output: introduce state struct

This simplifies the handling of the current/pending tags and will be
used in the future for atomic layout updates involving layer surface
exclusive zones.

river/Cursor.zig

@@ -360,13 +360,13 @@ fn layerSurfaceAt(
 /// Find the topmost visible view surface (incl. popups) at ox,oy.
 fn viewSurfaceAt(output: Output, ox: f64, oy: f64, sx: *f64, sy: *f64) ?*c.wlr_surface {
     // Focused views are rendered on top, so look for them first.
-    var it = ViewStack(View).iterator(output.views.first, output.current_focused_tags);
+    var it = ViewStack(View).iterator(output.views.first, output.current.tags);
     while (it.next()) |node| {
         if (!node.view.focused) continue;
         if (node.view.surfaceAt(ox, oy, sx, sy)) |found| return found;
     }
 
-    it = ViewStack(View).iterator(output.views.first, output.current_focused_tags);
+    it = ViewStack(View).iterator(output.views.first, output.current.tags);
     while (it.next()) |node| {
         if (node.view.surfaceAt(ox, oy, sx, sy)) |found| return found;
     }

river/Output.zig

@@ -40,6 +40,11 @@ const OutputStatus = @import("OutputStatus.zig");
 // that it should never be encountered during normal usage.
 const minimum_size = 50;
 
+const State = struct {
+    /// A bit field of focused tags
+    tags: u32,
+};
+
 root: *Root,
 wlr_output: *c.wlr_output,
 
@@ -48,14 +53,15 @@ layers: [4]std.TailQueue(LayerSurface),
 
 /// The area left for views and other layer surfaces after applying the
 /// exclusive zones of exclusive layer surfaces.
+/// TODO: this should be part of the output's State
 usable_box: Box,
 
 /// The top of the stack is the "most important" view.
 views: ViewStack(View),
 
-/// A bit field of focused tags
+/// The double-buffered state of the output.
-current_focused_tags: u32,
+current: State,
-pending_focused_tags: ?u32,
+pending: State,
 
 /// Number of views in "master" section of the screen.
 master_count: u32,
@@ -98,8 +104,10 @@ pub fn init(self: *Self, root: *Root, wlr_output: *c.wlr_output) !void {
 
     self.views.init();
 
-    self.current_focused_tags = 1 << 0;
+    self.current = .{
-    self.pending_focused_tags = null;
+        .tags = 1 << 0,
+    };
+    self.pending = self.current;
 
     self.master_count = 1;
 
@@ -297,17 +305,12 @@ fn layoutExternal(self: *Self, visible_count: u32, output_tags: u32) !void {
 /// pending state, the changes are not appplied until a transaction is started
 /// and completed.
 pub fn arrangeViews(self: *Self) void {
-    const output_tags = if (self.pending_focused_tags) |tags|
-        tags
-    else
-        self.current_focused_tags;
-
     const full_area = Box.fromWlrBox(c.wlr_output_layout_get_box(self.root.wlr_output_layout, self.wlr_output).*);
 
     // Make fullscreen views take the full area, count up views that will be
     // arranged by the layout.
     var layout_count: u32 = 0;
-    var it = ViewStack(View).pendingIterator(self.views.first, output_tags);
+    var it = ViewStack(View).pendingIterator(self.views.first, self.pending.tags);
     while (it.next()) |node| {
         const view = &node.view;
         if (view.pending.fullscreen) {
@@ -321,9 +324,9 @@ pub fn arrangeViews(self: *Self) void {
     // would cause an underflow and is pointless anyway.
     if (layout_count == 0 or self.usable_box.width == 0 or self.usable_box.height == 0) return;
 
-    if (std.mem.eql(u8, self.layout, "full")) return layoutFull(self, layout_count, output_tags);
+    if (std.mem.eql(u8, self.layout, "full")) return layoutFull(self, layout_count, self.pending.tags);
 
-    layoutExternal(self, layout_count, output_tags) catch |err| {
+    layoutExternal(self, layout_count, self.pending.tags) catch |err| {
         switch (err) {
             LayoutError.BadExitCode => log.err(.layout, "layout command exited with non-zero return code", .{}),
             LayoutError.BadWindowConfiguration => log.err(.layout, "invalid window configuration", .{}),
@@ -331,7 +334,7 @@ pub fn arrangeViews(self: *Self) void {
             else => log.err(.layout, "'{}' error while trying to use external layout", .{err}),
         }
         log.err(.layout, "falling back to internal layout", .{});
-        layoutFull(self, layout_count, output_tags);
+        layoutFull(self, layout_count, self.pending.tags);
     };
 }
 

river/OutputStatus.zig

@@ -78,5 +78,5 @@ pub fn sendViewTags(self: Self) void {
 
 /// Send the currently focused tags of the output to the client.
 pub fn sendFocusedTags(self: Self) void {
-    c.zriver_output_status_v1_send_focused_tags(self.wl_resource, self.output.current_focused_tags);
+    c.zriver_output_status_v1_send_focused_tags(self.wl_resource, self.output.current.tags);
 }

river/Root.zig

@@ -207,25 +207,24 @@ fn commitTransaction(self: *Self) void {
     while (output_it) |output_node| : (output_it = output_node.next) {
         const output = &output_node.data;
 
-        // If there were pending focused tags, make them the current focus
+        // Apply pending state of the output
-        if (output.pending_focused_tags) |tags| {
+        if (output.pending.tags != output.current.tags) {
             log.debug(
                 .output,
                 "changing current focus: {b:0>10} to {b:0>10}",
-                .{ output.current_focused_tags, tags },
+                .{ output.current.tags, output.pending.tags },
             );
-            output.current_focused_tags = tags;
-            output.pending_focused_tags = null;
             var it = output.status_trackers.first;
             while (it) |node| : (it = node.next) node.data.sendFocusedTags();
         }
+        output.current = output.pending;
 
         var view_tags_changed = false;
 
         var view_it = ViewStack(View).iterator(output.views.first, std.math.maxInt(u32));
         while (view_it.next()) |view_node| {
             const view = &view_node.view;
-            // Apply pending state
+            // Apply pending state of the view
             view.pending_serial = null;
             if (view.pending.tags != view.current.tags) view_tags_changed = true;
             view.current = view.pending;

river/Seat.zig

@@ -125,13 +125,13 @@ pub fn focus(self: *Self, _view: ?*View) void {
     // If the view is not currently visible, behave as if null was passed
     if (view) |v| {
         if (v.output != self.focused_output or
-            v.current.tags & self.focused_output.current_focused_tags == 0) view = null;
+            v.current.tags & self.focused_output.current.tags == 0) view = null;
     }
 
     // If the target view is not fullscreen or null, then a fullscreen view
     // will grab focus if visible.
     if (if (view) |v| !v.current.fullscreen else true) {
-        var it = ViewStack(*View).iterator(self.focus_stack.first, self.focused_output.current_focused_tags);
+        var it = ViewStack(*View).iterator(self.focus_stack.first, self.focused_output.current.tags);
         view = while (it.next()) |node| {
             if (node.view.output == self.focused_output and node.view.current.fullscreen) break node.view;
         } else view;
@@ -139,7 +139,7 @@ pub fn focus(self: *Self, _view: ?*View) void {
 
     if (view == null) {
         // Set view to the first currently visible view in the focus stack if any
-        var it = ViewStack(*View).iterator(self.focus_stack.first, self.focused_output.current_focused_tags);
+        var it = ViewStack(*View).iterator(self.focus_stack.first, self.focused_output.current.tags);
         view = while (it.next()) |node| {
             if (node.view.output == self.focused_output) break node.view;
         } else null;

river/Server.zig

@@ -181,7 +181,7 @@ fn handleNewXdgSurface(listener: ?*c.wl_listener, data: ?*c_void) callconv(.C) v
     // The View will add itself to the output's view stack on map
     const output = self.input_manager.default_seat.focused_output;
     const node = util.gpa.create(ViewStack(View).Node) catch unreachable;
-    node.view.init(output, output.current_focused_tags, wlr_xdg_surface);
+    node.view.init(output, output.current.tags, wlr_xdg_surface);
 }
 
 /// This event is raised when the layer_shell recieves a new surface from a client.
@@ -256,5 +256,5 @@ fn handleNewXwaylandSurface(listener: ?*c.wl_listener, data: ?*c_void) callconv(
     // The View will add itself to the output's view stack on map
     const output = self.input_manager.default_seat.focused_output;
     const node = util.gpa.create(ViewStack(View).Node) catch unreachable;
-    node.view.init(output, output.current_focused_tags, wlr_xwayland_surface);
+    node.view.init(output, output.current.tags, wlr_xwayland_surface);
 }

river/View.zig

@@ -107,7 +107,6 @@ pub fn init(self: *Self, output: *Output, tags: u32, surface: var) void {
         .float = false,
         .fullscreen = false,
     };
-
     self.pending = self.current;
 
     self.pending_serial = null;

river/command/focus_view.zig

@@ -44,8 +44,8 @@ pub fn focusView(
         // If there is a currently focused view, focus the next visible view in the stack.
         const focused_node = @fieldParentPtr(ViewStack(View).Node, "view", current_focus);
         var it = switch (direction) {
-            .Next => ViewStack(View).iterator(focused_node, output.current_focused_tags),
+            .Next => ViewStack(View).iterator(focused_node, output.current.tags),
-            .Prev => ViewStack(View).reverseIterator(focused_node, output.current_focused_tags),
+            .Prev => ViewStack(View).reverseIterator(focused_node, output.current.tags),
         };
 
         // Skip past the focused node
@@ -60,8 +60,8 @@ pub fn focusView(
     // There is either no currently focused view or the last visible view in the
     // stack is focused and we need to wrap.
     var it = switch (direction) {
-        .Next => ViewStack(View).iterator(output.views.first, output.current_focused_tags),
+        .Next => ViewStack(View).iterator(output.views.first, output.current.tags),
-        .Prev => ViewStack(View).reverseIterator(output.views.last, output.current_focused_tags),
+        .Prev => ViewStack(View).reverseIterator(output.views.last, output.current.tags),
     };
 
     seat.focus(if (it.next()) |node| &node.view else null);

river/command/tags.zig

@@ -28,8 +28,8 @@ pub fn setFocusedTags(
     out: *?[]const u8,
 ) Error!void {
     const tags = try parseTags(allocator, args, out);
-    if (seat.focused_output.current_focused_tags != tags) {
+    if (seat.focused_output.pending.tags != tags) {
-        seat.focused_output.pending_focused_tags = tags;
+        seat.focused_output.pending.tags = tags;
         seat.input_manager.server.root.arrange();
     }
 }
@@ -57,9 +57,9 @@ pub fn toggleFocusedTags(
 ) Error!void {
     const tags = try parseTags(allocator, args, out);
     const output = seat.focused_output;
-    const new_focused_tags = output.current_focused_tags ^ tags;
+    const new_focused_tags = output.pending.tags ^ tags;
     if (new_focused_tags != 0) {
-        output.pending_focused_tags = new_focused_tags;
+        output.pending.tags = new_focused_tags;
         seat.input_manager.server.root.arrange();
     }
 }

river/command/zoom.zig

@@ -41,7 +41,7 @@ pub fn zoom(
 
         // If the the first view that is part of the layout is focused, zoom
         // the next view in the layout. Otherwise zoom the focused view.
-        var it = ViewStack(View).iterator(output.views.first, output.current_focused_tags);
+        var it = ViewStack(View).iterator(output.views.first, output.current.tags);
         const layout_first = while (it.next()) |node| {
             if (!node.view.pending.float and !node.view.pending.fullscreen) break node;
         } else unreachable;

river/render.zig

@@ -57,7 +57,7 @@ pub fn renderOutput(output: *Output) void {
     c.wlr_renderer_begin(wlr_renderer, width, height);
 
     // Find the first visible fullscreen view in the stack if there is one
-    var it = ViewStack(View).iterator(output.views.first, output.current_focused_tags);
+    var it = ViewStack(View).iterator(output.views.first, output.current.tags);
     const fullscreen_view = while (it.next()) |node| {
         if (node.view.current.fullscreen) break &node.view;
     } else null;
@@ -76,7 +76,7 @@ pub fn renderOutput(output: *Output) void {
         renderLayer(output.*, output.layers[c.ZWLR_LAYER_SHELL_V1_LAYER_BOTTOM], &now);
 
         // The first view in the list is "on top" so iterate in reverse.
-        it = ViewStack(View).reverseIterator(output.views.last, output.current_focused_tags);
+        it = ViewStack(View).reverseIterator(output.views.last, output.current.tags);
         while (it.next()) |node| {
             const view = &node.view;
 
@@ -92,7 +92,7 @@ pub fn renderOutput(output: *Output) void {
         }
 
         // Render focused views
-        it = ViewStack(View).reverseIterator(output.views.last, output.current_focused_tags);
+        it = ViewStack(View).reverseIterator(output.views.last, output.current.tags);
         while (it.next()) |node| {
             const view = &node.view;