Lag and dark flashing when resizing

[eldinoyev]

Describe the bug:

Seeing some lag in the form of a black line on the right side when resizing horizontally. Seeing flash of black between items in the window on resize.

To Reproduce:

Steps to reproduce the behaviour:

1. cd ~/go/src/github.com/fyne-io/fyne/cmd/fyne_demo
2. go run main.go
3. Drag side of window in and out quickly to resize.

Screenshots:

Lag

Black flash

Device:

• OS: Ubuntu
• Version: 18.04.4 LTS
• Graphics: Nvidia Quadro P1000/PCIe/SSE2 with nvidia-driver-440
• Go version: go1.14.2 linux/amd64
• Fyne version: v1.3.0

[andydotxyz]

If possible can you test the patch in PR #1120? It is possible that this makes step to improve resize.

[eldinoyev]

@andydotxyz Looks like both flicker and slight lag on resize are still happening after I pull latest develop (with #1120 ) merged

[andydotxyz]

With a GL backend it may not be possible to have windows that respond to resize quickly without having this content lag.
The 1.2.x releases were slow to resize. It's looking like one or the other frustratingly.
Keen for any cunning ideas about how we can do better, but right now I can't see a solution.

[andydotxyz]

Fix is on develop for testing

[eldinoyev]

Tested on 102ff9e:

When quickly resizing, the canvas appears to resize and keep up with the border better than before #1150 , but still seeing a bit of black flicker.

I don't believe this should block 1.3.1 - I've only been able to reproduce on the demo's Graphics tab, and fyne_demo seems to be running smoother than before #1150.

[AlbinoGeek]

This has significantly improved but still occurs for me in an application with a layout tree as follows:

Window ->
  container.Border ->
    top: nil
    bottom: nil
    left: NavigationDrawer (container.Vbox) ->
      []widget.Button
    right: nil
    contents: container.Scroll ->
      container.Vbox ->
        []container.Hbox

Specifically, the flickering/blackness shows up within the "contents" area for me (right side of window while resizing.)

[andydotxyz]

If the issue is now limited to just 1 container then I think it could be a different problem. Initially this was around the whole window, or edge of it.
Can you capture the issue in a video @AlbinoGeek so we can figure if it's still the same issue?

[AlbinoGeek]

Peek.2021-01-23.14-58.mp4

I actually don't even need to resize the window very quickly to reproduce the issue.

You can see the UI's contents pane flash black 3 times in the above video.
It occurred many more times, but my screen capture was only 30fps.

The widget tree is a little different on this pane (easiest to reproduce):

Window ->
  container.Border ->
    top: nil
    bottom: nil
    left: NavigationDrawer (container.Vbox) ->
      []widget.Button
    right: nil
    contents: container.Scroll ->
      container.Vbox ->
-        []container.HBox
+        []widget.Card ->
+          []container.HBox

Also not sure why making the window taller causes the expansion to come from the top of the window and not the bottom... but that is an entirely different issue to the black flickering.

[jcbritobr]

It happens for me in the latest 2.4 version.
fedora 38, x64, kernel 6.4

[jcbritobr]

The performance for is good for resizing in a simple application, but black flicks still happens.
https://youtu.be/nAza2X_n3vU