Rework things to stop invalidating pointers

src/cursor.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 const c = @import("c.zig").c;
 
 const Seat = @import("seat.zig").Seat;
+const Server = @import("server.zig").Server;
 const View = @import("view.zig").View;
 
 const CursorMode = enum {
@@ -12,7 +13,6 @@ const CursorMode = enum {
 
 pub const Cursor = struct {
     seat: *Seat,
-
     wlr_cursor: *c.wlr_cursor,
     wlr_xcursor_manager: *c.wlr_xcursor_manager,
 
@@ -32,11 +32,13 @@ pub const Cursor = struct {
     grab_height: c_int,
     resize_edges: u32,
 
-    pub fn init(seat: *Seat) !@This() {
+    pub fn create(seat: *Seat) !@This() {
         var cursor = @This(){
             .seat = seat,
 
             // Creates a wlroots utility for tracking the cursor image shown on screen.
+            //
+            // TODO: free this, it allocates!
             .wlr_cursor = c.wlr_cursor_create() orelse
                 return error.CantCreateWlrCursor,
 
@@ -44,6 +46,8 @@ pub const Cursor = struct {
             // Xcursor themes to source cursor images from and makes sure that cursor
             // images are available at all scale factors on the screen (necessary for
             // HiDPI support). We add a cursor theme at scale factor 1 to begin with.
+            //
+            // TODO: free this, it allocates!
             .wlr_xcursor_manager = c.wlr_xcursor_manager_create(null, 24) orelse
                 return error.CantCreateWlrXCursorManager,
 
@@ -86,22 +90,24 @@ pub const Cursor = struct {
         c.wlr_cursor_attach_output_layout(cursor.wlr_cursor, seat.server.wlr_output_layout);
         _ = c.wlr_xcursor_manager_load(cursor.wlr_xcursor_manager, 1);
 
+        return cursor;
+    }
+
+    pub fn init(self: *@This()) void {
         // wlr_cursor *only* displays an image on screen. It does not move around
         // when the pointer moves. However, we can attach input devices to it, and
         // it will generate aggregate events for all of them. In these events, we
         // can choose how we want to process them, forwarding them to clients and
         // moving the cursor around. See following post for more detail:
         // https://drewdevault.com/2018/07/17/Input-handling-in-wlroots.html
-        c.wl_signal_add(&cursor.wlr_cursor.*.events.motion, &cursor.listen_motion);
+        c.wl_signal_add(&self.wlr_cursor.*.events.motion, &self.listen_motion);
-        c.wl_signal_add(&cursor.wlr_cursor.*.events.motion_absolute, &cursor.listen_motion_absolute);
+        c.wl_signal_add(&self.wlr_cursor.*.events.motion_absolute, &self.listen_motion_absolute);
-        c.wl_signal_add(&cursor.wlr_cursor.*.events.button, &cursor.listen_button);
+        c.wl_signal_add(&self.wlr_cursor.*.events.button, &self.listen_button);
-        c.wl_signal_add(&cursor.wlr_cursor.*.events.axis, &cursor.listen_axis);
+        c.wl_signal_add(&self.wlr_cursor.*.events.axis, &self.listen_axis);
-        c.wl_signal_add(&cursor.wlr_cursor.*.events.frame, &cursor.listen_frame);
+        c.wl_signal_add(&self.wlr_cursor.*.events.frame, &self.listen_frame);
 
         // This listens for clients requesting a specific cursor image
-        c.wl_signal_add(&seat.wlr_seat.events.request_set_cursor, &cursor.listen_request_set_cursor);
+        c.wl_signal_add(&self.seat.wlr_seat.events.request_set_cursor, &self.listen_request_set_cursor);
-
-        return cursor;
     }
 
     fn process_move(self: *@This(), time: u32) void {

src/keyboard.zig

@@ -10,20 +10,9 @@ pub const Keyboard = struct {
     listen_modifiers: c.wl_listener,
     listen_key: c.wl_listener,
 
-    pub fn init(seat: *Seat, device: *c.wlr_input_device) @This() {
+    pub fn init(self: *@This(), seat: *Seat, device: *c.wlr_input_device) !void {
-        var keyboard = @This(){
+        self.seat = seat;
-            .seat = seat,
+        self.device = device;
-            .device = device,
-
-            .listen_modifiers = c.wl_listener{
-                .link = undefined,
-                .notify = handle_modifiers,
-            },
-            .listen_key = c.wl_listener{
-                .link = undefined,
-                .notify = handle_key,
-            },
-        };
 
         // We need to prepare an XKB keymap and assign it to the keyboard. This
         // assumes the defaults (e.g. layout = "us").
@@ -34,25 +23,29 @@ pub const Keyboard = struct {
             .variant = null,
             .options = null,
         };
-        const context = c.xkb_context_new(c.enum_xkb_context_flags.XKB_CONTEXT_NO_FLAGS);
+        const context = c.xkb_context_new(c.enum_xkb_context_flags.XKB_CONTEXT_NO_FLAGS) orelse
+            return error.CantCreateXkbContext;
         defer c.xkb_context_unref(context);
 
         const keymap = c.xkb_keymap_new_from_names(
             context,
             &rules,
             c.enum_xkb_keymap_compile_flags.XKB_KEYMAP_COMPILE_NO_FLAGS,
-        );
+        ) orelse
+            return error.CantCreateXkbKeymap;
         defer c.xkb_keymap_unref(keymap);
 
-        var keyboard_device = device.*.unnamed_37.keyboard;
+        var keyboard_device = self.device.unnamed_37.keyboard;
+        // TODO: handle failure after https://github.com/swaywm/wlroots/pull/2081
         c.wlr_keyboard_set_keymap(keyboard_device, keymap);
         c.wlr_keyboard_set_repeat_info(keyboard_device, 25, 600);
 
         // Setup listeners for keyboard events
-        c.wl_signal_add(&keyboard_device.*.events.modifiers, &keyboard.listen_modifiers);
+        self.listen_modifiers.notify = handle_modifiers;
-        c.wl_signal_add(&keyboard_device.*.events.key, &keyboard.listen_key);
+        c.wl_signal_add(&keyboard_device.*.events.modifiers, &self.listen_modifiers);
 
-        return keyboard;
+        self.listen_key.notify = handle_key;
+        c.wl_signal_add(&keyboard_device.*.events.key, &self.listen_key);
     }
 
     fn handle_modifiers(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {

src/main.zig

@@ -8,7 +8,9 @@ pub fn main() !void {
 
     c.wlr_log_init(c.enum_wlr_log_importance.WLR_DEBUG, null);
 
-    var server = try Server.init(std.heap.c_allocator);
+    var server = try Server.create(std.heap.c_allocator);
+
+    try server.init();
     defer server.deinit();
 
     try server.start();

src/output.zig

@@ -16,7 +16,7 @@ pub const Output = struct {
     wlr_output: *c.wlr_output,
     listen_frame: c.wl_listener,
 
-    pub fn init(server: *Server, wlr_output: *c.wlr_output) !@This() {
+    pub fn init(self: *@This(), server: *Server, wlr_output: *c.wlr_output) !void {
         // Some backends don't have modes. DRM+KMS does, and we need to set a mode
         // before we can use the output. The mode is a tuple of (width, height,
         // refresh rate), and each monitor supports only a specific set of modes. We
@@ -33,17 +33,12 @@ pub const Output = struct {
             }
         }
 
-        var output = @This(){
+        self.server = server;
-            .server = server,
+        self.wlr_output = wlr_output;
-            .wlr_output = wlr_output,
-            .listen_frame = c.wl_listener{
-                .link = undefined,
-                .notify = handle_frame,
-            },
-        };
 
         // Sets up a listener for the frame notify event.
-        c.wl_signal_add(&wlr_output.events.frame, &output.listen_frame);
+        self.listen_frame.notify = handle_frame;
+        c.wl_signal_add(&wlr_output.events.frame, &self.listen_frame);
 
         // Add the new output to the layout. The add_auto function arranges outputs
         // from left-to-right in the order they appear. A more sophisticated
@@ -55,8 +50,6 @@ pub const Output = struct {
         // clients can see to find out information about the output (such as
         // DPI, scale factor, manufacturer, etc).
         c.wlr_output_create_global(wlr_output);
-
-        return output;
     }
 
     fn handle_frame(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {
@@ -83,8 +76,11 @@ pub const Output = struct {
         c.wlr_renderer_clear(renderer, &color);
 
         // Each subsequent view is rendered on top of the last.
-        for (output.*.server.views.span()) |*view| {
+        // The first view in the list is "on top" so iterate in reverse.
-            if (!view.*.mapped) {
+        var it = output.server.views.last;
+        while (it) |node| : (it = node.prev) {
+            var view = &node.data;
+            if (!view.mapped) {
                 // An unmapped view should not be rendered.
                 continue;
             }

src/seat.zig

@@ -8,41 +8,48 @@ const Server = @import("server.zig").Server;
 // TODO: InputManager and multi-seat support
 pub const Seat = struct {
     server: *Server,
-
     wlr_seat: *c.wlr_seat,
     listen_new_input: c.wl_listener,
 
     // Multiple mice are handled by the same Cursor
     cursor: Cursor,
     // Mulitple keyboards are handled separately
-    keyboards: std.ArrayList(Keyboard),
+    keyboards: std.TailQueue(Keyboard),
 
-    pub fn init(server: *Server, allocator: *std.mem.Allocator) !@This() {
+    pub fn create(server: *Server) !@This() {
         var seat = @This(){
             .server = server,
-            // This seems to be the default seat name used by compositors
+            .wlr_seat = undefined,
-            .wlr_seat = c.wlr_seat_create(server.*.wl_display, "seat0"),
-            .cursor = undefined,
-            .keyboards = std.ArrayList(Keyboard).init(allocator),
-
             .listen_new_input = c.wl_listener{
                 .link = undefined,
                 .notify = handle_new_input,
             },
+            .cursor = undefined,
+            .keyboards = std.TailQueue(Keyboard).init(),
         };
 
-        seat.cursor = try Cursor.init(&seat);
+        // This seems to be the default seat name used by compositors
-
+        seat.wlr_seat = c.wlr_seat_create(server.*.wl_display, "seat0") orelse
-        // Set up handler for all new input devices made available. This
+            return error.CantCreateWlrSeat;
-        // includes keyboards, pointers, touch, etc.
-        c.wl_signal_add(&server.wlr_backend.events.new_input, &seat.listen_new_input);
 
         return seat;
     }
 
+    pub fn init(self: *@This()) !void {
+        self.cursor = try Cursor.create(self);
+        self.cursor.init();
+
+        // Set up handler for all new input devices made available. This
+        // includes keyboards, pointers, touch, etc.
+        c.wl_signal_add(&self.server.wlr_backend.events.new_input, &self.listen_new_input);
+    }
+
     fn add_keyboard(self: *@This(), device: *c.wlr_input_device) !void {
-        try self.keyboards.append(Keyboard.init(self, device));
         c.wlr_seat_set_keyboard(self.wlr_seat, device);
+
+        var node = try self.keyboards.allocateNode(self.server.allocator);
+        try node.data.init(self, device);
+        self.keyboards.append(node);
     }
 
     fn add_pointer(self: *@This(), device: *c.struct_wlr_input_device) void {
@@ -69,7 +76,7 @@ pub const Seat = struct {
         // there are no pointer devices, so we always include that capability.
         var caps: u32 = @intCast(u32, c.WL_SEAT_CAPABILITY_POINTER);
         // if list not empty
-        if (seat.keyboards.span().len > 0) {
+        if (seat.keyboards.len > 0) {
             caps |= @intCast(u32, c.WL_SEAT_CAPABILITY_KEYBOARD);
         }
         c.wlr_seat_set_capabilities(seat.wlr_seat, caps);

src/server.zig

@@ -6,25 +6,28 @@ const Seat = @import("seat.zig").Seat;
 const View = @import("view.zig").View;
 
 pub const Server = struct {
+    allocator: *std.mem.Allocator,
+
     wl_display: *c.wl_display,
     wlr_backend: *c.wlr_backend,
     wlr_renderer: *c.wlr_renderer,
 
     wlr_output_layout: *c.wlr_output_layout,
-    outputs: std.ArrayList(Output),
+    outputs: std.TailQueue(Output),
 
     listen_new_output: c.wl_listener,
 
     wlr_xdg_shell: *c.wlr_xdg_shell,
     listen_new_xdg_surface: c.wl_listener,
 
-    // Must stay ordered bottom to top
+    // Must stay ordered, first in list is "on top" visually
-    views: std.ArrayList(View),
+    views: std.TailQueue(View),
 
     seat: Seat,
 
-    pub fn init(allocator: *std.mem.Allocator) !@This() {
+    pub fn create(allocator: *std.mem.Allocator) !@This() {
         var server: @This() = undefined;
+        server.allocator = allocator;
 
         // The Wayland display is managed by libwayland. It handles accepting
         // clients from the Unix socket, manging Wayland globals, and so on.
@@ -36,7 +39,7 @@ pub const Server = struct {
         // the best option based on the environment, for example DRM when run from
         // a tty or wayland if WAYLAND_DISPLAY is set.
         //
-        // This frees itself when the wl_display is destroyed.
+        // This frees itserver.when the wl_display is destroyed.
         server.wlr_backend = c.zag_wlr_backend_autocreate(server.wl_display) orelse
             return error.CantCreateWlrBackend;
 
@@ -46,7 +49,7 @@ pub const Server = struct {
         server.wlr_renderer = c.zag_wlr_backend_get_renderer(server.wlr_backend) orelse
             return error.CantGetWlrRenderer;
         // TODO: Handle failure after https://github.com/swaywm/wlroots/pull/2080
-        c.wlr_renderer_init_wl_display(server.wlr_renderer, server.wl_display);// orelse
+        c.wlr_renderer_init_wl_display(server.wlr_renderer, server.wl_display); // orelse
         //    return error.CantInitWlDisplay;
 
         // These both free themselves when the wl_display is destroyed
@@ -61,26 +64,30 @@ pub const Server = struct {
             return error.CantCreateWlrOutputLayout;
         errdefer c.wlr_output_layout_destroy(server.wlr_output_layout);
 
-        server.outputs = std.ArrayList(Output).init(std.heap.c_allocator);
+        // Don't register the wl_listeners yet as they must first be pointer-stable
-
+        server.outputs = std.TailQueue(Output).init();
-        // Setup a listener for new outputs
         server.listen_new_output.notify = handle_new_output;
-        c.wl_signal_add(&server.wlr_backend.*.events.new_output, &server.listen_new_output);
 
-        // Set up our list of views and the xdg-shell. The xdg-shell is a Wayland
+        server.views = std.TailQueue(View).init();
-        // protocol which is used for application windows.
-        // https://drewdevault.com/2018/07/29/Wayland-shells.html
-        server.views = std.ArrayList(View).init(std.heap.c_allocator);
         server.wlr_xdg_shell = c.wlr_xdg_shell_create(server.wl_display) orelse
             return error.CantCreateWlrXdgShell;
         server.listen_new_xdg_surface.notify = handle_new_xdg_surface;
-        c.wl_signal_add(&server.wlr_xdg_shell.*.events.new_surface, &server.listen_new_xdg_surface);
-
-        server.seat = try Seat.init(&server, std.heap.c_allocator);
 
         return server;
     }
 
+    pub fn init(self: *@This()) !void {
+        self.seat = try Seat.create(self);
+        try self.seat.init();
+
+        // Register our listeners for new outputs and xdg_surfaces.
+        // This can't be done in create() as wl_signal_add() creates a pointer
+        // to the wl_list link in our wl_listener, a pointer that would be
+        // broken when returning from create();
+        c.wl_signal_add(&self.wlr_backend.*.events.new_output, &self.listen_new_output);
+        c.wl_signal_add(&self.wlr_xdg_shell.*.events.new_surface, &self.listen_new_xdg_surface);
+    }
+
     /// Free allocated memory and clean up
     pub fn deinit(self: @This()) void {
         c.wl_display_destroy_clients(self.wl_display);
@@ -141,7 +148,9 @@ pub const Server = struct {
         var wlr_output = @ptrCast(*c.wlr_output, @alignCast(@alignOf(*c.wlr_output), data));
 
         // TODO: Handle failure
-        server.outputs.append(Output.init(server, wlr_output) catch unreachable) catch unreachable;
+        var node = server.outputs.allocateNode(server.allocator) catch unreachable;
+        node.data.init(server, wlr_output) catch unreachable;
+        server.outputs.append(node);
     }
 
     fn handle_new_xdg_surface(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {
@@ -154,16 +163,19 @@ pub const Server = struct {
             return;
         }
 
-        // Init a View to handle this surface
+        // Create a View to handle this toplevel surface
-        server.*.views.append(View.init(server, wlr_xdg_surface)) catch unreachable;
+        var node = server.views.allocateNode(server.allocator) catch unreachable;
+        node.data.init(server, wlr_xdg_surface);
+        server.views.append(node);
     }
 
     /// Finds the top most view under the output layout coordinates lx, ly
     /// returns the view if found, and a pointer to the wlr_surface as well as the surface coordinates
     pub fn desktop_view_at(self: *@This(), lx: f64, ly: f64, surface: *?*c.wlr_surface, sx: *f64, sy: *f64) ?*View {
-        for (self.views.span()) |*view| {
+        var it = self.views.last;
-            if (view.is_at(lx, ly, surface, sx, sy)) {
+        while (it) |node| : (it = node.prev) {
-                return view;
+            if (node.data.is_at(lx, ly, surface, sx, sy)) {
+                return &node.data;
             }
         }
         return null;

src/view.zig

@@ -7,55 +7,36 @@ pub const View = struct {
     server: *Server,
     wlr_xdg_surface: *c.wlr_xdg_surface,
 
+    mapped: bool,
+    x: c_int,
+    y: c_int,
+
     listen_map: c.wl_listener,
     listen_unmap: c.wl_listener,
     listen_destroy: c.wl_listener,
     // listen_request_move: c.wl_listener,
     // listen_request_resize: c.wl_listener,
 
-    mapped: bool,
+    pub fn init(self: *@This(), server: *Server, wlr_xdg_surface: *c.wlr_xdg_surface) void {
-    x: c_int,
+        self.server = server;
-    y: c_int,
+        self.wlr_xdg_surface = wlr_xdg_surface;
 
-    pub fn init(server: *Server, wlr_xdg_surface: *c.wlr_xdg_surface) @This() {
+        self.mapped = false;
-        var view = @This(){
+        self.x = 0;
-            .server = server,
+        self.y = 0;
-            .wlr_xdg_surface = wlr_xdg_surface,
-            .listen_map = c.wl_listener{
-                .link = undefined,
-                .notify = handle_map,
-            },
-            .listen_unmap = c.wl_listener{
-                .link = undefined,
-                .notify = handle_unmap,
-            },
-            .listen_destroy = c.wl_listener{
-                .link = undefined,
-                .notify = handle_destroy,
-            },
-            // .listen_request_move = c.wl_listener{
-            //     .link = undefined,
-            //     .notify = handle_request_move,
-            // },
-            // .listen_request_resize = c.wl_listener{
-            //     .link = undefined,
-            //     .notify = handle_request_resize,
-            // },
-            .mapped = false,
-            .x = 0,
-            .y = 0,
-        };
 
-        // Listen to the various events it can emit
+        self.listen_map.notify = handle_map;
-        c.wl_signal_add(&view.wlr_xdg_surface.events.map, &view.listen_map);
+        c.wl_signal_add(&self.wlr_xdg_surface.events.map, &self.listen_map);
-        c.wl_signal_add(&view.wlr_xdg_surface.events.unmap, &view.listen_unmap);
+
-        c.wl_signal_add(&view.wlr_xdg_surface.events.destroy, &view.listen_destroy);
+        self.listen_unmap.notify = handle_unmap;
+        c.wl_signal_add(&self.wlr_xdg_surface.events.unmap, &self.listen_unmap);
+
+        self.listen_destroy.notify = handle_destroy;
+        c.wl_signal_add(&self.wlr_xdg_surface.events.destroy, &self.listen_destroy);
 
         // var toplevel = xdg_surface.*.unnamed_160.toplevel;
         // c.wl_signal_add(&toplevel.*.events.request_move, &view.*.request_move);
         // c.wl_signal_add(&toplevel.*.events.request_resize, &view.*.request_resize);
-
-        return view;
     }
 
     fn handle_map(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {
@@ -72,13 +53,17 @@ pub const View = struct {
 
     fn handle_destroy(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {
         var view = @fieldParentPtr(View, "listen_destroy", listener);
-        var server = view.*.server;
+        var server = view.server;
-        const idx = for (server.*.views.span()) |*v, i| {
+
-            if (v == view) {
+        var it = server.views.first;
-                break i;
+        const target = while (it) |node| : (it = node.next) {
+            if (&node.data == view) {
+                break node;
             }
-        } else return;
+        } else unreachable;
-        _ = server.*.views.orderedRemove(idx);
+
+        server.views.remove(target);
+        server.views.destroyNode(target, server.allocator);
     }
 
     // fn xdg_toplevel_request_move(listener: [*c]c.wl_listener, data: ?*c_void) callconv(.C) void {
@@ -107,20 +92,20 @@ pub const View = struct {
             _ = c.wlr_xdg_toplevel_set_activated(prev_xdg_surface, false);
         }
 
-        // Find the index
+        // Find the node
-        const idx = for (server.views.span()) |*v, i| {
+        var it = server.views.first;
-            if (self == v) {
+        const target = while (it) |node| : (it = node.next) {
-                break i;
+            if (&node.data == self) {
+                break node;
             }
         } else unreachable;
 
         // Move the view to the front
-        server.views.append(server.views.orderedRemove(idx)) catch unreachable;
+        server.views.remove(target);
-
+        server.views.prepend(target);
-        var moved_self = &server.views.span()[server.views.span().len - 1];
 
         // Activate the new surface
-        _ = c.wlr_xdg_toplevel_set_activated(moved_self.wlr_xdg_surface, true);
+        _ = c.wlr_xdg_toplevel_set_activated(self.wlr_xdg_surface, true);
 
         // Tell the seat to have the keyboard enter this surface. wlroots will keep
         // track of this and automatically send key events to the appropriate
@@ -128,7 +113,7 @@ pub const View = struct {
         var keyboard = c.wlr_seat_get_keyboard(wlr_seat);
         c.wlr_seat_keyboard_notify_enter(
             wlr_seat,
-            moved_self.wlr_xdg_surface.surface,
+            self.wlr_xdg_surface.surface,
             &keyboard.*.keycodes,
             keyboard.*.num_keycodes,
             &keyboard.*.modifiers,