utils.py

import pyglet
import inspect
import mahi_gui
from mahi_gui import imgui

def redirect_pyglet():
    import pyglet
    # Do not create a hidden window and opengl context
    pyglet.options['shadow_window'] = False
    # Trick pyglet into using an external context
    import pyglet.gl
    ctx = pyglet.gl.Context(None)
    ctx.canvas = pyglet.canvas.base.Canvas(None)
    ctx.set_current()

def screenshot(x=500,y=200):
    def wrapper(func):
        screenshotName = func.__name__
        screenshotName = "docs/testShots/"+screenshotName+".png"
        print(screenshotName)
        screenShot = ScreenshotTest(func, x, y,"Test Runner", False,screenshotPath=screenshotName)
        screenShot.run()
        return func
    return wrapper

class ScreenshotTest(mahi_gui.Application):
    def __init__(self, drawFunc, *args, screenshotPath="./screenshot.png"):
        self.screenshotPath=screenshotPath
        self.drawFunc=drawFunc
        self.ticks=0
        super().__init__(*args)
        imgui.disable_viewports()

    def screenshot(self):
        redirect_pyglet()
        pyglet.image.get_buffer_manager().get_color_buffer().save(self.screenshotPath)

    def _update(self):
        width, height = self.get_window_size()
        imgui.begin(
            "Test Window",
            imgui.Bool(True),
            imgui.WindowFlags.NoTitleBar | imgui.WindowFlags.NoResize | imgui.WindowFlags.NoMove)

        imgui.set_window_pos(imgui.Vec2(0,0))
        imgui.set_window_size(imgui.Vec2(width, height))
        self.drawFunc()
        imgui.end()
        if self.ticks > 1:
            self.screenshot()
            self.quit()

        self.ticks+=1

@screenshot(500,200)
def test_hello_world():
    imgui.text("Hello world")

Utils for taking screenshots in https://github.com/JoelLinn/py-mahi-gui intended to be part of test running infrastructure.