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Tkinter canvas drag/drop obstacle

Tkinter makes it very easy to drag jpeg images around on a
canvas, but I would like to have a "target" change color when
the cursor dragging an image passes over it. I seem to be
blocked by the fact that the callbacks that might tell the
target that the mouse has entered it (<Enter>, <Any-Enter>,
even <Motion>) aren't called if the mouse's button is down.
What am I missing? Have I failed to find the right Tkinter
document? Is Tkinter the wrong tool for this job? Thanks.

--
To email me, substitute nowhere->spamcop, invalid->net.
Jun 27 '08 #1
7 4697
On Fri, Jun 20, 2008 at 1:11 PM, Peter Pearson <pp******@nowhe re.invalidwrote :
Tkinter makes it very easy to drag jpeg images around on a
canvas, but I would like to have a "target" change color when
the cursor dragging an image passes over it. I seem to be
blocked by the fact that the callbacks that might tell the
target that the mouse has entered it (<Enter>, <Any-Enter>,
even <Motion>) aren't called if the mouse's button is down.
What am I missing? Have I failed to find the right Tkinter
document? Is Tkinter the wrong tool for this job? Thanks.
I believe the only way to achieve this is binding <Motionto the
entire canvas, then checking if the x, y coords are inside the
"target".
--
To email me, substitute nowhere->spamcop, invalid->net.
--
http://mail.python.org/mailman/listinfo/python-list
--
-- Guilherme H. Polo Goncalves
Jun 27 '08 #2
On Jun 20, 9:11*am, Peter Pearson <ppear...@nowhe re.invalidwrote :
Tkinter makes it very easy to drag jpeg images around on a
canvas, but I would like to have a "target" change color when
the cursor dragging an image passes over it. *I seem to be
blocked by the fact that the callbacks that might tell the
target that the mouse has entered it (<Enter>, <Any-Enter>,
even <Motion>) aren't called if the mouse's button is down.
What am I missing? *Have I failed to find the right Tkinter
document? *Is Tkinter the wrong tool for this job? *Thanks.

--
To email me, substitute nowhere->spamcop, invalid->net.
I have used a combination of <Motionand <B1-Motion>. You might also
throw in a <Button-1event to keep track of whether or not the mouse
button was down when it entered the widget or not.

Depending on what you really want to do though, you might take
advantage of the 'active' state:

import Tkinter as tk

can = tk.Canvas()
can.pack(fill=t k.BOTH, expand=True)

can.create_rect angle(
10,10,100,100,
fill="black",
activewidth=5,
activeoutline=" blue"
)

can.mainloop()

The 'active*' options take effect when the mouse is on top of that
item.

If all you are _really_ interested in is a visual indicator, this
should work for you. Note that there is also a disabled state. I only
discovered this by looking at the options available and guessing.
>>from pprint import pprint
import Tkinter as tk
can = tk.Canvas()
can.pack(fill =tk.BOTH, expand=True)
r = can.create_rect angle(10,10,100 ,100)
pprint(can.it emconfig(r))
{'activedash': ('activedash', '', '', '', ''),
'activefill': ('activefill', '', '', '', ''),
'activeoutline' : ('activeoutline ', '', '', '', ''),
'activeoutlines tipple': ('activeoutline stipple', '', '', '', ''),
'activestipple' : ('activestipple ', '', '', '', ''),
'activewidth': ('activewidth', '', '', '0.0', '0.0'),
'dash': ('dash', '', '', '', ''),
'dashoffset': ('dashoffset', '', '', '0', '0'),
'disableddash': ('disableddash' , '', '', '', ''),
'disabledfill': ('disabledfill' , '', '', '', ''),
'disabledoutlin e': ('disabledoutli ne', '', '', '', ''),
'disabledoutlin estipple': ('disabledoutli nestipple', '', '', '', ''),
'disabledstippl e': ('disabledstipp le', '', '', '', ''),
'disabledwidth' : ('disabledwidth ', '', '', '0.0', '0'),
'fill': ('fill', '', '', '', ''),
'offset': ('offset', '', '', '0,0', '0,0'),
'outline': ('outline', '', '', 'black', 'black'),
'outlineoffset' : ('outlineoffset ', '', '', '0,0', '0,0'),
'outlinestipple ': ('outlinestippl e', '', '', '', ''),
'state': ('state', '', '', '', ''),
'stipple': ('stipple', '', '', '', ''),
'tags': ('tags', '', '', '', ''),
'width': ('width', '', '', '1.0', '1.0')}

The 'state' option can be set to 'normal', 'hidden' or 'disabled'. So
if you want to make your canvas items look different when they are
disabled, set the disabled* options and set 'state' to 'disabled'.

Matt
Jun 27 '08 #3
On Jun 20, 11:10*am, Matimus <mccre...@gmail .comwrote:
On Jun 20, 9:11*am, Peter Pearson <ppear...@nowhe re.invalidwrote :
Tkinter makes it very easy to drag jpeg images around on a
canvas, but I would like to have a "target" change color when
the cursor dragging an image passes over it. *I seem to be
blocked by the fact that the callbacks that might tell the
target that the mouse has entered it (<Enter>, <Any-Enter>,
even <Motion>) aren't called if the mouse's button is down.
What am I missing? *Have I failed to find the right Tkinter
document? *Is Tkinter the wrong tool for this job? *Thanks.
--
To email me, substitute nowhere->spamcop, invalid->net.

I have used a combination of <Motionand <B1-Motion>. You might also
throw in a <Button-1event to keep track of whether or not the mouse
button was down when it entered the widget or not.

Depending on what you really want to do though, you might take
advantage of the 'active' state:

import Tkinter as tk

can = tk.Canvas()
can.pack(fill=t k.BOTH, expand=True)

can.create_rect angle(
* * * * 10,10,100,100,
* * * * fill="black",
* * * * activewidth=5,
* * * * activeoutline=" blue"
* * * * )

can.mainloop()

The 'active*' options take effect when the mouse is on top of that
item.

If all you are _really_ interested in is a visual indicator, this
should work for you. Note that there is also a disabled state. I only
discovered this by looking at the options available and guessing.
>from pprint import pprint
import Tkinter as tk
can = tk.Canvas()
can.pack(fill= tk.BOTH, expand=True)
r = can.create_rect angle(10,10,100 ,100)
pprint(can.ite mconfig(r))

{'activedash': ('activedash', '', '', '', ''),
*'activefill': ('activefill', '', '', '', ''),
*'activeoutline ': ('activeoutline ', '', '', '', ''),
*'activeoutline stipple': ('activeoutline stipple', '', '', '', ''),
*'activestipple ': ('activestipple ', '', '', '', ''),
*'activewidth': ('activewidth', '', '', '0.0', '0.0'),
*'dash': ('dash', '', '', '', ''),
*'dashoffset': ('dashoffset', '', '', '0', '0'),
*'disableddash' : ('disableddash' , '', '', '', ''),
*'disabledfill' : ('disabledfill' , '', '', '', ''),
*'disabledoutli ne': ('disabledoutli ne', '', '', '', ''),
*'disabledoutli nestipple': ('disabledoutli nestipple', '', '', '', ''),
*'disabledstipp le': ('disabledstipp le', '', '', '', ''),
*'disabledwidth ': ('disabledwidth ', '', '', '0.0', '0'),
*'fill': ('fill', '', '', '', ''),
*'offset': ('offset', '', '', '0,0', '0,0'),
*'outline': ('outline', '', '', 'black', 'black'),
*'outlineoffset ': ('outlineoffset ', '', '', '0,0', '0,0'),
*'outlinestippl e': ('outlinestippl e', '', '', '', ''),
*'state': ('state', '', '', '', ''),
*'stipple': ('stipple', '', '', '', ''),
*'tags': ('tags', '', '', '', ''),
*'width': ('width', '', '', '1.0', '1.0')}

The 'state' option can be set to 'normal', 'hidden' or 'disabled'. So
if you want to make your canvas items look different when they are
disabled, set the disabled* options and set 'state' to 'disabled'.

Matt
I appologize. I didn't actually test this before posting the code, but
if you have the mouse button down before entering an item on the
canvas, even the active state doesn't seem apply. So, well, I hope
someone finds this information useful, but I guess it isn't going to
solve the original posters issue.

Matt
Jun 27 '08 #4

I have this class:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=TOL ):
print tolerance
shortened for clarity obviously. so I want to subclass this class like
so:

class BigVector(Vecto r)
TOL = 100
for example if I was working with large vectors which I knew would never
be very close hence the large tolerance. this doesn't work however -
the TOL class variable, while overridden in BigVector, is still using
the Vector.TOL variable in the __eq__ method.
which kinda makes sense to a certain degree, but how do I get the
behaviour where doing:

BigVector().__e q__( otherVec )
prints 100 instead of 1e-5?

does this question make sense? not sure how clearly I'm phrasing my
question... any of you guys python experts?
I *could* do this, but its ugly:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=None ):
if tolerance is None: tolerance = self.TOL
print tolerance
Jun 27 '08 #5
On Fri, Jun 20, 2008 at 6:19 PM, Hamish McKenzie
<ha****@valveso ftware.comwrote :
>
I have this class:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=TOL ):
print tolerance
shortened for clarity obviously. so I want to subclass this class like
so:

class BigVector(Vecto r)
TOL = 100
for example if I was working with large vectors which I knew would never
be very close hence the large tolerance. this doesn't work however -
the TOL class variable, while overridden in BigVector, is still using
the Vector.TOL variable in the __eq__ method.
which kinda makes sense to a certain degree, but how do I get the
behaviour where doing:

BigVector().__e q__( otherVec )
No, don't do this. Just do "avector == othervector"
>

prints 100 instead of 1e-5?

does this question make sense? not sure how clearly I'm phrasing my
question... any of you guys python experts?
I *could* do this, but its ugly:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=None ):
if tolerance is None: tolerance = self.TOL
print tolerance
class Vector(object):
TOL = 1e-5
def __eq__(self, other):
print self.TOL
>
--
http://mail.python.org/mailman/listinfo/python-list


--
-- Guilherme H. Polo Goncalves
Jun 27 '08 #6
On Fri, 20 Jun 2008 13:41:35 -0300, Guilherme Polo <gg****@gmail.c omwrote:
On Fri, Jun 20, 2008 at 1:11 PM, Peter Pearson <pp******@nowhe re.invalidwrote :
>Tkinter makes it very easy to drag jpeg images around on a
canvas, but I would like to have a "target" change color when
the cursor dragging an image passes over it. I seem to be
blocked by the fact that the callbacks that might tell the
target that the mouse has entered it (<Enter>, <Any-Enter>,
even <Motion>) aren't called if the mouse's button is down.
What am I missing? Have I failed to find the right Tkinter
document? Is Tkinter the wrong tool for this job? Thanks.

I believe the only way to achieve this is binding <Motionto the
entire canvas, then checking if the x, y coords are inside the
"target".
Ugh. OK, thanks.

--
To email me, substitute nowhere->spamcop, invalid->net.
Jun 27 '08 #7
Preamble: when posting a brand new question, you'd better not replying to
an existing completely unrelated message. In most viewers, this will cause
your message to appear in the thread for the original question and far
less people will see it. So better create a brand new thread.

On Fri, 20 Jun 2008 23:19:37 +0200, Hamish McKenzie
<ha****@valveso ftware.comwrote :
I have this class:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=TOL ):
print tolerance
shortened for clarity obviously. so I want to subclass this class like
so:

class BigVector(Vecto r)
TOL = 100
for example if I was working with large vectors which I knew would never
be very close hence the large tolerance. this doesn't work however -
the TOL class variable, while overridden in BigVector, is still using
the Vector.TOL variable in the __eq__ method.
which kinda makes sense to a certain degree, but how do I get the
behaviour where doing:

BigVector().__e q__( otherVec )
prints 100 instead of 1e-5?

does this question make sense? not sure how clearly I'm phrasing my
question... any of you guys python experts?
There's just no way. The default values for function/method arguments are
evaluated when the function definition is interpreted. When the __eq__
method is defined, TOL is 1e-5, so that will be the value used in the
method, whatever you may do afterwards.
>
I *could* do this, but its ugly:

class Vector(object):
TOL = 1e-5
def __eq__( self, other, tolerance=None ):
if tolerance is None: tolerance = self.TOL
print tolerance
Well, ugliness is in the eye of the beholder... ;-) Even if you find it
ugly, that's the Python way to do it.

HTH
--
python -c "print ''.join([chr(154 - ord(c)) for c in
'U(17zX(%,5.zmz 5(17l8(%,5.Z*(9 3-965$l7+-'])"
Jun 27 '08 #8

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