Tweak events example

README.md

@@ -77,12 +77,14 @@ from rendercanvas.auto import RenderCanvas, loop
 canvas = RenderCanvas(update_mode="continuous")
 context = canvas.get_bitmap_context()
 
+
 @canvas.request_draw
 def animate():
     w, h = canvas.get_logical_size()
     bitmap = np.random.uniform(0, 255, (h, w)).astype(np.uint8)
     context.set_bitmap(bitmap)
 
+
 loop.run()
 ```
 
@@ -106,8 +108,8 @@ Embed in a Qt application:
 from PySide6 import QtWidgets
 from rendercanvas.qt import QRenderWidget
 
-class Main(QtWidgets.QWidget):
 
+class Main(QtWidgets.QWidget):
     def __init__(self):
         super().__init__()
 

examples/events.py

@@ -2,19 +2,103 @@
 Events
 ------
 
-A simple example to demonstrate events. Events are printed to the console.
+An example that display events. Events are printed to stdout and shown in the canvas.
 """
 
+import json
+
 from rendercanvas.auto import RenderCanvas, loop
+from PIL import Image, ImageDraw, ImageFont
+import numpy as np
+
+
+canvas = RenderCanvas(title="RenderCanvas events on $backend")
+ctx = canvas.get_bitmap_context()
 
+events_list = []
+event_count = 0
 
-canvas = RenderCanvas(title="RenderCanvas events")
+
+# Create an event handler that gets all events ('*')
 
 
 @canvas.add_event_handler("*")
 def process_event(event):
-    if event["event_type"] not in ["pointer_move", "before_draw", "draw"]:
-        print(event)
+    global event_count
+
+    # Skip specific events
+    if event["event_type"] in ["before_draw"]:
+        return
+
+    # Just print the dict
+    print(event)
+
+    # Add to list for drawing in the canvas
+    event_count += 1
+    events_list.append(event_to_string(event))
+    events_list[:-32] = []  # limit to 32 entries
+
+    # Invoke a draw
+    canvas.request_draw()
+
+
+# Draw the events in the canvas itself. A bit complex because of text padding etc.
+
+
+@canvas.request_draw
+def draw():
+    w, h = ctx.physical_size
+    ratio = ctx.pixel_ratio
+
+    img = Image.new("RGBA", (w, h), "#abc")
+    draw = ImageDraw.Draw(img)
+
+    font_size = 16
+    line_height = font_size * 1.25
+    font = ImageFont.load_default(size=font_size * ratio)
+
+    x = 10.0 * ratio
+    y = 0.0
+
+    draw.text((x, y), text=f"{event_count} events", fill=(0, 0, 0), font=font)
+    y += 10 * ratio
+
+    a = 1
+    for event_str in reversed(events_list):
+        y += line_height * ratio
+        if y > h:
+            break
+        a = max(0, a - 0.04)
+        fill = round(160 * (1 - a)), round(170 * (1 - a)), round(180 * (1 - a))
+        draw.text(
+            (x, y),
+            text=event_str,
+            fill=fill,
+            font=font,
+        )
+
+    ctx.set_bitmap(np.asarray(img))
+
+
+def event_to_string(event):
+    """Function to turn an event dict into a string, with consistent space for float values."""
+    float_keys = ["x", "y", "dx", "dy", "timestamp"]
+    s = "{ "
+    for key, value in event.items():
+        v = json.dumps(value)
+        if key in float_keys:
+            try:
+                i = v.index(".")
+            except ValueError:
+                v += ".0"
+            else:
+                v = v[: i + 2]
+            pad = 6 - len(v)
+            if pad > 0:
+                v = " " * pad + v
+        s += f"{key}: {v}, "
+    s += " }"
+    return s
 
 
 if __name__ == "__main__":