Addressing memory leak in status bar

I'm still not 100% confident that this is the last of the memory leak
issues in the status bar but at least locally for me this gets things
under control. There was a build up of un-acked expose / noexpose events
for the status bar being mapped that look to have been the remaining
source of leaked memory. Strangely, In working on this I repeatedly
ended up in a situation where x11rb was building up a large internal vec
(multiple MB) of what I _think_ was cookies for outstanding requests
that it had not received a reply for? I couldn't find any way of
inspecting that vec or forcing it to be cleared so if there continues to
be memory leak issues in this area I will likely need to reach out to
Psychon and check what it is I am missing here.

crates/penrose_ui/src/bar/mod.rs

@@ -237,6 +237,7 @@ impl<X: XConn> StatusBar<X> {
 
         self.draw.set_font(&self.font, ps.point_size)?;
         let mut ctx = self.draw.context_for(id)?;
+        ctx.clear()?;
 
         let mut extents = Vec::new();
         let mut greedy_indices = Vec::new();

crates/penrose_ui/src/core/fontset.rs

@@ -248,18 +248,11 @@ impl Font {
             FcConfigSubstitute(std::ptr::null::<FcConfig>() as *mut _, pat, FcMatchPattern);
             FcDefaultSubstitute(pat);
 
-            // https://doc.rust-lang.org/std/alloc/trait.GlobalAlloc.html#tymethod.alloc
-            let layout = Layout::new::<FcResult>();
-            let ptr = alloc(layout);
-            if ptr.is_null() {
-                handle_alloc_error(layout);
-            }
-            let res = ptr as *mut FcResult;
+            let mut res = FcResult::NoMatch;
 
             // Passing the pointer from fontconfig_sys to x11 here
-            let fc_pattern = XftFontMatch(dpy, SCREEN, pat as *const _, res);
+            let fc_pattern = XftFontMatch(dpy, SCREEN, pat as *const _, &mut res as *mut _);
 
-            dealloc(res as *mut u8, layout);
             FcCharSetDestroy(charset);
             FcPatternDestroy(pat);
 

crates/penrose_ui/src/core/mod.rs

@@ -31,13 +31,15 @@ use x11::{
         CapButt, Complex, CoordModeOrigin, Display, Drawable, False, JoinMiter, LineSolid, Window,
         XCopyArea, XCreateGC, XCreatePixmap, XDefaultColormap, XDefaultDepth, XDefaultVisual,
         XDrawRectangle, XFillPolygon, XFillRectangle, XFreeGC, XFreePixmap, XOpenDisplay, XPoint,
-        XSetForeground, XSetLineAttributes, XSync, GC,
+        XSetForeground, XSetGraphicsExposures, XSetLineAttributes, XSync, GC,
     },
 };
 
 mod fontset;
 use fontset::Fontset;
 
+// Xlib manual: https://www.x.org/releases/current/doc/libX11/libX11/libX11.pdf
+
 pub(crate) const SCREEN: i32 = 0;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -203,6 +205,7 @@ impl Draw {
             let drawable = XCreatePixmap(self.dpy, root, r.w, r.h, depth);
             let gc = XCreateGC(self.dpy, root, 0, std::ptr::null_mut());
             XSetLineAttributes(self.dpy, gc, 1, LineSolid, CapButt, JoinMiter);
+            XSetGraphicsExposures(self.dpy, gc, False);
 
             (drawable, gc)
         };

src/builtin/actions/mod.rs

@@ -69,9 +69,12 @@ where
 
 /// Exit penrose
 ///
-/// Immediately exit the window manager with exit code 0.
+/// Signal the `WindowManager` to exit it's main event loop.
 pub fn exit<X: XConn>() -> Box<dyn KeyEventHandler<X>> {
-    key_handler(|_, _| std::process::exit(0))
+    key_handler(|s: &mut State<X>, _| {
+        s.running = false;
+        Ok(())
+    })
 }
 
 /// Info log the current window manager [State] for debugging purposes.

src/core/mod.rs

@@ -84,6 +84,7 @@ where
     pub(crate) pending_unmap: HashMap<Xid, usize>,
     pub(crate) current_event: Option<XEvent>,
     pub(crate) diff: Diff<Xid>,
+    pub(crate) running: bool,
     // pub(crate) mouse_focused: bool,
     // pub(crate) mouse_position: Option<(Point, Point)>,
 }
@@ -111,6 +112,7 @@ where
             pending_unmap: HashMap::new(),
             current_event: None,
             diff,
+            running: false,
         })
     }
 
@@ -472,8 +474,9 @@ where
         }
 
         manage_existing_clients(&mut self.state, &self.x)?;
+        self.state.running = true;
 
-        loop {
+        while self.state.running {
             match self.x.next_event() {
                 Ok(event) => {
                     let span = span!(target: "penrose", Level::INFO, "XEvent", %event);
@@ -492,6 +495,8 @@ where
                 Err(e) => self.handle_error(e),
             }
         }
+
+        Ok(())
     }
 
     fn handle_xevent(&mut self, event: XEvent) -> Result<()> {

src/pure/stack_set.rs

@@ -760,6 +760,7 @@ impl StackSet<Xid> {
             pending_unmap: Default::default(),
             current_event: None,
             diff: Default::default(),
+            running: false,
         };
 
         s.visible_client_positions(&crate::x::StubXConn)

src/x11rb/mod.rs

@@ -385,13 +385,13 @@ where
     }
 
     fn map(&self, client: Xid) -> Result<()> {
-        self.conn.map_window(*client)?;
+        self.conn.map_window(*client)?.ignore_error();
 
         Ok(())
     }
 
     fn unmap(&self, client: Xid) -> Result<()> {
-        self.conn.unmap_window(*client)?;
+        self.conn.unmap_window(*client)?.ignore_error();
 
         Ok(())
     }