1 files changed, 81 insertions, 0 deletions
diff --git a/src/debug/gdk-event-latency-tracker.cpp b/src/debug/gdk-event-latency-tracker.cpp
new file mode 100644
index 0000000..db93912
--- /dev/null
+++ b/src/debug/gdk-event-latency-tracker.cpp
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Inkscape::Debug::GdkEventLatencyTracker - tracks backlog of GDK events
+ *
+ * Authors:
+ *   MenTaLguY <mental@rydia.net>
+ *
+ * Copyright (C) 2008 MenTaLguY
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#include <gdk/gdk.h>
+
+#include "debug/gdk-event-latency-tracker.h"
+#include "preferences.h"
+
+namespace Inkscape {
+namespace Debug {
+
+GdkEventLatencyTracker::GdkEventLatencyTracker()
+    : start_seconds(0.0), max_latency(0.0), skew(1.0), last_elapsed(0.0), last_seconds(0.0)
+{
+    elapsed.stop();
+    elapsed.reset();
+}
+
+std::optional<double> GdkEventLatencyTracker::process(GdkEvent const *event) {
+    guint32 const timestamp=gdk_event_get_time(const_cast<GdkEvent *>(event));
+    if (timestamp == GDK_CURRENT_TIME) {
+        return std::optional<double>();
+    }
+    double const timestamp_seconds = timestamp / 1000.0;
+
+    if (start_seconds == 0.0) {
+        elapsed.start();
+        start_seconds = timestamp_seconds;
+        Inkscape::Preferences *prefs = Inkscape::Preferences::get();
+        skew = prefs->getDoubleLimited("/debug/latency/skew", 1.0, 0.5, 2.0);
+        return std::optional<double>(0.0);
+    } else {
+        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;
+            delta = 0.0;
+        } else if (delta > max_latency) {
+            max_latency = delta;
+        }
+        return std::optional<double>(delta);
+    }
+}
+
+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;
+}
+
+}
+}
+
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :