Fix thrashing issue with multitextured atlas.

To try to reduce memory usage, the atlas will look for space in
the earliest created pages and then invalidate plots in the latest
page to try to move those plots into an earlier one. The problem
was that the available space was not being evicted, so we kept loading
data back into the latest page.

Bug: skia:
Change-Id: Ic8668f6f66bf1153dbcb5edae7622fa9edfa71dd
Reviewed-on: https://skia-review.googlesource.com/98801
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/samplecode/SampleChineseFling.cpp b/samplecode/SampleChineseFling.cpp
index ef86747..76222e9 100644
--- a/samplecode/SampleChineseFling.cpp
+++ b/samplecode/SampleChineseFling.cpp
@@ -130,7 +130,7 @@
 
 class ChineseZoomView : public SampleView {
 public:
-    ChineseZoomView() : fBlobs(kNumBlobs), fScale(1.0f) {}
+    ChineseZoomView() : fBlobs(kNumBlobs), fScale(15.0f), fTranslate(0.0f) {}
 
 protected:
     bool onQuery(SkEvent* evt) override {
@@ -153,6 +153,7 @@
     }
 
     void onDrawContent(SkCanvas* canvas) override {
+        bool afterFirstFrame = fInitialized;
         if (!fInitialized) {
             this->init();
             fInitialized = true;
@@ -167,26 +168,30 @@
         paint.setTextSize(11);
         paint.setTextEncoding(SkPaint::kUTF32_TextEncoding);
 
+        if (afterFirstFrame) {
 #if SK_SUPPORT_GPU
-        GrContext* grContext = canvas->getGrContext();
-        if (grContext) {
-            sk_sp<SkImage> image =
-            grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 0);
-            canvas->drawImageRect(image,
-                                  SkRect::MakeXYWH(512.0f, 10.0f, 512.0f, 512.0), &paint);
-            image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 1);
-            canvas->drawImageRect(image,
-                                  SkRect::MakeXYWH(1024.0f, 10.0f, 512.f, 512.0f), &paint);
-            image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 2);
-            canvas->drawImageRect(image,
-                                  SkRect::MakeXYWH(512.0f, 522.0f, 512.0f, 512.0f), &paint);
-            image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 3);
-            canvas->drawImageRect(image,
-                                  SkRect::MakeXYWH(1024.0f, 522.0f, 512.0f, 512.0f), &paint);
-        }
+            GrContext* grContext = canvas->getGrContext();
+            if (grContext) {
+                sk_sp<SkImage> image =
+                grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 0);
+                canvas->drawImageRect(image,
+                                      SkRect::MakeXYWH(10.0f, 10.0f, 512.0f, 512.0), &paint);
+                image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 1);
+                canvas->drawImageRect(image,
+                                      SkRect::MakeXYWH(522.0f, 10.0f, 512.f, 512.0f), &paint);
+                image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 2);
+                canvas->drawImageRect(image,
+                                      SkRect::MakeXYWH(10.0f, 522.0f, 512.0f, 512.0f), &paint);
+                image = grContext->getFontAtlasImage_ForTesting(GrMaskFormat::kA8_GrMaskFormat, 3);
+                canvas->drawImageRect(image,
+                                      SkRect::MakeXYWH(522.0f, 522.0f, 512.0f, 512.0f), &paint);
+            }
 #endif
+        }
 
         canvas->scale(fScale, fScale);
+        canvas->translate(0, fTranslate);
+        fTranslate -= 0.5f;
 
         // draw a consistent run of the 'words' - one word per line
         SkScalar y = 0;
@@ -247,6 +252,7 @@
     SkTArray<sk_sp<SkTextBlob>> fBlobs;
     SkRandom                    fRand;
     SkScalar                    fScale;
+    SkScalar                    fTranslate;
     int                         fIndex;
 
     typedef SkView INHERITED;
diff --git a/src/gpu/GrDrawOpAtlas.cpp b/src/gpu/GrDrawOpAtlas.cpp
index b2780e6..0f18325 100644
--- a/src/gpu/GrDrawOpAtlas.cpp
+++ b/src/gpu/GrDrawOpAtlas.cpp
@@ -371,7 +371,7 @@
     // a blinking cursor is drawn.
     // TODO: consider if we should also do this if it's been a long time since the last atlas use
     if (atlasUsedThisFlush) {
-        int availablePlots = 0;
+        SkTArray<Plot*> availablePlots;
         uint32_t lastPageIndex = fNumPages - 1;
 
         // For all plots but the last one, update number of flushes since used, and check to see
@@ -400,7 +400,7 @@
                 // Count plots we can potentially upload to in all pages except the last one
                 // (the potential compactee).
                 if (plot->flushesSinceLastUsed() > kRecentlyUsedCount) {
-                    ++availablePlots;
+                    availablePlots.push_back() = plot;
                 }
 
                 plotIter.next();
@@ -439,9 +439,10 @@
                 // see if there's room in an earlier page and if so evict.
                 // We need to be somewhat harsh here so that one plot that is consistently in use
                 // doesn't end up locking the page in memory.
-                if (availablePlots) {
+                if (availablePlots.count() > 0) {
                     this->processEvictionAndResetRects(plot);
-                    --availablePlots;
+                    this->processEvictionAndResetRects(availablePlots.back());
+                    availablePlots.pop_back();
                 }
             } else if (plot->lastUseToken() != GrDeferredUploadToken::AlreadyFlushedToken()) {
                 // otherwise if aged out just evict it.