This commit removes the "merge-fragments" pass from inline reflow,
instead merging "on the fly". This ended up being simpler, as well as
more fine grained. Additionally, this patch makes the line breaker no
longer clone every fragment (!)
This functionality will be used in the implementation of
`text-overflow`.
This property is used by approximately 55% of page loads.
To implement the line breaking behavior, the "breaking strategy" has
been cleaned up and abstracted. This should allow us to easily support
other similar properties in the future, such as `text-overflow` and
`word-break`.
I had to use a somewhat unconventional method of computing text
indentation (propagating from blocks down to inlines) because of the way
containing blocks are handled in Servo.
(As a side note, neither Gecko nor WebKit correctly handles percentages
in `text-align`, at least incrementally -- i.e. when the percentages are
relative to the viewport and the viewport is resized.)
This adds the infrastructure necessary to support stacking contexts that
are not containing blocks for absolutely-positioned elements. Our
infrastructure did not support that before. This minor revamp actually
ended up simplifying the logic around display list building and
stacking-relative position computation for absolutely-positioned flows,
which was nice.
first-class.
This implements the scheme described here:
https://groups.google.com/forum/#!topic/mozilla.dev.servo/sZVPSfPVfkg
This commit changes Servo to generate one display list per stacking
context instead of one display list per layer. This is purely a
refactoring; there are no functional changes. Performance is essentially
the same as before. However, there should be numerous future benefits
that this is intended to allow for:
* It makes the code simpler to understand because the "new layer needed"
vs. "no new layer needed" code paths are more consolidated.
* It makes it easy to support CSS properties that did not fit into our
previous flat display list model (without unconditionally layerizing
them):
o `opacity` should be easy to support because the stacking context
provides the higher-level grouping of display items to which opacity
is to be applied.
o `transform` can be easily supported because the stacking context
provides a place to stash the transformation matrix. This has the side
benefit of nicely separating the transformation matrix from the
clipping regions.
* The `flatten` logic is now O(1) instead of O(n) and now only needs to
be invoked for pseudo-stacking contexts (right now: just floats),
instead of for every stacking context.
* Layers are now a proper tree instead of a flat list as far as layout
is concerned, bringing us closer to a production-quality
compositing/layers framework.
* This commit opens the door to incremental display list construction at
the level of stacking contexts.
Future performance improvements could come from optimizing allocation of
display list items, and, of course, incremental display list
construction.
Instead of looking at the display tree, have ContentBox(es)Query consult
the flow tree. This allow optimizing away parts of the display tree
later. To do this we need to be more careful about how we send reflow
requests, only querying the flow tree when possible.
Fixes#3790.
construction to avoid cloning and moving flows so much.
Besides amounting to a 5%-10% win on a page with a lot of text, this
simplifies and refactors the text layout code.
This also adds some extra debugging infrastructure which I found useful tracking
this bug down. A regression in the br reftests is also uncovered by this patch,
which I'll work on fixing next.
r? @pcwalton
This implements fragment merging, in order to incrementally reflow linebroken
text. This makes the `whitespace_pre.html` reftest pass with incremental reflow
turned on with `-i`.
match L. David Baron's work-in-progress specification.
http://dbaron.org/css/intrinsic/
Column spans are not yet supported.
This effectively adds support for percentage widths, and it also fixes
many bugs, improving the layout of Google and Wikipedia.
matching, and use it for `<input size>` and `<td width>`.
This implements a general framework for legacy presentational attributes
to the DOM and style calculation, so that adding more of them later will
be straightforward.
We push down clipping areas during absolute position calculation. This
makes display items into a flat list, improving cache locality. It
dramatically simplifies the code all around.
Because we need to push down clip rects even for absolutely-positioned
children of non-absolutely-positioned flows, this patch alters the
parallel traversal to compute absolute positions for
absolutely-positioned children at the same time it computes absolute
positions for other children. This doesn't seem to break anything either
in theory (since the overall order remains correct) or in practice. It
simplifies the parallel traversal code quite a bit.
See the relevant Gecko bug:
https://bugzilla.mozilla.org/show_bug.cgi?id=615734
r? @mrobinson
a separate `ClipDisplayItem`.
We push down clipping areas during absolute position calculation. This
makes display items into a flat list, improving cache locality. It
dramatically simplifies the code all around.
Because we need to push down clip rects even for absolutely-positioned
children of non-absolutely-positioned flows, this patch alters the
parallel traversal to compute absolute positions for
absolutely-positioned children at the same time it computes absolute
positions for other children. This doesn't seem to break anything either
in theory (since the overall order remains correct) or in practice. It
simplifies the parallel traversal code quite a bit.
See the relevant Gecko bug:
https://bugzilla.mozilla.org/show_bug.cgi?id=615734
I don't think it will be possible to avoid splitting fragments in the
presence of `vertical-align`, because one `ScannedTextFragment` could
potentially be split into arbitrary many fragments, each having its own
vertical position that can influence layout of other fragments.
This code also removes parts of `Range` that were no longer used.
r? @glennw
This makes layout more idempotent, which is important for incremental
layout.
Also converts `is_root` to a set of flags and fixes a `TODO` concerning
percentage inline heights of images.
r? @glennw
splitting fragments.
I don't think it will be possible to avoid splitting fragments in the
presence of `vertical-align`, because one `ScannedTextFragment` could
potentially be split into arbitrary many fragments, each having its own
vertical position that can influence layout of other fragments.
This code also removes parts of `Range` that were no longer used.
writing it to a temporary location and overwriting it.
This makes layout more idempotent, which is important for incremental
layout.
Also converts `is_root` to a set of flags and fixes a `TODO` concerning
percentage inline heights of images.
This patch puts in the initial framework for incremental reflow. Nodes' styles
are no longer recalculated unless the node has changed.
I've been hacking on the general problem of incremental reflow for the past
couple weeks, and I've yet to get a full implementation that actually passes all
the reftests + wikipedia + cnn. Therefore, I'm going to try to land the different
parts of it one by one.
This patch only does incremental style recalc, without incremental flow
construction, inline-size bubbling, reflow, or display lists. Those will be coming
in that order as I finish them.
At least with this strategy, I can land a working version of incremental reflow,
even if not yet complete.
r? @pcwalton
absolutely-positioned elements declared with `display: inline`.
Although the computed `display` property of elements with `position:
absolute` is `block`, `position: absolute; display: inline` can still
behave differently from `position: absolute; display: block`. This is
because the hypothetical box for `position: absolute` can be at the
position it would have been if it had `display: inline`. CSS 2.1 §
10.3.7 describes this case in a parenthetical:
"The static-position containing block is the containing block of a
hypothetical box that would have been the first box of the element if
its specified 'position' value had been 'static' and its specified
'float' had been 'none'. (Note that due to the rules in section 9.7 this
hypothetical calculation might require also assuming a different
computed value for 'display'.)"
To handle this, I had to change both style computation and layout. For
the former, I added an internal property
`-servo-display-for-hypothetical-box`, which stores the `display` value
supplied by the author, before the computed value is calculated. Flow
construction now uses this value.
As for layout, implementing the proper behavior is tricky because the
position of an inline fragment in the inline direction cannot be
determined until height assignment, which is a parallelism hazard
because in parallel layout widths are computed before heights. However,
in this particular case we can avoid the parallelism hazard because the
inline direction of a hypothetical box only affects the layout if an
absolutely-positioned element is unconstrained in the inline direction.
Therefore, we can just lay out such absolutely-positioned elements with
a bogus inline position and fix it up once the true inline position of
the hypothetical box is computed. The name for this fix-up process is
"late computation of inline position" (and the corresponding fix-up for
the block position is called "late computation of block position").
This improves the header on /r/rust.
* Enabled acid2 on mac + linux. Updated the reference image. The only difference from the
real acid2 now is the paint order and a 1 pixel horizontal offset on the nose.
* Change line-height to be calculated correctly.
* Apply enclosing element style to text fragments.
