refactor bitmapshader to use a controller

src/core/SkBitmapController.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkBitmap.h"
+#include "SkBitmapController.h"
+#include "SkMatrix.h"
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+static bool valid_for_drawing(const SkBitmap& bm) {
+    if (0 == bm.width() || 0 == bm.height()) {
+        return false;   // nothing to draw
+    }
+    if (NULL == bm.pixelRef()) {
+        return false;   // no pixels to read
+    }
+    if (bm.getTexture()) {
+        // we can handle texture (ugh) since lockPixels will perform a read-back
+        return true;
+    }
+    if (kIndex_8_SkColorType == bm.colorType()) {
+        SkAutoLockPixels alp(bm); // but we need to call it before getColorTable() is safe.
+        if (!bm.getColorTable()) {
+            return false;
+        }
+    }
+    return true;
+}
+
+SkBitmapController::State* SkBitmapController::requestBitmap(const SkBitmap& bm,
+                                                             const SkMatrix& inv,
+                                                             SkFilterQuality quality,
+                                                             void* storage, size_t storageSize) {
+    
+    if (!valid_for_drawing(bm)) {
+        return NULL;
+    }
+
+    State* state = this->onRequestBitmap(bm, inv, quality, storage, storageSize);
+    if (state) {
+        if (!state->fLockedBitmap.getPixels()) {
+            state->fLockedBitmap.lockPixels();
+            if (!state->fLockedBitmap.getPixels()) {
+                SkInPlaceDeleteCheck(state, storage);
+                state = NULL;
+            }
+        }
+    }
+    return state;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+#include "SkBitmapCache.h"
+#include "SkBitmapScaler.h"
+#include "SkMipMap.h"
+#include "SkResourceCache.h"
+
+class SkDefaultBitmapControllerState : public SkBitmapController::State {
+public:
+    SkDefaultBitmapControllerState(const SkBitmap& src, const SkMatrix& inv, SkFilterQuality qual);
+
+private:
+    SkAutoTUnref<const SkMipMap> fCurrMip;
+    
+    bool processHQRequest(const SkBitmap& orig);
+    bool processMediumRequest(const SkBitmap& orig);
+};
+
+// Check to see that the size of the bitmap that would be produced by
+// scaling by the given inverted matrix is less than the maximum allowed.
+static inline bool cache_size_okay(const SkBitmap& bm, const SkMatrix& invMat) {
+    size_t maximumAllocation = SkResourceCache::GetEffectiveSingleAllocationByteLimit();
+    if (0 == maximumAllocation) {
+        return true;
+    }
+    // float matrixScaleFactor = 1.0 / (invMat.scaleX * invMat.scaleY);
+    // return ((origBitmapSize * matrixScaleFactor) < maximumAllocationSize);
+    // Skip the division step:
+    const size_t size = bm.info().getSafeSize(bm.info().minRowBytes());
+    return size < (maximumAllocation * invMat.getScaleX() * invMat.getScaleY());
+}
+
+/*
+ *  High quality is implemented by performing up-right scale-only filtering and then
+ *  using bilerp for any remaining transformations.
+ */
+bool SkDefaultBitmapControllerState::processHQRequest(const SkBitmap& origBitmap) {
+    if (fQuality != kHigh_SkFilterQuality) {
+        return false;
+    }
+    
+    // Our default return state is to downgrade the request to Medium, w/ or w/o setting fBitmap
+    // to a valid bitmap. If we succeed, we will set this to Low instead.
+    fQuality = kMedium_SkFilterQuality;
+    
+    if (kN32_SkColorType != origBitmap.colorType() || !cache_size_okay(origBitmap, fInvMatrix) ||
+        fInvMatrix.hasPerspective())
+    {
+        return false; // can't handle the reqeust
+    }
+    
+    SkScalar invScaleX = fInvMatrix.getScaleX();
+    SkScalar invScaleY = fInvMatrix.getScaleY();
+    if (fInvMatrix.getType() & SkMatrix::kAffine_Mask) {
+        SkSize scale;
+        if (!fInvMatrix.decomposeScale(&scale)) {
+            return false;
+        }
+        invScaleX = scale.width();
+        invScaleY = scale.height();
+    }
+    if (SkScalarNearlyEqual(invScaleX, 1) && SkScalarNearlyEqual(invScaleY, 1)) {
+        return false; // no need for HQ
+    }
+    
+    SkScalar trueDestWidth  = origBitmap.width() / invScaleX;
+    SkScalar trueDestHeight = origBitmap.height() / invScaleY;
+    SkScalar roundedDestWidth = SkScalarRoundToScalar(trueDestWidth);
+    SkScalar roundedDestHeight = SkScalarRoundToScalar(trueDestHeight);
+    
+    if (!SkBitmapCache::Find(origBitmap, roundedDestWidth, roundedDestHeight, &fLockedBitmap)) {
+        if (!SkBitmapScaler::Resize(&fLockedBitmap,
+                                    origBitmap,
+                                    SkBitmapScaler::RESIZE_BEST,
+                                    roundedDestWidth,
+                                    roundedDestHeight,
+                                    SkResourceCache::GetAllocator())) {
+            return false; // we failed to create fScaledBitmap
+        }
+        
+        SkASSERT(fLockedBitmap.getPixels());
+        fLockedBitmap.setImmutable();
+        SkBitmapCache::Add(origBitmap, roundedDestWidth, roundedDestHeight, fLockedBitmap);
+    }
+    
+    SkASSERT(fLockedBitmap.getPixels());
+    
+    fInvMatrix.postScale(roundedDestWidth / origBitmap.width(),
+                         roundedDestHeight / origBitmap.height());
+    fQuality = kLow_SkFilterQuality;
+    return true;
+}
+
+/*
+ *  Modulo internal errors, this should always succeed *if* the matrix is downscaling
+ *  (in this case, we have the inverse, so it succeeds if fInvMatrix is upscaling)
+ */
+bool SkDefaultBitmapControllerState::processMediumRequest(const SkBitmap& origBitmap) {
+    SkASSERT(fQuality <= kMedium_SkFilterQuality);
+    if (fQuality != kMedium_SkFilterQuality) {
+        return false;
+    }
+    
+    // Our default return state is to downgrade the request to Low, w/ or w/o setting fBitmap
+    // to a valid bitmap.
+    fQuality = kLow_SkFilterQuality;
+    
+    SkSize invScaleSize;
+    if (!fInvMatrix.decomposeScale(&invScaleSize, NULL)) {
+        return false;
+    }
+    SkScalar invScale = SkScalarSqrt(invScaleSize.width() * invScaleSize.height());
+    
+    if (invScale > SK_Scalar1) {
+        fCurrMip.reset(SkMipMapCache::FindAndRef(origBitmap));
+        if (NULL == fCurrMip.get()) {
+            fCurrMip.reset(SkMipMapCache::AddAndRef(origBitmap));
+            if (NULL == fCurrMip.get()) {
+                return false;
+            }
+        }
+        // diagnostic for a crasher...
+        if (NULL == fCurrMip->data()) {
+            sk_throw();
+        }
+        
+        SkScalar levelScale = SkScalarInvert(invScale);
+        SkMipMap::Level level;
+        if (fCurrMip->extractLevel(levelScale, &level)) {
+            SkScalar invScaleFixup = level.fScale;
+            fInvMatrix.postScale(invScaleFixup, invScaleFixup);
+            
+            const SkImageInfo info = origBitmap.info().makeWH(level.fWidth, level.fHeight);
+            // todo: if we could wrap the fCurrMip in a pixelref, then we could just install
+            //       that here, and not need to explicitly track it ourselves.
+            return fLockedBitmap.installPixels(info, level.fPixels, level.fRowBytes);
+        } else {
+            // failed to extract, so release the mipmap
+            fCurrMip.reset(NULL);
+        }
+    }
+    return false;
+}
+
+SkDefaultBitmapControllerState::SkDefaultBitmapControllerState(const SkBitmap& src,
+                                                               const SkMatrix& inv,
+                                                               SkFilterQuality qual) {
+    fInvMatrix = inv;
+    fQuality = qual;
+
+    if (!this->processHQRequest(src) && !this->processMediumRequest(src)) {
+        fLockedBitmap = src;
+    }
+    SkASSERT(fQuality <= kLow_SkFilterQuality);
+}
+
+SkBitmapController::State* SkDefaultBitmapController::onRequestBitmap(const SkBitmap& bm,
+                                                                      const SkMatrix& inverse,
+                                                                      SkFilterQuality quality,
+                                                                      void* storage, size_t size) {
+    return SkInPlaceNewCheck<SkDefaultBitmapControllerState>(storage, size, bm, inverse, quality);
+}
+