New approach for GPU font atlas

src/gpu/GrAtlas.cpp

Index: src/gpu/GrAtlas.cpp
diff --git a/src/gpu/GrAtlas.cpp b/src/gpu/GrAtlas.cpp
index 646c213b8675a738aa190daeece4ebc2088f49ab..775bd1285a626e0c702681f11827135e5205fb5d 100644
--- a/src/gpu/GrAtlas.cpp
+++ b/src/gpu/GrAtlas.cpp
@@ -46,6 +46,7 @@ static int g_UploadCount = 0;
 #endif
 
 GrPlot::GrPlot() : fDrawToken(NULL, 0)
+                 , fPrev(NULL)
                  , fNext(NULL)
                  , fTexture(NULL)
                  , fAtlasMgr(NULL)
@@ -94,6 +95,11 @@ bool GrPlot::addSubImage(int width, int height, const void* image,
     return true;
 }
 
+void GrPlot::resetRects() { 
+    SkASSERT(NULL != fRects); 
+    fRects->reset(); 
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 GrAtlasMgr::GrAtlasMgr(GrGpu* gpu, GrPixelConfig config) {
@@ -105,7 +111,9 @@ GrAtlasMgr::GrAtlasMgr(GrGpu* gpu, GrPixelConfig config) {
     // set up allocated plots
     size_t bpp = GrBytesPerPixel(fPixelConfig);
     fPlots = SkNEW_ARRAY(GrPlot, (GR_PLOT_WIDTH*GR_PLOT_HEIGHT));
-    fFreePlots = NULL;
+    fHead = NULL;
+    fTail = NULL;
+
     GrPlot* currPlot = fPlots;
     for (int y = GR_PLOT_HEIGHT-1; y >= 0; --y) {
         for (int x = GR_PLOT_WIDTH-1; x >= 0; --x) {
@@ -113,10 +121,16 @@ GrAtlasMgr::GrAtlasMgr(GrGpu* gpu, GrPixelConfig config) {
             currPlot->fOffset.set(x, y);
             currPlot->fBytesPerPixel = bpp;
 
-            // add to free list
-            currPlot->fNext = fFreePlots;
-            fFreePlots = currPlot;
-
+            // build LRU list
+            if (fHead == NULL) {
+                currPlot->fPrev = NULL;
+                currPlot->fNext = NULL;
+                fHead = fTail = currPlot;
+            } else {
+                currPlot->fNext = fHead;
+                fHead->fPrev = currPlot;
+                fHead = currPlot;
+            }
             ++currPlot;
         }
     }
@@ -132,25 +146,42 @@ GrAtlasMgr::~GrAtlasMgr() {
 #endif
 }
 
+void GrAtlasMgr::moveToHead(GrPlot* plot) {
+    if (NULL == plot || NULL == plot->fPrev) {

[bsalomon, 2014/02/28 16:28:53]

I wonder if we should be using SkTInternalLList

[jvanverth1, 2014/02/28 19:55:27]

Done.

+        SkASSERT(plot == fHead);
+        return;
+    }
+
+    if (plot == fTail) {
+        fTail = plot->fPrev;
+    } else {
+        plot->fNext->fPrev = plot->fPrev;
+    }
+
+    plot->fPrev->fNext = plot->fNext;
+    plot->fNext = fHead;
+    fHead->fPrev = plot;
+    fHead = plot;
+    plot->fPrev = NULL;
+    SkASSERT(plot == fHead);
+    SkASSERT(plot->fPrev == NULL);
+    SkASSERT(plot->fNext->fPrev == plot);
+}
+
 GrPlot* GrAtlasMgr::addToAtlas(GrAtlas* atlas,
                                int width, int height, const void* image,
                                GrIPoint16* loc) {
-    // iterate through entire plot list, see if we can find a hole
-    GrPlot* plotIter = atlas->fPlots;
-    while (plotIter) {
-        if (plotIter->addSubImage(width, height, image, loc)) {
-            return plotIter;
+    // iterate through entire plot list for this atlas, see if we can find a hole
+    // last one was most recently added and probably most empty
+    for (int i = atlas->fPlots.count()-1; i >= 0; --i) {
+        GrPlot* plot = atlas->fPlots[i];
+        if (plot->addSubImage(width, height, image, loc)) {
+            moveToHead(plot);

[bsalomon, 2014/02/28 16:28:53]

this->

[jvanverth1, 2014/02/28 19:55:27]

Done.

+            return plot;
         }
-        plotIter = plotIter->fNext;
-    }
-
-    // If the above fails, then either we have no starting plot, or the current
-    // plot list is full. Either way we need to allocate a new plot
-    GrPlot* newPlot = this->allocPlot();
-    if (NULL == newPlot) {
-        return NULL;
     }
 
+    // before we get a new plot, make sure we have a backing texture
     if (NULL == fTexture) {
         // TODO: Update this to use the cache rather than directly creating a texture.
         GrTextureDesc desc;
@@ -164,77 +195,49 @@ GrPlot* GrAtlasMgr::addToAtlas(GrAtlas* atlas,
             return NULL;
         }
     }
-    // be sure to set texture for fast lookup
-    newPlot->fTexture = fTexture;
 
-    if (!newPlot->addSubImage(width, height, image, loc)) {
-        this->freePlot(newPlot);
-        return NULL;
+    // now look through all allocated plots for one we can share, in MRU order
+    GrPlot* plotIter = fHead;
+    while (plotIter) {
+        // make sure texture is set for quick lookup
+        plotIter->fTexture = fTexture;
+        if (plotIter->addSubImage(width, height, image, loc)) {
+            moveToHead(plotIter);
+            // new plot for atlas, put at end of array
+            *(atlas->fPlots.append()) = plotIter;
+            return plotIter;
+        }
+        plotIter = plotIter->fNext;
     }
 
-    // new plot, put at head
-    newPlot->fNext = atlas->fPlots;
-    atlas->fPlots = newPlot;
-
-    return newPlot;
+    // If the above fails, then the current plot list has no room
+    return NULL;
 }
 
-bool GrAtlasMgr::removeUnusedPlots(GrAtlas* atlas) {
-
-    // GrPlot** is used so that the head element can be easily
-    // modified when the first element is deleted
-    GrPlot** plotRef = &atlas->fPlots;
-    GrPlot* plot = atlas->fPlots;
-    bool removed = false;
-    while (NULL != plot) {
-        if (plot->drawToken().isIssued()) {
-            *plotRef = plot->fNext;
-            this->freePlot(plot);
-            plot = *plotRef;
-            removed = true;
-        } else {
-            plotRef = &plot->fNext;
-            plot = plot->fNext;
+bool GrAtlasMgr::removePlot(GrAtlas* atlas, const GrPlot* plot) {
+    // iterate through plot list for this atlas
+    int count = atlas->fPlots.count();
+    for (int i = 0; i < count; ++i) {
+        if (plot == atlas->fPlots[i]) {
+            atlas->fPlots.remove(i);
+            return true;
         }
     }
 
-    return removed;
-}
-
-void GrAtlasMgr::deletePlotList(GrPlot* plot) {
-    while (NULL != plot) {
-        GrPlot* next = plot->fNext;
-        this->freePlot(plot);
-        plot = next;
-    }
+    return false;
 }
 
-GrPlot* GrAtlasMgr::allocPlot() {
-    if (NULL == fFreePlots) {
-        return NULL;
-    } else {
-        GrPlot* alloc = fFreePlots;
-        fFreePlots = alloc->fNext;
-#ifdef SK_DEBUG
-//        GrPrintf(" GrPlot %p [%d %d] %d\n", this, alloc->fOffset.fX, alloc->fOffset.fY, gCounter);
-        gCounter += 1;
-#endif
-        return alloc;
+// get a plot that only contains drawn content
+GrPlot* GrAtlasMgr::getUnusedPlot() {
+    GrPlot* plotIter = fTail;
+    while (plotIter) {
+        if (plotIter->drawToken().isIssued()) {
+            return plotIter;
+        }
+        plotIter = plotIter->fPrev;
     }
 
-}
-
-void GrAtlasMgr::freePlot(GrPlot* plot) {
-    SkASSERT(this == plot->fAtlasMgr);
-
-    plot->fRects->reset();
-    plot->fNext = fFreePlots;
-    fFreePlots = plot;
-
-#ifdef SK_DEBUG
-    --gCounter;
-//    GrPrintf("~GrPlot %p [%d %d] %d\n", this, plot->fOffset.fX, plot->fOffset.fY, gCounter);
-#endif
+    return NULL;
 }
 
 SkISize GrAtlas::getSize() const {