Documentation for RenderTexture incomplete

[wolfgang371]

SFML seems to have a problem with RenderTextures in combination with Sprites. Typically, the sprites will get drawn upside down.

This also took me a while, but finally I came across https://stackoverflow.com/questions/22424124/sfml-rendertexture-flipped-output, which helped me solve the problem easily.

Maybe you want to update your code example accordingly in https://oprypin.github.io/crsfml/api/SF/RenderTexture.html.

frame = SF::Image.from_file("some.jpg")
texture = SF::RenderTexture.new(frame.size.x, frame.size.y)
texture.draw(SF::Sprite.new(SF::Texture.from_image(frame))) # this will get drawn flipped except...
rectangle = SF::RectangleShape.new
rectangle.size = SF.vector2f(100, 50)
rectangle.outline_color = SF::Color::Red
rectangle.outline_thickness = 5
rectangle.position = {300, 200}
texture.draw(rectangle)
texture.display
sprite = SF::Sprite.new(texture.texture.dup) # ... you use `.dup` here!

ImGui.image_button(sprite)

[oprypin]

Why is there ImGui here O_o
Is this about SFML or what?

[oprypin]

Code is this, and it does indeed reproduce. Only for the interaction with ImGui though.

require "crsfml"
require "imgui"
require "imgui-sfml"

window = SF::RenderWindow.new(SF::VideoMode.new(1280, 720), "ImGui + SFML = <3")
window.framerate_limit = 60
ImGui::SFML.init(window)

delta_clock = SF::Clock.new
while window.open?
  while (event = window.poll_event)
    ImGui::SFML.process_event(event)

    if event.is_a? SF::Event::Closed
      window.close
    end
  end

  ImGui::SFML.update(window, delta_clock.restart)

  frame = SF::Image.from_file("some.jpg")
  texture = SF::RenderTexture.new(frame.size.x, frame.size.y)
  texture.clear
  texture.draw(SF::Sprite.new(SF::Texture.from_image(frame)))
  texture.display()
  sprite = SF::Sprite.new(texture.texture)

  ImGui.image_button(sprite)

  window.clear
  window.draw sprite
  ImGui::SFML.render(window)
  window.display
end

ImGui::SFML.shutdown

[oprypin]

But the issue is with "imgui-sfml" (not even its Crystal binding).
SFML/imgui-sfml#35

If you were getting this effect without ImGui, then it'd be about not having called .display() - a general SFML issue
https://en.sfml-dev.org/forums/index.php?topic=10582.0
(But we're NOT in this situation)

Either way, this is not about CrSFML. Also I almost never add my own examples to https://oprypin.github.io/crsfml/api/, everything there is directly ported from SFML's own docs.

[oprypin]

SFML/imgui-sfml#35 (comment) - it seems like they never ended up adding those overloads like they planned.
https://github.com/eliasdaler/imgui-sfml/search?q=RenderTexture&type=code
Maybe I can add it directly here though

[oprypin]

No, I'm not finding an appropriate way to implement this as part of imgui-sfml. They really just need to add that overload, then I'll do the same.

[wolfgang371]

I also saw those comments/promises about the overloads years ago; but obviously they didn't come. Nevertheless users have an issue with those RenderTextures. So I was searching for a workaround and the easiest I could find was the .dup one. But this is completely unintuitive, so I thought (for the next couple of years) users might be grateful for this hint.

[eliasdaler]

Hello, I'm sorry about the delay - the problem was pretty complex and I kinda procrastinated, yep.
Check out this comment which has some explanations about the possible overload.

If you check out "render-texture-fixes" branch and it'll work for you, then I'll merge it into master soon.

[oprypin]

Yes, that branch works well, thank you!

Then the example above just needs to be changed ImGui.image_button(sprite) → ImGui.image_button(texture)

[wolfgang371]

I can also confirm - thank you!

[eliasdaler]

The fix merged into master, here: SFML/imgui-sfml@ee41e16
Also added a note about sf::RenderTexture in README.