initial import of Chrome's trace_event into skia framework

include/utils/SkEventTracer.h

+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

[reed1, 2014/01/29 18:38:40]

This copyright header seems a lot bigger than the one we've been using (now that
we're in chrome). Look at include/gpu/GrTypes.h for a sample.

[humper, 2014/01/29 18:52:06]

Whoops, you're right.  Shortened.

+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef EventTracer_h
+#define EventTracer_h

[reed1, 2014/01/29 18:38:40]

skia's pattern would be to qualify this guard thusly -- 

#ifndef SkEventTracer_DEFINED

[humper, 2014/01/29 18:52:06]

Yeah, this is another copy/paste bug; fixed.

+
+#include "SkTypes.h"
+
+// This will mark the trace event as disabled by default. The user will need
+// to explicitly enable the event.
+#define TRACE_DISABLED_BY_DEFAULT(name) "disabled-by-default-" name
+
+namespace skia {

[reed1, 2014/01/29 18:38:40]

skia namespace not needed for types like SkEventTracer.

+namespace tracing {

[reed1, 2014/01/29 18:38:40]

why this other namespace? Is this explicitly to access types from Chrome?

[humper, 2014/01/29 18:52:06]

It's probably unnecessary; it just mirrors the Chrome structure.  I can make
more of it top-level and make sure that the types (e.g., TraceEventHandle) are
properly prefixed with Sk

+
+typedef uint32_t TraceEventHandle;
+
+// FIXME: Make these global variables thread-safe. Make a value update atomic.
+SK_API extern long* traceSamplingState[3];
+
+class SK_API SkEventTracer {

[reed1, 2014/01/29 18:38:40]

This name is very generic looking (and somewhat a near-collision with SkEvent
and SkEventHandler. Can you document more specifically its scope and use? That
may help us find the best name.

[humper, 2014/01/29 18:52:06]

Sure, I'm open to any name here.

SkEventTracer implementations provide a narrow interface that the tracing macros
bolt on to.  There's a single instance of this class created; either the default
one (which currently does nothing), or the one that Chrome will provide, which
will hook the events to its own tracing mechanism.

Maybe something like SkTraceEventProcessor or something?

+public:
+
+    static SkEventTracer* GetInstance();
+
+    static void SetInstance(SkEventTracer* tracer) { 
+        SkDELETE(SkEventTracer::_instance);
+        SkEventTracer::_instance = tracer;
+    }
+
+    virtual ~SkEventTracer() { SkDELETE(SkEventTracer::_instance); }
+
+    // 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.
+        ENABLED_FOR_RECORDING = 1 << 0,
+        // Category group enabled for the monitoring mode.
+        ENABLED_FOR_MONITORING = 1 << 1,
+        // Category group enabled by SetEventCallbackEnabled().
+        ENABLED_FOR_EVENT_CALLBACK = 1 << 2,
+    };
+
+    virtual const unsigned char* GetCategoryGroupEnabled(const char* name) = 0;
+    virtual const char* GetCategoryGroupName(
+      const unsigned char* category_group_enabled) = 0;
+    
+    virtual TraceEventHandle 
+        AddTraceEvent(char phase,
+                      const unsigned char* categoryEnabledFlag,
+                      const char* name,
+                      unsigned long long id,
+                      int numArgs,
+                      const char** argNames,
+                      const unsigned char* argTypes,
+                      const unsigned long long* argValues,
+                      unsigned char flags) = 0;
+    
+    virtual void 
+        UpdateTraceEventDuration(const unsigned char* categoryEnabledFlag, 
+                                 const char* name, 
+                                 tracing::TraceEventHandle) = 0;
+private:
+    static SkEventTracer *_instance;
+};
+
+} // namespace tracing
+} // namespace skia
+
+#endif // EventTracer_h