Improve performance of wayland screenshot

[nik-rev]

Wayland screenshot is captured in src/linux/wayland_capture:

   let res = org_gnome_shell_screenshot(conn, x, y, width, height)
        .or_else(|e| {
            log::debug!("org_gnome_shell_screenshot failed {}", e);

            org_freedesktop_portal_screenshot(conn, x, y, width, height)
        })
        .or_else(|e| {
            log::debug!("org_freedesktop_portal_screenshot failed {}", e);
            wlroots_screenshot(x, y, width, height)
        });

I inserted these statements after each step:

println!("{:?}", now.elapsed());

• A: gnome_shell
• B: org_freedesktop_portal
• C: wlroots

Currently, xcap will try A, if it fails try B, if it fails try C
These are the results for the screenshot capture time:

A: 7.63007ms
B: 1.453836723s
C: 1.453845008s

Step B takes an extremely long time which completely blocks Step C

I think what xcap should do instead is use some heuristics to determine which of A, B or C to use. Such as reading env variable

If heuristics does not work, then changing the order from A -> B -> C to C -> B -> A will help

[nashaofu]

Perhaps writing it this way works.

let res = {
    let desktop_env = std::env::var("XDG_CURRENT_DESKTOP").unwrap_or_default().to_lowercase();
    let session_type = std::env::var("XDG_SESSION_TYPE").unwrap_or_default().to_lowercase();
    
    if desktop_env.contains("gnome") || desktop_env.contains("wayland") || session_type == "wayland" {
        org_gnome_shell_screenshot(conn, x, y, width, height)
    } else if desktop_env.contains("kde") || desktop_env.contains("plasma") {
        org_freedesktop_portal_screenshot(conn, x, y, width, height)
    } else if desktop_env.contains("x11") || session_type == "x11" {
        wlroots_screenshot(x, y, width, height)
    } else {
        // 默认情况，尝试第一个方法
        org_gnome_shell_screenshot(conn, x, y, width, height)
    }
}
.or_else(|e| {
    log::debug!("First method failed: {}", e);
    if desktop_env.contains("kde") || desktop_env.contains("plasma") {
        wlroots_screenshot(x, y, width, height)
    } else {
        org_freedesktop_portal_screenshot(conn, x, y, width, height)
    }
})
.or_else(|e| {
    log::debug!("Second method failed: {}", e);
    wlroots_screenshot(x, y, width, height)
});

[IAmJSD]

I will say I am currently having some issues when it comes to Gnome + Manjaro where I cannot get the screenshotting to work nicely (also it does a whole screen flash and takes seconds, which is unideal when I'm writing a screenshotting tool). So maybe that could be handled during this too?

[IAmJSD]

(on my distro, capture seems to fall through all wayland cases)