From 1d55f93a54a61c40523eaa9e1d55fc836ac880f9 Mon Sep 17 00:00:00 2001
From: joncruz <joncruz@users.sourceforge.net>
Date: Sun, 27 Jul 2008 06:22:56 +0000
Subject: [PATCH] Add tracking of skew factor and display in warning message.

---
 src/debug/gdk-event-latency-tracker.cpp | 14 ++++++++++++--
 src/debug/gdk-event-latency-tracker.h   |  3 +++
 src/display/sp-canvas.cpp               |  2 +-
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/debug/gdk-event-latency-tracker.cpp b/src/debug/gdk-event-latency-tracker.cpp
index 6a8a48eb3..cfd5a9b71 100644
--- a/src/debug/gdk-event-latency-tracker.cpp
+++ b/src/debug/gdk-event-latency-tracker.cpp
@@ -16,7 +16,7 @@ namespace Inkscape {
 namespace Debug {
 
 GdkEventLatencyTracker::GdkEventLatencyTracker()
-    : start_seconds(0.0), max_latency(0.0), skew(1.0)
+    : start_seconds(0.0), max_latency(0.0), skew(1.0), last_elapsed(0.0), last_seconds(0.0)
 {
     elapsed.stop();
     elapsed.reset();
@@ -35,7 +35,9 @@ boost::optional<double> GdkEventLatencyTracker::process(GdkEvent const *event) {
         skew = prefs_get_double_attribute_limited("debug.latency", "skew", 1.0, 0.5, 2.0);
         return boost::optional<double>(0.0);
     } else {
-        double const current_seconds = (elapsed.elapsed() * skew) + start_seconds;
+        last_elapsed = elapsed.elapsed();
+        last_seconds = timestamp_seconds;
+        double const current_seconds = (last_elapsed * skew) + start_seconds;
         double delta = current_seconds - timestamp_seconds;
         if (delta < 0.0) {
             start_seconds += -delta;
@@ -47,6 +49,14 @@ boost::optional<double> GdkEventLatencyTracker::process(GdkEvent const *event) {
     }
 }
 
+double GdkEventLatencyTracker::getSkew() {
+    double val = 0.0;
+    if ((last_elapsed > 0.0) && (last_seconds > 0.0)) {
+        val = (last_seconds - start_seconds) / last_elapsed;
+    }
+    return val;
+}
+
 GdkEventLatencyTracker &GdkEventLatencyTracker::default_tracker() {
     static GdkEventLatencyTracker tracker;
     return tracker;
diff --git a/src/debug/gdk-event-latency-tracker.h b/src/debug/gdk-event-latency-tracker.h
index cb04ee035..5a05baf48 100644
--- a/src/debug/gdk-event-latency-tracker.h
+++ b/src/debug/gdk-event-latency-tracker.h
@@ -24,6 +24,7 @@ public:
     GdkEventLatencyTracker();
     boost::optional<double> process(GdkEvent const *e);
     double maxLatency() const { return max_latency; }
+    double getSkew();
 
     static GdkEventLatencyTracker &default_tracker();
 
@@ -34,6 +35,8 @@ private:
     double start_seconds;
     double max_latency;
     double skew;
+    double last_elapsed;
+    double last_seconds;
     Glib::Timer elapsed;
 };
 
diff --git a/src/display/sp-canvas.cpp b/src/display/sp-canvas.cpp
index ba0209969..592085bcd 100644
--- a/src/display/sp-canvas.cpp
+++ b/src/display/sp-canvas.cpp
@@ -1105,7 +1105,7 @@ static void track_latency(GdkEvent const *event) {
     GdkEventLatencyTracker &tracker = GdkEventLatencyTracker::default_tracker();
     boost::optional<double> latency = tracker.process(event);
     if (latency && *latency > 2.0) {
-        g_warning("Event latency reached %f sec", *latency);
+        g_warning("Event latency reached %f sec (%1.4f)", *latency, tracker.getSkew());
     }
 }
 
-- 
2.30.2