optimize Bitmap::Erase() for Skia by delaying the erase (tdf#134363)

Tdf#134363 causes OutputDevice::DrawTransformBitmapExDirect()
to create a huge 1bpp bitmap as mask, and Skia code then tries
to convert all the bits to a format Skia would understand. Which
is wasteful, as SkShader with the color given will do the same
task much more efficiently.

Change-Id: If0bba16f56fed9c3720be801b25a1e703054ed8d
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/97488
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

3 files changed, 25 insertions, 1 deletions

diff --git a/vcl/inc/salbmp.hxx b/vcl/inc/salbmp.hxx
index 4244ae1a376f..ab16b317d7eb 100644
--- a/vcl/inc/salbmp.hxx
+++ b/vcl/inc/salbmp.hxx
@@ -86,6 +86,11 @@ public:
         return false;
     }
 
+    virtual bool            Erase( const Color& /*color*/ )
+    {
+        return false;
+    }
+
     void GetChecksum(BitmapChecksum& rChecksum) const
     {
         updateChecksum();
diff --git a/vcl/inc/skia/gdiimpl.hxx b/vcl/inc/skia/gdiimpl.hxx
index 73fbee394072..c98038807287 100644
--- a/vcl/inc/skia/gdiimpl.hxx
+++ b/vcl/inc/skia/gdiimpl.hxx
@@ -200,10 +200,14 @@ public:
 #endif
 
     // Default blend mode for SkPaint is SkBlendMode::kSrcOver
+    void drawBitmap(const SalTwoRect& rPosAry, const SkiaSalBitmap& bitmap,
+                    SkBlendMode blendMode = SkBlendMode::kSrcOver);
+
     void drawImage(const SalTwoRect& rPosAry, const sk_sp<SkImage>& aImage,
                    SkBlendMode eBlendMode = SkBlendMode::kSrcOver);
 
-    void drawShader(const SalTwoRect& rPosAry, const sk_sp<SkShader>& shader);
+    void drawShader(const SalTwoRect& rPosAry, const sk_sp<SkShader>& shader,
+                    SkBlendMode blendMode = SkBlendMode::kSrcOver);
 
     enum class GlyphOrientation
     {
diff --git a/vcl/inc/skia/salbmp.hxx b/vcl/inc/skia/salbmp.hxx
index d5491e367700..4ee6e4908ee7 100644
--- a/vcl/inc/skia/salbmp.hxx
+++ b/vcl/inc/skia/salbmp.hxx
@@ -59,13 +59,24 @@ public:
                          sal_uInt8 nTol) override;
     virtual bool InterpretAs8Bit() override;
     virtual bool ConvertToGreyscale() override;
+    virtual bool Erase(const Color& color) override;
 
     const BitmapPalette& Palette() const { return mPalette; }
+
+    // True if GetSkShader() should be preferred to GetSkImage() (or the Alpha variants).
+    bool PreferSkShader() const;
+
     // Returns the contents as SkImage (possibly GPU-backed).
     const sk_sp<SkImage>& GetSkImage() const;
+    sk_sp<SkShader> GetSkShader() const;
 
     // Returns the contents as alpha SkImage (possibly GPU-backed)
     const sk_sp<SkImage>& GetAlphaSkImage() const;
+    sk_sp<SkShader> GetAlphaSkShader() const;
+
+    // Key for caching/hashing.
+    OString GetImageKey() const;
+    OString GetAlphaImageKey() const;
 
 #ifdef DBG_UTIL
     void dump(const char* file) const;
@@ -86,6 +97,7 @@ private:
     void EnsureBitmapUniqueData();
     // Allocate mBuffer (with uninitialized contents).
     bool CreateBitmapData();
+    void EraseInternal();
     SkBitmap GetAsSkBitmap() const;
 #ifdef DBG_UTIL
     void verify() const;
@@ -126,6 +138,9 @@ private:
     // data in mBuffer, if it differs from mSize, then there is a scaling operation pending.
     Size mPixelsSize;
     SkFilterQuality mScaleQuality = kHigh_SkFilterQuality; // quality for on-demand scaling
+    // Erase() is delayed, just sets these two instead of filling the buffer.
+    bool mEraseColorSet = false;
+    Color mEraseColor;
 #ifdef DBG_UTIL
     int mWriteAccessCount = 0; // number of write AcquireAccess() that have not been released
 #endif