Minihtml popup flickers when updating.

[deathaxe]

Description

Calling view.show_panel() sequencially in order to update the content, size or positon of a popup causes it to shortly disapear. It feels noisy especially in situations the popup is tight to key strokes or changing selections.

The recently announced Emmet 2 plugin is a very prominent example for that issue as it displays a preview popup right below the typed text.

Quickly typing an appreviation causes the popup to heavily flicker.

Related with #3099

Steps to reproduce

1. Open ST vanilla
2. Create a plugin with the following code

   import sublime_plugin
   
   
   class PopupListener(sublime_plugin.EventListener):
   
       def on_selection_modified(self, view):
           view.show_popup("Hello World", location=view.sel()[0].begin())

3. Start typing
4. See how the popup flickers each time its position is updated.

Expected behavior

Move and/or resize the minihtml popup window seemlessly.

Actual behavior

The popup window disapears for some millisecons each time it is to be updated or moved via view.show_popup() API function.

Environment

• Build: 3xxx and 4055
• Operating system and version: Windows 10 x64 1903

[jrappen]

/cc @sergeche

[sergeche]

More flickering caused by *_async version of event listeners: tried to use them to reduce work load on every update but flickering was too annoying. It also happens with phantoms (see abbreviations in CSS)

[deathaxe]

@jskinner added a fix for that in Sublime Merge during the last dev cycle. Hope it would find its way over to Sublime Text.

[FichteFoll]

For now, you should probably resort to holding back changes with a timeout and only update every x ms.

[daveleroy]

This can be worked around right now using update_popup if you do not need to reposition the popup and your popup is still visible.

If you are creating a phantom to replace an existing one you should do it in the main sublime thread (if you generate your html on a background thread use sublime.set_timeout) otherwise you will get flickering when the phantom is replaced. (fixed? version > 4000)

[jrappen]

Reference links for plugin authors using mdpopups.update_popup:

• http://facelessuser.github.io/sublime-markdown-popups/api/#update-popup
• https://github.com/facelessuser/sublime-markdown-popups/blob/master/st3/mdpopups/__init__.py

[deathaxe]

... need to reposition the popup ...

That's the root cause of raising this issue.

[sergeche]

It seems like the problem is that popup automatically hides on each update (at least in my case) so I can’t just update its contents. Maybe because I use view.add_regions() on every update?

[jskinner]

FWIW the next build of S4 will have an additional flag, sublime.KEEP_ON_SELECTION_MODIFIED, which will keep a popup open when the selection changes

[deathaxe]

Just retried my debug snippet with the new flag on ST4057. Unfortunatelly it seems to have no effect on Windows.

This is my updated debug code:

import sublime
import sublime_plugin


class PopupListener(sublime_plugin.EventListener):

    def on_selection_modified(self, view):
        try:
            view.show_popup(
                "Hello World",
                flags=sublime.KEEP_ON_SELECTION_MODIFIED,
                location=view.sel()[0].begin()
            )
        except IndexError:
            pass

[jskinner]

That's right, it won't reduce flickering if you're calling view.show_popup(), but it will allow view.update_popup() to be used in more circumstances.

True flicker free updating of the popup under all circumstance will require using 'virtual' popups, which would be constrained to the window area, as I haven't found a way to change both a window position and content in a synchronous manner under X11. I'm planning on experimenting with this approach.

[deathaxe]

Thanks for the info and looking into it. I guess it is the same for auto-completion popups then?

[wbond]

Build 4075 moves all popups from child windows to child controls of the main window. I believe this should improve this issue.

Do you see any improvement @deathaxe?

[deathaxe]

It's moving smoothly.