Added support for scissor testing.

[binary1248]

This is a subset of #846 and implements a part of #1.

Test with:

#include <SFML/Graphics.hpp>

int main()
{
    auto window = sf::RenderWindow{sf::VideoMode{{200u, 200u}}, "Test"};

    auto shape = sf::CircleShape{100.f};
    shape.setFillColor(sf::Color::Green);

    auto left = window.getView();
    left.setScissor(sf::FloatRect{{0.f, 0.f}, {0.5f, 1.f}});

    auto right = window.getView();
    right.setScissor(sf::FloatRect{{0.5f, 0.f}, {0.5f, 1.f}});

    while (window.isOpen())
    {
        for (auto event = sf::Event{}; window.pollEvent(event);)
        {
            if (event.type == sf::Event::Closed)
                window.close();
        }

        window.setView(window.getDefaultView());
        window.clear();

        window.setView(left);
        window.clear(sf::Color::Red);

        window.setView(right);
        window.draw(shape);

        window.display();
    }
}

[codecov]

Codecov Report

Merging #1451 (283c636) into master (c1f92ed) will increase coverage by 0.06%.
The diff coverage is 48.21%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1451      +/-   ##
==========================================
+ Coverage   39.28%   39.35%   +0.06%     
==========================================
  Files         236      236              
  Lines       20763    20816      +53     
  Branches     5151     5179      +28     
==========================================
+ Hits         8157     8192      +35     
- Misses      11785    11804      +19     
+ Partials      821      820       -1     

Files	Coverage Δ
include/SFML/Graphics/RenderTarget.hpp	66.66% <ø> (ø)
include/SFML/Graphics/View.hpp	80.00% <100.00%> (+5.00%)	⬆️
src/SFML/Graphics/View.cpp	100.00% <100.00%> (ø)
src/SFML/Graphics/Texture.cpp	73.18% <66.66%> (-0.03%)	⬇️
src/SFML/Graphics/RenderTextureImplFBO.cpp	34.45% <0.00%> (-0.80%)	⬇️
src/SFML/Graphics/RenderTarget.cpp	30.39% <27.58%> (+1.93%)	⬆️

... and 1 file with indirect coverage changes

---

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[binary1248]

Updated to current master.

[binary1248]

Updated to current master and added tests.

[ChrisThrasher]

I found a few items you should consider but besides that I'm cool with this PR 👍

[binary1248]

Fixed.

[binary1248]

Updated.

[eXpl0it3r]

Looks good! 👍

Some small, mostly documentation comments.
Plus, we may want to document somewhere, what the difference between viewport and scissor testing is.

[binary1248]

Updated.

Plus, we may want to document somewhere, what the difference between viewport and scissor testing is.

Added a paragraph to the sf::View documentation regarding this issue.

[kimci86]

It doesn't work well in interaction with sf::Font. EDIT: It is now fixed.

See the result of the following code:

#include <SFML/Graphics.hpp>

int main()
{
    auto target = sf::RenderTexture{};
    if (!target.create({400, 300}))
        return 1;

    auto font = sf::Font{};
    // https://github.com/SFML/SFML/raw/master/test/Graphics/tuffy.ttf
    if (!font.loadFromFile("tuffy.ttf"))
        return 1;

    auto text = sf::Text{font, "0123456789ABCDEFGHIJKLMNOPQ", 30};
    text.setFillColor(sf::Color::White);
    text.setPosition({0.f, 100.f});

    target.clear(sf::Color{64, 64, 64});

    auto scissorView = target.getDefaultView();
    scissorView.setScissor({{0.1f, 0.1f}, {0.8f, 0.8f}});
    target.setView(scissorView);
    target.clear(sf::Color{128, 192, 128});
    target.draw(text);

    target.display();

    if (!target.getTexture().copyToImage().saveToFile("result.png"))
        return 1;

    return 0;
}

Below is the expected result, which I get after applying this patch (quick hack, probably not a proper solution).

diff --git a/src/SFML/Graphics/Texture.cpp b/src/SFML/Graphics/Texture.cpp
index 7c6df2e5..70b5286d 100644
--- a/src/SFML/Graphics/Texture.cpp
+++ b/src/SFML/Graphics/Texture.cpp
@@ -463,6 +463,8 @@ void Texture::update(const std::uint8_t* pixels, const Vector2u& size, const Vec
         // Make sure that the current texture binding will be preserved
         const priv::TextureSaver save;
 
+        glCheck(glDisable(GL_SCISSOR_TEST));
+
         // Copy pixels from the given array to the texture
         glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
         glCheck(glTexSubImage2D(GL_TEXTURE_2D,

[binary1248]

Updated. Turns out scissor testing was having an affect on our texture copying when the FBO blit implementation is used.

[binary1248]

Updated.

[kimci86]

I confirm the problem with font rendering is not there anymore. Looks good to me besides minor comments below.

Changes have been addressed

[binary1248]

Updated.