The new `ElementContext` was originally introduced to ensure the element
APIs could only be used inside of elements. Unfortunately, there were
many places where some of those APIs needed to be used, so
`WindowContext::with_element_context` was introduced, which defeated the
original safety purposes of having a specific context for elements.
This pull request merges `ElementContext` into `WindowContext` and adds
(debug) runtime checks to APIs that can only be used during certain
phases of element drawing.
Release Notes:
- N/A
---------
Co-authored-by: Nathan Sobo <nathan@zed.dev>
This pull request introduces the new
`ElementContext::request_autoscroll(bounds)` and
`ElementContext::take_autoscroll()` methods in GPUI. These new APIs
enable container elements such as `List` to change their scroll position
if one of their children requested an autoscroll. We plan to use this in
the revamped assistant.
As a drive-by, we also:
- Renamed `Element::before_layout` to `Element::request_layout`
- Renamed `Element::after_layout` to `Element::prepaint`
- Introduced a new `List::splice_focusable` method to splice focusable
elements into the list, which enables rendering offscreen elements that
are focused.
Release Notes:
- N/A
---------
Co-authored-by: Nathan <nathan@zed.dev>
See https://zed.dev/channel/gpui-536
Fixes https://github.com/zed-industries/zed/issues/9010
Fixes https://github.com/zed-industries/zed/issues/8883
Fixes https://github.com/zed-industries/zed/issues/8640
Fixes https://github.com/zed-industries/zed/issues/8598
Fixes https://github.com/zed-industries/zed/issues/8579
Fixes https://github.com/zed-industries/zed/issues/8363
Fixes https://github.com/zed-industries/zed/issues/8207
### Problem
After transitioning Zed to GPUI 2, we started noticing that interacting
with the mouse on many UI elements would lead to a pretty annoying
flicker. The main issue with the old approach was that hover state was
calculated based on the previous frame. That is, when computing whether
a given element was hovered in the current frame, we would use
information about the same element in the previous frame.
However, inspecting the previous frame tells us very little about what
should be hovered in the current frame, as elements in the current frame
may have changed significantly.
### Solution
This pull request's main contribution is the introduction of a new
`after_layout` phase when redrawing the window. The key idea is that
we'll give every element a chance to register a hitbox (see
`ElementContext::insert_hitbox`) before painting anything. Then, during
the `paint` phase, elements can determine whether they're the topmost
and draw their hover state accordingly.
We are also removing the ability to give an arbitrary z-index to
elements. Instead, we will follow the much simpler painter's algorithm.
That is, an element that gets painted after will be drawn on top of an
element that got painted earlier. Elements can still escape their
current "stacking context" by using the new `ElementContext::defer_draw`
method (see `Overlay` for an example). Elements drawn using this method
will still be logically considered as being children of their original
parent (for keybinding, focus and cache invalidation purposes) but their
layout and paint passes will be deferred until the currently-drawn
element is done.
With these changes we also reworked geometry batching within the
`Scene`. The new approach uses an AABB tree to determine geometry
occlusion, which allows the GPU to render non-overlapping geometry in
parallel.
### Performance
Performance is slightly better than on `main` even though this new
approach is more correct and we're maintaining an extra data structure
(the AABB tree).
Release Notes:
- Fixed a bug that was causing popovers to flicker.
---------
Co-authored-by: Nathan Sobo <nathan@zed.dev>
Co-authored-by: Thorsten <thorsten@zed.dev>
I want to use this on another branch, but it's a sweeping change,
so this prepares the ground for it. This can always be reverted if
it doesn't work out.
Multi-element are now generic over any drawable child, which can be converted
into an element.
Co-Authored-By: Nathan Sobo <nathan@zed.dev>
Co-Authored-By: Max Brunsfeld <max@zed.dev>
