[Solved] Display/draw error in high DPI window sys with SFML 2.5.1

[waterdrop]

Subject of the issue

Things are not drawn at the positions they are supposed to in high DPI systems.
Since this problem does not happen when I am testing it on my low resolution PC (1680x1050), it seems to be DPI-related.

Environment

• System: Windows 10 home edition version 1703 build 15063.608
• System type: 64bit
• Version of SFML: 2.5.1 for VS2013-32bit and VS2017-32bit (from https://www.sfml-dev.org/download/sfml/2.5.1/)
• Visual Studio version: VS2013 update5, VS2017
• Configuration: Debug, Release
• Resolution: 1920x1080

Steps to reproduce
The testing code should draw 4 triangles whose top-left vertex are at (100, 100), (100, 600), (600, 100), (600, 600).

#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <cstdio>

void appen_triangle(sf::VertexArray& data, float x0, float y0, float dx, float dy, sf::Color color = sf::Color::White) {
    data.append(sf::Vertex({ x0, y0 }, color));
    data.append(sf::Vertex({ x0 + dx, y0 }, color));
    data.append(sf::Vertex({ x0, y0 + dy }, color));
}

int main() {
    // create the window
    int w_width = 800, w_height = 800;
    sf::ContextSettings settings(0U, 0U, 4);
    sf::RenderWindow window(sf::VideoMode(w_width, w_height), "Test", sf::Style::Default, settings);
    window.setView(sf::View(sf::FloatRect(0.0f, 0.0f, (float)w_width, (float)w_height)));

    sf::VertexArray data;
    data.setPrimitiveType(sf::PrimitiveType::Triangles);
    appen_triangle(data, 100.0f, 100.0f, 100.0f, 100.0f);
    appen_triangle(data, 600.0f, 100.0f, 100.0f, 100.0f);
    appen_triangle(data, 100.0f, 600.0f, 100.0f, 100.0f);
    appen_triangle(data, 600.0f, 600.0f, 100.0f, 100.0f);

    while (window.isOpen()) {
        sf::Event event;
        while (window.pollEvent(event)) {
            if (event.type == sf::Event::Closed) {
                window.close();
            }
            else if (event.type == sf::Event::MouseButtonPressed) {
                printf("Mouse, by pixel = (%d, %d), ", event.mouseButton.x, event.mouseButton.y);
                auto p = window.mapPixelToCoords({ event.mouseButton.x, event.mouseButton.y });
                printf("by coords=(%.2f, %.2f)\n", p.x, p.y);
            }
        }

        window.clear(sf::Color::Black);
        window.draw(data);
        window.display();
    }

    return 0;
}
 

Expected behavior

4 triangles whose top-left vertex are at (100, 100), (100, 600), (600, 100), (600, 600).

Actual behavior

Screenshot of the program.


I clicked at each of the top-left vertex of the triangles and the coordinates printed by the program are as follows (Top-Left, Top-Right, Bottom-Left, Bottom-Right).

Mouse, by pixel = (95, 70), by coords=(95.00, 70.00)
Mouse, by pixel = (605, 69), by coords=(605.00, 69.00)
Mouse, by pixel = (94, 600), by coords=(94.00, 600.00)
Mouse, by pixel = (607, 599), by coords=(607.00, 599.00)

Examining the screenshot, assume the top-left corner is (1, 1), the pixel coordinates of the top-left vertex of the triangles are as follows (Top-Left, Top-Right, Bottom-Left, Bottom-Right).

94  69
605 69
94   598
605 598

This suggest that the pixel coordinates returned by SFML are correct but somehow vertices are not drawn at positions they're supposed to.

Edit
Many thanks to FRex.
Something I tried.

• Run the test program on a high DPI Windows 10 build 1803 laptop. Things good.
• Update my laptop to Windows 10 build 1803. Problem remained.
• Run the test program using the Nvidia graphic card. Problem solved.
• Run the test program using the Intel HD graphic card (default). Problem remained.
• Update my Intel HD graphic card driver.  Problem solved.

Conclusion:

• Should be a problem with the Intel graphic card driver.
• The system build version may or may not have an influence on this.

Some other information.

• CPU: Intel Core i7-7700HQ
• GPU: Intel HD Graphics 630
• Version of the old driver that causes problems: 21.20.16.4664
• Version of the new driver: 23.20.16.4973

[FRex]

This might not be it but this setting breaks/unbreaks many old games, programs (a maximized window whose width is less than my screen width = WTF) and such. In exe properties > Compatibility > Change high DPI settings > 'Scaling performed by X' does it say Application and if not then when you set it to Application does it help?

Maybe it's related to different rounding on different axes that was mentioned here: https://en.sfml-dev.org/forums/index.php?topic=24876

Your screenshot looks off too, mine doesn't have jagged edges of triangles. I tried with the downloaded SFML and my VS2017 and Windows 10 Pro are all up to date (1809 winver).