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LibWeb: Support font-size: calc()

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Now that we have a way to resolve calc() lengths without a layout node,
we can finally support calc() values in font-size.

This wasn't possible before because font-related properties have to be
resolved eagerly in StyleComputer due to font-relative CSS length units
depending on the computed font being known.
This commit is contained in:
Andreas Kling 2023-06-02 12:47:21 +02:00
parent df8a96ee00
commit 7115446995
3 changed files with 38 additions and 25 deletions
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7
Tests/LibWeb/Layout/expected/css-font-size-calc.txt Normal file
View file

@ -0,0 +1,7 @@
Viewport <#document> at (0,0) content-size 800x600 children: not-inline
BlockContainer <html> at (0,0) content-size 800x125.179687 [BFC] children: not-inline
BlockContainer <body> at (8,8) content-size 784x109.179687 children: inline
line 0 width: 644.628906, height: 109.179687, bottom: 109.179687, baseline: 84.570312
frag 0 from TextNode start: 0, length: 13, rect: [8,8 644.628906x109.179687]
"Hello friends"
TextNode <#text>

3
Tests/LibWeb/Layout/input/css-font-size-calc.html Normal file
View file

@ -0,0 +1,3 @@
<!doctype html><style>
body { font-size: calc(100px); }
</style>Hello friends

53
Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
View file

@ -1757,6 +1757,28 @@ void StyleComputer::compute_font(StyleProperties& style, DOM::Element const* ele
// FIXME: Should be based on "user's default font size"
float font_size_in_px = 16;
auto parent_line_height = parent_or_root_element_line_height(element, pseudo_element);
Gfx::FontPixelMetrics font_pixel_metrics;
if (parent_element && parent_element->computed_css_values())
font_pixel_metrics = parent_element->computed_css_values()->computed_font().pixel_metrics();
else
font_pixel_metrics = Platform::FontPlugin::the().default_font().pixel_metrics();
auto parent_font_size = [&]() -> CSSPixels {
if (!parent_element || !parent_element->computed_css_values())
return font_size_in_px;
auto value = parent_element->computed_css_values()->property(CSS::PropertyID::FontSize);
if (value->is_length()) {
auto length = value->as_length().length();
auto parent_line_height = parent_or_root_element_line_height(parent_element, {});
if (length.is_absolute() || length.is_relative()) {
Length::FontMetrics font_metrics { font_size_in_px, font_pixel_metrics, parent_line_height };
return length.to_px(viewport_rect(), font_metrics, m_root_element_font_metrics);
}
}
return font_size_in_px;
};
Length::FontMetrics font_metrics { parent_font_size(), font_pixel_metrics, parent_line_height };
if (font_size->is_identifier()) {
// https://w3c.github.io/csswg-drafts/css-fonts/#absolute-size-mapping
AK::HashMap<Web::CSS::ValueID, float> absolute_size_mapping = {
@ -1787,25 +1809,10 @@ void StyleComputer::compute_font(StyleProperties& style, DOM::Element const* ele
font_size_in_px *= multiplier;
} else {
Gfx::FontPixelMetrics font_pixel_metrics;
if (parent_element && parent_element->computed_css_values())
font_pixel_metrics = parent_element->computed_css_values()->computed_font().pixel_metrics();
else
font_pixel_metrics = Platform::FontPlugin::the().default_font().pixel_metrics();
auto parent_font_size = [&]() -> CSSPixels {
if (!parent_element || !parent_element->computed_css_values())
return font_size_in_px;
auto value = parent_element->computed_css_values()->property(CSS::PropertyID::FontSize);
if (value->is_length()) {
auto length = value->as_length().length();
auto parent_line_height = parent_or_root_element_line_height(parent_element, {});
if (length.is_absolute() || length.is_relative()) {
Length::FontMetrics font_metrics { font_size_in_px, font_pixel_metrics, parent_line_height };
return length.to_px(viewport_rect(), font_metrics, m_root_element_font_metrics);
}
}
return font_size_in_px;
Length::ResolutionContext const length_resolution_context {
.viewport_rect = viewport_rect(),
.font_metrics = font_metrics,
.root_font_metrics = m_root_element_font_metrics,
};
Optional<Length> maybe_length;
@ -1815,15 +1822,11 @@ void StyleComputer::compute_font(StyleProperties& style, DOM::Element const* ele
} else if (font_size->is_length()) {
maybe_length = font_size->as_length().length();
} else if (font_size->is_calculated()) {
// FIXME: Support font-size: calc(...)
// Theoretically we can do this now, but to resolve it we need a layout_node which we might not have. :^(
maybe_length = font_size->as_calculated().resolve_length(length_resolution_context);
}
if (maybe_length.has_value()) {
auto parent_line_height = parent_or_root_element_line_height(element, pseudo_element);
Length::FontMetrics font_metrics { parent_font_size(), font_pixel_metrics, parent_line_height };
auto px = maybe_length.value().to_px(viewport_rect(), font_metrics, m_root_element_font_metrics).value();
auto px = maybe_length.value().to_px(length_resolution_context).value();
if (px != 0)
font_size_in_px = px;
}