LibWeb: Improve fallback font selection

Try to find a font that has at least some of the requested properties.
This makes e.g. rfcs on tools.ietf.org easier to read since their
headers are now bold.

Userland/Libraries/LibWeb/CSS/StyleProperties.cpp

@@ -92,10 +92,15 @@ void StyleProperties::load_font() const
  auto family_parts = family_value.split(',');
  auto family = family_parts[0];
 
- if (family.is_one_of("monospace", "ui-monospace"))
+ auto monospace = false;
+ auto bold = false;
+
+ if (family.is_one_of("monospace", "ui-monospace")) {
+ monospace = true;
  family = "Csilla";
- else if (family.is_one_of("serif", "sans-serif", "cursive", "fantasy", "ui-serif", "ui-sans-serif", "ui-rounded"))
+ } else if (family.is_one_of("serif", "sans-serif", "cursive", "fantasy", "ui-serif", "ui-sans-serif", "ui-rounded")) {
  family = "Katica";
+ }
 
  int weight = 400;
  if (font_weight->is_identifier()) {
@@ -127,6 +132,8 @@ void StyleProperties::load_font() const
  weight = 900;
  }
 
+ bold = weight > 400;
+
  int size = 10;
  if (font_size->is_identifier()) {
  switch (static_cast<const IdentifierStyleValue&>(*font_size).id()) {
@@ -177,13 +184,27 @@ void StyleProperties::load_font() const
 
  if (!found_font) {
  dbgln("Font not found: '{}' {} {}", family, size, weight);
- found_font = Gfx::FontDatabase::default_font();
+ found_font = font_fallback(monospace, bold);
  }
 
  m_font = found_font;
  FontCache::the().set(font_selector, *m_font);
 }
 
+RefPtr<Gfx::Font> StyleProperties::font_fallback(bool monospace, bool bold) const
+{
+ if (monospace && bold)
+ return Gfx::FontDatabase::default_bold_fixed_width_font();
+
+ if (monospace)
+ return Gfx::FontDatabase::default_fixed_width_font();
+
+ if (bold)
+ return Gfx::FontDatabase::default_bold_font();
+
+ return Gfx::FontDatabase::default_font();
+}
+
 float StyleProperties::line_height(const Layout::Node& layout_node) const
 {
  auto line_height_length = length_or_fallback(CSS::PropertyID::LineHeight, Length::make_auto());

Userland/Libraries/LibWeb/CSS/StyleProperties.h

@@ -76,6 +76,7 @@ class StyleProperties : public RefCounted<StyleProperties> {
  Optional<CSS::Overflow> overflow(CSS::PropertyID) const;
 
  void load_font() const;
+ RefPtr<Gfx::Font> font_fallback(bool monospace, bool bold) const;
 
  mutable RefPtr<Gfx::Font> m_font;
 };