experimental/skpdiff/SkDiffContext.h

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkDiffContext_DEFINED
#define SkDiffContext_DEFINED

#include "SkString.h"
#include "SkTArray.h"
#include "SkTDArray.h"

class SkWStream;
class SkImageDiffer;

/**
 * Collects records of diffs and outputs them as JSON.
 */
class SkDiffContext {
public:
    SkDiffContext();
    ~SkDiffContext();

    /**
     * Sets the differs to be used in each diff. Already started diffs will not retroactively use
     * these.
     * @param differs An array of differs to use. The array is copied, but not the differs
     *                themselves.
     */
    void setDiffers(const SkTDArray<SkImageDiffer*>& differs);

    /**
     * Compares two directories of images with the given differ
     * @param baselinePath The baseline directory's path
     * @param testPath     The test directory's path
     */
    void diffDirectories(const char baselinePath[], const char testPath[]);

    /**
     * Compares two sets of images identified by glob style patterns with the given differ
     * @param baselinePattern A pattern for baseline files
     * @param testPattern     A pattern for test files that matches each file of the baseline file
     */
    void diffPatterns(const char baselinePattern[], const char testPattern[]);

    /**
     * Compares the images at the given paths
     * @param baselinePath The baseline file path
     * @param testPath     The matching test file path
     */
    void addDiff(const char* baselinePath, const char* testPath);

    /**
     * Output the records of each diff in JSON.
     *
     * The format of the JSON document is one top level array named "records".
     * Each record in the array is an object with both a "baselinePath" and "testPath" string field.
     * They also have an array named "diffs" with each element being one diff record for the two
     * images indicated in the above field.
     * A diff record includes:
     *    "differName"       : string name of the diff metric used
     *    "result"           : numerical result of the diff
     *    "pointsOfInterest" : an array of coordinates (stored as a 2-array of ints) of interesting
     *                         points
     *
     * Here is an example:
     *
     * {
     *     "records": [
     *         {
     *             "baselinePath": "queue.png",
     *             "testPath": "queue.png",
     *             "diffs": [
     *                 {
     *                     "differName": "different_pixels",
     *                     "result": 1,
     *                     "pointsOfInterest": [
     *                         [285,279],
     *                     ]
     *                 }
     *             ]
     *         }
     *     ]
     * }
     *
     * @param stream   The stream to output the diff to
     * @param useJSONP True to adding padding to the JSON output to make it cross-site requestable.
     */
    void outputRecords(SkWStream& stream, bool useJSONP);

private:
    struct DiffData {
        const char* fDiffName;
        double fResult;
        SkTDArray<SkIPoint> fPointsOfInterest;
    };

    struct DiffRecord {
        SkString           fBaselinePath;
        SkString               fTestPath;
        SkTArray<DiffData>        fDiffs;
        DiffRecord*                fNext;
    };

    // We use linked list for the records so that their pointers remain stable. A resizable array
    // might change its pointers, which would make it harder for async diffs to record their
    // results.
    DiffRecord * fRecords;

    SkImageDiffer** fDiffers;
    int fDifferCount;
};

#endif