We can embolden via cairo_ft_font_face_create_for_pattern

If we're able to build a font from a pattern, then we can smuggle
into cairo the info that we want this font to be artificially
emboldened.

vcl/inc/vcl/impfont.hxx

@@ -166,7 +166,7 @@ public:
         { return meAntiAlias == ANTIALIAS_FALSE; }
     bool DontUseHinting() const
         { return (meHinting == HINTING_FALSE) || (GetHintStyle() == HINT_NONE); }
-    virtual void *GetPattern(void * /*pFace*/) const
+    virtual void *GetPattern(void * /*pFace*/, bool /*bEmbolden*/) const
         { return NULL; }
 };
 

vcl/unx/inc/salgdi.h

@@ -63,14 +63,27 @@ namespace basegfx {
 
 class CairoFontsCache
 {
+public:
+    struct CacheId
+    {
+        const void *mpFace;
+        const void *mpOptions;
+        bool mbEmbolden;
+        bool operator ==(const CacheId& rOther) const
+        {
+            return mpFace == rOther.mpFace &&
+                mpOptions == rOther.mpOptions &&
+                mbEmbolden == rOther.mbEmbolden;
+        }
+    };
 private:
     static int mnRefCount;
-    typedef std::deque< std::pair<void *, void*> > LRUFonts;
+    typedef std::deque< std::pair<void *, CacheId> > LRUFonts;
     static LRUFonts maLRUFonts;
 public:
     CairoFontsCache();
-    static void  CacheFont(void *pFont, void *pId);
-    static void* FindCachedFont(void *pId);
+    static void  CacheFont(void *pFont, const CacheId &rId);
+    static void* FindCachedFont(const CacheId &rId);
     ~CairoFontsCache();
 };
 

vcl/unx/source/fontmanager/fontconfig.cxx

@@ -59,6 +59,9 @@ using namespace psp;
     #ifndef FC_FT_FACE
         #define FC_FT_FACE "ftface"
     #endif
+    #ifndef FC_EMBOLDEN
+        #define FC_EMBOLDEN "embolden"
+    #endif
 #else
     typedef void FcConfig;
     typedef void FcObjectSet;
@@ -1165,11 +1168,14 @@ public:
         if( rWrapper.isValid() )
             rWrapper.FcPatternDestroy( mpPattern );
     }
-    virtual void *GetPattern(void * face) const
+    virtual void *GetPattern(void * face, bool bEmbolden) const
     {
         FontCfgWrapper& rWrapper = FontCfgWrapper::get();
         if( rWrapper.isValid() )
+        {
             rWrapper.FcPatternAddFTFace(mpPattern, FC_FT_FACE, static_cast<FT_Face>(face));
+            rWrapper.FcPatternAddBool(mpPattern, FC_EMBOLDEN, bEmbolden ? FcTrue : FcFalse);
+        }
         return mpPattern;
     }
     FcPattern* mpPattern;

vcl/unx/source/gdi/salgdi3.cxx

@@ -271,7 +271,7 @@ private:
     void (*mp_set_font_options)(cairo_t *, const void *);
     void (*mp_ft_font_options_substitute)(const void*, void*);
 
-    bool canEmbolden() const { return false; }
+    bool canEmbolden() const { return mp_ft_font_face_create_for_pattern != NULL; }
 
     CairoWrapper();
 public:
@@ -447,9 +447,9 @@ CairoFontsCache::~CairoFontsCache()
     }
 }
 
-void CairoFontsCache::CacheFont(void *pFont, void* pId)
+void CairoFontsCache::CacheFont(void *pFont, const CairoFontsCache::CacheId &rId)
 {
-    maLRUFonts.push_front( std::pair<void*, void *>(pFont, pId) );
+    maLRUFonts.push_front( std::pair<void*, CairoFontsCache::CacheId>(pFont, rId) );
     if (maLRUFonts.size() > 8)
     {
         CairoWrapper &rCairo = CairoWrapper::get();
@@ -458,11 +458,11 @@ void CairoFontsCache::CacheFont(void *pFont, void* pId)
     }
 }
 
-void* CairoFontsCache::FindCachedFont(void *pId)
+void* CairoFontsCache::FindCachedFont(const CairoFontsCache::CacheId &rId)
 {
     LRUFonts::iterator aEnd = maLRUFonts.end();
     for (LRUFonts::iterator aI = maLRUFonts.begin(); aI != aEnd; ++aI)
-        if (aI->second == pId)
+        if (aI->second == rId)
             return aI->first;
     return NULL;
 }
@@ -533,17 +533,21 @@ void X11SalGraphics::DrawCairoAAFontString( const ServerFontLayout& rLayout )
 
     cairo_font_face_t* font_face = NULL;
 
-    void *pId = rFont.GetFtFace();
-    font_face = (cairo_font_face_t*)m_aCairoFontsCache.FindCachedFont(pId);
+    void* pFace = rFont.GetFtFace();
+    CairoFontsCache::CacheId aId;
+    aId.mpFace = pFace;
+    aId.mpOptions = rFont.GetFontOptions();
+    aId.mbEmbolden = rFont.NeedsArtificialBold();
+    font_face = (cairo_font_face_t*)m_aCairoFontsCache.FindCachedFont(aId);
     if (!font_face)
     {
         const ImplFontOptions *pOptions = rFont.GetFontOptions();
-        void *pPattern = pOptions ? pOptions->GetPattern(pId) : NULL;
+        void *pPattern = pOptions ? pOptions->GetPattern(pFace, aId.mbEmbolden) : NULL;
         if (pPattern)
             font_face = rCairo.ft_font_face_create_for_pattern(pPattern);
         if (!font_face)
-            font_face = rCairo.ft_font_face_create_for_ft_face(pId, rFont.GetLoadFlags());
-        m_aCairoFontsCache.CacheFont(font_face, pId);
+            font_face = rCairo.ft_font_face_create_for_ft_face(pFace, rFont.GetLoadFlags());
+        m_aCairoFontsCache.CacheFont(font_face, aId);
     }
 
     rCairo.set_font_face(cr, font_face);