rendercanvas

rendercanvas

One canvas API, multiple backends 🚀

This project is part of pygfx.org

Introduction

See how the two windows above look the same? That's the idea; they also look the same to the code that renders to them. Yet, the GUI systems are very different (Qt vs glfw in this case). Now that's a powerful abstraction!

Coming from wgpu.gui? Check from_wgpu_canvas.md.

Purpose

• Provide a generic canvas API to render to.
• Provide an event loop for scheduling events and draws.
• Provide a simple but powerful event system with standardized event objects.
• Provide various canvas implementations:
  • One that is light and easily installed (glfw).
  • For various GUI libraries (e.g. qt and wx), so visuzalizations can be embedded in a GUI.
  • For specific platforms (e.g. Jupyter, browser).

The main use-case is rendering with wgpu, but rendercanvascan be used by anything that can render based on a window-id or by producing bitmap images.

Installation

pip install rendercanvas

To have at least one backend, we recommend:

pip install rendercanvas glfw

Usage

Also see the online documentation and the examples.

A minimal example that renders noise:

import numpy as np
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()

Run wgpu visualizations:

from rendercanvas.auto import RenderCanvas, loop
from rendercanvas.utils.cube import setup_drawing_sync


canvas = RenderCanvas(
    title="The wgpu cube example on $backend", update_mode="continuous"
)
draw_frame = setup_drawing_sync(canvas)
canvas.request_draw(draw_frame)

loop.run()

Embed in a Qt application:

from PySide6 import QtWidgets
from rendercanvas.qt import QRenderWidget

class Main(QtWidgets.QWidget):

    def __init__(self):
        super().__init__()

        splitter = QtWidgets.QSplitter()
        self.canvas = QRenderWidget(splitter)
        ...


app = QtWidgets.QApplication([])
main = Main()
app.exec()

Async or not async

We support both; a render canvas can be used in a fully async setting using e.g. Asyncio or Trio, or in an event-drived framework like Qt. If you like callbacks, loop.call_later() always works. If you like async, use loop.add_task(). Event handlers can always be async. See the docs on async for details.

License

This code is distributed under the 2-clause BSD license.

Developers

• Clone the repo.
• Install rendercanvas and developer deps using pip install -e .[dev].
• Use ruff format to apply autoformatting.
• Use ruff check to check for linting errors.
• Optionally, if you install pre-commit hooks with pre-commit install, lint fixes and formatting will be automatically applied on git commit.
• Use pytest tests to run the tests.
• Use pytest examples to run a subset of the examples.