setting tooltip in pyqtgraph

[pyqtuser123]

Hi,

I am plotting some data points using ScatterPlotItems(). I am trying to show a tooltip that should appear when the mouse hovers over a datapoint.

Can anybody help me with this?

[Luke Campagnola]

On Fri, Dec 20, 2013 at 12:25 AM, pyqtuser123 <pankaj.k...@gmail.com> wrote:

I am plotting some data points using ScatterPlotItems(). I am trying to show a tooltip that should appear when the mouse hovers over a datapoint.

Can anybody help me with this?

I recommend the following strategy:

1) Connect to GraphicsScene.sigMouseMoved to get updates on mouse position

2) Map the scene coordinates of the mouse cursor to the local coordinates of the ScatterPlotItem

3) Use ScatterPlotItem.pointsAt(pos) to determine which point(s) are under the cursor

4) Use a TextItem to display your tooltip

Give this a try and let me know if you need further help.

Luke

[pyqtuser123]

Hi Luke,

I followed your strategy and I could sucessfully implement the tooltip feature that I was looking for.

However, when I try to implement the solution using classes it doesn't work. Following is the code that I have written:

class Tooltip_example:

         def __init__(self,x,y,widget):

              self.scatterPoints = pg.ScatterPlotItem(x,y,size=10, pen=pg.mkPen(None), brush=pg.mkBrush(255, 255, 255, 120))

              self.display_text= pg.TextItem(text='',color=(176,23,31),anchor=(1,1))

              self.display_text.hide()

              widget.addItem(self.scatterPoints)

              widget.addItem(self.display_text)

              self.scatterPoints.scene().sigMouseMoved.connect(self.onMove)

        def onMove(self,pos):

             act_pos = self.scatterPoints.mapFromScene(pos)

             p1 = self.scatterPoints.pointsAt(act_pos)

             if len(p1)!=0:

                  self.display_text.setText('x=%f\nY=%f'%(x[i],y[i]))

                  self.display_text.setPos(x[i],y[i])

                  self.display_text.show()

             else:

                   display_text.hide() 

I am new to python so, please excuse me for any stupid mistake that I might have made in my code.                           

[Luke Campagnola]

On Mon, Dec 23, 2013 at 5:47 AM, pyqtuser123 <pankaj.k...@gmail.com> wrote:

Hi Luke,

I followed your strategy and I could sucessfully implement the tooltip feature that I was looking for.

However, when I try to implement the solution using classes it doesn't work. Following is the code that I have written:

Your code looks good to me; this is very close to the way I would have implemented it. Can you explain what part of your solution does not work?

[Mike]

Looks like you have an error in your class. x and y are passed in to __init__, but are also used in OnMove even though they are out of scope. If you want to use them in OnMove, you will need to add

self.x = x
self.y = y

and then replace x and y in OnMove with self.x and self.y.

Mike

[pyqtuser123]

Thanks Mike. It works now.:)

However, there's one more thing that I have noticed. 

When I create an instance of Tooltip_example class and and do not assign it to any variable on the L.H.S the control is never passed to the 'onMove' event.

            

             Tooltip_example(x, y, widget1)            # doesn't work

             t = Tooltip_example(x, y, widget1)       # works fine

Any reason for the above mentioned behavior? Or have I missed something?

[Luke Campagnola]

On Tue, Dec 24, 2013 at 12:51 AM, pyqtuser123 <pankaj.k...@gmail.com> wrote:

When I create an instance of Tooltip_example class and and do not assign it to any variable on the L.H.S the control is never passed to the 'onMove' event.

            

             Tooltip_example(x, y, widget1)            # doesn't work

             t = Tooltip_example(x, y, widget1)       # works fine

Any reason for the above mentioned behavior? Or have I missed something?

Most likely, the instance is being garbage collected because there are no references to it. One might think that adding the item to a scene should increment its reference count, but I guess the PyQt / PySide developers decided against that for some reason.

 

[Kernc]

On Saturday, December 21, 2013 at 9:39:08 PM UTC+1, Luke Campagnola wrote:

4) Use a TextItem to display your tooltip

Could it instead make sense to call Qt's

    scatterplotitem.setTooltip('...')

for a consistent, native look?