Project/Editor Settings contents displayed weirdly depending on the scroll position (regression from #32959)

[YeldhamDev]

Godot version:
78074fe

Issue description:
Depending on the position of scroll, the contents of both Project and Editor Settings dialogs display weirdly. This doesn't happen in 3.2:

[akien-mga]

Confirmed, I've seen that today too.
It also happens in the Inspector.

[akien-mga]

Bisected, that's a regression from #32959 (@georgwacker @groud).
However I don't get the bug in dfb7d46 itself (the original commit of the PR, pre-3.2), so it seems to be the merge which triggers the bug due to an intermediate change.

[georgwacker]

Depending on the position of scroll

What does position of scroll mean exactly, do you have to do something to trigger the glitch?

I don't see this bug in my build of 3e3f8a4, if I just open the project settings for example and scroll in one of the view containers. I also tested this with a fresh Godot profile in Windows.

[akien-mga]

What does position of scroll mean exactly, do you have to do something to trigger the glitch?

Reduce the size of the Editor Settings dialog to have a long enough scrollable section, and scroll down. At some specific scroll values (likely non-integer ones), the bug is triggered.

[akien-mga]

Also seems to affect game controls. I think we'd better revert for now (including the cherry pick in 3.2.1 RC 1).

[georgwacker]

I had a hard time reproducing this bug on my machine, I took another look with master and finally saw a similar one pixel line cutoff, but nothing like the above.

It seems we need another solution for control node animation after all.

Looking at the code again, it seems like the control nodes currently rely on the xform[2].round() that gets called by scrolling and thus calling NOTIFICATION_DRAW. This must mean that without the rounding, all the control nodes in the editor somehow have non-integer transforms?
The workaround isn't that old, I wonder which other change made this rounding necessary.

Anyways, until a better solution is found, the old workaround should be restored. Sorry for the regression.

[georgwacker]

This is the output of control node positions in the project settings after scrolling and before the rounding. They have integer positions when drawing initially and have fractions after scrolling.

[georgwacker]

I tracked this down to ScrollContainer, where scroll is directly used for the Rect2D to reposition the children.

godot/scene/gui/scroll_container.cpp

Line 302 in e437bcb

Rect2 r = Rect2(-scroll, minsize);

Now the question is if we just round the x/y components of scroll before using it as a position for child nodes OR round the scrolling data in gui_input?

godot/scene/gui/scroll_container.cpp

Line 90 in e437bcb

void ScrollContainer::_gui_input(const Ref<InputEvent> &p_gui_input) {

[bojidar-bg]

I would suggest rounding the scroll, since the input event value is divided by 8 and multiplied by some OS-defined factor at

godot/scene/gui/scroll_container.cpp

Line 104 in e437bcb

v_scroll->set_value(v_scroll->get_value() - v_scroll->get_page() / 8 * mb->get_factor());

[georgwacker]

Your answer could be interpreted both ways :-)

I guess you mean to round all the calculations in gui_input, including the one you linked on Line 104? Since in the context of the ScrollContainer, all control nodes should be spaced with integer numbers, always?

[akien-mga]

Reverted the cherry-pick from the 3.2 branch for now until we find a fix for the regression. I did not revert from the master branch though so we can still experience and fix the bug there first.

[akien-mga]

I'm not sure if this is still reproducible, I couldn't see the issue in Project Settings anymore in a recent master build.

There's now a similar issue in popup menus (e.g. Scene menu), but it might be a different cause, as it doesn't seem to be caused by #32959 unlike what was debugged here back in March.

[georgwacker]

I’ll take a look at the original jitter problem and the fix I have for the ScrollContainer. As mentioned above it seems to be a rounding issue.

[georgwacker]

In master the workaround

godot/scene/gui/control.cpp

Line 465 in 07f169a

// We use a little workaround to avoid flickering when moving the pivot with _edit_set_pivot()

is removed and

godot/scene/gui/scroll_container.cpp

Line 321 in ae6b2d6

r.position = r.position.floor();

flooring the position fixes the regression when scrolling.

I tested these two changes on the 3.2 branch and they work as expected. As of my original findings, the position based on the scroll value should always be an integer.

Should I create a cherrypick pull request for this?

[georgwacker]

This is fixed with #46409