GrAuditTrail can now be enabled/disabled at runtime

include/private/GrAuditTrail.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrAuditTrail_DEFINED
 #define GrAuditTrail_DEFINED
 
 #include "GrConfig.h"
 #include "SkRect.h"
 #include "SkString.h"
 #include "SkTArray.h"
 
 /*
  * GrAuditTrail collects a list of draw ops, detailed information about those ops, and can dump them
  * to json.
+ *
+ * Capturing this information is expensive and consumes a lot of memory, therefore it is important
+ * to enable auditing only when required and disable it promptly. The AutoEnable class helps to 
+ * ensure that the audit trail is disabled in a timely fashion. Once the information has been dealt
+ * with, be sure to call reset(), or the log will simply keep growing.
  */
 class GrAuditTrail {
 public:
-    GrAuditTrail() : fUniqueID(0) {}
+    GrAuditTrail() 
+    : fEnabled(false)
+    , fUniqueID(0) {}
 
     class AutoFrame {
     public:
         AutoFrame(GrAuditTrail* auditTrail, const char* name)
             : fAuditTrail(auditTrail) {
-            if (GR_BATCH_DEBUGGING_OUTPUT) {
+            if (fAuditTrail->fEnabled) {
                 fAuditTrail->pushFrame(name);
             }
         }
 
         ~AutoFrame() {
-            if (GR_BATCH_DEBUGGING_OUTPUT) {
+            if (fAuditTrail->fEnabled) {
                 fAuditTrail->popFrame();
             }
         }
 
     private:
         GrAuditTrail* fAuditTrail;
     };
 
+    class AutoEnable {
+    public:
+        AutoEnable(GrAuditTrail* auditTrail)
+            : fAuditTrail(auditTrail) {
+            SkASSERT(!fAuditTrail->isEnabled());
+            fAuditTrail->setEnabled(true);
+        }
+
+        ~AutoEnable() {
+            SkASSERT(fAuditTrail->isEnabled());
+            fAuditTrail->setEnabled(false);
+        }
+
+    private:
+        GrAuditTrail* fAuditTrail;
+    };
+
     void pushFrame(const char* name) {
-        SkASSERT(GR_BATCH_DEBUGGING_OUTPUT);
+        SkASSERT(fEnabled);
         Frame* frame = new Frame;
         if (fStack.empty()) {
             fFrames.emplace_back(frame);
         } else {
             fStack.back()->fChildren.emplace_back(frame);
         }
 
         frame->fUniqueID = fUniqueID++;
         frame->fName = name;
         fStack.push_back(frame);
     }
 
     void popFrame() {
-        SkASSERT(GR_BATCH_DEBUGGING_OUTPUT);
+        SkASSERT(fEnabled);
         fStack.pop_back();
     }
 
     void addBatch(const char* name, const SkRect& bounds) {
-        SkASSERT(GR_BATCH_DEBUGGING_OUTPUT && !fStack.empty());
+        SkASSERT(fEnabled && !fStack.empty());
         Batch* batch = new Batch;
         fStack.back()->fChildren.emplace_back(batch);
         batch->fName = name;
         batch->fBounds = bounds;
     }
 
     SkString toJson(bool prettyPrint = false) const;
 
-    void reset() { SkASSERT(GR_BATCH_DEBUGGING_OUTPUT && fStack.empty()); fFrames.reset(); }
+    bool isEnabled() { return fEnabled; }
+    void setEnabled(bool enabled) { fEnabled = enabled; }
+
+    void reset() { SkASSERT(fEnabled && fStack.empty()); fFrames.reset(); }
 
 private:
     // TODO if performance becomes an issue, we can move to using SkVarAlloc
     struct Event {
         virtual ~Event() {}
         virtual SkString toJson() const=0;
 
         const char* fName;
         uint64_t fUniqueID;
     };
 
     typedef SkTArray<SkAutoTDelete<Event>, true> FrameArray;
     struct Frame : public Event {
         SkString toJson() const override;
         FrameArray fChildren;
     };
 
     struct Batch : public Event {
         SkString toJson() const override;
         SkRect fBounds;
     };
 
     static void JsonifyTArray(SkString* json, const char* name, const FrameArray& array,
                               bool addComma);
 
+    bool fEnabled;
     FrameArray fFrames;
     SkTArray<Frame*> fStack;
     uint64_t fUniqueID;
 };
 
-#define GR_AUDIT_TRAIL_INVOKE_GUARD(invoke, ...) \
-    if (GR_BATCH_DEBUGGING_OUTPUT) {             \
-        invoke(__VA_ARGS__);                     \
+#define GR_AUDIT_TRAIL_INVOKE_GUARD(audit_trail, invoke, ...) \
+    if (audit_trail->isEnabled()) {                           \
+        audit_trail->invoke(__VA_ARGS__);                     \
     }
 
 #define GR_AUDIT_TRAIL_AUTO_FRAME(audit_trail, framename) \
     GrAuditTrail::AutoFrame SK_MACRO_APPEND_LINE(auto_frame)(audit_trail, framename);
 
 #define GR_AUDIT_TRAIL_RESET(audit_trail) \
-    GR_AUDIT_TRAIL_INVOKE_GUARD(audit_trail->reset);
+    GR_AUDIT_TRAIL_INVOKE_GUARD(audit_trail, reset);
 
 #define GR_AUDIT_TRAIL_ADDBATCH(audit_trail, batchname, bounds) \
-    GR_AUDIT_TRAIL_INVOKE_GUARD(audit_trail->addBatch, batchname, bounds);
+    GR_AUDIT_TRAIL_INVOKE_GUARD(audit_trail, addBatch, batchname, bounds);
 
 #endif