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DPI scaling: implement get_scaling function for X11

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Charles Saracco 2020-05-25 16:59:47 -04:00
parent f045c99cbf
commit 587e4e0bb1
1 changed files with 27 additions and 0 deletions
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27
src/x11.rs
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@ -2,6 +2,8 @@
// TODO: actually handle events // TODO: actually handle events
// TODO: set window title // TODO: set window title
// TODO: close window // TODO: close window
// TODO: proper error handling (no bare `unwrap`s)
// TODO: refactor X connections (+setup, +screen) to a new struct
use crate::Parent; use crate::Parent;
use crate::WindowOpenOptions; use crate::WindowOpenOptions;
@ -108,3 +110,28 @@ impl X11Window {
pub fn run(options: WindowOpenOptions) { pub fn run(options: WindowOpenOptions) {
X11Window::run(options); X11Window::run(options);
} }
// Figure out the DPI scaling by opening a new temporary connection and asking XCB
// TODO: currently returning (96, 96) on my system, even though I have 4k screens. Problem with my setup perhaps?
pub fn get_scaling() -> (u32, u32) {
let (conn, screen_num) = xcb::Connection::connect_with_xlib_display().unwrap();
// Figure out screen information
let setup = conn.get_setup();
let screen = setup.roots().nth(screen_num as usize).unwrap();
// Get the DPI from the screen struct
//
// there are 2.54 centimeters to an inch; so there are 25.4 millimeters.
// dpi = N pixels / (M millimeters / (25.4 millimeters / 1 inch))
// = N pixels / (M inch / 25.4)
// = N * 25.4 pixels / M inch
let width_px = screen.width_in_pixels() as f64;
let width_mm = screen.width_in_millimeters() as f64;
let height_px = screen.height_in_pixels() as f64;
let height_mm = screen.height_in_millimeters() as f64;
let xres = width_px * 25.4 / width_mm;
let yres = height_px * 25.4 / height_mm;
((xres + 0.5) as u32, (yres + 0.5) as u32)
}