SOLVED: turns out that I didn't recompile the file which loaded shader, so sf::Shader::Fragment was still equal to 1 in this source file... I'm not smart at times. ;D
I've just update to SFML 2.4 from SFML 2.3.2 and now none of my shaders work.
I used pixelate.frag (https://github.com/SFML/SFML/blob/340ebfb2724d05750ad074ea4b6e3e8d9df7946a/examples/shader/resources/pixelate.frag) shader from examples and I load it like this:
shader.loadFromFile("res/shaders/pixelate.frag", sf::Shader::Fragment);
For some reason, however, SFML displays the following errors:
Failed to compile geometry shader:
Geometry shader failed to compile with the following errors:
ERROR: 0:8: error(#143) Undeclared identified gl_FragColor
ERROR: 0:8: error(#143) Undeclared identified gl_FragColor
WARNING: 0:8: warning(#402) Implicit truncation of vector from size 4 to size 1.
ERROR: error(#273) 2 compilation errors. No code generated
How can I fix it?