LibPDF: Add very basic support for Adobe Type 1 font rendering

Previously we would draw all text, no matter what font type, as
Liberation Serif, which results in things like ugly character spacing.

We now have partial support for drawing Type 1 glyphs, which are part of
a PostScript font program. We completely ignore hinting for now, which
results in ugly looking characters at low resolutions, but gain support
for a large number of typefaces, including most of the default fonts
used in TeX.

Userland/Libraries/LibPDF/Fonts/PS1FontProgram.h

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2022, Julian Offenhäuser <offenhaeuser@protonmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+#include <LibGfx/AffineTransform.h>
+#include <LibGfx/Path.h>
+#include <LibPDF/Error.h>
+
+namespace PDF {
+
+class Reader;
+class Encoding;
+
+class PS1FontProgram : public RefCounted<PS1FontProgram> {
+public:
+    PDFErrorOr<void> parse(ReadonlyBytes const&, size_t cleartext_length, size_t encrypted_length);
+
+    Gfx::Path build_char(u32 code_point, Gfx::FloatPoint const& point, float width);
+
+    RefPtr<Encoding> encoding() const { return m_encoding; }
+
+private:
+    struct Glyph {
+        Gfx::Path path;
+        float width;
+    };
+
+    struct GlyphParserState {
+        Glyph glyph;
+
+        Gfx::FloatPoint point;
+
+        bool flex_feature { false };
+        size_t flex_index;
+        Array<float, 14> flex_sequence;
+
+        size_t sp { 0 };
+        Array<float, 24> stack;
+
+        size_t postscript_sp { 0 };
+        Array<float, 24> postscript_stack;
+    };
+
+    PDFErrorOr<Glyph> parse_glyph(ReadonlyBytes const&, GlyphParserState&);
+    PDFErrorOr<void> parse_encrypted_portion(ByteBuffer const&);
+    PDFErrorOr<Vector<ByteBuffer>> parse_subroutines(Reader&);
+    PDFErrorOr<Vector<float>> parse_number_array(Reader&, size_t length);
+    PDFErrorOr<String> parse_word(Reader&);
+    PDFErrorOr<float> parse_float(Reader&);
+    PDFErrorOr<int> parse_int(Reader&);
+
+    PDFErrorOr<ByteBuffer> decrypt(ReadonlyBytes const&, u16 key, size_t skip);
+    bool seek_name(Reader&, String const&);
+
+    static Error error(
+        String const& message
+#ifdef PDF_DEBUG
+        ,
+        SourceLocation loc = SourceLocation::current()
+#endif
+    );
+
+    Vector<ByteBuffer> m_subroutines;
+    Vector<ByteBuffer> m_character_names;
+    HashMap<u16, Glyph> m_glyph_map;
+
+    Gfx::AffineTransform m_font_matrix;
+
+    RefPtr<Encoding> m_encoding;
+
+    u16 m_encryption_key { 4330 };
+    int m_lenIV { 4 };
+};
+
+}