Ladybird: Add a FontPlugin and try much harder to find suitable fonts

Instead of only looking at the SerenityOS default fonts, we now also
look recursively in /usr/share/fonts for suitable fonts that we can
load and use.

Ladybird/CMakeLists.txt

@@ -50,6 +50,7 @@ set(SOURCES
     ConsoleGlobalObject.cpp
     CookieJar.cpp
     EventLoopPluginQt.cpp
+    FontPluginQt.cpp
     RequestManagerQt.cpp
     main.cpp
     WebView.cpp

Ladybird/FontPluginQt.cpp

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#define AK_DONT_REPLACE_STD
+
+#include "FontPluginQt.h"
+#include <AK/String.h>
+#include <LibGfx/Font/FontDatabase.h>
+#include <QFont>
+#include <QFontInfo>
+
+extern String s_serenity_resource_root;
+
+namespace Ladybird {
+
+FontPluginQt::FontPluginQt()
+{
+    // Load the default SerenityOS fonts...
+    Gfx::FontDatabase::set_default_fonts_lookup_path(String::formatted("{}/res/fonts", s_serenity_resource_root));
+
+    // ...and also anything we can find in /usr/share/fonts
+    Gfx::FontDatabase::the().load_all_fonts_from_path("/usr/share/fonts");
+
+    Gfx::FontDatabase::set_default_font_query("Katica 10 400 0");
+    Gfx::FontDatabase::set_fixed_width_font_query("Csilla 10 400 0");
+
+    update_generic_fonts();
+}
+
+FontPluginQt::~FontPluginQt() = default;
+
+void FontPluginQt::update_generic_fonts()
+{
+    // How we choose which system font to use for each CSS font:
+    // 1. Ask Qt via the QFont::StyleHint mechanism for the user's preferred font.
+    // 2. Try loading that font through Gfx::FontDatabase
+    // 3. If we don't support that font for whatever reason (e.g missing TrueType features in LibGfx)...
+    //    1. Try a list of known-suitable fallback fonts with their names hard-coded below
+    //    2. If that didn't work, fall back to Gfx::FontDatabase::default_font() (or default_fixed_width_font())
+
+    // This is rather weird, but it's how things work right now, as we can only draw with fonts loaded by LibGfx.
+
+    m_generic_font_names.resize(static_cast<size_t>(Web::Platform::GenericFont::__Count));
+
+    auto update_mapping = [&](Web::Platform::GenericFont generic_font, QFont::StyleHint qfont_style_hint, Vector<String> fallbacks = {}) {
+        QFont qt_font;
+        qt_font.setStyleHint(qfont_style_hint);
+        QFontInfo qt_info(qt_font);
+        auto qt_font_family = qt_info.family();
+
+        auto gfx_font = Gfx::FontDatabase::the().get(qt_font_family.toUtf8().data(), 16, 400, 0, Gfx::Font::AllowInexactSizeMatch::Yes);
+        if (!gfx_font) {
+            for (auto& fallback : fallbacks) {
+                gfx_font = Gfx::FontDatabase::the().get(fallback, 16, 400, 0, Gfx::Font::AllowInexactSizeMatch::Yes);
+                if (gfx_font)
+                    break;
+            }
+        }
+
+        if (!gfx_font) {
+            if (generic_font == Web::Platform::GenericFont::Monospace || generic_font == Web::Platform::GenericFont::UiMonospace)
+                gfx_font = Gfx::FontDatabase::default_fixed_width_font();
+            else
+                gfx_font = Gfx::FontDatabase::default_font();
+        }
+
+        m_generic_font_names[static_cast<size_t>(generic_font)] = gfx_font->family();
+    };
+
+    // Fallback fonts to look for if Gfx::Font can't load the font suggested by Qt.
+    // The lists are basically arbitrary, taken from https://www.w3.org/Style/Examples/007/fonts.en.html
+    Vector<String> cursive_fallbacks { "Comic Sans MS", "Comic Sans", "Apple Chancery", "Bradley Hand", "Brush Script MT", "Snell Roundhand", "URW Chancery L" };
+    Vector<String> fantasy_fallbacks { "Impact", "Luminari", "Chalkduster", "Jazz LET", "Blippo", "Stencil Std", "Marker Felt", "Trattatello" };
+    Vector<String> monospace_fallbacks { "Andale Mono", "Courier New", "Courier", "FreeMono", "OCR A Std", "DejaVu Sans Mono", "Liberation Mono", "Csilla" };
+    Vector<String> sans_serif_fallbacks { "Arial", "Helvetica", "Verdana", "Trebuchet MS", "Gill Sans", "Noto Sans", "Avantgarde", "Optima", "Arial Narrow", "Liberation Sans", "Katica" };
+    Vector<String> serif_fallbacks { "Times", "Times New Roman", "Didot", "Georgia", "Palatino", "Bookman", "New Century Schoolbook", "American Typewriter", "Liberation Serif", "Roman" };
+
+    update_mapping(Web::Platform::GenericFont::Cursive, QFont::StyleHint::Cursive, cursive_fallbacks);
+    update_mapping(Web::Platform::GenericFont::Fantasy, QFont::StyleHint::Fantasy, fantasy_fallbacks);
+    update_mapping(Web::Platform::GenericFont::Monospace, QFont::StyleHint::Monospace, monospace_fallbacks);
+    update_mapping(Web::Platform::GenericFont::SansSerif, QFont::StyleHint::SansSerif, sans_serif_fallbacks);
+    update_mapping(Web::Platform::GenericFont::Serif, QFont::StyleHint::Serif, serif_fallbacks);
+    update_mapping(Web::Platform::GenericFont::UiMonospace, QFont::StyleHint::Monospace, monospace_fallbacks);
+    update_mapping(Web::Platform::GenericFont::UiRounded, QFont::StyleHint::SansSerif, sans_serif_fallbacks);
+    update_mapping(Web::Platform::GenericFont::UiSansSerif, QFont::StyleHint::SansSerif, sans_serif_fallbacks);
+    update_mapping(Web::Platform::GenericFont::UiSerif, QFont::StyleHint::Serif, serif_fallbacks);
+}
+
+String FontPluginQt::generic_font_name(Web::Platform::GenericFont generic_font)
+{
+    return m_generic_font_names[static_cast<size_t>(generic_font)];
+}
+
+}

Ladybird/FontPluginQt.h

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibWeb/Platform/FontPlugin.h>
+
+namespace Ladybird {
+
+class FontPluginQt final : public Web::Platform::FontPlugin {
+public:
+    FontPluginQt();
+    virtual ~FontPluginQt();
+
+    virtual String generic_font_name(Web::Platform::GenericFont) override;
+
+    void update_generic_fonts();
+
+private:
+    Vector<String> m_generic_font_names;
+};
+
+}

Ladybird/WebView.cpp

@@ -11,6 +11,7 @@
 #include "ConsoleClient.h"
 #include "CookieJar.h"
 #include "EventLoopPluginQt.h"
+#include "FontPluginQt.h"
 #include "RequestManagerQt.h"
 #include <AK/Assertions.h>
 #include <AK/ByteBuffer.h>
@@ -830,12 +831,8 @@ void initialize_web_engine()
     platform_init();
 
     Web::FrameLoader::set_default_favicon_path(String::formatted("{}/res/icons/16x16/app-browser.png", s_serenity_resource_root));
-    dbgln("Set favicon path to {}", String::formatted("{}/res/icons/16x16/app-browser.png", s_serenity_resource_root));
 
-    Gfx::FontDatabase::set_default_fonts_lookup_path(String::formatted("{}/res/fonts", s_serenity_resource_root));
-
-    Gfx::FontDatabase::set_default_font_query("Katica 10 400 0");
-    Gfx::FontDatabase::set_fixed_width_font_query("Csilla 10 400 0");
+    Web::Platform::FontPlugin::install(*new Ladybird::FontPluginQt);
 
     Web::FrameLoader::set_error_page_url(String::formatted("file://{}/res/html/error.html", s_serenity_resource_root));
 }

Ladybird/main.cpp

@@ -18,6 +18,8 @@ Browser::Settings* s_settings;
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
 {
+    QApplication app(arguments.argc, arguments.argv);
+
     initialize_web_engine();
 
     String url;
@@ -28,7 +30,6 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     s_settings = new Browser::Settings();
 
-    QApplication app(arguments.argc, arguments.argv);
     BrowserWindow window;
     window.setWindowTitle("Ladybird");
     window.resize(800, 600);