implement pruning in SkiaGlobalWinGlyphCache

Currently based on identifying the SkBitmap's by their getPixels(),
but this may need changed later since it's probably going to be
more performant to use SkSurface.
Also move the cache pruning out of AllocateTexture(), as that may
possibly remove elements that would be used by DrawCachedGlyphs().

Change-Id: Ide2de752f634593b97573667af49b7aa9ec1f47f

1 files changed, 42 insertions, 1 deletions

diff --git a/vcl/skia/win/winlayout.cxx b/vcl/skia/win/winlayout.cxx
index bd232c1d2bbf..5b38b0e63f81 100644
--- a/vcl/skia/win/winlayout.cxx
+++ b/vcl/skia/win/winlayout.cxx
@@ -17,10 +17,51 @@ bool SkiaGlobalWinGlyphCache::AllocateTexture(WinGlyphDrawElement& rElement, int
     assert(rElement.maTexture.get() == nullptr);
     SkiaCompatibleDC::Texture* texture = new SkiaCompatibleDC::Texture;
     rElement.maTexture.reset(texture);
+    // TODO use something GPU-backed?
+    // TODO is it possible to have an atlas?
     if (!texture->bitmap.tryAllocN32Pixels(nWidth, nHeight))
         return false;
-    // TODO prune cache
+    mLRUOrder.push_back(texture->bitmap.getPixels());
     return true;
 }
 
+void SkiaGlobalWinGlyphCache::Prune()
+{
+    const int MAXSIZE = 64; // TODO
+    if (mLRUOrder.size() > MAXSIZE)
+    {
+        size_t toRemove = mLRUOrder.size() - MAXSIZE;
+        std::vector<void*> pixelsToRemove(mLRUOrder.begin(), mLRUOrder.begin() + toRemove);
+        mLRUOrder.erase(mLRUOrder.begin(), mLRUOrder.begin() + toRemove);
+        for (auto& pWinGlyphCache : maWinGlyphCaches)
+            static_cast<SkiaWinGlyphCache*>(pWinGlyphCache)->RemoveTextures(pixelsToRemove);
+    }
+}
+
+void SkiaGlobalWinGlyphCache::NotifyElementUsed(WinGlyphDrawElement& rElement)
+{
+    SkiaCompatibleDC::Texture* texture
+        = static_cast<SkiaCompatibleDC::Texture*>(rElement.maTexture.get());
+    // make the most recently used
+    auto it = find(mLRUOrder.begin(), mLRUOrder.end(), texture->bitmap.getPixels());
+    if (it != mLRUOrder.end())
+        mLRUOrder.erase(it);
+    mLRUOrder.push_back(texture->bitmap.getPixels());
+}
+
+void SkiaWinGlyphCache::RemoveTextures(const std::vector<void*>& pixelsToRemove)
+{
+    auto it = maWinTextureCache.begin();
+    while (it != maWinTextureCache.end())
+    {
+        assert(dynamic_cast<SkiaCompatibleDC::Texture*>(it->second.maTexture.get()));
+        void* pixels = static_cast<SkiaCompatibleDC::Texture*>(it->second.maTexture.get())
+                           ->bitmap.getPixels();
+        if (std::find(pixelsToRemove.begin(), pixelsToRemove.end(), pixels) != pixelsToRemove.end())
+            it = maWinTextureCache.erase(it);
+        else
+            ++it;
+    }
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */