SkEventTracer.h

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/*
 * Copyright (C) 2014 Google Inc. All rights reserved.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
#ifndef SkEventTracer_DEFINED
#define SkEventTracer_DEFINED
 
// The class in this header defines the interface between Skia's internal
// tracing macros and an external entity (e.g., Chrome) that will consume them.
// Such an entity should subclass SkEventTracer and provide an instance of
// that event to SkEventTracer::SetInstance.
 
// If you're looking for the tracing macros to instrument Skia itself, those
// live in src/core/SkTraceEvent.h
 
#include "include/core/SkTypes.h"
 
#include <cstdint>
 
class SK_API SkEventTracer {
public:
 
    typedef uint64_t Handle;
 
    /**
     * If this is the first call to SetInstance or GetInstance then the passed instance is
     * installed and true is returned. Otherwise, false is returned. In either case ownership of the
     * tracer is transferred and it will be deleted when no longer needed.
     *
     * Not deleting the tracer on process exit should not cause problems as
     * the whole heap is about to go away with the process. This can also
     * improve performance by reducing the amount of work needed.
     *
     * @param leakTracer Do not delete tracer on process exit.
     */
    static bool SetInstance(SkEventTracer*, bool leakTracer = false);
 
    /**
     * Gets the event tracer. If this is the first call to SetInstance or GetIntance then a default
     * event tracer is installed and returned.
     */
    static SkEventTracer* GetInstance();
 
    virtual ~SkEventTracer() = default;
 
    // The pointer returned from GetCategoryGroupEnabled() points to a
    // value with zero or more of the following bits. Used in this class only.
    // The TRACE_EVENT macros should only use the value as a bool.
    // These values must be in sync with macro values in trace_event.h in chromium.
    enum CategoryGroupEnabledFlags {
        // Category group enabled for the recording mode.
        kEnabledForRecording_CategoryGroupEnabledFlags = 1 << 0,
        // Category group enabled for the monitoring mode.
        kEnabledForMonitoring_CategoryGroupEnabledFlags = 1 << 1,
        // Category group enabled by SetEventCallbackEnabled().
        kEnabledForEventCallback_CategoryGroupEnabledFlags = 1 << 2,
    };
 
    virtual const uint8_t* getCategoryGroupEnabled(const char* name) = 0;
    virtual const char* getCategoryGroupName(const uint8_t* categoryEnabledFlag) = 0;
 
    virtual SkEventTracer::Handle
        addTraceEvent(char phase,
                      const uint8_t* categoryEnabledFlag,
                      const char* name,
                      uint64_t id,
                      int32_t numArgs,
                      const char** argNames,
                      const uint8_t* argTypes,
                      const uint64_t* argValues,
                      uint8_t flags) = 0;
 
    virtual void
        updateTraceEventDuration(const uint8_t* categoryEnabledFlag,
                                 const char* name,
                                 SkEventTracer::Handle handle) = 0;
 
    // Optional method that can be implemented to allow splitting up traces into different sections.
    virtual void newTracingSection(const char*) {}
 
protected:
    SkEventTracer() = default;
    SkEventTracer(const SkEventTracer&) = delete;
    SkEventTracer& operator=(const SkEventTracer&) = delete;
};
 
#endif // SkEventTracer_DEFINED