tdf#94682 limit the number of textures for the glyph texture atlas

Previously the number of textures in a packed texture atlas was
not limited. After some time the number of the textures could
grow quite a lot, however the first textures could contain very
little glyphs that are valid. In this commit we add a new method
ReduceTextureNumber which when called, reduces the number of
textures that are tracked by the texutre atlas to the specified
input number, and returnes the texture IDs that were removed so
the caller can now clean-up any invalid (OpenGLTexutre) objects.

Change-Id: I7790e8dddb4586167f860e0ecc81bda1f4dae21a
Reviewed-on: https://gerrit.libreoffice.org/24071
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>

3 files changed, 96 insertions, 11 deletions

diff --git a/vcl/inc/opengl/PackedTextureAtlas.hxx b/vcl/inc/opengl/PackedTextureAtlas.hxx
index 17501f368208..4d9015f33572 100644
--- a/vcl/inc/opengl/PackedTextureAtlas.hxx
+++ b/vcl/inc/opengl/PackedTextureAtlas.hxx
@@ -35,10 +35,16 @@ class VCL_PLUGIN_PUBLIC PackedTextureAtlasManager
     void CreateNewTexture();
 
 public:
+
+    /**
+     * nTextureWidth and nTextureHeight are the dimensions of the common texture(s)
+     * nTextureLimit is the maximum limit of that a texture atlas can have (0 or less - unlimited)
+     */
     PackedTextureAtlasManager(int nTextureWidth, int nTextureHeight);
     ~PackedTextureAtlasManager();
     OpenGLTexture InsertBuffer(int nWidth, int nHeight, int nFormat, int nType, sal_uInt8* pData);
     OpenGLTexture Reserve(int nWidth, int nHeight);
+    std::vector<GLuint> ReduceTextureNumber(int nMaxNumberOfTextures);
 };
 
 #endif // INCLUDED_VCL_INC_OPENGL_PACKEDTEXTUREATLAS_HXX
diff --git a/vcl/opengl/PackedTextureAtlas.cxx b/vcl/opengl/PackedTextureAtlas.cxx
index 60fa1e98fc41..0231cbdda530 100644
--- a/vcl/opengl/PackedTextureAtlas.cxx
+++ b/vcl/opengl/PackedTextureAtlas.cxx
@@ -24,12 +24,21 @@ struct Node
     std::unique_ptr<Node> mRightNode;
     bool mOccupied;
 
+    Node(int nWidth, int nHeight);
+
     Node(Rectangle& aRectangle);
 
     bool isLeaf();
     Node* insert(int nWidth, int nHeight, int nPadding);
 };
 
+Node::Node(int nWidth, int nHeight)
+    : mRectangle(Rectangle(Point(), Size(nWidth, nHeight)))
+    , mLeftNode()
+    , mRightNode()
+    , mOccupied(false)
+{}
+
 Node::Node(Rectangle& aRectangle)
     : mRectangle(aRectangle)
     , mLeftNode()
@@ -101,8 +110,15 @@ Node* Node::insert(int nWidth, int nHeight, int nPadding)
 
 struct PackedTexture
 {
-    std::unique_ptr<Node> mpRootNode;
     ImplOpenGLTexture* mpTexture;
+    std::unique_ptr<Node> mpRootNode;
+    int mnDeallocatedArea;
+
+    PackedTexture(int nWidth, int nHeight)
+        : mpTexture(new ImplOpenGLTexture(nWidth, nHeight, true))
+        , mpRootNode(new Node(nWidth, nHeight))
+        , mnDeallocatedArea(0)
+    {}
 };
 
 PackedTextureAtlasManager::PackedTextureAtlasManager(int nTextureWidth, int nTextureHeight)
@@ -116,18 +132,17 @@ PackedTextureAtlasManager::~PackedTextureAtlasManager()
     for (std::unique_ptr<PackedTexture>& pPackedTexture : maPackedTextures)
     {
         // Free texture early in VCL shutdown while we have a context.
-        pPackedTexture->mpTexture->Dispose();
-        pPackedTexture->mpTexture->DecreaseRefCount(0);
+        delete pPackedTexture->mpTexture;
     }
 }
 
 void PackedTextureAtlasManager::CreateNewTexture()
 {
-    std::unique_ptr<PackedTexture> pPackedTexture(new PackedTexture);
-    pPackedTexture->mpTexture = new ImplOpenGLTexture(mnTextureWidth, mnTextureHeight, true);
-    Rectangle aInitialRect(Point(0, 0), Size(mnTextureWidth, mnTextureHeight));
-    pPackedTexture->mpRootNode.reset(new Node(aInitialRect));
+    std::unique_ptr<PackedTexture> pPackedTexture(new PackedTexture(mnTextureWidth, mnTextureHeight));
+    GLuint nTextureID = pPackedTexture->mpTexture->mnTexture;
     maPackedTextures.push_back(std::move(pPackedTexture));
+    VCL_GL_INFO("PackedTextureAtlas::CreateNewTexture adding texture: " << nTextureID <<
+                " atlases: " << maPackedTextures.size());
 }
 
 OpenGLTexture PackedTextureAtlasManager::Reserve(int nWidth, int nHeight)
@@ -161,4 +176,19 @@ OpenGLTexture PackedTextureAtlasManager::InsertBuffer(int nWidth, int nHeight, i
     return aTexture;
 }
 
+std::vector<GLuint> PackedTextureAtlasManager::ReduceTextureNumber(int nMaxNumberOfTextures)
+{
+    std::vector<GLuint> aTextureIDs;
+    while (int(maPackedTextures.size()) > nMaxNumberOfTextures)
+    {
+        // Remove oldest created texture
+        GLuint nTextureID = maPackedTextures[0]->mpTexture->mnTexture;
+        aTextureIDs.push_back(nTextureID);
+        maPackedTextures.erase(maPackedTextures.begin());
+        VCL_GL_INFO("PackedTextureAtlas::ReduceTextureNumber removing texture: " << nTextureID <<
+                    " atlases: " << maPackedTextures.size());
+    }
+    return aTextureIDs;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/win/source/gdi/winlayout.cxx b/vcl/win/source/gdi/winlayout.cxx
index 49aa0c4a3034..f5b3a6ba8f2d 100644
--- a/vcl/win/source/gdi/winlayout.cxx
+++ b/vcl/win/source/gdi/winlayout.cxx
@@ -48,6 +48,7 @@
 #include <winver.h>
 
 #include <unordered_map>
+#include <unordered_set>
 
 typedef std::unordered_map<int,int> IntMap;
 
@@ -97,19 +98,66 @@ struct OpenGLGlyphDrawElement
     }
 };
 
+class GlyphCache;
+
+struct GlobalGlyphCache
+{
+    GlobalGlyphCache()
+        : maPackedTextureAtlas(2048, 2048)
+    {}
+
+    PackedTextureAtlasManager maPackedTextureAtlas;
+    std::unordered_set<GlyphCache*> maGlyphCaches;
+};
+
 class GlyphCache
 {
 private:
-    static PackedTextureAtlasManager sPackedTextureAtlas;
+    static std::unique_ptr<GlobalGlyphCache> gGlobalGlyphCache;
     std::unordered_map<int, OpenGLGlyphDrawElement> maOpenGLTextureCache;
 
 public:
     GlyphCache()
-    {}
+    {
+        gGlobalGlyphCache.get()->maGlyphCaches.insert(this);
+    }
+
+    ~GlyphCache()
+    {
+        gGlobalGlyphCache.get()->maGlyphCaches.erase(this);
+    }
 
     void ReserveTextureSpace(OpenGLGlyphDrawElement& rElement, int nWidth, int nHeight)
     {
-        rElement.maTexture = sPackedTextureAtlas.Reserve(nWidth, nHeight);
+        GlobalGlyphCache* pGlobalGlyphCache = gGlobalGlyphCache.get();
+        rElement.maTexture = pGlobalGlyphCache->maPackedTextureAtlas.Reserve(nWidth, nHeight);
+        std::vector<GLuint> aTextureIDs = pGlobalGlyphCache->maPackedTextureAtlas.ReduceTextureNumber(8);
+        if (!aTextureIDs.empty())
+        {
+            for (auto& pGlyphCache: pGlobalGlyphCache->maGlyphCaches)
+            {
+                pGlyphCache->RemoveTextures(aTextureIDs);
+            }
+        }
+    }
+
+    void RemoveTextures(std::vector<GLuint>& rTextureIDs)
+    {
+        auto it = maOpenGLTextureCache.begin();
+
+        while (it != maOpenGLTextureCache.end())
+        {
+            GLuint nTextureID = it->second.maTexture.Id();
+
+            if (std::find(rTextureIDs.begin(), rTextureIDs.end(), nTextureID) != rTextureIDs.end())
+            {
+                it = maOpenGLTextureCache.erase(it);
+            }
+            else
+            {
+                it++;
+            }
+        }
     }
 
     void PutDrawElementInCache(const OpenGLGlyphDrawElement& rElement, int nGlyphIndex)
@@ -130,7 +178,8 @@ public:
     }
 };
 
-PackedTextureAtlasManager GlyphCache::sPackedTextureAtlas(2048, 2048);
+// static initialization
+std::unique_ptr<GlobalGlyphCache> GlyphCache::gGlobalGlyphCache(new GlobalGlyphCache);
 
 // win32 specific physical font instance
 class ImplWinFontEntry : public ImplFontEntry