(disabled) Initial work for OpenGL glyph caching on Windows

Shows text roughly correctly, but many problems. Conditional at
run-time on the SAL_ENABLE_GLYPH_CACHING environment variable in
addition to SAL_FORCEGL.

One obvious thing that needs fixing is making sure that the glyphs are
rendered into the texture without overlap. Compensating negative
values in the ABC::abcA and ABC::abdC width is not enough.

Also, the cache should be changed to actually have "cache"
functionality, i.e. entries should expire based on some criterion.

Change-Id: I66a37d3354a09011a654f15a7d2bd8efaa14ad1e
Signed-off-by: Michael Meeks <michael.meeks@collabora.com>

vcl/inc/win/salgdi.h

@@ -187,6 +187,7 @@ class WinSalGraphics : public SalGraphics
     friend class ScopedFont;
     friend class OpenGLCompatibleDC;
     friend class WinLayout;
+    friend class UniscribeLayout;
 
 protected:
     std::unique_ptr<SalGraphicsImpl> mpImpl;

vcl/win/source/gdi/winlayout.hxx

@@ -54,7 +54,9 @@ public:
     /// Draw to the provided HDC.
     virtual void        DrawTextImpl(HDC hDC) const = 0;
 
-protected:
+    virtual bool        CacheGlyphs(SalGraphics& rGraphics) const = 0;
+    virtual bool        DrawCachedGlyphs(SalGraphics& rGraphics) const = 0;
+
     HDC                 mhDC;               // WIN32 device handle
     HFONT               mhFont;             // WIN32 font handle
     int                 mnBaseAdv;          // x-offset relative to Layout origin
@@ -73,6 +75,8 @@ public:
     virtual bool    LayoutText( ImplLayoutArgs& ) SAL_OVERRIDE;
     virtual void    AdjustLayout( ImplLayoutArgs& ) SAL_OVERRIDE;
     virtual void    DrawTextImpl(HDC hDC) const SAL_OVERRIDE;
+    virtual bool    CacheGlyphs(SalGraphics& rGraphics) const SAL_OVERRIDE;
+    virtual bool    DrawCachedGlyphs(SalGraphics& rGraphics) const SAL_OVERRIDE;
     virtual int     GetNextGlyphs( int nLen, sal_GlyphId* pGlyphs, Point& rPos, int&,
                                    DeviceCoordinate* pGlyphAdvances, int* pCharPosAry,
                                    const PhysicalFontFace** pFallbackFonts = NULL ) const SAL_OVERRIDE;
@@ -160,6 +164,8 @@ public:
     virtual bool  LayoutText( ImplLayoutArgs& ) SAL_OVERRIDE;    // first step of layout
     virtual void  AdjustLayout( ImplLayoutArgs& ) SAL_OVERRIDE;  // adjusting after fallback etc.
     virtual void  DrawTextImpl(HDC hDC) const SAL_OVERRIDE;
+    virtual bool  CacheGlyphs(SalGraphics& rGraphics) const SAL_OVERRIDE;
+    virtual bool  DrawCachedGlyphs(SalGraphics& rGraphics) const SAL_OVERRIDE;
 
     // methods using string indexing
     virtual sal_Int32 GetTextBreak(DeviceCoordinate nMaxWidth, DeviceCoordinate nCharExtra=0, int nFactor=1) const SAL_OVERRIDE;