[pyqtgraph] scene() returning None?

[Oscar Branson]

Hello,

I'm attempting to implement an action based on sigMouseMoved, but have got
seriously confused about how to access this signal.

*The Project*

I am creating multi-panel plots inside a larger pyqt application. To do
this, I have contained everything within a GraphicsView, which contains a
central GraphicsLayout that contains the plots.

I am using PlotItem to create plots, which I then add to the GraphicsLayout
using addItem.

This is all working fine, and I end up with two plots displayed - let's
call them Plot1 and Plot2.

Now, I want to display the cursor position in a label, so I created a label
and a mouseMoved function to update the label text.

*The problem: I can't work out how to connect sigMouseMoved to my
mouseMoved function.*

Following the documentation and examples, I tried setting up a SignalProxy:

SignalProxy(Plot1.scene().sigMouseMoved, rateLimit=60, slot=mouseMoved)


When I try to run this, I get an AttributeError telling me that 'NoneType'
object has no attribute 'sigMouseMoved'. I can't work out why calling
scene() on my plots returns None!

The only difference I can see from the examples is that I'm manually
creating 'PlotItem' rather than pyqtgraph.plot to create my plots... but as
far as I can tell the .plot function is just a wrapper for creating a
PlotItem.

Any help/pointers would be greatly appreciated... this is driving me mad!

Thanks,

Oscar.

[Patrick]

Hi,

I don't think the issue is just because you create the PlotItems
separately. If I change the Crosshair/Mouse interaction example lines from
p1 = win.addPlot(row=1, col=0)
p2 = win.addPlot(row=2, col=0)

to
p1 = pg.PlotItem()
p2 = pg.PlotItem()
win.addItem(p1, row=1, col=0)
win.addItem(p2, row=2, col=0)

then the example still works fine.


I'm taking a guess and saying you're trying to connect the signal to the
PlotItem before adding it to the GraphicsLayout. Until that happens, it
doesn't know what GraphicsScene it's part of.



Patrick

Post by Oscar Branson
Hello,
I'm attempting to implement an action based on sigMouseMoved, but have got
seriously confused about how to access this signal.
*The Project*
I am creating multi-panel plots inside a larger pyqt application. To do
this, I have contained everything within a GraphicsView, which contains a
central GraphicsLayout that contains the plots.
I am using PlotItem to create plots, which I then add to the
GraphicsLayout using addItem.
This is all working fine, and I end up with two plots displayed - let's
call them Plot1 and Plot2.
Now, I want to display the cursor position in a label, so I created a
label and a mouseMoved function to update the label text.
*The problem: I can't work out how to connect sigMouseMoved to my
mouseMoved function.*
SignalProxy(Plot1.scene().sigMouseMoved, rateLimit=60, slot=mouseMoved)
When I try to run this, I get an AttributeError telling me that 'NoneType'
object has no attribute 'sigMouseMoved'. I can't work out why calling
scene() on my plots returns None!
The only difference I can see from the examples is that I'm manually
creating 'PlotItem' rather than pyqtgraph.plot to create my plots... but as
far as I can tell the .plot function is just a wrapper for creating a
PlotItem.
Any help/pointers would be greatly appreciated... this is driving me mad!
Thanks,
Oscar.

...

[Oscar Branson]

Yep - that solved it. Was trying to make the connection before adding the
plots. Doh! Thanks v much.

Post by Patrick
Hi,
I don't think the issue is just because you create the PlotItems
separately. If I change the Crosshair/Mouse interaction example lines from
p1 = win.addPlot(row=1, col=0)
p2 = win.addPlot(row=2, col=0)
to
p1 = pg.PlotItem()
p2 = pg.PlotItem()
win.addItem(p1, row=1, col=0)
win.addItem(p2, row=2, col=0)
then the example still works fine.
I'm taking a guess and saying you're trying to connect the signal to the
PlotItem before adding it to the GraphicsLayout. Until that happens, it
doesn't know what GraphicsScene it's part of.
Patrick

Post by Oscar Branson
Hello,
I'm attempting to implement an action based on sigMouseMoved, but have
got seriously confused about how to access this signal.
*The Project*
I am creating multi-panel plots inside a larger pyqt application. To do
this, I have contained everything within a GraphicsView, which contains a
central GraphicsLayout that contains the plots.
I am using PlotItem to create plots, which I then add to the
GraphicsLayout using addItem.
This is all working fine, and I end up with two plots displayed - let's
call them Plot1 and Plot2.
Now, I want to display the cursor position in a label, so I created a
label and a mouseMoved function to update the label text.
*The problem: I can't work out how to connect sigMouseMoved to my
mouseMoved function.*
SignalProxy(Plot1.scene().sigMouseMoved, rateLimit=60, slot=mouseMoved)
When I try to run this, I get an AttributeError telling me that
'NoneType' object has no attribute 'sigMouseMoved'. I can't work out why
calling scene() on my plots returns None!
The only difference I can see from the examples is that I'm manually
creating 'PlotItem' rather than pyqtgraph.plot to create my plots... but as
far as I can tell the .plot function is just a wrapper for creating a
PlotItem.
Any help/pointers would be greatly appreciated... this is driving me mad!
Thanks,
Oscar.

...