1736042 - Demo at https://codepen.io/t_afif/pen/qBXOroE has visual artifacts

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Mayank Bansal]

go to https://codepen.io/t_afif/pen/qBXOroE

The demo will have some visual artifacts. If they are not apparent, resize the browser window horizontally till you see the artifact. The artifact is like a triangle on the bottom of the demo.

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[Mayank Bansal]

Attachment: image.png

Comment 3

[Lee Salzman [:lsalzman]]

Can you check for a regression window on this to see if it was anything recent?

Comment 4

[Mayank Bansal]

Not a recent regression. I remember trying a build from last year, and I could still repro.
Edit1 : The bug is reproducible with sw-wr as well.

Edit2: I tested a build from 2020-06-23 and can still repro this bug (so its not a new regression). Then i tried an older build from 2019-06-23 which had Dx11 rendering enabled and couldnt repro.
Then I force enabled WR, and could repro again.
This implies that this particular testcase worked fine on D3d11, but has been broken on WR for years

Comment 5

[Mayank Bansal]

This was fixed by Bug 1749380.

---

Bug 1749380 - Improve how WR handles bounding rects for off-screen surfaces r=gfx-reviewers,kvark

This patch introduces a number of subtle but important changes
to how we deal with off-screen surfaces. The overall goals are:

• Improve rendering correctness in a number of edge cases.
• Begin reducing complexity related to surfaces, scaling
  factors, surface size adjustments and clipping.
• Improve CPU performance by removing some per-primitive work.
• Simplify implementation of future SVG and CSS filters by
  having explicit support for picture rects + inflation regions.
• Lay the groundwork for caching child picture surfaces,
  reduction of per-primitive work during visibility pass,
  simplifying picture code.

Unfortunately, the nature of the changes make it impossible to
split up in to small isolated patches. Details below:

• Introduce LocalRectKind concept. This allows us to separate
  out the bounding rect of the surface (a group of primitives
  backed by a texture) from the bounding rect of the picture
  compositing that surface (e.g. a drop-shadow which draws the
  surface once at the local origin and once at a specific offset

  • blur-radius). This fixes a number of correctness bugs we have
    related to culling, clipping, invalidation regions of complex
    primitives such as drop-shadows and blur filters. Importantly,
    it makes it simpler to implement (or fix) SVG filter chains,
    backdrop-filter implementations.

• Establish raster roots for all off-screen surfaces. Every off-screen
  surface uses the spatial node of the enclosing stacking context as
  a coordinate system root, ensuring that each off-screen surface is
  drawn in a 2D coordinate system, with appropriate scaling factors
  applied to ensure high quality rendering. The primary goal is to make
  it possible to correctly inflate and clip off-screen surfaces, removing
  some correctness issues we currently have with complex filters interacting
  with transforms. The initial work here doesn't reduce complexity a huge
  amount, but will allow us to simplify large parts of the picture/surface
  handling code in future, as well as simplify a number of shaders that
  currently must handle arbitrarily complex transform matrices. This will
  also allow us to simplify the implementation of features such as
  mix-blend-mode and backdrop-filter, which rely on readback and UV mapping
  from the parent surface.

• Remove concepts of estimated and precise local rects for pictures. This
  is both a performance optimization and a code simplification. Instead, we
  only determine the estimated local rect during bounding rect propagation,
  and rely on the clipping regions from the tile dirty regions to reduce which
  parts of the picture we allocate if drawing to an off-screen surface. This
  removes some per-primitive work during the visibility pass, and also means
  we can rely on the final picture bounding rect from the start of the visibility
  pass. This also removes much of the complexity in take_context where we
  previously determined surface scale factors and device pixel ratio - instead
  these can be determined earlier during propagate_bounding_rects.

• Remove some complexity in update_prim_visibility. This is still recursive,
  but follow up patches will aim to remove this recursion and integrate this
  pass with the picture graph (similar to how propagate_bounding_rects works).

• Remove PictureOptions struct. Instead, store inflate_if_required with
  the Blur filter enum, which is the only place that uses it.

• Remove root_scaling_factor from text runs - this is handled implicitly
  by the surface device-pixel scale.

• Skip calling update_clip_task for pass-through pictures (since they have
  no defined local rect).

• Improve scaling factors used for determining the render task cache size for
  complex line decorations.

Differential Revision: https://phabricator.services.mozilla.com/D137569

2022-03-13T09:53:49.398000: DEBUG : Did not find a branch, checking all integration branches
2022-03-13T09:53:49.413000: INFO : The bisection is done.
2022-03-13T09:53:49.413000: INFO : Stopped