LibGfx: Don't try to paint glyphs that aren't in a font

Fixes https://github.com/LadybirdBrowser/ladybird/issues/88

(cherry picked from commit fbc42e7d4282053414c7cf85a3ef7a74e07f4d46;
amended to handle bitmap fonts)

Userland/Libraries/LibAccelGfx/GlyphAtlas.cpp

@@ -25,12 +25,12 @@ void GlyphAtlas::update(HashMap<Gfx::Font const*, HashTable<u32>> const& unique_
     for (auto const& [font, code_points] : unique_glyphs) {
         for (auto const& code_point : code_points) {
             auto glyph = font->glyph(code_point);
+            if (!glyph.has_value())
+                continue;
             auto atlas_key = GlyphsTextureKey { font, code_point };
             if (!m_glyphs_texture_map.contains(atlas_key))
                 need_to_rebuild_texture = true;
-            if (glyph.bitmap()) {
-                glyph_bitmaps.set(atlas_key, *glyph.bitmap());
-            }
+            glyph_bitmaps.set(atlas_key, *glyph->bitmap());
         }
     }
 

Userland/Libraries/LibGfx/Font/BitmapFont.cpp

@@ -282,11 +282,12 @@ ErrorOr<void> BitmapFont::write_to_file(NonnullOwnPtr<Core::File> file)
     return {};
 }
 
-Glyph BitmapFont::glyph(u32 code_point) const
+Optional<Glyph> BitmapFont::glyph(u32 code_point) const
 {
-    // Note: Until all fonts support the 0xFFFD replacement
-    // character, fall back to painting '?' if necessary.
-    auto index = glyph_index(code_point).value_or('?');
+    auto maybe_index = glyph_index(code_point);
+    if (!maybe_index.has_value())
+        return {};
+    auto index = maybe_index.release_value();
     auto width = m_glyph_widths[index];
     auto glyph_byte_count = m_glyph_height * GlyphBitmap::bytes_per_row();
     return Glyph(

Userland/Libraries/LibGfx/Font/BitmapFont.h

@@ -60,8 +60,8 @@ public:
     virtual u8 slope() const override { return m_slope; }
     void set_slope(u8 slope) { m_slope = slope; }
 
-    Glyph glyph(u32 code_point) const override;
-    Glyph glyph(u32 code_point, GlyphSubpixelOffset) const override { return glyph(code_point); }
+    Optional<Glyph> glyph(u32 code_point) const override;
+    Optional<Glyph> glyph(u32 code_point, GlyphSubpixelOffset) const override { return glyph(code_point); }
     Optional<Glyph> glyph_for_postscript_name(StringView, GlyphSubpixelOffset) const override { return {}; }
 
     float glyph_left_bearing(u32) const override { return 0; }

Userland/Libraries/LibGfx/Font/Font.h

@@ -173,8 +173,8 @@ public:
     virtual u16 width() const = 0;
 
     virtual u16 weight() const = 0;
-    virtual Glyph glyph(u32 code_point) const = 0;
-    virtual Glyph glyph(u32 code_point, GlyphSubpixelOffset) const = 0;
+    virtual Optional<Glyph> glyph(u32 code_point) const = 0;
+    virtual Optional<Glyph> glyph(u32 code_point, GlyphSubpixelOffset) const = 0;
     virtual Optional<Glyph> glyph_for_postscript_name(StringView, GlyphSubpixelOffset) const = 0;
     virtual bool contains_glyph(u32 code_point) const = 0;
     virtual bool contains_glyph_for_postscript_name(StringView name) const = 0;

Userland/Libraries/LibGfx/Font/ScaledFont.cpp

@@ -99,19 +99,21 @@ bool ScaledFont::append_glyph_path_to(Gfx::Path& path, u32 glyph_id) const
     return success;
 }
 
-Gfx::Glyph ScaledFont::glyph(u32 code_point) const
+Optional<Gfx::Glyph> ScaledFont::glyph(u32 code_point) const
 {
     return glyph(code_point, GlyphSubpixelOffset { 0, 0 });
 }
 
-Glyph ScaledFont::glyph_for_id(u32 id, GlyphSubpixelOffset subpixel_offset) const
+Optional<Glyph> ScaledFont::glyph_for_id(u32 id, GlyphSubpixelOffset subpixel_offset) const
 {
     auto bitmap = rasterize_glyph(id, subpixel_offset);
+    if (!bitmap)
+        return {};
     auto metrics = glyph_metrics(id);
     return Gfx::Glyph(bitmap, metrics.left_side_bearing, metrics.advance_width, metrics.ascender, m_font->has_color_bitmaps());
 }
 
-Gfx::Glyph ScaledFont::glyph(u32 code_point, GlyphSubpixelOffset subpixel_offset) const
+Optional<Gfx::Glyph> ScaledFont::glyph(u32 code_point, GlyphSubpixelOffset subpixel_offset) const
 {
     auto id = glyph_id_for_code_point(code_point);
     return glyph_for_id(id, subpixel_offset);

Userland/Libraries/LibGfx/Font/ScaledFont.h

@@ -42,10 +42,10 @@ public:
     virtual u8 slope() const override { return m_font->slope(); }
     virtual u16 width() const override { return m_font->width(); }
     virtual u16 weight() const override { return m_font->weight(); }
-    virtual Gfx::Glyph glyph(u32 code_point) const override;
+    virtual Optional<Gfx::Glyph> glyph(u32 code_point) const override;
     virtual float glyph_left_bearing(u32 code_point) const override;
     Optional<float> glyph_left_bearing_for_postscript_name(StringView) const override;
-    virtual Glyph glyph(u32 code_point, GlyphSubpixelOffset) const override;
+    virtual Optional<Glyph> glyph(u32 code_point, GlyphSubpixelOffset) const override;
     Optional<Glyph> glyph_for_postscript_name(StringView, GlyphSubpixelOffset) const override;
     virtual bool contains_glyph(u32 code_point) const override { return m_font->glyph_id_for_code_point(code_point) > 0; }
     virtual bool contains_glyph_for_postscript_name(StringView name) const override { return m_font->glyph_id_for_postscript_name(name).has_value(); }
@@ -80,7 +80,7 @@ public:
     virtual bool has_color_bitmaps() const override { return m_font->has_color_bitmaps(); }
 
 private:
-    Glyph glyph_for_id(u32 id, GlyphSubpixelOffset) const;
+    Optional<Glyph> glyph_for_id(u32 id, GlyphSubpixelOffset) const;
 
     NonnullRefPtr<VectorFont> m_font;
     float m_x_scale { 0.0f };

Userland/Libraries/LibGfx/Painter.cpp

@@ -1364,7 +1364,10 @@ FLATTEN void Painter::draw_glyph(FloatPoint point, u32 code_point, Font const& f
 {
     auto top_left = point + FloatPoint(font.glyph_left_bearing(code_point), 0);
     auto glyph_position = Gfx::GlyphRasterPosition::get_nearest_fit_for(top_left);
-    auto glyph = font.glyph(code_point, glyph_position.subpixel_offset);
+    auto maybe_glyph = font.glyph(code_point, glyph_position.subpixel_offset);
+    if (!maybe_glyph.has_value())
+        return;
+    auto glyph = maybe_glyph.release_value();
     draw_glyph_internal(point, glyph_position, top_left, glyph, color);
 }