LibGfx: Allow extracting paths from fonts and add Gfx::Path::text()

This updates fonts so rather than rastering directly to a bitmap, you
can extract paths for glyphs. This is then used to implement a
Gfx::Path::text("some text", font) API, that if given a vector font
appends the path of the text to your Gfx::Path. This then allows
arbitrary manipulation of the text (rotation, skewing, etc), paving the
way for Word Art in Serenity.

Userland/Libraries/LibGfx/Font/OpenType/Font.cpp

@@ -14,6 +14,7 @@
 #include <AK/Try.h>
 #include <LibCore/MappedFile.h>
 #include <LibCore/Resource.h>
+#include <LibGfx/AntiAliasingPainter.h>
 #include <LibGfx/Font/OpenType/Cmap.h>
 #include <LibGfx/Font/OpenType/Font.h>
 #include <LibGfx/Font/OpenType/Glyf.h>
@@ -708,14 +709,25 @@ float Font::glyphs_horizontal_kerning(u32 left_glyph_id, u32 right_glyph_id, flo
     return 0.0f;
 }
 
-RefPtr<Gfx::Bitmap> Font::rasterize_glyph(u32 glyph_id, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset) const
+Font::AscenderAndDescender Font::resolve_ascender_and_descender() const
 {
-    if (auto bitmap = color_bitmap(glyph_id)) {
-        return bitmap;
-    }
+    i16 ascender = 0;
+    i16 descender = 0;
 
+    if (m_os2.has_value() && m_os2->use_typographic_metrics()) {
+        ascender = m_os2->typographic_ascender();
+        descender = m_os2->typographic_descender();
+    } else {
+        ascender = m_hhea.ascender();
+        descender = m_hhea.descender();
+    }
+    return { ascender, descender };
+}
+
+Optional<Glyf::Glyph> Font::extract_and_append_glyph_path_to(Gfx::Path& path, u32 glyph_id, i16 ascender, i16 descender, float x_scale, float y_scale) const
+{
     if (!m_loca.has_value() || !m_glyf.has_value()) {
-        return nullptr;
+        return {};
     }
 
     if (glyph_id >= glyph_count()) {
@@ -727,30 +739,50 @@ RefPtr<Gfx::Bitmap> Font::rasterize_glyph(u32 glyph_id, float x_scale, float y_s
 
     // If a glyph has no outline, then loca[n] = loca [n+1].
     if (glyph_offset0 == glyph_offset1)
-        return nullptr;
+        return {};
 
     auto glyph = m_glyf->glyph(glyph_offset0);
     if (!glyph.has_value())
-        return nullptr;
+        return {};
 
-    i16 ascender = 0;
-    i16 descender = 0;
-
-    if (m_os2.has_value() && m_os2->use_typographic_metrics()) {
-        ascender = m_os2->typographic_ascender();
-        descender = m_os2->typographic_descender();
-    } else {
-        ascender = m_hhea.ascender();
-        descender = m_hhea.descender();
-    }
-
-    return glyph->rasterize(ascender, descender, x_scale, y_scale, subpixel_offset, [&](u16 glyph_id) {
+    bool success = glyph->append_path(path, ascender, descender, x_scale, y_scale, [&](u16 glyph_id) {
         if (glyph_id >= glyph_count()) {
             glyph_id = 0;
         }
         auto glyph_offset = m_loca->get_glyph_offset(glyph_id);
         return m_glyf->glyph(glyph_offset);
     });
+
+    if (success)
+        return glyph;
+    return {};
+}
+
+bool Font::append_glyph_path_to(Gfx::Path& path, u32 glyph_id, float x_scale, float y_scale) const
+{
+    auto ascender_and_descender = resolve_ascender_and_descender();
+    return extract_and_append_glyph_path_to(path, glyph_id, ascender_and_descender.ascender, ascender_and_descender.descender, x_scale, y_scale).has_value();
+}
+
+RefPtr<Gfx::Bitmap> Font::rasterize_glyph(u32 glyph_id, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset) const
+{
+    if (auto bitmap = color_bitmap(glyph_id))
+        return bitmap;
+
+    auto ascender_and_descender = resolve_ascender_and_descender();
+    Gfx::Path path;
+    path.move_to(subpixel_offset.to_float_point());
+    auto glyph = extract_and_append_glyph_path_to(path, glyph_id, ascender_and_descender.ascender, ascender_and_descender.descender, x_scale, y_scale);
+    if (!glyph.has_value())
+        return {};
+
+    u32 width = (u32)(ceilf((glyph->xmax() - glyph->xmin()) * x_scale)) + 2;
+    u32 height = (u32)(ceilf((ascender_and_descender.ascender - ascender_and_descender.descender) * y_scale)) + 2;
+    auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, { width, height }).release_value_but_fixme_should_propagate_errors();
+    Gfx::Painter painter { bitmap };
+    Gfx::AntiAliasingPainter aa_painter(painter);
+    aa_painter.fill_path(path, Gfx::Color::White);
+    return bitmap;
 }
 
 u32 Font::glyph_count() const

Userland/Libraries/LibGfx/Font/OpenType/Font.h

@@ -31,6 +31,7 @@ public:
     virtual Gfx::ScaledGlyphMetrics glyph_metrics(u32 glyph_id, float x_scale, float y_scale, float point_width, float point_height) const override;
     virtual float glyphs_horizontal_kerning(u32 left_glyph_id, u32 right_glyph_id, float x_scale) const override;
     virtual RefPtr<Gfx::Bitmap> rasterize_glyph(u32 glyph_id, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset) const override;
+    virtual bool append_glyph_path_to(Gfx::Path&, u32 glyph_id, float x_scale, float y_scale) const override;
     virtual u32 glyph_count() const override;
     virtual u16 units_per_em() const override;
     virtual u32 glyph_id_for_code_point(u32 code_point) const override;
@@ -47,6 +48,15 @@ public:
     Optional<ReadonlyBytes> glyph_program(u32 glyph_id) const;
 
 private:
+    struct AscenderAndDescender {
+        i16 ascender;
+        i16 descender;
+    };
+
+    AscenderAndDescender resolve_ascender_and_descender() const;
+
+    Optional<Glyf::Glyph> extract_and_append_glyph_path_to(Gfx::Path&, u32 glyph_id, i16 ascender, i16 descender, float x_scale, float y_scale) const;
+
     RefPtr<Gfx::Bitmap> color_bitmap(u32 glyph_id) const;
 
     struct EmbeddedBitmapWithFormat17 {

Userland/Libraries/LibGfx/Font/OpenType/Glyf.cpp

@@ -245,7 +245,7 @@ ReadonlyBytes Glyf::Glyph::program() const
     return m_slice.slice(instructions_start + 2, num_instructions);
 }
 
-void Glyf::Glyph::rasterize_impl(Gfx::Painter& painter, Gfx::AffineTransform const& transform) const
+void Glyf::Glyph::append_path_impl(Gfx::Path& path, Gfx::AffineTransform const& transform) const
 {
     // Get offset for flags, x, and y.
     u16 num_points = be_u16(m_slice.offset((m_num_contours - 1) * 2)) + 1;
@@ -256,7 +256,6 @@ void Glyf::Glyph::rasterize_impl(Gfx::Painter& painter, Gfx::AffineTransform con
     get_ttglyph_offsets(m_slice, num_points, flags_offset, &x_offset, &y_offset);
 
     // Prepare to render glyph.
-    Gfx::Path path;
     PointIterator point_iterator(m_slice, num_points, flags_offset, x_offset, y_offset, transform);
 
     u32 current_point_index = 0;
@@ -297,32 +296,24 @@ void Glyf::Glyph::rasterize_impl(Gfx::Painter& painter, Gfx::AffineTransform con
             }
         }
     }
-
-    constexpr auto base_color = Color::White;
-    Gfx::AntiAliasingPainter aa_painter { painter };
-    aa_painter.fill_path(path, base_color);
 }
 
-RefPtr<Gfx::Bitmap> Glyf::Glyph::rasterize_simple(i16 font_ascender, i16 font_descender, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset) const
+bool Glyf::Glyph::append_simple_path(Gfx::Path& path, i16 font_ascender, i16 font_descender, float x_scale, float y_scale) const
 {
     if (m_xmin > m_xmax) [[unlikely]] {
         dbgln("OpenType: Glyph has invalid xMin ({}) > xMax ({})", m_xmin, m_xmax);
-        return nullptr;
+        return false;
     }
     if (font_descender > font_ascender) [[unlikely]] {
         dbgln("OpenType: Glyph has invalid ascender ({}) > descender ({})", font_ascender, font_descender);
-        return nullptr;
+        return false;
     }
-    u32 width = (u32)(ceilf((m_xmax - m_xmin) * x_scale)) + 2;
-    u32 height = (u32)(ceilf((font_ascender - font_descender) * y_scale)) + 2;
-    auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, { width, height }).release_value_but_fixme_should_propagate_errors();
     auto affine = Gfx::AffineTransform()
-                      .translate(subpixel_offset.to_float_point())
+                      .translate(path.last_point())
                       .scale(x_scale, -y_scale)
                       .translate(-m_xmin, -font_ascender);
-    Gfx::Painter painter { bitmap };
-    rasterize_impl(painter, affine);
-    return bitmap;
+    append_path_impl(path, affine);
+    return true;
 }
 
 Optional<Glyf::Glyph> Glyf::glyph(u32 offset) const

Userland/Libraries/LibGfx/Font/OpenType/Glyf.h

@@ -14,6 +14,7 @@
 #include <LibGfx/Font/Font.h>
 #include <LibGfx/Font/OpenType/Tables.h>
 #include <LibGfx/Painter.h>
+#include <LibGfx/Size.h>
 #include <math.h>
 
 namespace OpenType {
@@ -71,17 +72,22 @@ public:
                 m_type = Type::Simple;
             }
         }
+
         template<typename GlyphCb>
-        RefPtr<Gfx::Bitmap> rasterize(i16 font_ascender, i16 font_descender, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset, GlyphCb glyph_callback) const
+        bool append_path(Gfx::Path& path, i16 font_ascender, i16 font_descender, float x_scale, float y_scale, GlyphCb glyph_callback) const
         {
             switch (m_type) {
             case Type::Simple:
-                return rasterize_simple(font_ascender, font_descender, x_scale, y_scale, subpixel_offset);
+                return append_simple_path(path, font_ascender, font_descender, x_scale, y_scale);
             case Type::Composite:
-                return rasterize_composite(font_ascender, font_descender, x_scale, y_scale, subpixel_offset, glyph_callback);
+                return append_composite_path(path, font_ascender, x_scale, y_scale, glyph_callback);
             }
             VERIFY_NOT_REACHED();
         }
+
+        i16 xmax() const { return m_xmax; }
+        i16 xmin() const { return m_xmin; }
+
         int ascender() const { return m_ymax; }
         int descender() const { return m_ymin; }
 
@@ -112,11 +118,11 @@ public:
             u32 m_offset { 0 };
         };
 
-        void rasterize_impl(Gfx::Painter&, Gfx::AffineTransform const&) const;
-        RefPtr<Gfx::Bitmap> rasterize_simple(i16 ascender, i16 descender, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset) const;
+        void append_path_impl(Gfx::Path&, Gfx::AffineTransform const&) const;
+        bool append_simple_path(Gfx::Path&, i16 ascender, i16 descender, float x_scale, float y_scale) const;
 
         template<typename GlyphCb>
-        void rasterize_composite_loop(Gfx::Painter& painter, Gfx::AffineTransform const& transform, GlyphCb glyph_callback) const
+        void resolve_composite_path_loop(Gfx::Path& path, Gfx::AffineTransform const& transform, GlyphCb glyph_callback) const
         {
             ComponentIterator component_iterator(m_slice);
 
@@ -133,28 +139,22 @@ public:
                     continue;
 
                 if (glyph->m_type == Type::Simple) {
-                    glyph->rasterize_impl(painter, affine_here);
+                    glyph->append_path_impl(path, affine_here);
                 } else {
-                    glyph->rasterize_composite_loop(painter, transform, glyph_callback);
+                    glyph->resolve_composite_path_loop(path, transform, glyph_callback);
                 }
             }
         }
 
         template<typename GlyphCb>
-        RefPtr<Gfx::Bitmap> rasterize_composite(i16 font_ascender, i16 font_descender, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset, GlyphCb glyph_callback) const
+        bool append_composite_path(Gfx::Path& path, i16 font_ascender, float x_scale, float y_scale, GlyphCb glyph_callback) const
         {
-            u32 width = (u32)(ceilf((m_xmax - m_xmin) * x_scale)) + 1;
-            u32 height = (u32)(ceilf((font_ascender - font_descender) * y_scale)) + 1;
-            auto bitmap = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, { width, height }).release_value_but_fixme_should_propagate_errors();
             auto affine = Gfx::AffineTransform()
-                              .translate(subpixel_offset.to_float_point())
+                              .translate(path.last_point())
                               .scale(x_scale, -y_scale)
                               .translate(-m_xmin, -font_ascender);
-
-            Gfx::Painter painter { bitmap };
-            rasterize_composite_loop(painter, affine, glyph_callback);
-
-            return bitmap;
+            resolve_composite_path_loop(path, affine, glyph_callback);
+            return true;
         }
 
         Type m_type { Type::Composite };

Userland/Libraries/LibGfx/Font/ScaledFont.cpp

@@ -83,6 +83,11 @@ RefPtr<Gfx::Bitmap> ScaledFont::rasterize_glyph(u32 glyph_id, GlyphSubpixelOffse
     return glyph_bitmap;
 }
 
+bool ScaledFont::append_glyph_path_to(Gfx::Path& path, u32 glyph_id) const
+{
+    return m_font->append_glyph_path_to(path, glyph_id, m_x_scale, m_y_scale);
+}
+
 Gfx::Glyph ScaledFont::glyph(u32 code_point) const
 {
     return glyph(code_point, GlyphSubpixelOffset { 0, 0 });

Userland/Libraries/LibGfx/Font/ScaledFont.h

@@ -31,6 +31,7 @@ public:
     ScaledFontMetrics metrics() const { return m_font->metrics(m_x_scale, m_y_scale); }
     ScaledGlyphMetrics glyph_metrics(u32 glyph_id) const { return m_font->glyph_metrics(glyph_id, m_x_scale, m_y_scale, m_point_width, m_point_height); }
     RefPtr<Gfx::Bitmap> rasterize_glyph(u32 glyph_id, GlyphSubpixelOffset) const;
+    bool append_glyph_path_to(Gfx::Path&, u32 glyph_id) const;
 
     // ^Gfx::Font
     virtual NonnullRefPtr<Font> clone() const override { return MUST(try_clone()); } // FIXME: clone() should not need to be implemented

Userland/Libraries/LibGfx/Font/VectorFont.h

@@ -10,6 +10,7 @@
 #include <AK/RefCounted.h>
 #include <LibGfx/Font/Font.h>
 #include <LibGfx/Forward.h>
+#include <LibGfx/Path.h>
 
 namespace Gfx {
 
@@ -39,6 +40,8 @@ public:
     virtual ScaledGlyphMetrics glyph_metrics(u32 glyph_id, float x_scale, float y_scale, float point_width, float point_height) const = 0;
     virtual float glyphs_horizontal_kerning(u32 left_glyph_id, u32 right_glyph_id, float x_scale) const = 0;
     virtual RefPtr<Gfx::Bitmap> rasterize_glyph(u32 glyph_id, float x_scale, float y_scale, GlyphSubpixelOffset) const = 0;
+    virtual bool append_glyph_path_to(Gfx::Path&, u32 glyph_id, float x_scale, float y_scale) const = 0;
+
     virtual u32 glyph_count() const = 0;
     virtual u16 units_per_em() const = 0;
     virtual u32 glyph_id_for_code_point(u32 code_point) const = 0;

Userland/Libraries/LibGfx/Font/WOFF/Font.h

@@ -28,6 +28,8 @@ public:
     virtual Gfx::ScaledGlyphMetrics glyph_metrics(u32 glyph_id, float x_scale, float y_scale, float point_width, float point_height) const override { return m_input_font->glyph_metrics(glyph_id, x_scale, y_scale, point_width, point_height); }
     virtual float glyphs_horizontal_kerning(u32 left_glyph_id, u32 right_glyph_id, float x_scale) const override { return m_input_font->glyphs_horizontal_kerning(left_glyph_id, right_glyph_id, x_scale); }
     virtual RefPtr<Gfx::Bitmap> rasterize_glyph(u32 glyph_id, float x_scale, float y_scale, Gfx::GlyphSubpixelOffset subpixel_offset) const override { return m_input_font->rasterize_glyph(glyph_id, x_scale, y_scale, subpixel_offset); }
+    virtual bool append_glyph_path_to(Gfx::Path& path, u32 glyph_id, float x_scale, float y_scale) const override { return m_input_font->append_glyph_path_to(path, glyph_id, x_scale, y_scale); }
+
     virtual u32 glyph_count() const override { return m_input_font->glyph_count(); }
     virtual u16 units_per_em() const override { return m_input_font->units_per_em(); }
     virtual u32 glyph_id_for_code_point(u32 code_point) const override { return m_input_font->glyph_id_for_code_point(code_point); }

Userland/Libraries/LibGfx/Font/WOFF2/Font.h

@@ -32,6 +32,7 @@ public:
     {
         return m_input_font->rasterize_glyph(glyph_id, x_scale, y_scale, subpixel_offset);
     }
+    virtual bool append_glyph_path_to(Gfx::Path& path, u32 glyph_id, float x_scale, float y_scale) const override { return m_input_font->append_glyph_path_to(path, glyph_id, x_scale, y_scale); }
     virtual u32 glyph_count() const override { return m_input_font->glyph_count(); }
     virtual u16 units_per_em() const override { return m_input_font->units_per_em(); }
     virtual u32 glyph_id_for_code_point(u32 code_point) const override { return m_input_font->glyph_id_for_code_point(code_point); }