change kMedium_SkFilterQuality to never pop if we're scaling

src/core/SkBitmapProcState.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapCache.h"
 #include "SkBitmapController.h"
 #include "SkBitmapProcState.h"
@@ skipping 115 matching lines @@
  *    - else we downgrade to the next lower level and try again.
  *  We can always fulfill requests for Low and None
  *  - sometimes we will "ignore" Low and give None, but this is likely a legacy perf hack
  *    and may be removed.
  */
 bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
     fPixmap.reset();
     fInvMatrix = inv;
     fFilterLevel = paint.getFilterQuality();
 
+    const int origW = fProvider.info().width();
+    const int origH = fProvider.info().height();
+    bool allow_ignore_fractional_translate = true;  // historical default
+#ifndef SK_SUPPORT_LEGACY_TRANSLATEROUNDHACK
+    if (kMedium_SkFilterQuality == fFilterLevel) {
+        allow_ignore_fractional_translate = false;
+    }
+#endif
+
     SkDefaultBitmapController controller;
     fBMState = controller.requestBitmap(fProvider, inv, paint.getFilterQuality(),
                                         fBMStateStorage.get(), fBMStateStorage.size());
     // Note : we allow the controller to return an empty (zero-dimension) result. Should we?
     if (nullptr == fBMState || fBMState->pixmap().info().isEmpty()) {
         return false;
     }
     fPixmap = fBMState->pixmap();
     fInvMatrix = fBMState->invMatrix();
     fFilterLevel = fBMState->quality();
@@ skipping 18 matching lines @@
     // to see if we're really close to a no-scale matrix.  If so, explicitly
     // set it to be so.  Subsequent code may inspect this matrix to choose
     // a faster path in this case.
 
     // This code will only execute if the matrix has some scale component;
     // if it's already pure translate then we won't do this inversion.
 
     if (matrix_only_scale_translate(fInvMatrix)) {
         SkMatrix forward;
         if (fInvMatrix.invert(&forward)) {
-            if (clampClamp ? just_trans_clamp(forward, fPixmap)
+            if ((clampClamp && allow_ignore_fractional_translate)
+                           ? just_trans_clamp(forward, fPixmap)
                            : just_trans_general(forward)) {
 #ifdef SK_SUPPORT_LEGACY_TRANSLATEROUNDHACK
                 SkScalar tx = -SkScalarRoundToScalar(forward.getTranslateX());
                 SkScalar ty = -SkScalarRoundToScalar(forward.getTranslateY());
                 fInvMatrix.setTranslate(tx, ty);
 #else
                 fInvMatrix.setTranslate(-forward.getTranslateX(), -forward.getTranslateY());
 #endif
             }
         }
@@ skipping 10 matching lines @@
 
     fShaderProc32 = nullptr;
     fShaderProc16 = nullptr;
     fSampleProc32 = nullptr;
 
     // recompute the triviality of the matrix here because we may have
     // changed it!
 
     trivialMatrix = (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask) == 0;
 
-    if (kLow_SkFilterQuality == fFilterLevel) {
+    // If our target pixmap is the same as the original, then we revert back to legacy behavior
+    // and allow the code to ignore fractional translate.
+    //
+    // The width/height check allows allow_ignore_fractional_translate to stay false if we
+    // previously set it that way (e.g. we started in kMedium).
+    //
+    if (fPixmap.width() == origW && fPixmap.height() == origH) {
+        allow_ignore_fractional_translate = true;
+    }
+
+    if (kLow_SkFilterQuality == fFilterLevel && allow_ignore_fractional_translate) {
         // Only try bilerp if the matrix is "interesting" and
         // the image has a suitable size.
 
         if (fInvType <= SkMatrix::kTranslate_Mask ||
             !valid_for_filtering(fPixmap.width() | fPixmap.height()))
         {
             fFilterLevel = kNone_SkFilterQuality;
         }
     }
 
@@ skipping 587 matching lines @@
             fx += dx;
         }
     } else {
         for (int i = 0; i < count; ++i) {
             dst[i] = src[SkClampMax(SkFractionalIntToInt(fx), maxX)];
             fx += dx;
         }
     }
 }