LibPDF: Introduce loading of common font data in PDFFont base class

This font data is shared between Type 1 and TrueType fonts, which is
why we can now load it in the base class that they both use.

Userland/Libraries/LibPDF/Fonts/PDFFont.cpp

@@ -12,6 +12,61 @@
 
 namespace PDF {
 
+static bool is_standard_latin_font(FlyString const& font)
+{
+    return font.is_one_of(
+        "Times-Roman",
+        "Helvetica",
+        "Courier",
+        "Times-Bold",
+        "Helvetica-Bold",
+        "Courier-Bold",
+        "Times-Italic",
+        "Helvetica-Oblique",
+        "Courier-Oblique",
+        "Times-BoldItalic",
+        "Helvetica-BoldOblique",
+        "Courier-BoldOblique");
+}
+
+PDFErrorOr<void> PDFFont::CommonData::load_from_dict(Document* document, NonnullRefPtr<DictObject> dict)
+{
+    auto base_font = TRY(dict->get_name(document, CommonNames::BaseFont))->name();
+    is_standard_font = is_standard_latin_font(base_font);
+
+    if (dict->contains(CommonNames::Encoding)) {
+        auto encoding_object = MUST(dict->get_object(document, CommonNames::Encoding));
+        encoding = TRY(Encoding::from_object(document, encoding_object));
+    } else {
+        // FIXME: The spec doesn't specify what the encoding should be in this case
+        if (is_standard_font)
+            encoding = Encoding::standard_encoding();
+        // Otherwise, use the built-in encoding of the font.
+    }
+
+    if (dict->contains(CommonNames::ToUnicode))
+        to_unicode = TRY(dict->get_stream(document, CommonNames::ToUnicode));
+
+    if (dict->contains(CommonNames::FirstChar) && dict->contains(CommonNames::LastChar) && dict->contains(CommonNames::Widths)) {
+        auto first_char = dict->get_value(CommonNames::FirstChar).get<int>();
+        auto last_char = dict->get_value(CommonNames::LastChar).get<int>();
+        auto widths_array = TRY(dict->get_array(document, CommonNames::Widths));
+
+        VERIFY(widths_array->size() == static_cast<size_t>(last_char - first_char + 1));
+
+        for (size_t i = 0; i < widths_array->size(); i++)
+            widths.set(first_char + i, widths_array->at(i).to_int());
+    }
+
+    if (dict->contains(CommonNames::FontDescriptor)) {
+        auto descriptor = TRY(dict->get_dict(document, CommonNames::FontDescriptor));
+        if (descriptor->contains(CommonNames::MissingWidth))
+            missing_width = descriptor->get_value(CommonNames::MissingWidth).to_int();
+    }
+
+    return {};
+}
+
 PDFErrorOr<NonnullRefPtr<PDFFont>> PDFFont::create(Document* document, NonnullRefPtr<DictObject> dict)
 {
     auto subtype = TRY(dict->get_name(document, CommonNames::Subtype))->name();

Userland/Libraries/LibPDF/Fonts/PDFFont.h

@@ -6,8 +6,10 @@
 
 #pragma once
 
+#include <AK/HashMap.h>
 #include <LibGfx/Forward.h>
 #include <LibPDF/Document.h>
+#include <LibPDF/Encoding.h>
 
 namespace PDF {
 
@@ -19,6 +21,17 @@ public:
         TrueType
     };
 
+    // This is used both by Type 1 and TrueType fonts.
+    struct CommonData {
+        RefPtr<StreamObject> to_unicode;
+        RefPtr<Encoding> encoding;
+        HashMap<u16, u16> widths;
+        u16 missing_width;
+        bool is_standard_font;
+
+        PDFErrorOr<void> load_from_dict(Document*, NonnullRefPtr<DictObject>);
+    };
+
     static PDFErrorOr<NonnullRefPtr<PDFFont>> create(Document*, NonnullRefPtr<DictObject>);
 
     virtual ~PDFFont() = default;