DPI for everyone (#548)

src/platform/linux/x11/util/mod.rs

@@ -27,10 +27,16 @@ pub use self::wm::*;
 
 use std::mem;
 use std::ptr;
+use std::ops::BitAnd;
 use std::os::raw::*;
 
 use super::{ffi, XConnection, XError};
 
+pub fn reinterpret<'a, A, B>(a: &'a A) -> &'a B {
+    let b_ptr = a as *const _ as *const B;
+    unsafe { &*b_ptr }
+}
+
 pub fn maybe_change<T: PartialEq>(field: &mut Option<T>, value: T) -> bool {
     let wrapped = Some(value);
     if *field != wrapped {
@@ -41,6 +47,13 @@ pub fn maybe_change<T: PartialEq>(field: &mut Option<T>, value: T) -> bool {
     }
 }
 
+pub fn has_flag<T>(bitset: T, flag: T) -> bool
+where T:
+    Copy + PartialEq + BitAnd<T, Output = T>
+{
+    bitset & flag == flag
+}
+
 #[must_use = "This request was made asynchronously, and is still in the output buffer. You must explicitly choose to either `.flush()` (empty the output buffer, sending the request now) or `.queue()` (wait to send the request, allowing you to continue to add more requests without additional round-trips). For more information, see the documentation for `util::flush_requests`."]
 pub struct Flusher<'a> {
     xconn: &'a XConnection,