[SFML 2] Shaders

[gsaurus]

Well I have a few questions about Shaders on SFML 2

1 - PostFX was applied to the screen, now Shaders are applied to drawables when drawn on a RenderTarget. This is great, but is it still possible to apply shaders to the current state of the screen as before?
This may be explained somewhere but I didn't find it.

2 - I can only apply one shader to a drawable, right? Shaders can't be applied one after another on the same drawable (on 1.x it was possible to apply several PostFX on the screen).

[Laurent]

1- You can, this is explained in the class documentation. Just capture the current contents of the window in a sf::Image, and draw it with a sprite and the shader.

2- Like with PostFx, you have to repeat the procedure explained above to produce the desired result. There's technically no way to apply N shaders in one pass, you must do N passes.

[gsaurus]

Ah, thanks. I was searching on the Shader documentation, I found now that there is a reference to it on the RenderImage  

Just capture the current contents of the window in a sf::Image, and draw it with a sprite and the shader.

You mean by using the Image::CopyScreen function? I think I'd better to render everything in a RenderImage and then draw with the shader on the screen.

Edit: Ok I understand now that to apply a shader between draws I need an additional image in witch to render the current content with the shader, and replace the original content with that.

[Laurent]

Ah, thanks. I was searching on the Shader documentation, I found now that there is a reference to it on the RenderImage

Sorry, I thought this was explained in the class headern but it is not
It's explained in this thread, and it should probably be added to the class documentation.

You mean by using the Image::CopyScreen function? I think I'd better to render everything in a RenderImage and then draw with the shader on the screen.

Both solutions work. Using Copy::Screen is a little more expensive, but has the advantage of not impacting the rendering flow, you can use it exactly like you used sf::PostFx.

[gsaurus]

It's explained in this thread

Ah, I knew this thread exists! I haven't searched well enough (it wasn't on the first, let's say, 20 results of a search for "Shader" )
Thank you