This commit adds some finagling and shrinking of the corner bitmap
to handle drawing shadows on elements where the shadow radius >
half the width or height of the element. Previously things would
go horribly wrong when this happend.
There could still be some edge cases, but things seem to be working
fairly well now.
This now allows passing a 'fill_color' to the blur, any fully
transparent pixels will be replaced with this color (with the alpha
set to 0).
For box-shadows, if this color is set to the same as the shadow,
the issues around the fringes are fixed. This also fixes some places
where dark shadows appeared light / the wrong color.
With this change the blur no longer dominates the profile. On my PC
it is down to 27% (which is the same as the AA ellipse painting).
The box-shadow.html test page now also feels more responsive.
This commit adds support for using all your favorite border radii with
box-shadow, that is elliptical, circular, rounded rectangle etc. :^)
There is some work needed to make this more performant. The larger
your border radius is the larger the corner bitmap needs to be,
which means more time spent in FastBoxBlurFilter. There are probably
some tricks to bring this down.
Fixes#14325
This avoids a bunch of unnecessary work in Painter which not only took
time, but sometimes also led to alignment issues. draw_text_run() will
draw the text where we tell it, and that's it.
We don't yet take the spread-distance parameter into account, since we
don't have a way to "inflate" the text shadow.
Also, I'm not sure if we need to inflate the shadow slightly anyway.
Blurred shadows of our pixel fonts seem very faint. Part of this is
that a blur of < 3px does nothing, see #13231, but even so we might
want to inflate it a little.
The `text-shadow` property is almost identical to `box-shadow`:
> Values are interpreted as for box-shadow [CSS-BACKGROUNDS-3].
> (But note that the inset keyword are not allowed.)
So, let's use the same data structures and parsing code for both. :^)
Our previous code roughly did this:
1. Generate a bitmap as large as the shadow would end up.
2. Paint a rectangle onto it.
3. Blur the whole bitmap.
4. Split it up and render each section.
This patch takes advantage of the fact that (aside from corners) each
horizontal or vertical strip of a box-shadow is identical to the
others, to generate and blur a much smaller bitmap - only large enough
for the four corners and 1px of central "side" in each direction. This
greatly reduces the memory footprint, and should also speed things up,
since there is much less to blur.
We also pass whether the shadow goes inside or outside the element. Only
outer shadows are rendered currently, and inner ones may want to be
handled separately from them, as they will never interfere with each
other.
