X11: util design improvements (#534)

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

@@ -0,0 +1,62 @@
+use std::ops::{Deref, DerefMut};
+
+use super::*;
+
+pub struct XSmartPointer<'a, T> {
+    xconn: &'a XConnection,
+    pub ptr: *mut T,
+}
+
+impl<'a, T> XSmartPointer<'a, T> {
+    // You're responsible for only passing things to this that should be XFree'd.
+    // Returns None if ptr is null.
+    pub fn new(xconn: &'a XConnection, ptr: *mut T) -> Option<Self> {
+        if !ptr.is_null() {
+            Some(XSmartPointer {
+                xconn,
+                ptr,
+            })
+        } else {
+            None
+        }
+    }
+}
+
+impl<'a, T> Deref for XSmartPointer<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        unsafe { &*self.ptr }
+    }
+}
+
+impl<'a, T> DerefMut for XSmartPointer<'a, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.ptr }
+    }
+}
+
+impl<'a, T> Drop for XSmartPointer<'a, T> {
+    fn drop(&mut self) {
+        unsafe {
+            (self.xconn.xlib.XFree)(self.ptr as *mut _);
+        }
+    }
+}
+
+impl XConnection {
+    pub fn alloc_class_hint(&self) -> XSmartPointer<ffi::XClassHint> {
+        XSmartPointer::new(self, unsafe { (self.xlib.XAllocClassHint)() })
+            .expect("`XAllocClassHint` returned null; out of memory")
+    }
+
+    pub fn alloc_size_hints(&self) -> XSmartPointer<ffi::XSizeHints> {
+        XSmartPointer::new(self, unsafe { (self.xlib.XAllocSizeHints)() })
+            .expect("`XAllocSizeHints` returned null; out of memory")
+    }
+
+    pub fn alloc_wm_hints(&self) -> XSmartPointer<ffi::XWMHints> {
+        XSmartPointer::new(self, unsafe { (self.xlib.XAllocWMHints)() })
+            .expect("`XAllocWMHints` returned null; out of memory")
+    }
+}