scrollbar does not work in recent chaco releases

[sancelot]

This program was running fine in chaco 3.2, but with chaco 4, scrollbar does not show at all.

I would like either to find the problem or find a workaround.

PanTool may be a workaround, but this will conflict with some linecursors used with mouse.

 #!/usr/bin/env python
# Major library imports
from numpy import linspace

from scipy.special import jn

# Enthought library imports
from enthought.enable.api import Component, ComponentEditor
from enthought.traits.api import HasTraits, Instance
from enthought.traits.ui.api import Item, Group, View

# Chaco imports
from enthought.chaco.api import ArrayPlotData, VPlotContainer, \
    Plot, OverlayPlotContainer, add_default_axes, add_default_grids
from enthought.chaco.plotscrollbar import PlotScrollBar
from enthought.chaco.tools.api import PanTool, ZoomTool

#===============================================================================
# # Create the Chaco plot.
#===============================================================================
def _create_plot_component():
    # Create some x-y data series to plot
    x = linspace(-2.0, 10.0, 100)
    pd = ArrayPlotData(index = x)
    for i in range(5):
        pd.set_data("y" + str(i), jn(i,x))

    # Create some line plots of some of the data
    plot1 = Plot(pd)
    plot1.plot(("index", "y0", "y1", "y2"), name="j_n, n<3", color="red")[0]
    p = plot1.plot(("index", "y3"), name="j_3", color="blue")[0]

    # Add the scrollbar
    plot1.padding_top = 0

    p.index_range.high_setting = 1
    # Create a container and add our plots
    container = OverlayPlotContainer(padding = 5,fill_padding = True,
                                     bgcolor = "lightgray", use_backbuffer=True)
    hscrollbar = PlotScrollBar(component=p, mapper=p.index_mapper,axis="index", resizable="",use_backbuffer = False,
                               height=15,position=(0,0))
    hscrollbar.force_data_update()

    plot1.overlays.append(hscrollbar)


    hgrid,vgrid = add_default_grids(plot1)
    add_default_axes(plot1)
    container.add(plot1)

    container.invalidate_and_redraw()
    return container

#===============================================================================
# Attributes to use for the plot view.
size=(900,500)
title="Scrollbar example"

#===============================================================================
# # Demo class that is used by the demo.py application.
#===============================================================================
class Demo(HasTraits):
    plot = Instance(Component)

    traits_view = View(
                    Group(
                        Item('plot', editor=ComponentEditor(size=size),
                             show_label=False),
                        orientation = "vertical"),
                    resizable=True, title=title
                    )

    def _plot_default(self):
         return _create_plot_component()

demo = Demo()

if __name__ == "__main__":
    demo.configure_traits()

[corranwebster]

Thanks for the report. Which platform are you seeing the issue on, and what backend (Wx or Qt4)? Recent versions of TraitsUI have switched to Qt4 as the default, and I know that some versions of Enable/Chaco had problems with the Qt4 scrollbars on some platforms, so that could be a cause of the problem.

The plot scrollbar code is very old and has not been touched for a long time, so it is not surprising that there are issues. I notice that you are still using imports from the old enthought.* namespace, so you may want to update your code to reflect the new top-level package names.

The other things which might be worth trying is to switch to using the github master versions of Enable and Chaco, since some effort was recently put into fixing the Enable scrollbar and viewport code. If things still don't work, you may be able to get a scrollbar by using the lower-level Enable scrollbar/viewport system (see https://github.com/enthought/enable/blob/master/examples/enable/scrolled_demo.py and https://github.com/enthought/enable/blob/master/examples/enable/scrolled_canvas_demo.py).

Finally, using PanTool is frequently more efficient (it tends to be what I use, in preference to scrollbars). Is there a reason why the LineInspectorTool isn't handling your needs as far as a mouse line cursor, as it should be compatible with scrolling with a line tool?

[corranwebster]

A couple of comments on looking into this further:

• it looks like the PlotScrollBar class was not ever properly completed, based on the commit comments in git, so its a bit surprising that it works at all.
• Your sample code is drawing the scrollbar as an overlay on a plot renderer, which is rarely the right thing to do. Usually you want to draw on the Plot. That said, drawing as an overlay seems to not be currently working, at least with the Qt backend.
• The following code at least will draw the scrollbar, and seems to cover your use-case, even if it is not visually perfect. Hopefully this is enough to get your code into a working and useful state.

def _create_plot_component():
    # Create some x-y data series to plot
    x = linspace(-2.0, 10.0, 100)
    pd = ArrayPlotData(index = x)
    for i in range(5):
        pd.set_data("y" + str(i), jn(i,x))

    # Create some line plots of some of the data
    plot1 = Plot(pd)
    plot1.plot(("index", "y0", "y1", "y2"), name="j_n, n<3", color="red")[0]
    p = plot1.plot(("index", "y3"), name="j_3", color="blue")[0]

    # Add the scrollbar
    plot1.padding_top = 0

    p.index_range.high_setting = 1
    # Create a container and add our plots
    hscrollbar = PlotScrollBar(component=plot1, mapper=plot1.index_mapper, axis="index",
                               resizable="h", height=15, padding=(50, 50, 0, 0))
    hscrollbar.force_data_update()

    container = VPlotContainer()
    container.add(plot1)
    container.add(hscrollbar)

    container.invalidate_and_redraw()
    return container

[sancelot]

Hi,
I am using wx backend, I will try it.

I had setted up the scrollbar in an overlay container, because linking it to the container has failed.

You are saying Lineinspector should work. my Lineinspector tool is disturbing scrolling, I will try again and give some details.

[sancelot]

Hi,
I ran a fresh install with latest traits, ui, enable, chaco releases from github.

scrollbar has worked using qt4 backend.
using wx backend it has not worked. no scrollbar available.

I am using wx backend, because the graph view is embedded in a wx application.

I have a look at both scrolled_demo.py and scrolled_canvas_demo.py.
they works with qt4 backend, scrollbars not available with wx...only a comment regarding this app: the circle move is very limited as soon your mouse leave the circle, no more drag is possible. it should follow the mouse.

[sancelot]

regarding usage of Pan and LineInspector :

I am using 2 Draggable LineInspectors. this Draggable LineInspector behaves not correctly, because it can not catch left up event , when pan is active....

Application is dedicated to touchscreen interface too, so I can not use other buttons .

[sancelot]

We investigated and found some problems in the code, that had disallowed the scrollbar to display in wx backend.

The following patch solves the problem.

There are other issues, like height setting that does not work, we will continue to investigate.

diff --git a/enable/wx/scrollbar.py b/enable/wx/scrollbar.py
index 02d0da0..003cc90 100644
--- a/enable/wx/scrollbar.py
+++ b/enable/wx/scrollbar.py
@@ -136,7 +136,7 @@
         # We have to do this flip_y business because wx and enable use opposite
         # coordinate systems, and enable defines the component's position as its
         # lower left corner, while wx defines it as the upper left corner.
-        window = getattr(gc, "window", None)
+        window = getattr(self, "window", None)
         if window is None:
             return
         wx_ypos = window._flip_y(wx_ypos)