New option to display frame latency.

Better property to evaluate simulation performance than frame rate.

Nasal/gui.nas

@@ -138,6 +138,7 @@ _setlistener("/sim/signals/nasal-dir-initialized", func {
     menuEnable("tutorial-start", size(props.globals.getNode("/sim/tutorials", 1).getChildren("tutorial")));
     menuEnable("joystick-info", size(props.globals.getNode("/input/joysticks").getChildren("js")));
 
+    # frame-per-second display
     var fps = props.globals.getNode("/sim/rendering/fps-display", 1);
     setlistener(fps, fpsDisplay, 1);
     setlistener("/sim/startup/xsize", func {
@@ -147,6 +148,16 @@ _setlistener("/sim/signals/nasal-dir-initialized", func {
         }
     });
 
+    # frame-latency display
+    var latency = props.globals.getNode("/sim/rendering/frame-latency-display", 1);
+    setlistener(latency, latencyDisplay, 1);
+    setlistener("/sim/startup/xsize", func {
+        if (latency.getValue()) {
+            latencyDisplay(0);
+            latencyDisplay(1);
+        }
+    });
+
     # only enable precipitation if gui *and* aircraft want it
     var p = "/sim/rendering/precipitation-";
     var precip_gui = getprop(p ~ "gui-enable");
@@ -197,7 +208,10 @@ var fpsDisplay = func(n) {
     var w = isa(n, props.Node) ? n.getValue() : n;
     fgcommand(w ? "dialog-show" : "dialog-close", props.Node.new({"dialog-name": "fps"}));
 }
-
+var latencyDisplay = func(n) {
+    var w = isa(n, props.Node) ? n.getValue() : n;
+    fgcommand(w ? "dialog-show" : "dialog-close", props.Node.new({"dialog-name": "frame-latency"}));
+}
 
 ##
 # How many seconds do we show the tip?

gui/dialogs/display.xml

@@ -43,6 +43,15 @@
       </binding>
     </checkbox>
 
+    <checkbox>
+      <halign>left</halign>
+      <label>Show worst-case frame latency</label>
+      <property>/sim/rendering/frame-latency-display</property>
+      <binding>
+        <command>dialog-apply</command>
+      </binding>
+    </checkbox>
+
     <checkbox>
       <halign>left</halign>
       <label>Show chat messages</label>
@@ -106,7 +115,6 @@
       <text>
         <label>sec.</label>
       </text>
-
     </group>
 
   </group>

gui/dialogs/fps.xml

@@ -18,6 +18,7 @@
 	<text>
 		<label>000</label>
 		<property>/sim/frame-rate</property>
+                <format>%3.0f</format>
 		<live>true</live>
 		<color>
 			<red>0.9</red>

gui/dialogs/frame-latency.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0"?>
+
+<PropertyList>
+	<name>frame-latency</name>
+	<x>2</x>
+	<y>2</y>
+	<layout>hbox</layout>
+	<default-padding>0</default-padding>
+	<font>
+		<name>HELVETICA_12</name>
+	</font>
+	<color>
+		<red>0</red>
+		<green>0</green>
+		<blue>0</blue>
+		<alpha>0</alpha>
+	</color>
+	<text>
+		<label>0000 ms</label>
+		<property>/sim/frame-latency-max-ms</property>
+                <format>%4.0f ms</format>
+		<live>true</live>
+		<color>
+			<red>0.9</red>
+			<green>0.4</green>
+			<blue>0.2</blue>
+			<alpha>1</alpha>
+		</color>
+	</text>
+</PropertyList>

preferences.xml

@@ -131,6 +131,7 @@ Started September 2000 by David Megginson, david@megginson.com
    <shader-experimental type="bool" userarchive="y">false</shader-experimental>
    <shader-effects type="bool" userarchive="y">true</shader-effects>
    <fps-display type="bool" userarchive="y">false</fps-display>
+   <frame-latency-display type="bool" userarchive="y">false</frame-latency-display>
    <on-screen-statistics type="int">0</on-screen-statistics>
    <glide-slope-tunnel type="bool" userarchive="y">false</glide-slope-tunnel>
    <redout>