LibGfx: Validate that (almost) all glyphs in a GlyphRun can be drawn

Author: implicitfield

Userland/Libraries/LibGfx/TextLayout.h

@@ -114,6 +114,19 @@ class GlyphRun : public RefCounted<GlyphRun> {
         , m_font(move(font))
         , m_text_type(text_type)
     {
+        for (auto const& glyph_or_emoji : m_glyphs) {
+            if (!glyph_or_emoji.has<DrawGlyph>())
+                continue;
+            auto code_point = glyph_or_emoji.get<DrawGlyph>().code_point;
+            if (m_font->contains_glyph(code_point))
+                continue;
+            if (code_point == 0xFFFD) {
+                dbgln("FIXME: Font \"{}\" does not contain the replacement character", m_font->name());
+                continue;
+            }
+            dbgln("Font \"{}\" does not contain code point {:X} (this should've been filtered out earlier)", m_font->name(), code_point);
+            VERIFY_NOT_REACHED();
+        }
     }
 
     [[nodiscard]] Font const& font() const { return m_font; }