LibWeb+WebContent: Add abstraction layer for generic font families

Instead of hard-coding the names of system fonts to use for the CSS
generic fonts (like "sans-serif", "monospace", etc.) we now call out
to a Platform::FontPlugin and ask for the generic names.

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -352,6 +352,7 @@ set(SOURCES
     Painting/StackingContext.cpp
     Painting/TextPaintable.cpp
     Platform/EventLoopPlugin.cpp
+    Platform/FontPlugin.cpp
     Platform/Timer.cpp
     RequestIdleCallback/IdleDeadline.cpp
     ResizeObserver/ResizeObserver.cpp

Userland/Libraries/LibWeb/CSS/StyleComputer.cpp

@@ -27,6 +27,7 @@
 #include <LibWeb/FontCache.h>
 #include <LibWeb/HTML/HTMLHtmlElement.h>
 #include <LibWeb/Loader/ResourceLoader.h>
+#include <LibWeb/Platform/FontPlugin.h>
 #include <stdio.h>
 
 namespace Web::CSS {
@@ -1029,28 +1030,39 @@ void StyleComputer::compute_font(StyleProperties& style, DOM::Element const* ele
         return {};
     };
 
-    // FIXME: Replace hard-coded font names with a relevant call to FontDatabase.
-    // Currently, we cannot request the default font's name, or request it at a specific size and weight.
-    // So, hard-coded font names it is.
     auto find_generic_font = [&](ValueID font_id) -> RefPtr<Gfx::Font> {
+        Platform::GenericFont generic_font {};
         switch (font_id) {
         case ValueID::Monospace:
         case ValueID::UiMonospace:
+            generic_font = Platform::GenericFont::Monospace;
             monospace = true;
-            return find_font("Csilla");
+            break;
         case ValueID::Serif:
-            return find_font("Roman");
+            generic_font = Platform::GenericFont::Serif;
+            break;
         case ValueID::Fantasy:
-            return find_font("Comic Book");
+            generic_font = Platform::GenericFont::Fantasy;
+            break;
         case ValueID::SansSerif:
+            generic_font = Platform::GenericFont::SansSerif;
+            break;
         case ValueID::Cursive:
+            generic_font = Platform::GenericFont::Cursive;
+            break;
         case ValueID::UiSerif:
+            generic_font = Platform::GenericFont::UiSerif;
+            break;
         case ValueID::UiSansSerif:
+            generic_font = Platform::GenericFont::UiSansSerif;
+            break;
         case ValueID::UiRounded:
-            return find_font("Katica");
+            generic_font = Platform::GenericFont::UiRounded;
+            break;
         default:
             return {};
         }
+        return find_font(Platform::FontPlugin::the().generic_font_name(generic_font));
     };
 
     RefPtr<Gfx::Font> found_font;

Userland/Libraries/LibWeb/Platform/FontPlugin.cpp

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Platform/FontPlugin.h>
+
+namespace Web::Platform {
+
+static FontPlugin* s_the;
+
+FontPlugin& FontPlugin::the()
+{
+    VERIFY(s_the);
+    return *s_the;
+}
+
+void FontPlugin::install(FontPlugin& plugin)
+{
+    VERIFY(!s_the);
+    s_the = &plugin;
+}
+
+FontPlugin::~FontPlugin() = default;
+
+}

Userland/Libraries/LibWeb/Platform/FontPlugin.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace Web::Platform {
+
+enum class GenericFont {
+    Cursive,
+    Fantasy,
+    Monospace,
+    SansSerif,
+    Serif,
+    UiMonospace,
+    UiRounded,
+    UiSansSerif,
+    UiSerif,
+    __Count,
+};
+
+class FontPlugin {
+public:
+    static FontPlugin& the();
+    static void install(FontPlugin&);
+
+    virtual ~FontPlugin();
+
+    virtual String generic_font_name(GenericFont) = 0;
+};
+
+}

Userland/Services/WebContent/CMakeLists.txt

@@ -11,6 +11,7 @@ set(SOURCES
     ConnectionFromClient.cpp
     ConsoleGlobalObject.cpp
     EventLoopPluginSerenity.cpp
+    FontPluginSerenity.cpp
     PageHost.cpp
     TimerSerenity.cpp
     WebContentClientEndpoint.h

Userland/Services/WebContent/FontPluginSerenity.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "FontPluginSerenity.h"
+#include <AK/String.h>
+#include <LibGfx/Font/FontDatabase.h>
+
+namespace WebContent {
+
+FontPluginSerenity::FontPluginSerenity()
+{
+}
+
+FontPluginSerenity::~FontPluginSerenity() = default;
+
+String FontPluginSerenity::generic_font_name(Web::Platform::GenericFont generic_font)
+{
+    // FIXME: Replace hard-coded font names with a relevant call to FontDatabase.
+    // Currently, we cannot request the default font's name, or request it at a specific size and weight.
+    // So, hard-coded font names it is.
+    switch (generic_font) {
+    case Web::Platform::GenericFont::SansSerif:
+    case Web::Platform::GenericFont::UiSansSerif:
+    case Web::Platform::GenericFont::Cursive:
+    case Web::Platform::GenericFont::UiRounded:
+        return "Katica";
+    case Web::Platform::GenericFont::Monospace:
+    case Web::Platform::GenericFont::UiMonospace:
+        return "Csilla";
+    case Web::Platform::GenericFont::Serif:
+    case Web::Platform::GenericFont::UiSerif:
+        return "Roman";
+    case Web::Platform::GenericFont::Fantasy:
+        return "Comic Book";
+    case Web::Platform::GenericFont::__Count:
+        VERIFY_NOT_REACHED();
+    }
+    VERIFY_NOT_REACHED();
+}
+
+}

Userland/Services/WebContent/FontPluginSerenity.h

@@ -0,0 +1,22 @@
+/*
+ * 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 WebContent {
+
+class FontPluginSerenity final : public Web::Platform::FontPlugin {
+public:
+    FontPluginSerenity();
+    virtual ~FontPluginSerenity();
+
+    virtual String generic_font_name(Web::Platform::GenericFont) override;
+};
+
+}

Userland/Services/WebContent/main.cpp

@@ -1,10 +1,11 @@
 /*
- * Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2020-2022, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include "EventLoopPluginSerenity.h"
+#include "FontPluginSerenity.h"
 #include <LibCore/EventLoop.h>
 #include <LibCore/LocalServer.h>
 #include <LibCore/System.h>
@@ -31,6 +32,7 @@ ErrorOr<int> serenity_main(Main::Arguments)
     TRY(Core::System::unveil(nullptr, nullptr));
 
     Web::Platform::EventLoopPlugin::install(*new WebContent::EventLoopPluginSerenity);
+    Web::Platform::FontPlugin::install(*new WebContent::FontPluginSerenity);
 
     Web::ImageDecoding::Decoder::initialize(WebView::ImageDecoderClientAdapter::create());
     Web::WebSockets::WebSocketClientManager::initialize(TRY(WebView::WebSocketClientManagerAdapter::try_create()));