fix Skia Windows text rendering

There are two cases in WinSalGraphics::DrawTextLayout(), with and
without cached glyphs:
- Cached case DeferredTextDraw() gets data as BGRA with the glyph
drawn in white, it just needs to be modulated to the proper color
and drawn.
- Uncached case DrawTextMask() gets data as BGRA with A invalid,
it must be used as mask for the color to drawn, but without
the inverse alpha VCL idiosyncracy that DrawMask() handles.

Change-Id: I05dcec994df68d5986cd85cffa42a8f9f23c42c4

7 files changed, 90 insertions, 25 deletions

diff --git a/vcl/inc/opengl/win/gdiimpl.hxx b/vcl/inc/opengl/win/gdiimpl.hxx
index 02b8b3850cab..2130654a3951 100644
--- a/vcl/inc/opengl/win/gdiimpl.hxx
+++ b/vcl/inc/opengl/win/gdiimpl.hxx
@@ -26,8 +26,8 @@ class OpenGLCompatibleDC : public CompatibleDC
 public:
     OpenGLCompatibleDC(SalGraphics &rGraphics, int x, int y, int width, int height);
 
-    virtual std::unique_ptr<Texture> getTexture() override;
-    // overload, caller must delete
+    virtual std::unique_ptr<Texture> getAsMaskTexture() override;
+    // caller must delete
     OpenGLTexture* getOpenGLTexture();
 
     virtual bool copyToTexture(Texture& aTexture) override;
@@ -68,7 +68,7 @@ public:
     virtual bool UseTextDraw() const override { return true; }
     virtual void PreDrawText() override;
     virtual void PostDrawText() override;
-    virtual void DrawMask( CompatibleDC::Texture* rTexture, Color nMaskColor, const SalTwoRect& rPosAry ) override;
+    virtual void DrawTextMask( CompatibleDC::Texture* rTexture, Color nMaskColor, const SalTwoRect& rPosAry ) override;
     using OpenGLSalGraphicsImpl::DrawMask;
     virtual void DeferredTextDraw(const CompatibleDC::Texture* pTexture, Color nMaskColor, const SalTwoRect& rPosAry) override;
 
diff --git a/vcl/inc/skia/win/gdiimpl.hxx b/vcl/inc/skia/win/gdiimpl.hxx
index bc177337b3de..6bd52b073aa5 100644
--- a/vcl/inc/skia/win/gdiimpl.hxx
+++ b/vcl/inc/skia/win/gdiimpl.hxx
@@ -28,10 +28,12 @@ class SkiaCompatibleDC : public CompatibleDC
 public:
     SkiaCompatibleDC(SalGraphics& rGraphics, int x, int y, int width, int height);
 
-    virtual std::unique_ptr<Texture> getTexture() override;
+    virtual std::unique_ptr<Texture> getAsMaskTexture() override;
 
     virtual bool copyToTexture(Texture& aTexture) override;
 
+    virtual bool wantsTextColorWhite() const override { return true; }
+
     struct Texture;
 };
 
@@ -65,8 +67,8 @@ public:
     virtual bool UseTextDraw() const override { return true; }
     virtual void PreDrawText() override;
     virtual void PostDrawText() override;
-    virtual void DrawMask(CompatibleDC::Texture* rTexture, Color nMaskColor,
-                          const SalTwoRect& rPosAry) override;
+    virtual void DrawTextMask(CompatibleDC::Texture* rTexture, Color nMaskColor,
+                              const SalTwoRect& rPosAry) override;
     virtual void DeferredTextDraw(const CompatibleDC::Texture* pTexture, Color nMaskColor,
                                   const SalTwoRect& rPosAry) override;
 
diff --git a/vcl/inc/win/salgdi.h b/vcl/inc/win/salgdi.h
index f7fb206624b5..fc12bc823b93 100644
--- a/vcl/inc/win/salgdi.h
+++ b/vcl/inc/win/salgdi.h
@@ -138,11 +138,14 @@ public:
     /// Base texture class (OpenGL and Skia will provide their implementations).
     struct Texture;
 
-    /// Obtain the texture.
-    virtual std::unique_ptr<Texture> getTexture() { abort(); };
+    /// Obtain the texture in format for WinSalGraphicsImplBase::DrawTextMask().
+    virtual std::unique_ptr<Texture> getAsMaskTexture() { abort(); };
 
     /// Copy bitmap data to the texture. Texture must be initialized and the correct size to hold the bitmap.
     virtual bool copyToTexture(Texture& /*aTexture*/) { abort(); };
+
+    /// Return true if text glyphs should be drawn as white instead of black.
+    virtual bool wantsTextColorWhite() const { return false; }
 };
 
 struct CompatibleDC::Texture
diff --git a/vcl/inc/win/wingdiimpl.hxx b/vcl/inc/win/wingdiimpl.hxx
index 2264eecf353d..84884220318f 100644
--- a/vcl/inc/win/wingdiimpl.hxx
+++ b/vcl/inc/win/wingdiimpl.hxx
@@ -39,8 +39,8 @@ public:
     virtual bool UseTextDraw() const { return false; }
     virtual void PreDrawText() {}
     virtual void PostDrawText() {}
-    virtual void DrawMask(CompatibleDC::Texture* /*rTexture*/, Color /*nMaskColor*/,
-                          const SalTwoRect& /*rPosAry*/)
+    virtual void DrawTextMask(CompatibleDC::Texture* /*rTexture*/, Color /*nMaskColor*/,
+                              const SalTwoRect& /*rPosAry*/)
     {
         abort();
     };
diff --git a/vcl/opengl/win/gdiimpl.cxx b/vcl/opengl/win/gdiimpl.cxx
index d71a03714198..bb6e5bf0a16c 100644
--- a/vcl/opengl/win/gdiimpl.cxx
+++ b/vcl/opengl/win/gdiimpl.cxx
@@ -770,7 +770,7 @@ OpenGLTexture* OpenGLCompatibleDC::getOpenGLTexture()
     return new OpenGLTexture(maRects.mnSrcWidth, maRects.mnSrcHeight, GL_BGRA, GL_UNSIGNED_BYTE, mpData);
 }
 
-std::unique_ptr<CompatibleDC::Texture> OpenGLCompatibleDC::getTexture()
+std::unique_ptr<CompatibleDC::Texture> OpenGLCompatibleDC::getAsMaskTexture()
 {
     auto ret = std::make_unique<OpenGLCompatibleDC::Texture>();
     ret->texture = OpenGLTexture(maRects.mnSrcWidth, maRects.mnSrcHeight, GL_BGRA, GL_UNSIGNED_BYTE, mpData);
@@ -881,7 +881,7 @@ void WinOpenGLSalGraphicsImpl::DeferredTextDraw(const CompatibleDC::Texture* pTe
     PostBatchDraw();
 }
 
-void WinOpenGLSalGraphicsImpl::DrawMask( CompatibleDC::Texture* pTexture, Color nMaskColor, const SalTwoRect& rPosAry )
+void WinOpenGLSalGraphicsImpl::DrawTextMask( CompatibleDC::Texture* pTexture, Color nMaskColor, const SalTwoRect& rPosAry )
 {
     assert(dynamic_cast<OpenGLCompatibleDC::Texture*>(pTexture));
     DrawMask( static_cast<OpenGLCompatibleDC::Texture*>(pTexture)->texture, nMaskColor, rPosAry );
diff --git a/vcl/skia/win/gdiimpl.cxx b/vcl/skia/win/gdiimpl.cxx
index 9a41ffc7da27..e583cea86f3c 100644
--- a/vcl/skia/win/gdiimpl.cxx
+++ b/vcl/skia/win/gdiimpl.cxx
@@ -12,6 +12,9 @@
 #include <tools/sk_app/win/WindowContextFactory_win.h>
 #include <tools/sk_app/WindowContext.h>
 
+#include <SkColorFilter.h>
+#include <SkPixelRef.h>
+
 WinSkiaSalGraphicsImpl::WinSkiaSalGraphicsImpl(WinSalGraphics& rGraphics,
                                                SalGeometryProvider* mpProvider)
     : SkiaSalGraphicsImpl(rGraphics, mpProvider)
@@ -102,18 +105,54 @@ void WinSkiaSalGraphicsImpl::PreDrawText() { preDraw(); }
 
 void WinSkiaSalGraphicsImpl::PostDrawText() { postDraw(); }
 
+SkColor toSkColor(Color color)
+{
+    return SkColorSetARGB(255 - color.GetTransparency(), color.GetRed(), color.GetGreen(),
+                          color.GetBlue());
+}
+
 void WinSkiaSalGraphicsImpl::DeferredTextDraw(const CompatibleDC::Texture* pTexture,
                                               Color aMaskColor, const SalTwoRect& rPosAry)
 {
     assert(dynamic_cast<const SkiaCompatibleDC::Texture*>(pTexture));
-    drawMask(rPosAry, static_cast<const SkiaCompatibleDC::Texture*>(pTexture)->bitmap, aMaskColor);
+    preDraw();
+    SkPaint paint;
+    // The glyph is painted as white, modulate it to be of the appropriate color.
+    // SkiaCompatibleDC::wantsTextColorWhite() ensures the glyph is white.
+    // TODO maybe other black/white in WinFontInstance::CacheGlyphToAtlas() should be swapped.
+    paint.setColorFilter(SkColorFilters::Blend(toSkColor(aMaskColor), SkBlendMode::kModulate));
+    mSurface->getCanvas()->drawBitmapRect(
+        static_cast<const SkiaCompatibleDC::Texture*>(pTexture)->bitmap,
+        SkRect::MakeXYWH(rPosAry.mnSrcX, rPosAry.mnSrcY, rPosAry.mnSrcWidth, rPosAry.mnSrcHeight),
+        SkRect::MakeXYWH(rPosAry.mnDestX, rPosAry.mnDestY, rPosAry.mnDestWidth,
+                         rPosAry.mnDestHeight),
+        &paint);
+    postDraw();
 }
 
-void WinSkiaSalGraphicsImpl::DrawMask(CompatibleDC::Texture* pTexture, Color nMaskColor,
-                                      const SalTwoRect& rPosAry)
+void WinSkiaSalGraphicsImpl::DrawTextMask(CompatibleDC::Texture* pTexture, Color nMaskColor,
+                                          const SalTwoRect& rPosAry)
 {
     assert(dynamic_cast<SkiaCompatibleDC::Texture*>(pTexture));
-    drawMask(rPosAry, static_cast<const SkiaCompatibleDC::Texture*>(pTexture)->bitmap, nMaskColor);
+    const SkBitmap& bitmap = static_cast<const SkiaCompatibleDC::Texture*>(pTexture)->bitmap;
+    preDraw();
+    SkBitmap tmpBitmap;
+    if (!tmpBitmap.tryAllocN32Pixels(bitmap.width(), bitmap.height()))
+        abort();
+    tmpBitmap.eraseColor(toSkColor(nMaskColor));
+    SkPaint paint;
+    // Draw the color with the given mask.
+    // TODO figure out the right blend mode to avoid the temporary bitmap
+    paint.setBlendMode(SkBlendMode::kDstOut);
+    SkCanvas canvas(tmpBitmap);
+    canvas.drawBitmap(bitmap, 0, 0, &paint);
+    mSurface->getCanvas()->drawBitmapRect(
+        tmpBitmap,
+        SkRect::MakeXYWH(rPosAry.mnSrcX, rPosAry.mnSrcY, rPosAry.mnSrcWidth, rPosAry.mnSrcHeight),
+        SkRect::MakeXYWH(rPosAry.mnDestX, rPosAry.mnDestY, rPosAry.mnDestWidth,
+                         rPosAry.mnDestHeight),
+        nullptr);
+    postDraw();
 }
 
 SkiaCompatibleDC::SkiaCompatibleDC(SalGraphics& rGraphics, int x, int y, int width, int height)
@@ -121,15 +160,35 @@ SkiaCompatibleDC::SkiaCompatibleDC(SalGraphics& rGraphics, int x, int y, int wid
 {
 }
 
-std::unique_ptr<CompatibleDC::Texture> SkiaCompatibleDC::getTexture()
+std::unique_ptr<CompatibleDC::Texture> SkiaCompatibleDC::getAsMaskTexture()
 {
     auto ret = std::make_unique<SkiaCompatibleDC::Texture>();
-    // TODO is this correct?
-    // TODO make copy of data?
-    if (!ret->bitmap.installPixels(SkImageInfo::Make(maRects.mnSrcWidth, maRects.mnSrcHeight,
-                                                     kBGRA_8888_SkColorType, kUnpremul_SkAlphaType),
-                                   mpData, maRects.mnSrcWidth * 4))
+    // mpData is in the BGRA format, with A unused (and set to 0), and RGB are grey,
+    // so convert it to Skia format, then to 8bit and finally use as alpha mask
+    SkBitmap tmpBitmap;
+    if (!tmpBitmap.installPixels(SkImageInfo::Make(maRects.mnSrcWidth, maRects.mnSrcHeight,
+                                                   kBGRA_8888_SkColorType, kOpaque_SkAlphaType),
+                                 mpData, maRects.mnSrcWidth * 4))
+        abort();
+    SkBitmap bitmap8;
+    if (!bitmap8.tryAllocPixels(SkImageInfo::Make(maRects.mnSrcWidth, maRects.mnSrcHeight,
+                                                  kGray_8_SkColorType, kOpaque_SkAlphaType)))
         abort();
+    SkCanvas canvas8(bitmap8);
+    SkPaint paint8;
+    paint8.setBlendMode(SkBlendMode::kSrc); // copy and convert depth
+    // The data we got is upside-down.
+    SkMatrix matrix;
+    matrix.preTranslate(0, maRects.mnSrcHeight);
+    matrix.setConcat(matrix, SkMatrix::MakeScale(1, -1));
+    canvas8.concat(matrix);
+    canvas8.drawBitmap(tmpBitmap, 0, 0, &paint8);
+    // use the 8bit data as an alpha channel
+    SkBitmap alpha;
+    alpha.setInfo(bitmap8.info().makeColorType(kAlpha_8_SkColorType), bitmap8.rowBytes());
+    alpha.setPixelRef(sk_ref_sp(bitmap8.pixelRef()), bitmap8.pixelRefOrigin().x(),
+                      bitmap8.pixelRefOrigin().y());
+    ret->bitmap = alpha;
     return ret;
 }
 
diff --git a/vcl/win/gdi/winlayout.cxx b/vcl/win/gdi/winlayout.cxx
index 06189c6a7643..cf264425ae17 100644
--- a/vcl/win/gdi/winlayout.cxx
+++ b/vcl/win/gdi/winlayout.cxx
@@ -171,7 +171,8 @@ bool WinFontInstance::CacheGlyphToAtlas(HDC hDC, HFONT hFont, int nGlyphIndex,
     auto pRT = pTxt->GetRenderTarget();
 
     ID2D1SolidColorBrush* pBrush = nullptr;
-    if (!SUCCEEDED(pRT->CreateSolidColorBrush(D2D1::ColorF(D2D1::ColorF::Black), &pBrush)))
+    D2D1::ColorF textColor = aDC->wantsTextColorWhite() ? D2D1::ColorF::White : D2D1::ColorF::Black;
+    if (!SUCCEEDED(pRT->CreateSolidColorBrush(textColor, &pBrush)))
         return false;
 
     D2D1_POINT_2F baseline = {
@@ -622,9 +623,9 @@ void WinSalGraphics::DrawTextLayout(const GenericSalLayout& rLayout)
         // the actual drawing
         DrawTextLayout(rLayout, aDC->getCompatibleHDC(), !bForceGDI);
 
-        std::unique_ptr<CompatibleDC::Texture> xTexture(aDC->getTexture());
+        std::unique_ptr<CompatibleDC::Texture> xTexture(aDC->getAsMaskTexture());
         if (xTexture)
-            pImpl->DrawMask(xTexture.get(), salColor, aDC->getTwoRect());
+            pImpl->DrawTextMask(xTexture.get(), salColor, aDC->getTwoRect());
 
         ::SelectFont(aDC->getCompatibleHDC(), hOrigFont);