event.y)
if item != None:
return TRUE
############################################################
def item_event(self, widget, event=None):
################ added part ##############################
if self.test_if_item(event):
############################################################
if event.type == GDK.BUTTON_PRESS:
if event.button == 1:
# Remember starting position.
self.remember_x = event.x
self.remember_y = event.y
return TRUE
elif event.button == 3:
# Destroy the item.
widget.destroy()
return TRUE
elif event.type == GDK._2BUTTON_PRESS:
# Change the item's color.
self.change_item_color(widget)
return TRUE
elif event.type == GDK.MOTION_NOTIFY:
if event.state & GDK.BUTTON1_MASK:
# Get the new position and move by the difference
new_x = event.x
new_y = event.y
widget.move(new_x - self.remember_x, new_y - self.remember_y)
self.remember_x = new_x
self.remember_y = new_y
return TRUE
elif event.type == GDK.ENTER_NOTIFY:
# Make the outline wide.
widget.set(width_units=3)
return TRUE
elif event.type == GDK.LEAVE_NOTIFY:
# Make the outline thin.
widget.set(width_units=1)
return TRUE
return FALSE
def add_object_clicked(self, widget, event=None):
x1 = self.generator.random() * self.width
y1 = self.generator.random() * self.height
x2 = self.generator.random() * self.width
y2 = self.generator.random() * self.height
if x1 > x2:
x2,x1 = x1,x2
if y1 > y2:
y2,y1 = y1,y2
if (x2 - x1) < 10:
x2 = x2 + 10
if (y2 - y1) < 10:
y2 = y2 + 10
if (self.generator.random() > .5):
type = 'rect'
else:
type = 'ellipse'
w = self.canvas.root().add(type, x1=x1, y1=y1, x2=x2, y2=y2,
fill_color='white', outline_color='black',
width_units=1.0)
w.connect("event", self.item_event)
self.all.append(w)
def main(self):
# Open window to hold canvas.
win = GtkWindow()
win.connect('destroy', mainquit)
win.set_title('Canvas Example')
# Create VBox to hold canvas and buttons.
vbox = GtkVBox()
win.add(vbox)
vbox.show()
# Some instructions for people using the example:
label = GtkLabel("Drag - move object.\n" +
"Double click - change colour\n" +
"Right click - delete object")
vbox.pack_start(label, expand=FALSE)
label.show()
# Create canvas.
self.canvas = GnomeCanvas()
self.canvas.set_usize(self.width, self.height)
self.canvas.set_scroll_region(0,0, self.width, self.height)
vbox.pack_start(self.canvas)
self.canvas.show()
# Create buttons.
hbox = GtkHBox()
vbox.pack_start(hbox, expand=FALSE)
hbox.show()
b = GtkButton("Add an object")
b.connect("clicked", self.add_object_clicked)
hbox.pack_start(b)
b.show()
b = GtkButton("Quit")
b.connect("clicked", mainquit)
hbox.pack_start(b)
b.show()
win.show()
if __name__ == '__main__':
c = CanvasExample()
c.main()
mainloop()
