LibDraw: Introduce (formerly known as SharedGraphics.)

Instead of LibGUI and WindowServer building their own copies of the drawing
and graphics code, let's it in a separate LibDraw library.

This avoids building the code twice, and will encourage better separation
of concerns. :^)

Libraries/LibDraw/Font.h

@@ -0,0 +1,95 @@
+#pragma once
+
+#include <AK/AKString.h>
+#include <AK/MappedFile.h>
+#include <AK/RefPtr.h>
+#include <AK/RefCounted.h>
+#include <AK/Types.h>
+#include <LibDraw/Rect.h>
+
+// FIXME: Make a MutableGlyphBitmap buddy class for FontEditor instead?
+class GlyphBitmap {
+    friend class Font;
+
+public:
+    const unsigned* rows() const { return m_rows; }
+    unsigned row(unsigned index) const { return m_rows[index]; }
+
+    bool bit_at(int x, int y) const { return row(y) & (1 << x); }
+    void set_bit_at(int x, int y, bool b)
+    {
+        auto& mutable_row = const_cast<unsigned*>(m_rows)[y];
+        if (b)
+            mutable_row |= 1 << x;
+        else
+            mutable_row &= ~(1 << x);
+    }
+
+    Size size() const { return m_size; }
+    int width() const { return m_size.width(); }
+    int height() const { return m_size.height(); }
+
+private:
+    GlyphBitmap(const unsigned* rows, Size size)
+        : m_rows(rows)
+        , m_size(size)
+    {
+    }
+
+    const unsigned* m_rows { nullptr };
+    Size m_size;
+};
+
+class Font : public RefCounted<Font> {
+public:
+    static Font& default_font();
+    static Font& default_bold_font();
+
+    static Font& default_fixed_width_font();
+
+    RefPtr<Font> clone() const;
+
+    static RefPtr<Font> load_from_file(const StringView& path);
+    bool write_to_file(const StringView& path);
+
+    ~Font();
+
+    GlyphBitmap glyph_bitmap(char ch) const { return GlyphBitmap(&m_rows[(u8)ch * m_glyph_height], { glyph_width(ch), m_glyph_height }); }
+
+    u8 glyph_width(char ch) const { return m_fixed_width ? m_glyph_width : m_glyph_widths[(u8)ch]; }
+    u8 glyph_height() const { return m_glyph_height; }
+    u8 min_glyph_width() const { return m_min_glyph_width; }
+    u8 max_glyph_width() const { return m_max_glyph_width; }
+    u8 glyph_spacing() const { return m_fixed_width ? 0 : 1; }
+    int width(const StringView& string) const;
+
+    String name() const { return m_name; }
+    void set_name(const StringView& name) { m_name = name; }
+
+    bool is_fixed_width() const { return m_fixed_width; }
+    void set_fixed_width(bool b) { m_fixed_width = b; }
+
+    void set_glyph_width(char ch, u8 width)
+    {
+        ASSERT(m_glyph_widths);
+        m_glyph_widths[(u8)ch] = width;
+    }
+
+private:
+    Font(const StringView& name, unsigned* rows, u8* widths, bool is_fixed_width, u8 glyph_width, u8 glyph_height);
+
+    static RefPtr<Font> load_from_memory(const u8*);
+
+    String m_name;
+
+    unsigned* m_rows { nullptr };
+    u8* m_glyph_widths { nullptr };
+    MappedFile m_mapped_file;
+
+    u8 m_glyph_width { 0 };
+    u8 m_glyph_height { 0 };
+    u8 m_min_glyph_width { 0 };
+    u8 m_max_glyph_width { 0 };
+
+    bool m_fixed_width { false };
+};