Trying to clena the mess opened by plugins

plugins/baseview/src/x11/xcb_connection.rs

@@ -0,0 +1,132 @@
+use std::cell::RefCell;
+use std::collections::hash_map::{Entry, HashMap};
+use std::error::Error;
+
+use x11::{xlib, xlib::Display, xlib_xcb};
+
+use x11rb::connection::Connection;
+use x11rb::cursor::Handle as CursorHandle;
+use x11rb::protocol::xproto::{Cursor, Screen};
+use x11rb::resource_manager;
+use x11rb::xcb_ffi::XCBConnection;
+
+use crate::MouseCursor;
+
+use super::cursor;
+
+x11rb::atom_manager! {
+    pub Atoms: AtomsCookie {
+        WM_PROTOCOLS,
+        WM_DELETE_WINDOW,
+    }
+}
+
+/// A very light abstraction around the XCB connection.
+///
+/// Keeps track of the xcb connection itself and the xlib display ID that was used to connect.
+pub struct XcbConnection {
+    pub(crate) dpy: *mut Display,
+    pub(crate) conn: XCBConnection,
+    pub(crate) screen: usize,
+    pub(crate) atoms: Atoms,
+    pub(crate) resources: resource_manager::Database,
+    pub(crate) cursor_handle: CursorHandle,
+    pub(super) cursor_cache: RefCell<HashMap<MouseCursor, u32>>,
+}
+
+impl XcbConnection {
+    pub fn new() -> Result<Self, Box<dyn Error>> {
+        let dpy = unsafe { xlib::XOpenDisplay(std::ptr::null()) };
+        assert!(!dpy.is_null());
+        let xcb_connection = unsafe { xlib_xcb::XGetXCBConnection(dpy) };
+        assert!(!xcb_connection.is_null());
+        let screen = unsafe { xlib::XDefaultScreen(dpy) } as usize;
+        let conn = unsafe { XCBConnection::from_raw_xcb_connection(xcb_connection, false)? };
+        unsafe {
+            xlib_xcb::XSetEventQueueOwner(dpy, xlib_xcb::XEventQueueOwner::XCBOwnsEventQueue)
+        };
+
+        let atoms = Atoms::new(&conn)?.reply()?;
+        let resources = resource_manager::new_from_default(&conn)?;
+        let cursor_handle = CursorHandle::new(&conn, screen, &resources)?.reply()?;
+
+        Ok(Self {
+            dpy,
+            conn,
+            screen,
+            atoms,
+            resources,
+            cursor_handle,
+            cursor_cache: RefCell::new(HashMap::new()),
+        })
+    }
+
+    // Try to get the scaling with this function first.
+    // If this gives you `None`, fall back to `get_scaling_screen_dimensions`.
+    // If neither work, I guess just assume 96.0 and don't do any scaling.
+    fn get_scaling_xft(&self) -> Result<Option<f64>, Box<dyn Error>> {
+        if let Some(dpi) = self.resources.get_value::<u32>("Xft.dpi", "")? {
+            Ok(Some(dpi as f64 / 96.0))
+        } else {
+            Ok(None)
+        }
+    }
+
+    // Try to get the scaling with `get_scaling_xft` first.
+    // Only use this function as a fallback.
+    // If neither work, I guess just assume 96.0 and don't do any scaling.
+    fn get_scaling_screen_dimensions(&self) -> f64 {
+        // Figure out screen information
+        let screen = self.screen();
+
+        // 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;
+
+        // TODO: choose between `xres` and `yres`? (probably both are the same?)
+        yres / 96.0
+    }
+
+    #[inline]
+    pub fn get_scaling(&self) -> Result<f64, Box<dyn Error>> {
+        Ok(self.get_scaling_xft()?.unwrap_or(self.get_scaling_screen_dimensions()))
+    }
+
+    #[inline]
+    pub fn get_cursor(&self, cursor: MouseCursor) -> Result<Cursor, Box<dyn Error>> {
+        // PANIC: this function is the only point where we access the cache, and we never call
+        // external functions that may make a reentrant call to this function
+        let mut cursor_cache = self.cursor_cache.borrow_mut();
+
+        match cursor_cache.entry(cursor) {
+            Entry::Occupied(entry) => Ok(*entry.get()),
+            Entry::Vacant(entry) => {
+                let cursor =
+                    cursor::get_xcursor(&self.conn, self.screen, &self.cursor_handle, cursor)?;
+                entry.insert(cursor);
+                Ok(cursor)
+            }
+        }
+    }
+
+    pub fn screen(&self) -> &Screen {
+        &self.conn.setup().roots[self.screen]
+    }
+}
+
+impl Drop for XcbConnection {
+    fn drop(&mut self) {
+        unsafe {
+            xlib::XCloseDisplay(self.dpy);
+        }
+    }
+}