Bugzilla

The reporter of the webcompat bug observed that we seem to be able to work around this by adjusting the `.x` member to `0` here:
https://searchfox.org/firefox-main/rev/c2e3c0aea49fb45082efdc129e79f84df7a07f48/layout/generic/nsIFrame.cpp#2760-2762,2796-2801,2803
```cpp
bool nsIFrame::ComputeOverflowClipRectRelativeToSelf(
    const PhysicalAxes aClipAxes, nsRect& aOutRect,
    nsRectCornerRadii& aOutRadii) const {
...
  if (MOZ_UNLIKELY(!aClipAxes.contains(PhysicalAxis::Horizontal))) {
    // NOTE(mats) We shouldn't be clipping at all in this dimension really,
    // but clipping in just one axis isn't supported by our GFX APIs so we
    // clip to our visual overflow rect instead.
    nsRect o = InkOverflowRect();
    aOutRect.x = o.x;
...
  }
```

That's likely not the right solution exactly, but it's a good clue about where to explore here.

Also, I'll move this to Layout given that that^ code is involved (in `ComputeOverflowClipRectRelativeToSelf`) which puts this probably more in the layout bucket than the web-painting bucket.

The reporter of the webcompat bug observed that we seem to be able to work around this by adjusting the `aOutRect.x` member to `0` here:
https://searchfox.org/firefox-main/rev/c2e3c0aea49fb45082efdc129e79f84df7a07f48/layout/generic/nsIFrame.cpp#2760-2762,2796-2801,2803
```cpp
bool nsIFrame::ComputeOverflowClipRectRelativeToSelf(
    const PhysicalAxes aClipAxes, nsRect& aOutRect,
    nsRectCornerRadii& aOutRadii) const {
...
  if (MOZ_UNLIKELY(!aClipAxes.contains(PhysicalAxis::Horizontal))) {
    // NOTE(mats) We shouldn't be clipping at all in this dimension really,
    // but clipping in just one axis isn't supported by our GFX APIs so we
    // clip to our visual overflow rect instead.
    nsRect o = InkOverflowRect();
    aOutRect.x = o.x;
...
  }
```

That's likely not the right solution exactly, but it's a good clue about where to explore here.

Also, I'll move this to Layout given that that^ code is involved (in `ComputeOverflowClipRectRelativeToSelf`) which puts this probably more in the layout bucket than the web-painting bucket.