move the guts of SkMaskFilter.h into SkMaskFilterBase.h

Bug: skia:
Change-Id: I29ad0960156562867429542d3cfbf3d639529cab
Reviewed-on: https://skia-review.googlesource.com/98802
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 251 insertions, 0 deletions

diff --git a/src/core/SkMaskFilterBase.h b/src/core/SkMaskFilterBase.h
new file mode 100644
index 0000000000..4b4b4258d6
--- /dev/null
+++ b/src/core/SkMaskFilterBase.h
@@ -0,0 +1,251 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkMaskFilterBase_DEFINED
+#define SkMaskFilterBase_DEFINED
+
+#include "SkBlurTypes.h"
+#include "SkFlattenable.h"
+#include "SkMask.h"
+#include "SkMaskFilter.h"
+#include "SkPaint.h"
+#include "SkStrokeRec.h"
+
+class GrClip;
+class GrContext;
+struct GrFPArgs;
+class GrRenderTargetContext;
+class GrPaint;
+class GrFragmentProcessor;
+class GrRenderTarget;
+class GrResourceProvider;
+class GrTexture;
+class GrTextureProxy;
+class SkBitmap;
+class SkBlitter;
+class SkCachedData;
+class SkMatrix;
+class SkPath;
+class SkRasterClip;
+class SkRRect;
+
+class SkMaskFilterBase : public SkMaskFilter {
+public:
+    /** Returns the format of the resulting mask that this subclass will return
+        when its filterMask() method is called.
+    */
+    virtual SkMask::Format getFormat() const = 0;
+
+    /** Create a new mask by filter the src mask.
+        If src.fImage == null, then do not allocate or create the dst image
+        but do fill out the other fields in dstMask.
+        If you do allocate a dst image, use SkMask::AllocImage()
+        If this returns false, dst mask is ignored.
+        @param  dst the result of the filter. If src.fImage == null, dst should not allocate its image
+        @param src the original image to be filtered.
+        @param matrix the CTM
+        @param margin   if not null, return the buffer dx/dy need when calculating the effect. Used when
+                        drawing a clipped object to know how much larger to allocate the src before
+                        applying the filter. If returning false, ignore this parameter.
+        @return true if the dst mask was correctly created.
+    */
+    virtual bool filterMask(SkMask* dst, const SkMask& src, const SkMatrix&,
+                            SkIPoint* margin) const;
+
+#if SK_SUPPORT_GPU
+    /**
+     *  Returns a processor if the filter can be expressed a single-pass GrProcessor without
+     *  requiring an explicit input mask. Per-pixel, the effect receives the incoming mask's
+     *  coverage as the input color and outputs the filtered covereage value. This means that each
+     *  pixel's filtered coverage must only depend on the unfiltered mask value for that pixel and
+     *  not on surrounding values.
+     */
+    std::unique_ptr<GrFragmentProcessor> asFragmentProcessor(const GrFPArgs& args) const;
+
+    /**
+     *  Returns true iff asFragmentProcessor() will return a processor
+     */
+    bool hasFragmentProcessor() const;
+
+    /**
+     *  If asFragmentProcessor() fails the filter may be implemented on the GPU by a subclass
+     *  overriding filterMaskGPU (declared below). That code path requires constructing a
+     *  src mask as input. Since that is a potentially expensive operation, the subclass must also
+     *  override this function to indicate whether filterTextureMaskGPU would succeeed if the mask
+     *  were to be created.
+     *
+     *  'maskRect' returns the device space portion of the mask that the filter needs. The mask
+     *  passed into 'filterMaskGPU' should have the same extent as 'maskRect' but be
+     *  translated to the upper-left corner of the mask (i.e., (maskRect.fLeft, maskRect.fTop)
+     *  appears at (0, 0) in the mask).
+     *
+     * Logically, how this works is:
+     *    canFilterMaskGPU is called
+     *    if (it returns true)
+     *        the returned mask rect is used for quick rejecting
+     *        either directFilterMaskGPU or directFilterRRectMaskGPU is then called
+     *        if (neither of them handle the blur)
+     *            the mask rect is used to generate the mask
+     *            filterMaskGPU is called to filter the mask
+     *
+     * TODO: this should work as:
+     *    if (canFilterMaskGPU(devShape, ...)) // rect, rrect, drrect, path
+     *        filterMaskGPU(devShape, ...)
+     * this would hide the RRect special case and the mask generation
+     */
+    virtual bool canFilterMaskGPU(const SkRRect& devRRect,
+                                  const SkIRect& clipBounds,
+                                  const SkMatrix& ctm,
+                                  SkRect* maskRect) const;
+
+    /**
+     *  Try to directly render the mask filter into the target. Returns true if drawing was
+     *  successful. If false is returned then paint is unmodified.
+     */
+    virtual bool directFilterMaskGPU(GrContext*,
+                                     GrRenderTargetContext* renderTargetContext,
+                                     GrPaint&& paint,
+                                     const GrClip&,
+                                     const SkMatrix& viewMatrix,
+                                     const SkStrokeRec& strokeRec,
+                                     const SkPath& path) const;
+    /**
+     *  Try to directly render a rounded rect mask filter into the target.  Returns
+     *  true if drawing was successful.  If false is returned then paint is unmodified.
+     */
+    virtual bool directFilterRRectMaskGPU(GrContext*,
+                                          GrRenderTargetContext* renderTargetContext,
+                                          GrPaint&& paint,
+                                          const GrClip&,
+                                          const SkMatrix& viewMatrix,
+                                          const SkStrokeRec& strokeRec,
+                                          const SkRRect& rrect,
+                                          const SkRRect& devRRect) const;
+
+    /**
+     * This function is used to implement filters that require an explicit src mask. It should only
+     * be called if canFilterMaskGPU returned true and the maskRect param should be the output from
+     * that call.
+     * Implementations are free to get the GrContext from the src texture in order to create
+     * additional textures and perform multiple passes.
+     */
+    virtual sk_sp<GrTextureProxy> filterMaskGPU(GrContext*,
+                                                sk_sp<GrTextureProxy> srcProxy,
+                                                const SkMatrix& ctm,
+                                                const SkIRect& maskRect) const;
+#endif
+
+    /**
+     * The fast bounds function is used to enable the paint to be culled early
+     * in the drawing pipeline. This function accepts the current bounds of the
+     * paint as its src param and the filter adjust those bounds using its
+     * current mask and returns the result using the dest param. Callers are
+     * allowed to provide the same struct for both src and dest so each
+     * implementation must accomodate that behavior.
+     *
+     *  The default impl calls filterMask with the src mask having no image,
+     *  but subclasses may override this if they can compute the rect faster.
+     */
+    virtual void computeFastBounds(const SkRect& src, SkRect* dest) const;
+
+    struct BlurRec {
+        SkScalar        fSigma;
+        SkBlurStyle     fStyle;
+        SkBlurQuality   fQuality;
+    };
+    /**
+     *  If this filter can be represented by a BlurRec, return true and (if not null) fill in the
+     *  provided BlurRec parameter. If this effect cannot be represented as a BlurRec, return false
+     *  and ignore the BlurRec parameter.
+     */
+    virtual bool asABlur(BlurRec*) const;
+
+protected:
+    SkMaskFilterBase() {}
+
+#if SK_SUPPORT_GPU
+    virtual std::unique_ptr<GrFragmentProcessor> onAsFragmentProcessor(const GrFPArgs&) const;
+    virtual bool onHasFragmentProcessor() const;
+#endif
+
+    enum FilterReturn {
+        kFalse_FilterReturn,
+        kTrue_FilterReturn,
+        kUnimplemented_FilterReturn
+    };
+
+    class NinePatch : ::SkNoncopyable {
+    public:
+        NinePatch() : fCache(nullptr) { }
+        ~NinePatch();
+
+        SkMask      fMask;      // fBounds must have [0,0] in its top-left
+        SkIRect     fOuterRect; // width/height must be >= fMask.fBounds'
+        SkIPoint    fCenter;    // identifies center row/col for stretching
+        SkCachedData* fCache;
+    };
+
+    /**
+     *  Override if your subclass can filter a rect, and return the answer as
+     *  a ninepatch mask to be stretched over the returned outerRect. On success
+     *  return kTrue_FilterReturn. On failure (e.g. out of memory) return
+     *  kFalse_FilterReturn. If the normal filterMask() entry-point should be
+     *  called (the default) return kUnimplemented_FilterReturn.
+     *
+     *  By convention, the caller will take the center rol/col from the returned
+     *  mask as the slice it can replicate horizontally and vertically as we
+     *  stretch the mask to fit inside outerRect. It is an error for outerRect
+     *  to be smaller than the mask's bounds. This would imply that the width
+     *  and height of the mask should be odd. This is not required, just that
+     *  the caller will call mask.fBounds.centerX() and centerY() to find the
+     *  strips that will be replicated.
+     */
+    virtual FilterReturn filterRectsToNine(const SkRect[], int count,
+                                           const SkMatrix&,
+                                           const SkIRect& clipBounds,
+                                           NinePatch*) const;
+    /**
+     *  Similar to filterRectsToNine, except it performs the work on a round rect.
+     */
+    virtual FilterReturn filterRRectToNine(const SkRRect&, const SkMatrix&,
+                                           const SkIRect& clipBounds,
+                                           NinePatch*) const;
+
+private:
+    friend class SkDraw;
+
+    /** Helper method that, given a path in device space, will rasterize it into a kA8_Format mask
+     and then call filterMask(). If this returns true, the specified blitter will be called
+     to render that mask. Returns false if filterMask() returned false.
+     This method is not exported to java.
+     */
+    bool filterPath(const SkPath& devPath, const SkMatrix& ctm, const SkRasterClip&, SkBlitter*,
+                    SkStrokeRec::InitStyle) const;
+
+    /** Helper method that, given a roundRect in device space, will rasterize it into a kA8_Format
+     mask and then call filterMask(). If this returns true, the specified blitter will be called
+     to render that mask. Returns false if filterMask() returned false.
+     */
+    bool filterRRect(const SkRRect& devRRect, const SkMatrix& ctm, const SkRasterClip&,
+                     SkBlitter*) const;
+
+    typedef SkFlattenable INHERITED;
+};
+
+inline SkMaskFilterBase* as_MFB(SkMaskFilter* mf) {
+    return static_cast<SkMaskFilterBase*>(mf);
+}
+
+inline const SkMaskFilterBase* as_MFB(const SkMaskFilter* mf) {
+    return static_cast<const SkMaskFilterBase*>(mf);
+}
+
+inline const SkMaskFilterBase* as_MFB(const sk_sp<SkMaskFilter>& mf) {
+    return static_cast<SkMaskFilterBase*>(mf.get());
+}
+
+#endif