[draft]extension/window: Introduce tvg::Window based on GLFW

[JSUYA]

Add an extension that uses GLFW-based tvg::Window.
This window has a canvas built into it.
The update() function receives a function that has tvg::Canvas as a parameter.
Users can build paint into the scene.
And call tvg::Window::loop().

Please refer to example/Window.cpp.

[APIs]
tvg::Window::gen(int width, int height, std::string name, tvg::CanvasEngine engine)
void close();
void resize(int width, int height);
void init(std::function<bool(tvg::Canvas*)> on_update);
void update(std::function<bool(tvg::Canvas*)> on_update);
static bool loop();

This idea was inspired by these:
https://github.com/DeriveSDK/experiments/tree/main/glfw_imgui_tvg_window
#1244 (comment)

[JSUYA]

tvg::Window usage

if (tvg::Initializer::init(tvgEngine, threads) == tvg::Result::Success) {
        window = tvg::Window::gen(WIDTH, HEIGHT, "GLFW Window Example");
        window->update([=](tvg::Scene* main_scene) {
            auto shape1 = tvg::Shape::gen();
            //...
            main_scene->push(move(shape1));
            auto picture = tvg::Picture::gen();
            //...
            main_scene->push(move(picture));
            return true;
        });
        window->run();
        window->close();
        tvg::Initializer::term(tvgEngine);
}

The code is not clean and tested yet. If you have any ideas, please let me know.

[hermet]

Thanks. one feedback:

I assume multiple canvases(windows) with different engines.

So this api is more compromised?
-> tvg::Window::gen(w, h, "title", engine = CanvasEngine::Sw); ?

[SergeyLebedkin]

1. glTexCoord2f(0, 0); glVertex2f(0, 0);
   OpenGL 1.1? I think that we should use GL2.0 at least

2. static tvg::Window* instance_window;
   Single window instance? We should support multiple windows with different render engines

[JSUYA]

1. glTexCoord2f(0, 0); glVertex2f(0, 0);
   OpenGL 1.1? I think that we should use GL2.0 at least

Thank you for feedback :) . I will update it.

2. static tvg::Window* instance_window;
   Single window instance? We should support multiple windows with different render engines

Actually, I didn't consider multi window.
I think we need more feature like a window manager.
How about like this?

auto window_manager = tvg::WindowManager::gen();

auto window1 = tvg::Window::gen(w, h, engine,"1", engine);
window1.update( ...);
window_manager->push(std::move(window1));

auto window2 = tvg::Window::gen(w, h, engine,"1", engine);
window2.update( ...);
window_manager->push(std::move(window2));

window_manager->run();
window_manager->close();

or
it can be changed to tvg:SingleWindow.

@SergeyLebedkin @hermet What do you think?

[hermet]

@JSUYA I don't think window mgr concept here is necceesary...

I think this looks enough.

auto window1 = tvg::Window::gen(w, h, engine,"1", engine);
window1.run();

auto window2 = tvg::Window::gen(w, h, engine,"2", engine);
window2.run();

[JSUYA]

Since we need to manage the loop for each window, I modified it to call the static method tvg::Window::loop().

tvg::Initializer::init(tvgEngine, threads);

window = tvg::Window::gen(WIDTH, HEIGHT, "GLFW Window Example 1 (Sw)", tvg::CanvasEngine::Sw);

window->init([](tvg::Canvas* canvas) {
    auto main_scene = tvg::Scene::gen();
    ...
    canvas->push(std::move(main_scene));
    return true;
});

window->update([](tvg::Canvas* canvas) {
    canvas->update();
    return true;
});

window2 = tvg::Window::gen(WIDTH, HEIGHT, "GLFW Window Example 2 (Gl)", tvg::CanvasEngine::Gl);

window2->init([](tvg::Canvas* canvas) {
    auto main_scene = tvg::Scene::gen();
    ...
    canvas->push(std::move(main_scene));
    return true;
});

window2->update([](tvg::Canvas* canvas) {
    canvas->update();
    return true;
});

tvg::Window::loop();

tvg::Initializer::term(tvgEngine);

+)
I haven't updated the GL API yet.
And calling multiple GL windows doesn't work yet.

[RuiwenTang]

If the texture is meant to cover the hole window, I think it's more convenient to use glBlitFramebuffer

[capnm]

Successfully tested on Debian 11 👍

Building the example depends on elementary.
Could this be e.g. restructuring the example folders avoided?

Currently the user have to copy and build it externally.

[JSUYA]

Thanks. one feedback:

I assume multiple canvases(windows) with different engines.

So this api is more compromised? -> tvg::Window::gen(w, h, "title", engine = CanvasEngine::Sw); ?

Hi Thanks feedback. I have questions :)

• Does initializer have to be included in tvg::window::gen? or Should support multiple windows after init both SW and GL?

• Do we allow this scenario? i didnt test yet.
  init(GL);
  init(SW);
  ...
  term(GL);
  term(SW);

[hermet]

Thanks. one feedback:
I assume multiple canvases(windows) with different engines.
So this api is more compromised? -> tvg::Window::gen(w, h, "title", engine = CanvasEngine::Sw); ?

Hi Thanks feedback. I have questions :)

• Does initializer have to be included in tvg::window::gen? or Should support multiple windows after init both SW and GL?
• Do we allow this scenario? i didnt test yet.
  init(GL);
  init(SW);
  ...
  term(GL);
  term(SW);

init (GL | SW);
window ....
term ();

[capnm]

This branch has conflicts that must be resolved

Could you rebase to current tip?
Thanks!

[JSUYA]

I know there are many members waiting for this task to progress, but I haven't been able to do it cleanly. I apologize for the delay.
If anyone wants to handle this, they can continue this PR or start anew.