This input event handling change is intended to address the following
design issues:
- Having `DOM::Position` is unnecessary complexity when `Selection`
exists because caret position could be described by the selection
object with a collapsed state. Before this change, we had to
synchronize those whenever one of them was modified, and there were
already bugs caused by that, i.e., caret position was not changed when
selection offset was modified from the JS side.
- Selection API exposes selection offset within `<textarea>` and
`<input>`, which is not supposed to happen. These objects should
manage their selection state by themselves and have selection offset
even when they are not displayed.
- `EventHandler` looks only at `DOM::Text` owned by `DOM::Position`
while doing text manipulations. It works fine for `<input>` and
`<textarea>`, but `contenteditable` needs to consider all text
descendant text nodes; i.e., if the cursor is moved outside of
`DOM::Text`, we need to look for an adjacent text node to move the
cursor there.
With this change, `EventHandler` no longer does direct manipulations on
caret position or text content, but instead delegates them to the active
`InputEventsTarget`, which could be either
`FormAssociatedTextControlElement` (for `<input>` and `<textarea>`) or
`EditingHostManager` (for `contenteditable`). The `Selection` object is
used to manage both selection and caret position for `contenteditable`,
and text control elements manage their own selection state that is not
exposed by Selection API.
This change improves text editing on Discord, as now we don't have to
refocus the `contenteditable` element after character input. The problem
was that selection manipulations from the JS side were not propagated
to `DOM::Position`.
I expect this change to make future correctness improvements for
`contenteditable` (and `designMode`) easier, as now it's decoupled from
`<input>` and `<textarea>` and separated from `EventHandler`, which is
quite a busy file.
After InlinePaintable is gone it's possible to make this function accept
a PaintableBox instead of more broad
Layout::NodeWithStyleAndBoxModelMetrics type.
InlinePaintable was an ad-hoc paintable type required to support the
fragmentation of inline nodes across multiple lines. It existed because
there was no way to associate multiple paintables with a single layout
node. This resulted in a lot of duplicated code between PaintableBox and
InlinePaintable. For example, most of the CSS properties like
background, border, shadows, etc. and hit-testing are almost identical
for both of them. However, the code had to be duplicated to account for
the fact that InlinePaintable creates a box for each line. And we had
quite many places that operate on paintables with a code like:
```
if (box.is_paintable_box()) {
// do something
} else (box.is_inline_paintable()) {
// do exactly the same as for paintable box but using InlinePaintable
}
```
This change replaces the usage of `InlinePaintable` with
`PaintableWithLines` created for each line, which is now possible
because we support having multiple paintables per layout node. By doing
that, we remove lots of duplicated code and bring our implementation
closer to the spec.
Before this change viewport was allowed to be scrolled whenever it has a
scrollable overflow, which is not correct when overflow is specified to
be hidden.
Horizontal scrollbar has to leave space at right edge for the vertical
scrollbar to fully extend from top-to-bottom edge of viewport. Before,
this was done by just moving it leftward beyond the edge of viewport.
Now, it gets scaled down appropriately to fit between left edge of
viewport & vertical scrollbar without clipping.
A hard-coded value of 50px is too large for text boxes with a size that
is less than 50px. Reduce this to 24px, and further limit it by the size
of the overflown box.
When performing a hit test of type TextCursor, it would check if the
position is around each fragment and not just inside it. This resulted
in always selecting the first fragment checked.
This commit computes the distance of each hit test result, and picks the
closest one.
Calls to `Document::set_needs_display()` and
`Paintable::set_needs_display()` now invalidate the display list by
default. This behavior can be changed by passing
`InvalidateDisplayList::No` to the function where invalidating the
display list is not necessary.
Scroll offset of body does not affect position of fixed elements, so
nearest scrollable lookup should early return from ancestor scrollable
lookup loop once "position: fixed" box is encountered.
Fixes regression introduced in 866608532a
Sticky positioning is implemented by modifying the algorithm for
assigning and refreshing scroll frames. Now, elements with
"position: sticky" are assigned their own scroll frame, and their
position is refreshed independently from regular scroll boxes.
Refreshing the scroll offsets for sticky boxes does not require display
list invalidation.
A separate hash map is used for the scroll frames of sticky boxes. This
is necessary because a single paintable box can have two scroll frames
if it 1) has "position: sticky" and 2) contains scrollable overflow.
This allows the calculation of the cumulative scroll offset for a scroll
frame by adding its scroll offset to the parent’s scroll offset, rather
than traversing the containing block chain. While it doesn't greatly
simplify calculations for typical scroll frames, it serves as a
preparation for supporting "position: sticky".
This change is intended to insure that the thumb control on the dialog
will never be narrower than 50 pixels no matter how long the line it's
displaying.
We *could* even skip creating a paintable for hidden nodes, but that
means that dynamic updates to the CSS visibility property would require
mutating the paint tree, so let's keep it simple for now.
Instead, it could be applied directly as a clip path in Skia painter.
As a side bonus, we get rid of some DeprecatedPath and
AntiAliasingPainter usage.
A new display list item type named PaintScrollBar is introduced. Having
a dedicated type for scroll bars allows the thumb position to be updated
without rebuilding a display list. This was not possible with
FillRectWithRoundedCorners that does not allow to tell whether it
belongs to scroll thumb.
A display list should not contain coordinates shifted by scroll offset.
Instead, "scroll frame id" needs to be used. In the future it's going to
allow us reuse a display list in cases when only scroll offsets need to
be updated.
Before this change AddClipRect was a "special" because it didn't respect
scroll frame offset and was meant to be recorded using viewport-relative
coordinates. The motivation behind this was to record a "final" clip
rectangle computed by intersecting all clip rectangles used by a clip
frame. The disadvantage of this approach is that it blocks us from
implementing an optimisation to reuse display list if the only change is
in the scroll offset, because any scroll offset change leads to
invalidating all AddClipRect items within a list.
This change aligns AddClipRect with the rest of display list items by
making it account for scroll frame offset. It required discontinuing
the recording of the intersection of all clip rectangles within a clip
frame and instead producing an AddClipRect for each of them.
A nice side effect is the removal of code that shifts clip rectangle by
`enclosing_scroll_offset()` in a bunch of places, because now it happens
automatically in `DisplayList::apply_scroll_offsets()`.
This change causes the viewport to be treated as a "scroll frame,"
similar to how it already works for boxes with "overflow: scroll."
This means that, instead of encoding the viewport translation into a
display list, the items will be assigned the scroll frame id of the
viewport and then shifted by the scroll offset before execution. In the
future it will allow us to reuse a display list for repainting if only
scroll offset has changed.
As a side effect, it also removes the need for special handling of
"position: fixed" because compensating for the viewport offset while
painting or hit-testing is no longer necessary. Instead, anything
contained within a "position: fixed" element is simply not assigned
a scroll frame id, which means it is not shifted by the scroll offset.
This change fixes layering violation by moving to_px() calls to happen
before display list recording. Also it should make display list
recording a bit faster by resolving background properties beforehand.
Navigables are re-used for navigations within the same tab. Its current
ownership of the cursor position is a bit ad-hoc, so nothing in the spec
indicates when to reset the cursor, nor do we manually do so. So when a
cursor update happens on one page, that cursor is retained on the next
page.
Instead, let's have the document own the cursor. Each navigation results
in a new document, thus we don't need to worry about resetting cursors.
This also makes many of the callsites feel nicer. We were previously
often going from the node, to the document, to the navigable, to the
cursor. This patch removes the navigable hop.
Overflow clipping is currently implemented as:
1. Create clip frame for each box with hidden overflow
2. Calculate clip rect for each clip frame by intersecting padding boxes
of all boxes with hidden overflow in containing block chain
3. Assign enclosing clip frame (closest clip frame in containing block
chain) to each PaintableBox
4. Apply clip rect of enclosing clip frame in Paintable::before_paint()
It breaks when any CSS transform other than simple translation is lying
between box with hidden overflow and a clipped box, because clip
rectangle will be applied when transform has already changed.
The fix is implemented by relying on the following rule:
"For elements whose layout is governed by the CSS box model, any value
other than none for the transform also causes the element to establish
a containing block for all descendants."
It means everything nested into a stacking context with CSS transform
can't escape its clip, so it's safe to apply its clip for all children.
Moves paint_table_borders() call into PaintableBox::paint() to make
scroll offset and clip rectangle of enclosing scrollable be applied
in ::before_paint().
Contrary to LibGfx, where corner clipping was implemented by sampling
and blitting pixels under corners into a temporary bitmap, Skia allows
us to simply apply a mask. As a result, we no longer need the
BlitCornerClipping command, which has become a no-op.
- SampleUnderCorners is renamed to AddRoundedRectClip
- The optimization that skipped unnecessary blit and sample commands has
been removed. However, this should not result in a performance
regression because Skia seems to perform mask rasterization lazily.
Having resolution of all properties for all paintable types in a single
function was hard to iterate on, so this change separates it into
smaller functions per paintable type.
Previously calling `PaintableBox::set_scroll_offset()` with a
PaintableBox whose content size was larger than its scrollble overflow
rect would cause a crash.
Found by Domato.
Previously, the scrollbar thumbs were (almost) invisible, when the page
background color was similar to the scrollbar thumb color (DarkGray).
Now, in addition to the filled rounded rectangle, the scrollbar thumbs
are painted with a 1px solid LightGrey border. On a white or light color
background the border stays invisible.
The ChunkIterator now limits a chunk to using only one font (before, it
was possible to have a chunk with >1 font, when `unicode-range` CSS
property is used).
This change allows us to reduce some complexity in the text shaping and
painting code and makes us compatible with the APIs in Skia and
HarfBuzz.
