Merge pull request #5993 from nibbbl/cjk-lazy-font-fallback

Fix missing CJK/Indic text on Linux with lazy font fallback

2 files changed, 54 insertions, 5 deletions

diff --git a/indra/llrender/llfontfreetype.cpp b/indra/llrender/llfontfreetype.cpp
index 075c496ec5..cc4d6ad5ef 100644
--- a/indra/llrender/llfontfreetype.cpp
+++ b/indra/llrender/llfontfreetype.cpp
@@ -52,6 +52,7 @@
 //#include "imdebug.h"
 #include "llfontbitmapcache.h"
 #include "llgl.h"
+#include "llwindow.h"
 
 #define ENABLE_OT_SVG_SUPPORT
 
@@ -188,7 +189,7 @@ bool LLFontFreetype::loadFace(const std::string& filename, F32 point_size, F32 v
         return false;
 
     openArgs.flags = FT_OPEN_MEMORY;
-    int error = FT_Open_Face( gFTLibrary, &openArgs, 0, &mFTFace );
+    int error = FT_Open_Face( gFTLibrary, &openArgs, face_n, &mFTFace );
 
     if (error)
         return false;
@@ -197,6 +198,9 @@ bool LLFontFreetype::loadFace(const std::string& filename, F32 point_size, F32 v
     mHinting = hinting;
     mFontFlags = flags;
     mWeight = weight;
+    mFaceIndex = face_n;
+    mVertDPI = vert_dpi;
+    mHorzDPI = horz_dpi;
 
     bool variable_font = false;
     if (weight >= 0)
@@ -314,7 +318,7 @@ S32 LLFontFreetype::getNumFaces(const std::string& filename)
 }
 
 void LLFontFreetype::addFallbackFont(const LLPointer<LLFontFreetype>& fallback_font,
-                                     const char_functor_t& functor)
+                                     const char_functor_t& functor) const
 {
     mFallbackFonts.emplace_back(fallback_font, functor);
 }
@@ -419,6 +423,18 @@ bool LLFontFreetype::hasGlyph(llwchar wch) const
     return(mCharGlyphInfoMap.find(wch) != mCharGlyphInfoMap.end());
 }
 
+bool LLFontFreetype::hasFallbackPath(const std::string& path) const
+{
+    for (const fallback_font_t& pair : mFallbackFonts)
+    {
+        if (pair.first->getName() == path)
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 LLFontGlyphInfo* LLFontFreetype::addGlyph(llwchar wch, EFontGlyphType glyph_type) const
 {
     if (!mFTFace)
@@ -501,6 +517,31 @@ LLFontGlyphInfo* LLFontFreetype::addGlyph(llwchar wch, EFontGlyphType glyph_type
                                         glyph_type);
             }
         }
+
+        // Nothing above covers this char: ask the OS for a font that does,
+        // load it and attach it.
+        if (mAttemptedFallbackChars.insert(wch).second)
+        {
+            LLFontFallbackMatch match = LLWindow::findFallbackFontForChar(wch);
+            if (!match.mPath.empty() && !hasFallbackPath(match.mPath))
+            {
+                LLPointer<LLFontFreetype> fallback = new LLFontFreetype;
+                if (fallback->loadFace(match.mPath, mPointSize, mVertDPI, mHorzDPI,
+                                       /*weight*/ -1, /*is_fallback*/ true,
+                                       match.mFaceIndex, mHinting, mFontFlags))
+                {
+                    glyph_index = FT_Get_Char_Index(fallback->mFTFace, wch);
+                    if (glyph_index)
+                    {
+                        LL_DEBUGS("Font") << "Lazy OS fallback for U+" << std::hex << (U32)wch << std::dec
+                                          << ": " << match.mPath << " (face " << match.mFaceIndex << ")" << LL_ENDL;
+                        addFallbackFont(fallback, nullptr);
+                        return addGlyphFromFont(fallback, wch, glyph_index, glyph_type);
+                    }
+                    // Matched font doesn't actually cover wch: discard it.
+                }
+            }
+        }
     }
 
     auto range_it = mCharGlyphInfoMap.equal_range(wch);
@@ -728,7 +769,7 @@ void LLFontFreetype::renderGlyph(EFontGlyphType bitmap_type, U32 glyph_index, ll
 void LLFontFreetype::reset(F32 vert_dpi, F32 horz_dpi)
 {
     resetBitmapCache();
-    loadFace(mName, mPointSize, vert_dpi ,horz_dpi, mWeight, mIsFallback, 0, mHinting, mFontFlags);
+    loadFace(mName, mPointSize, vert_dpi ,horz_dpi, mWeight, mIsFallback, mFaceIndex, mHinting, mFontFlags);
     if (!mIsFallback)
     {
         // This is the head of the list - need to rebuild ourself and all fallbacks.
diff --git a/indra/llrender/llfontfreetype.h b/indra/llrender/llfontfreetype.h
index d2164e8fa2..12a4052cae 100644
--- a/indra/llrender/llfontfreetype.h
+++ b/indra/llrender/llfontfreetype.h
@@ -34,6 +34,7 @@
 #include "llfontbitmapcache.h"
 
 #include <unordered_map>
+#include <unordered_set>
 
 // Hack.  FT_Face is just a typedef for a pointer to a struct,
 // but there's no simple forward declarations file for FreeType,
@@ -108,7 +109,7 @@ public:
     S32 getNumFaces(const std::string& filename);
 
     typedef std::function<bool(llwchar)> char_functor_t;
-    void addFallbackFont(const LLPointer<LLFontFreetype>& fallback_font, const char_functor_t& functor = nullptr);
+    void addFallbackFont(const LLPointer<LLFontFreetype>& fallback_font, const char_functor_t& functor = nullptr) const;
 
     // Global font metrics - in units of pixels
     F32 getLineHeight() const;
@@ -167,6 +168,7 @@ private:
     bool setSubImageBGRA(U32 x, U32 y, U32 bitmap_num, U16 width, U16 height, const U8* data, U32 stride) const;
     bool setVariationAxis(const std::string& axis_tag, F32 value);
     bool hasGlyph(llwchar wch) const;       // Has a glyph for this character
+    bool hasFallbackPath(const std::string& path) const; // Is a fallback font with this file path already attached?
     LLFontGlyphInfo* addGlyph(llwchar wch, EFontGlyphType glyph_type) const;        // Add a new character to the font if necessary
     LLFontGlyphInfo* addGlyphFromFont(
         const LLFontFreetype *fontp,
@@ -191,9 +193,15 @@ private:
     EFontHinting mHinting;
     S32 mFontFlags;
     S32 mWeight = -1;
+    S32 mFaceIndex = 0; // Face index within the (possibly collection) font file
+    F32 mVertDPI = 0.f; // Kept so lazily-discovered fallback faces can be
+    F32 mHorzDPI = 0.f; // opened at this font's size (see addGlyph)
     typedef std::pair<LLPointer<LLFontFreetype>, char_functor_t> fallback_font_t;
     typedef std::vector<fallback_font_t> fallback_font_vector_t;
-    fallback_font_vector_t mFallbackFonts; // A list of fallback fonts to look for glyphs in (for Unicode chars)
+    // mutable: fallback fonts are also discovered lazily in addGlyph (const)
+    mutable fallback_font_vector_t mFallbackFonts; // A list of fallback fonts to look for glyphs in (for Unicode chars)
+    // Codepoints we've already asked the OS about, so we only query once each
+    mutable std::unordered_set<llwchar> mAttemptedFallbackChars;
 
     // *NOTE: the same glyph can be present with multiple representations (but the pointer is always unique)
     typedef std::unordered_multimap<llwchar, LLFontGlyphInfo*> char_glyph_info_map_t;