Allow displaying frame-time in ms in title ($ms instead of $fps) (#140)

Author: almarklein

rendercanvas/_scheduler.py

@@ -209,11 +209,11 @@ def on_draw(self):
         count, last_time = self._draw_stats
         count += 1
         if time.perf_counter() - last_time > 1.0:
-            fps = count / (time.perf_counter() - last_time)
+            frame_time = (time.perf_counter() - last_time) / count
             self._draw_stats = 0, time.perf_counter()
         else:
-            fps = None
+            frame_time = None
             self._draw_stats = count, last_time
 
-        # Return fps or None. Will change with better stats at some point
-        return fps
+        # Return frame_time or None. Will change with better stats at some point
+        return frame_time

rendercanvas/base.py

@@ -90,7 +90,7 @@ class BaseRenderCanvas:
     Arguments:
         size (tuple): the logical size (width, height) of the canvas.
         title (str): The title of the canvas. Can use '$backend' to show the RenderCanvas class name,
-            and '$fps' to show the fps.
+            '$fps' to show the fps, and '$ms' to show the frame-time.
         update_mode (UpdateMode): The mode for scheduling draws and events. Default 'ondemand'.
         min_fps (float): A minimal frames-per-second to use when the ``update_mode`` is 'ondemand'. The default is 0:
         max_fps (float): A maximal frames-per-second to use when the ``update_mode`` is 'ondemand'
@@ -147,6 +147,7 @@ def __init__(
         self.__title_info = {
             "raw": "",
             "fps": "?",
+            "ms": "?",
             "backend": self.__class__.__name__,
             "loop": self._rc_canvas_group.get_loop().__class__.__name__
             if (self._rc_canvas_group and self._rc_canvas_group.get_loop())
@@ -533,12 +534,14 @@ def _draw_frame_and_present(self):
 
             # Notify the scheduler
             if self.__scheduler is not None:
-                fps = self.__scheduler.on_draw()
+                frame_time = self.__scheduler.on_draw()
 
                 # Maybe update title
-                if fps is not None:
-                    self.__title_info["fps"] = f"{fps:0.1f}"
-                    if "$fps" in self.__title_info["raw"]:
+                if frame_time is not None:
+                    self.__title_info["fps"] = f"{min(9999, 1 / frame_time):0.1f}"
+                    self.__title_info["ms"] = f"{min(9999, 1000 * frame_time):0.1f}"
+                    raw_title = self.__title_info["raw"]
+                    if "$fps" in raw_title or "$ms" in raw_title:
                         self.set_title(self.__title_info["raw"])
 
             # Perform the user-defined drawing code. When this errors,
@@ -630,8 +633,12 @@ def set_logical_size(self, width: float, height: float) -> None:
     def set_title(self, title: str) -> None:
         """Set the window title.
 
-        The words "$backend", "$loop", and "$fps" can be used as variables that
-        are filled in with the corresponding values.
+        A few special placeholders are supported:
+
+        * "$backend": the name of the backends's RenderCanvas subclass.
+        * "$loop": the name of the used Loop subclass.
+        * "$fps": the current frames per second, useful as an indication how smooth the rendering feels.
+        * "$ms": the time between two rendered frames in milliseconds, useful for benchmarking.
         """
         self.__title_info["raw"] = title
         for k, v in self.__title_info.items():