OS scaling not being applied on windows and Mac.

[medcelerate]

Bug Description

In version 1.15 scaling from the OS setting is not applying to slint windows. They retain the same size and ratios causing windows to flow off screen when scaling is too high. This effects both mac and windows 11 platforms. A workaround is to manually pass the scaling env variable when launching the application. This also does not respect the no scaling option in windows where specific apps can be set to not follow scaling.

Reproducible Code (if applicable)

export component App inherits Window {
    width: 400px;
    height: 200px;
    in-out property <string> tc_live_code: "00:00:00:00";
    in-out property <int> connection_status: 0; // 0 = disconnected, 1 = connecting, 2 = connected, 3 = error
    function state_to_color(status: int) -> brush {
        if (status == 0) {
            return rgb(200, 0, 0); // Disconnected - Red
        } else if (status == 1) {
            return rgb(255, 165, 0); // Connecting - Orange
        } else if (status == 2) {
            return rgb(0, 200, 0); // Connected - Green
        } else if (status == 3) {
            return rgb(200, 0, 200); // Error - Magenta
        } else {
            return rgb(100, 100, 100); // Unknown - Gray
        }
    }
    callback try_connect();
    VerticalLayout {
        HorizontalLayout {
            padding: 10px;
            alignment: space-between;
            LineEdit {
                placeholder-text: "Timecode Live Code";
                edited(text) => {
                    tc_live_code = text;
                }
                
            }
            OutlineButton {
                width: 100px;
                label: "Connect";
                background: state_to_color(connection_status);
                left_clicked() => {
                   try_connect();
                }
            }
        }
        BigTimecode {
            timecode: tc_live_code;
        }
    }

}

Environment Details

• Slint Version: 1.15/1.16
• Platform/OS: Mac/Win
• Programming Language: Rust
• Backend/Renderer: Skia

Product Impact

Prevents users fro seeing critical information, limits devices and displays software can be used on.

[tronical]

I tried to reproduce this on macOS. I've got two screens, one with a scale factor of 1 and one with a scale factor of 2. When I move a slint window between the two monitors, the scale factor applied to the application changes. The window retains is "physical" size (so for the user it's the same), but the content scales correctly.

The above code snippet is unfortunately not usable for me as it references components not included. But I suppose there's something about the setup or expectations here that's different.

How about the following trivial test case in your setup?

export component App inherits Window {
    width: 400px;
    height: 200px;

    Text {
        text: "Hello World";
    }
}