From 2d4bfac20e46e11f70cc9335b86bd901b8aad6ea Mon Sep 17 00:00:00 2001
From: Masayuki Nakano <masayuki@d-toybox.com>
Date: Mon, 26 Dec 2016 12:23:37 +0900
Subject: [PATCH] Bug 1256562 part.1 Implement
 nsCocoaUtils::GetEventTimeStamp() to convert from timeStamp of NSEvent to
 TimeStamp r=birtles,mstange

This patch implements nsCocoaUtils::GetEventTimeStamp() which hides how to get TimeStamp from timeStamp of NSEvent from other developers.

Different from Windows and GTK, we don't need to use SystemTimeConverter and implement CurrentTimeGetter class because the internal value of the macOS implementation of TimeStamp is based on mach_absolute_time(), which measures "ticks" since boot. Event timestamps are NSTimeIntervals (seconds) since boot. So the two time representations already have the same base; we only need to convert seconds into ticks.

MozReview-Commit-ID: LvioyJOM7S9
---
 widget/cocoa/nsCocoaUtils.h  |  7 +++++++
 widget/cocoa/nsCocoaUtils.mm | 19 +++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/widget/cocoa/nsCocoaUtils.h b/widget/cocoa/nsCocoaUtils.h
index c1cc7fbc6949..a9f267b62d7c 100644
--- a/widget/cocoa/nsCocoaUtils.h
+++ b/widget/cocoa/nsCocoaUtils.h
@@ -34,6 +34,7 @@ enum {
 class nsIWidget;
 
 namespace mozilla {
+class TimeStamp;
 namespace gfx {
 class SourceSurface;
 } // namespace gfx
@@ -377,6 +378,12 @@ public:
            const nsTArray<mozilla::FontRange>& aFontRanges,
            const bool aIsVertical,
            const CGFloat aBackingScaleFactor);
+
+  /**
+   * Compute TimeStamp from an event's timestamp.
+   * If aEventTime is 0, this returns current timestamp.
+   */
+  static mozilla::TimeStamp GetEventTimeStamp(NSTimeInterval aEventTime);
 };
 
 #endif // nsCocoaUtils_h_
diff --git a/widget/cocoa/nsCocoaUtils.mm b/widget/cocoa/nsCocoaUtils.mm
index 3138245aa785..4ed439592930 100644
--- a/widget/cocoa/nsCocoaUtils.mm
+++ b/widget/cocoa/nsCocoaUtils.mm
@@ -1020,3 +1020,22 @@ nsCocoaUtils::GetNSMutableAttributedString(
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NIL
 }
+
+TimeStamp
+nsCocoaUtils::GetEventTimeStamp(NSTimeInterval aEventTime)
+{
+  if (!aEventTime) {
+    // If the event is generated by a 3rd party application, its timestamp
+    // may be 0.  In this case, just return current timestamp.
+    // XXX Should we cache last event time?
+    return TimeStamp::Now();
+  }
+  // The internal value of the macOS implementation of TimeStamp is based on
+  // mach_absolute_time(), which measures "ticks" since boot.
+  // Event timestamps are NSTimeIntervals (seconds) since boot. So the two time
+  // representations already have the same base; we only need to convert
+  // seconds into ticks.
+  int64_t tick =
+    BaseTimeDurationPlatformUtils::TicksFromMilliseconds(aEventTime * 1000.0);
+  return TimeStamp::FromSystemTime(tick);
+}