Added the watcher class to UI

[antrikshmisri]

This PR adds support for a watcher class in the UI elements. The purpose of this class is to monitor a particular attribute from the UI element after it has been added to the scene. If the attribute changes in the real time, a user defined callback is triggered and the scene is force rendered. Is this something that the UI module needs? Below is the code example:-

from fury.ui import Panel2D
from fury import window

panel = Panel2D(size=(200, 200), position=(300, 300), color=(0.5, 0.3, 0.8))

current_size = (1000, 1000)
show_manager = window.ShowManager(size=current_size,
                                  title="Watcher Example")


def on_change(i_ren, obj, ui):
    print(f'{ui.watcher.attr} has changed from {ui.watcher.original_attr} to {ui.watcher.updated_attr}')


def change_opacity(i_ren, obj, panel_2d):
    panel_2d.opacity = 0.5

panel.watcher.callback = on_change
panel.background.on_left_mouse_button_clicked = change_opacity

show_manager.scene.add(panel)
show_manager.initialize()
panel.watcher.start(100, show_manager, 'opacity')

# To interact with the UI, set interactive = True
interactive = False

if interactive:
    show_manager.start()

[codecov]

Codecov Report

Merging #448 (27f2810) into master (f2bb0b5) will decrease coverage by 0.27%.
The diff coverage is 45.03%.

@@            Coverage Diff             @@
##           master     #448      +/-   ##
==========================================
- Coverage   88.31%   88.04%   -0.28%     
==========================================
  Files          31       31              
  Lines        6446     6483      +37     
  Branches      770      776       +6     
==========================================
+ Hits         5693     5708      +15     
- Misses        534      556      +22     
  Partials      219      219              

Impacted Files	Coverage Δ
fury/actor.py	89.04% <2.32%> (ø)
fury/ui/helpers.py	61.90% <37.14%> (-30.96%)	⬇️
fury/pick.py	72.27% <72.46%> (ø)
fury/ui/core.py	92.08% <100.00%> (+0.03%)	⬆️
fury/window.py	80.16% <100.00%> (ø)

[skoudoro]

Thank you for this PR @antrikshmisri.

I believe it can be useful and it would be good if many developers could try it before going further.

@Nibba2018 @guaje, could you test this new feature?

[antrikshmisri]

I believe it can be useful and it would be good if many developers could try it before going further.

Sure, makes sense.

[Nibba2018]

Hello, in my opinion I think this should be separate global watcher which could be user customizable instead of having separate watchers for each UI element. Also I think you can already perform such updates via callbacks itself.

@antrikshmisri Could you please provide an usage example so that its easier for us to understand. Thank you

[guaje]

Hi @antrikshmisri!

This seems to be a new cool feature, however, when I run the example you are providing it gives me the following error:

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-1-3bd41f4f3e0b> in <module>
     16     panel_2d.opacity = 0.5
     17 
---> 18 panel.watcher.callback = on_change
     19 panel.background.on_left_mouse_button_clicked = change_opacity
     20 

AttributeError: 'Panel2D' object has no attribute 'watcher'

Could you please add a unit test?

[antrikshmisri]

This seems to be a new cool feature, however, when I run the example you are providing it gives me the following error:

Hey @guaje, I have updated the PR, now it should work.

[antrikshmisri]

Hello, in my opinion I think this should be separate global watcher which could be user customizable instead of having separate watchers for each UI element. Also I think you can already perform such updates via callbacks itself.

Hey @Nibba2018, I didn't quite get what you mean by a global watcher. Does it mean a class that would be initialized on the top and we can observe properties from different classes through that same instance. Something like:-

watcher = Watcher(some args)

element = UI_element(some_args)
element_1 = UI_element(some_args)

watcher.start(element, args)
watcher.start(element_1, args)

Also, yes you can do such things by callbacks but those need to binded with an event first or should be user hook provided by a event callback.

@antrikshmisri Could you please provide an usage example so that its easier for us to understand. Thank you

A good use case for this would be something like resizing all the elements inside a panel when the panel size changes. As panel size can be changed from the bottom right corner as well as from WindowResizeEvent, currently a user hook needs to be binded with both of these, this will become really annoying when more panel resizing events/callbacks are added. A better approach would be to just listen for changes in the size and execute a callback accordingly.

[guaje]

Hey @guaje, I have updated the PR, now it should work.

Thanks.

I see you have added many class methods in the proposed class. Could you add some tests to make sure everything in the class works as expected?

Also, could you create a test case with the code provided in the example?

As a thumbs-up, adding a parent class for all the UI components is something we've been missing and will help us to discriminate between actors, visual elements associated with them, and UI elements.

As @Nibba2018 suggested could you create a more detailed example or tutorial showing and explaining how this new feature works and why it is important. This could be a good starting point:

A good use case for this would be something like resizing all the elements inside a panel when the panel size changes. As panel size can be changed from the bottom right corner as well as from WindowResizeEvent, currently a user hook needs to be binded with both of these, this will become really annoying when more panel resizing events/callbacks are added. A better approach would be to just listen for changes in the size and execute a callback accordingly.

Finally, could you fix the conflict with fury/ui.py?

[antrikshmisri]

I see you have added many class methods in the proposed class. Could you add some tests to make sure everything in the class works as expected?
Also, could you create a test case with the code provided in the example?

Sure, the tests will be up soon.

As @Nibba2018 suggested could you create a more detailed example or tutorial showing and explaining how this new feature works and why it is important. This could be a good starting point:

Sure, will create an example that demonstrates the use of the watcher class.

[skoudoro]

Closing, For now, this feature is not indeed and need more thinking.

Thank you for this @antrikshmisri