Skia Filter Quality and Scaling Metrics

src/core/SkDevice.cpp

Index: src/core/SkDevice.cpp
diff --git a/src/core/SkDevice.cpp b/src/core/SkDevice.cpp
index 78aa3ee52f9bcbd2419cf69db5016b16ae1534c3..adf13ab208e9201e894361d3cd2c27825739706e 100644
--- a/src/core/SkDevice.cpp
+++ b/src/core/SkDevice.cpp
@@ -442,3 +442,55 @@ uint32_t SkBaseDevice::filterTextFlags(const SkPaint& paint) const {
     return flags;
 }
 
+//////////////////////////////////////////////////////////////////////////////////////////
+
+void SkBaseDevice::logDrawScaleFactor(const SkMatrix& matrix, SkFilterQuality filterQuality) const {
+    enum ScaleFactor {
+        kUpscale_ScaleFactor,
+        kNoScale_ScaleFactor,
+        kDownscale_ScaleFactor,
+        kLargeDownscale_ScaleFactor,
+    };
+
+    SkASSERT(filterQuality != kNone_SkFilterQuality);
+    enum { kScaleFactorCount = kLargeDownscale_ScaleFactor + 1 };
+    float raw_scale_factor = matrix.getMinScale();
+
+    ScaleFactor scale_factor;
+    if (raw_scale_factor < 0.5f) {
+        scale_factor = kLargeDownscale_ScaleFactor;
+    } else if (raw_scale_factor < 1.0f) {
+        scale_factor = kDownscale_ScaleFactor;
+    } else if (raw_scale_factor > 1.0f) {
+        scale_factor = kUpscale_ScaleFactor;
+    } else {
+        scale_factor = kNoScale_ScaleFactor;
+    }
+
+    switch (filterQuality) {
+        case kNone_SkFilterQuality:
+            SK_HISTOGRAM_ENUMERATION("DrawScaleFactor.NoneFilterQuality", scale_factor,
+                                     kScaleFactorCount);
+            break;
+        case kLow_SkFilterQuality:
+            SK_HISTOGRAM_ENUMERATION("DrawScaleFactor.LowFilterQuality", scale_factor,
+                                     kScaleFactorCount);
+            break;
+        case kMedium_SkFilterQuality:
+            SK_HISTOGRAM_ENUMERATION("DrawScaleFactor.MediumFilterQuality", scale_factor,
+                                     kScaleFactorCount);
+            break;
+        case kHigh_SkFilterQuality:
+            SK_HISTOGRAM_ENUMERATION("DrawScaleFactor.HighFilterQuality", scale_factor,
+                                     kScaleFactorCount);
+            break;
+    }
+
+    // Also log filter quality independent scale factor.
+    SK_HISTOGRAM_ENUMERATION("DrawScaleFactor.AnyFilterQuality", scale_factor, kScaleFactorCount);
+
+    // Also log an overall histogram of filter quality.
+    enum { kFilterQualityCount = kHigh_SkFilterQuality + 1 };
+    SK_HISTOGRAM_ENUMERATION("FilterQuality", filterQuality, kFilterQualityCount);
+}
+