gen_example.py

# -*- coding: utf-8 -*-
from inspect import cleandoc
import os

import glfw
import OpenGL.GL as gl
from PIL import Image

import imgui
from imgui.integrations.glfw import GlfwRenderer

imgui.create_context()
io = imgui.get_io()


new_frame = imgui.new_frame

mouse_pos = (-1, -1)
mouse_down = 0


def _clear_mouse():
    global mouse_pos
    global mouse_down

    mouse_pos = (-1, -1)
    mouse_down = 0


def _new_frame_patched():
    global mouse_pos
    global mouse_down

    io.mouse_pos = mouse_pos
    io.mouse_down[0] = mouse_down

    return new_frame()


def _patch_imgui():
    if imgui.new_frame == new_frame:
        imgui.new_frame = _new_frame_patched

    _clear_mouse()


def simulate_click(x, y, state):
    global mouse_pos
    global mouse_down

    mouse_pos = x, y
    mouse_down = state


def find_fonts(source):
    # another day, another hack
    font_name = "DroidSans.ttf"

    font_path = os.path.join(
        os.path.dirname(__file__),
        '..', '..', 'imgui-cpp', 'misc', 'fonts', font_name
    )
    return source.replace(font_name, font_path)


def filter_source_lines(source_lines):
    return [
        (line if "# later" not in line else Ellipsis)
        if all([
            "imgui.new_frame()" not in line,
            "imgui.render()" not in line,
            "imgui.end_frame()" not in line
        ]) else "" for line in source_lines
    ]


def split_sources(source):
    source_lines = filter_source_lines(source.split("\n"))

    if Ellipsis in source_lines:
        init_block = source_lines[:source_lines.index(Ellipsis)]
        frame_block = source_lines[source_lines.index(Ellipsis)+1:]
    else:
        init_block = []
        frame_block = source_lines

    return "\n".join(init_block), "\n".join(frame_block)


def render_snippet(
    source,
    file_path,
    title="",
    width=200,
    height=200,
    auto_layout=False,
    output_dir='.',
    click=None,
):
    _patch_imgui()
    source = find_fonts(source)

    init_source, frame_source = split_sources(source)

    init_code = compile(init_source, '<str>', 'exec')
    frame_code = compile(frame_source, '<str>', 'exec')
    window_name = "minimal ImGui/GLFW3 example"

    if not glfw.init():
        print("Could not initialize OpenGL context")
        exit(1)

    # OS X supports only forward-compatible core profiles from 3.2
    glfw.window_hint(glfw.CONTEXT_VERSION_MAJOR, 3)
    glfw.window_hint(glfw.CONTEXT_VERSION_MINOR, 3)
    glfw.window_hint(glfw.OPENGL_PROFILE, glfw.OPENGL_CORE_PROFILE)
    glfw.window_hint(glfw.OPENGL_FORWARD_COMPAT, gl.GL_TRUE)
    # note: creating context without window is tricky so made window invisible
    glfw.window_hint(glfw.VISIBLE, False)

    window = glfw.create_window(
        int(width), int(height), window_name, None, None
    )

    glfw.make_context_current(window)

    if not window:
        glfw.terminate()
        print("Could not initialize Window")
        exit(1)

    impl = GlfwRenderer(window)

    if init_source:
        exec(init_code, locals(), globals())

    glfw.poll_events()

    # render target for framebuffer
    texture = gl.glGenTextures(1)
    gl.glBindTexture(gl.GL_TEXTURE_2D, texture)
    gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_RGBA, width, height, 0, gl.GL_RGB, gl.GL_UNSIGNED_BYTE, None)
    gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_NEAREST)
    gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_NEAREST)

    # create new framebuffer
    offscreen_fb = gl.glGenFramebuffers(1)
    gl.glBindFramebuffer(gl.GL_FRAMEBUFFER, offscreen_fb)
    # attach texture to framebuffer
    gl.glFramebufferTexture2D(gl.GL_FRAMEBUFFER, gl.GL_COLOR_ATTACHMENT0, gl.GL_TEXTURE_2D, texture, 0)

    # note: Clicking simulation is hacky as fuck and it
    #       requires at least three frames to be rendered:
    #       * 1st with mouse in position but without button pressed.
    #       * 2nd in roughly same posiotion of mouse to turn on hover
    #         mouse button starts to press but still does not trigger click.
    #       * 3rd in the same position with button pressed still to finally
    #         trigger the "clicked" state.
    # note: If clicking simulation is not required we draw only one frame.
    for m_state in ([None, None, None] if not click else [False, True, True]):

        # note: Mouse click MUST be simulated before new_frame call!
        if click:
            impl.io.mouse_draw_cursor = True
            simulate_click(click[0], click[1], m_state)
        else:
            # just make sure mouse state is clear
            _clear_mouse()

        impl.process_inputs()
        imgui.new_frame()

        with imgui.styled(imgui.STYLE_ALPHA, 1):
            imgui.core.set_next_window_size(0, 0)

            if auto_layout:
                imgui.set_next_window_size(width - 10, height - 10)
                imgui.set_next_window_position(
                    impl.io.display_size.x * 0.5,
                    impl.io.display_size.y * 0.5,
                    pivot_x=0.5,
                    pivot_y=0.5
                )
            exec(frame_code, locals(), globals())

        gl.glBindFramebuffer(gl.GL_FRAMEBUFFER, offscreen_fb)

        gl.glClearColor(1, 1, 1, 0)
        gl.glClear(gl.GL_COLOR_BUFFER_BIT)

        imgui.render()
        impl.render(imgui.get_draw_data())

    # retrieve pixels from framebuffer and write to file
    pixels = gl.glReadPixels(0, 0, width, height, gl.GL_RGBA, gl.GL_UNSIGNED_BYTE)

    image = Image.frombytes('RGBA', (width, height), pixels)
    # note: glReadPixels returns lines "bottom to top" but PIL reads bytes
    #       top to bottom
    image = image.transpose(Image.FLIP_TOP_BOTTOM)
    image.save(os.path.join(output_dir, file_path))

    glfw.terminate()


if __name__ == "__main__":
    example_source = cleandoc(
        """
        imgui.text("Bar")
        imgui.text_colored("Eggs", 0.2, 1., 0.)
        """
    )

    render_snippet(example_source, 'example_snippet.png')