mirror of
https://github.com/python/cpython.git
synced 2025-11-03 19:34:08 +00:00
321 lines
11 KiB
Python
321 lines
11 KiB
Python
"""Drag-and-drop support for Tkinter.
|
|
|
|
This is very preliminary. I currently only support dnd *within* one
|
|
application, between different windows (or within the same window).
|
|
|
|
I an trying to make this as generic as possible -- not dependent on
|
|
the use of a particular widget or icon type, etc. I also hope that
|
|
this will work with Pmw.
|
|
|
|
To enable an object to be dragged, you must create an event binding
|
|
for it that starts the drag-and-drop process. Typically, you should
|
|
bind <ButtonPress> to a callback function that you write. The function
|
|
should call Tkdnd.dnd_start(source, event), where 'source' is the
|
|
object to be dragged, and 'event' is the event that invoked the call
|
|
(the argument to your callback function). Even though this is a class
|
|
instantiation, the returned instance should not be stored -- it will
|
|
be kept alive automatically for the duration of the drag-and-drop.
|
|
|
|
When a drag-and-drop is already in process for the Tk interpreter, the
|
|
call is *ignored*; this normally averts starting multiple simultaneous
|
|
dnd processes, e.g. because different button callbacks all
|
|
dnd_start().
|
|
|
|
The object is *not* necessarily a widget -- it can be any
|
|
application-specific object that is meaningful to potential
|
|
drag-and-drop targets.
|
|
|
|
Potential drag-and-drop targets are discovered as follows. Whenever
|
|
the mouse moves, and at the start and end of a drag-and-drop move, the
|
|
Tk widget directly under the mouse is inspected. This is the target
|
|
widget (not to be confused with the target object, yet to be
|
|
determined). If there is no target widget, there is no dnd target
|
|
object. If there is a target widget, and it has an attribute
|
|
dnd_accept, this should be a function (or any callable object). The
|
|
function is called as dnd_accept(source, event), where 'source' is the
|
|
object being dragged (the object passed to dnd_start() above), and
|
|
'event' is the most recent event object (generally a <Motion> event;
|
|
it can also be <ButtonPress> or <ButtonRelease>). If the dnd_accept()
|
|
function returns something other than None, this is the new dnd target
|
|
object. If dnd_accept() returns None, or if the target widget has no
|
|
dnd_accept attribute, the target widget's parent is considered as the
|
|
target widget, and the search for a target object is repeated from
|
|
there. If necessary, the search is repeated all the way up to the
|
|
root widget. If none of the target widgets can produce a target
|
|
object, there is no target object (the target object is None).
|
|
|
|
The target object thus produced, if any, is called the new target
|
|
object. It is compared with the old target object (or None, if there
|
|
was no old target widget). There are several cases ('source' is the
|
|
source object, and 'event' is the most recent event object):
|
|
|
|
- Both the old and new target objects are None. Nothing happens.
|
|
|
|
- The old and new target objects are the same object. Its method
|
|
dnd_motion(source, event) is called.
|
|
|
|
- The old target object was None, and the new target object is not
|
|
None. The new target object's method dnd_enter(source, event) is
|
|
called.
|
|
|
|
- The new target object is None, and the old target object is not
|
|
None. The old target object's method dnd_leave(source, event) is
|
|
called.
|
|
|
|
- The old and new target objects differ and neither is None. The old
|
|
target object's method dnd_leave(source, event), and then the new
|
|
target object's method dnd_enter(source, event) is called.
|
|
|
|
Once this is done, the new target object replaces the old one, and the
|
|
Tk mainloop proceeds. The return value of the methods mentioned above
|
|
is ignored; if they raise an exception, the normal exception handling
|
|
mechanisms take over.
|
|
|
|
The drag-and-drop processes can end in two ways: a final target object
|
|
is selected, or no final target object is selected. When a final
|
|
target object is selected, it will always have been notified of the
|
|
potential drop by a call to its dnd_enter() method, as described
|
|
above, and possibly one or more calls to its dnd_motion() method; its
|
|
dnd_leave() method has not been called since the last call to
|
|
dnd_enter(). The target is notified of the drop by a call to its
|
|
method dnd_commit(source, event).
|
|
|
|
If no final target object is selected, and there was an old target
|
|
object, its dnd_leave(source, event) method is called to complete the
|
|
dnd sequence.
|
|
|
|
Finally, the source object is notified that the drag-and-drop process
|
|
is over, by a call to source.dnd_end(target, event), specifying either
|
|
the selected target object, or None if no target object was selected.
|
|
The source object can use this to implement the commit action; this is
|
|
sometimes simpler than to do it in the target's dnd_commit(). The
|
|
target's dnd_commit() method could then simply be aliased to
|
|
dnd_leave().
|
|
|
|
At any time during a dnd sequence, the application can cancel the
|
|
sequence by calling the cancel() method on the object returned by
|
|
dnd_start(). This will call dnd_leave() if a target is currently
|
|
active; it will never call dnd_commit().
|
|
|
|
"""
|
|
|
|
|
|
import tkinter
|
|
|
|
|
|
# The factory function
|
|
|
|
def dnd_start(source, event):
|
|
h = DndHandler(source, event)
|
|
if h.root:
|
|
return h
|
|
else:
|
|
return None
|
|
|
|
|
|
# The class that does the work
|
|
|
|
class DndHandler:
|
|
|
|
root = None
|
|
|
|
def __init__(self, source, event):
|
|
if event.num > 5:
|
|
return
|
|
root = event.widget._root()
|
|
try:
|
|
root.__dnd
|
|
return # Don't start recursive dnd
|
|
except AttributeError:
|
|
root.__dnd = self
|
|
self.root = root
|
|
self.source = source
|
|
self.target = None
|
|
self.initial_button = button = event.num
|
|
self.initial_widget = widget = event.widget
|
|
self.release_pattern = "<B%d-ButtonRelease-%d>" % (button, button)
|
|
self.save_cursor = widget['cursor'] or ""
|
|
widget.bind(self.release_pattern, self.on_release)
|
|
widget.bind("<Motion>", self.on_motion)
|
|
widget['cursor'] = "hand2"
|
|
|
|
def __del__(self):
|
|
root = self.root
|
|
self.root = None
|
|
if root:
|
|
try:
|
|
del root.__dnd
|
|
except AttributeError:
|
|
pass
|
|
|
|
def on_motion(self, event):
|
|
x, y = event.x_root, event.y_root
|
|
target_widget = self.initial_widget.winfo_containing(x, y)
|
|
source = self.source
|
|
new_target = None
|
|
while target_widget:
|
|
try:
|
|
attr = target_widget.dnd_accept
|
|
except AttributeError:
|
|
pass
|
|
else:
|
|
new_target = attr(source, event)
|
|
if new_target:
|
|
break
|
|
target_widget = target_widget.master
|
|
old_target = self.target
|
|
if old_target is new_target:
|
|
if old_target:
|
|
old_target.dnd_motion(source, event)
|
|
else:
|
|
if old_target:
|
|
self.target = None
|
|
old_target.dnd_leave(source, event)
|
|
if new_target:
|
|
new_target.dnd_enter(source, event)
|
|
self.target = new_target
|
|
|
|
def on_release(self, event):
|
|
self.finish(event, 1)
|
|
|
|
def cancel(self, event=None):
|
|
self.finish(event, 0)
|
|
|
|
def finish(self, event, commit=0):
|
|
target = self.target
|
|
source = self.source
|
|
widget = self.initial_widget
|
|
root = self.root
|
|
try:
|
|
del root.__dnd
|
|
self.initial_widget.unbind(self.release_pattern)
|
|
self.initial_widget.unbind("<Motion>")
|
|
widget['cursor'] = self.save_cursor
|
|
self.target = self.source = self.initial_widget = self.root = None
|
|
if target:
|
|
if commit:
|
|
target.dnd_commit(source, event)
|
|
else:
|
|
target.dnd_leave(source, event)
|
|
finally:
|
|
source.dnd_end(target, event)
|
|
|
|
|
|
|
|
# ----------------------------------------------------------------------
|
|
# The rest is here for testing and demonstration purposes only!
|
|
|
|
class Icon:
|
|
|
|
def __init__(self, name):
|
|
self.name = name
|
|
self.canvas = self.label = self.id = None
|
|
|
|
def attach(self, canvas, x=10, y=10):
|
|
if canvas is self.canvas:
|
|
self.canvas.coords(self.id, x, y)
|
|
return
|
|
if self.canvas:
|
|
self.detach()
|
|
if not canvas:
|
|
return
|
|
label = tkinter.Label(canvas, text=self.name,
|
|
borderwidth=2, relief="raised")
|
|
id = canvas.create_window(x, y, window=label, anchor="nw")
|
|
self.canvas = canvas
|
|
self.label = label
|
|
self.id = id
|
|
label.bind("<ButtonPress>", self.press)
|
|
|
|
def detach(self):
|
|
canvas = self.canvas
|
|
if not canvas:
|
|
return
|
|
id = self.id
|
|
label = self.label
|
|
self.canvas = self.label = self.id = None
|
|
canvas.delete(id)
|
|
label.destroy()
|
|
|
|
def press(self, event):
|
|
if dnd_start(self, event):
|
|
# where the pointer is relative to the label widget:
|
|
self.x_off = event.x
|
|
self.y_off = event.y
|
|
# where the widget is relative to the canvas:
|
|
self.x_orig, self.y_orig = self.canvas.coords(self.id)
|
|
|
|
def move(self, event):
|
|
x, y = self.where(self.canvas, event)
|
|
self.canvas.coords(self.id, x, y)
|
|
|
|
def putback(self):
|
|
self.canvas.coords(self.id, self.x_orig, self.y_orig)
|
|
|
|
def where(self, canvas, event):
|
|
# where the corner of the canvas is relative to the screen:
|
|
x_org = canvas.winfo_rootx()
|
|
y_org = canvas.winfo_rooty()
|
|
# where the pointer is relative to the canvas widget:
|
|
x = event.x_root - x_org
|
|
y = event.y_root - y_org
|
|
# compensate for initial pointer offset
|
|
return x - self.x_off, y - self.y_off
|
|
|
|
def dnd_end(self, target, event):
|
|
pass
|
|
|
|
class Tester:
|
|
|
|
def __init__(self, root):
|
|
self.top = tkinter.Toplevel(root)
|
|
self.canvas = tkinter.Canvas(self.top, width=100, height=100)
|
|
self.canvas.pack(fill="both", expand=1)
|
|
self.canvas.dnd_accept = self.dnd_accept
|
|
|
|
def dnd_accept(self, source, event):
|
|
return self
|
|
|
|
def dnd_enter(self, source, event):
|
|
self.canvas.focus_set() # Show highlight border
|
|
x, y = source.where(self.canvas, event)
|
|
x1, y1, x2, y2 = source.canvas.bbox(source.id)
|
|
dx, dy = x2-x1, y2-y1
|
|
self.dndid = self.canvas.create_rectangle(x, y, x+dx, y+dy)
|
|
self.dnd_motion(source, event)
|
|
|
|
def dnd_motion(self, source, event):
|
|
x, y = source.where(self.canvas, event)
|
|
x1, y1, x2, y2 = self.canvas.bbox(self.dndid)
|
|
self.canvas.move(self.dndid, x-x1, y-y1)
|
|
|
|
def dnd_leave(self, source, event):
|
|
self.top.focus_set() # Hide highlight border
|
|
self.canvas.delete(self.dndid)
|
|
self.dndid = None
|
|
|
|
def dnd_commit(self, source, event):
|
|
self.dnd_leave(source, event)
|
|
x, y = source.where(self.canvas, event)
|
|
source.attach(self.canvas, x, y)
|
|
|
|
def test():
|
|
root = tkinter.Tk()
|
|
root.geometry("+1+1")
|
|
tkinter.Button(command=root.quit, text="Quit").pack()
|
|
t1 = Tester(root)
|
|
t1.top.geometry("+1+60")
|
|
t2 = Tester(root)
|
|
t2.top.geometry("+120+60")
|
|
t3 = Tester(root)
|
|
t3.top.geometry("+240+60")
|
|
i1 = Icon("ICON1")
|
|
i2 = Icon("ICON2")
|
|
i3 = Icon("ICON3")
|
|
i1.attach(t1.canvas)
|
|
i2.attach(t2.canvas)
|
|
i3.attach(t3.canvas)
|
|
root.mainloop()
|
|
|
|
if __name__ == '__main__':
|
|
test()
|