winit/src/platform_impl/linux/x11/util/randr.rs

use std::{env, slice, str::FromStr};

use super::*;
use crate::{dpi::validate_hidpi_factor, monitor::VideoMode};

pub fn calc_dpi_factor(
    (width_px, height_px): (u32, u32),
    (width_mm, height_mm): (u64, u64),
) -> f64 {
    // Override DPI if `WINIT_HIDPI_FACTOR` variable is set
    let dpi_override = env::var("WINIT_HIDPI_FACTOR")
        .ok()
        .and_then(|var| f64::from_str(&var).ok());
    if let Some(dpi_override) = dpi_override {
        if !validate_hidpi_factor(dpi_override) {
            panic!(
                "`WINIT_HIDPI_FACTOR` invalid; DPI factors must be normal floats greater than 0. Got `{}`",
                dpi_override,
            );
        }
        return dpi_override;
    }

    // See http://xpra.org/trac/ticket/728 for more information.
    if width_mm == 0 || width_mm == 0 {
        warn!("XRandR reported that the display's 0mm in size, which is certifiably insane");
        return 1.0;
    }

    let ppmm = ((width_px as f64 * height_px as f64) / (width_mm as f64 * height_mm as f64)).sqrt();
    // Quantize 1/12 step size
    let dpi_factor = ((ppmm * (12.0 * 25.4 / 96.0)).round() / 12.0).max(1.0);
    assert!(validate_hidpi_factor(dpi_factor));
    dpi_factor
}

pub enum MonitorRepr {
    Monitor(*mut ffi::XRRMonitorInfo),
    Crtc(*mut ffi::XRRCrtcInfo),
}

impl MonitorRepr {
    pub unsafe fn get_output(&self) -> ffi::RROutput {
        match *self {
            // Same member names, but different locations within the struct...
            MonitorRepr::Monitor(monitor) => *((*monitor).outputs.offset(0)),
            MonitorRepr::Crtc(crtc) => *((*crtc).outputs.offset(0)),
        }
    }

    pub unsafe fn size(&self) -> (u32, u32) {
        match *self {
            MonitorRepr::Monitor(monitor) => ((*monitor).width as u32, (*monitor).height as u32),
            MonitorRepr::Crtc(crtc) => ((*crtc).width as u32, (*crtc).height as u32),
        }
    }

    pub unsafe fn position(&self) -> (i32, i32) {
        match *self {
            MonitorRepr::Monitor(monitor) => ((*monitor).x as i32, (*monitor).y as i32),
            MonitorRepr::Crtc(crtc) => ((*crtc).x as i32, (*crtc).y as i32),
        }
    }
}

impl From<*mut ffi::XRRMonitorInfo> for MonitorRepr {
    fn from(monitor: *mut ffi::XRRMonitorInfo) -> Self {
        MonitorRepr::Monitor(monitor)
    }
}

impl From<*mut ffi::XRRCrtcInfo> for MonitorRepr {
    fn from(crtc: *mut ffi::XRRCrtcInfo) -> Self {
        MonitorRepr::Crtc(crtc)
    }
}

impl XConnection {
    // Retrieve DPI from Xft.dpi property
    pub unsafe fn get_xft_dpi(&self) -> Option<f64> {
        (self.xlib.XrmInitialize)();
        let resource_manager_str = (self.xlib.XResourceManagerString)(self.display);
        if resource_manager_str == ptr::null_mut() {
            return None;
        }
        if let Ok(res) = ::std::ffi::CStr::from_ptr(resource_manager_str).to_str() {
            let name: &str = "Xft.dpi:\t";
            for pair in res.split("\n") {
                if pair.starts_with(&name) {
                    let res = &pair[name.len()..];
                    return f64::from_str(&res).ok();
                }
            }
        }
        None
    }
    pub unsafe fn get_output_info(
        &self,
        resources: *mut ffi::XRRScreenResources,
        repr: &MonitorRepr,
    ) -> Option<(String, f64, Vec<VideoMode>)> {
        let output_info =
            (self.xrandr.XRRGetOutputInfo)(self.display, resources, repr.get_output());
        if output_info.is_null() {
            // When calling `XRRGetOutputInfo` on a virtual monitor (versus a physical display)
            // it's possible for it to return null.
            // https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=816596
            let _ = self.check_errors(); // discard `BadRROutput` error
            return None;
        }

        let screen = (self.xlib.XDefaultScreen)(self.display);
        let bit_depth = (self.xlib.XDefaultDepth)(self.display, screen);

        let output_modes =
            slice::from_raw_parts((*output_info).modes, (*output_info).nmode as usize);
        let resource_modes = slice::from_raw_parts((*resources).modes, (*resources).nmode as usize);

        let modes = resource_modes
            .iter()
            // XRROutputInfo contains an array of mode ids that correspond to
            // modes in the array in XRRScreenResources
            .filter(|x| output_modes.iter().any(|id| x.id == *id))
            .map(|x| {
                let refresh_rate = if x.dotClock > 0 && x.hTotal > 0 && x.vTotal > 0 {
                    x.dotClock as u64 * 1000 / (x.hTotal as u64 * x.vTotal as u64)
                } else {
                    0
                };

                VideoMode {
                    size: (x.width, x.height),
                    refresh_rate: (refresh_rate as f32 / 1000.0).round() as u16,
                    bit_depth: bit_depth as u16,
                }
            });

        let name_slice = slice::from_raw_parts(
            (*output_info).name as *mut u8,
            (*output_info).nameLen as usize,
        );
        let name = String::from_utf8_lossy(name_slice).into();
        let hidpi_factor = if let Some(dpi) = self.get_xft_dpi() {
            dpi / 96.
        } else {
            calc_dpi_factor(
                repr.size(),
                (
                    (*output_info).mm_width as u64,
                    (*output_info).mm_height as u64,
                ),
            )
        };

        (self.xrandr.XRRFreeOutputInfo)(output_info);
        Some((name, hidpi_factor, modes.collect()))
    }
}