river: add focus-previous-tags command

 completions/bash/riverctl      |  1 +
 completions/fish/riverctl.fish |  1 +
 completions/zsh/_riverctl      |  1 +
 doc/riverctl.1.scd             |  4 ++++
 river/Output.zig               |  3 +++
 river/command.zig              |  1 +
 river/command/tags.zig         | 19 +++++++++++++++++++
 7 files changed, 30 insertions(+)

diff --git a/completions/bash/riverctl b/completions/bash/riverctl
index 6c5a52f..4dec1c5 100644
--- a/completions/bash/riverctl
+++ b/completions/bash/riverctl
@@ -25,6 +25,7 @@ function __riverctl_completion ()
 			set-layout-value \
 			mod-layout-value \
 			set-focused-tags \
+			focus-previous-tags \
 			set-view-tags \
 			toggle-focused-tags \
 			toggle-view-tags \
diff --git a/completions/fish/riverctl.fish b/completions/fish/riverctl.fish
index de8a5d9..eca0c25 100644
--- a/completions/fish/riverctl.fish
+++ b/completions/fish/riverctl.fish
@@ -64,6 +64,7 @@ complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a set-view-
 complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a toggle-focused-tags    -d 'Toggle visibility of views with tags corresponding to the set bits of tags'
 complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a toggle-view-tags       -d 'Toggle the tags of the currently focused view'
 complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a spawn-tagmask          -d 'Set a tagmask to filter the tags assigned to newly spawned views on the focused output'
+complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a focus-previous-tags    -d 'Sets tags to their previous value on the focused output'
 # Mappings
 complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a declare-mode           -d 'Create a new mode'
 complete -c riverctl -x -n '__fish_riverctl_complete_no_subcommand' -a enter-mode             -d 'Switch to given mode if it exists'
diff --git a/completions/zsh/_riverctl b/completions/zsh/_riverctl
index a39aa0e..e7fdaa2 100644
--- a/completions/zsh/_riverctl
+++ b/completions/zsh/_riverctl
@@ -33,6 +33,7 @@ _riverctl_subcommands()
         'toggle-focused-tags:Toggle visibility of views with tags corresponding to the set bits of tags'
         'toggle-view-tags:Toggle the tags of the currently focused view'
         'spawn-tagmask:Set a tagmask to filter the tags assigned to newly spawned views on the focused output'
+        'focus-previous-tags:Sets tags to their previous value on the focused output'
         # Mappings
         'declare-mode:Create a new mode'
         'enter-mode:Switch to given mode if it exists'
diff --git a/doc/riverctl.1.scd b/doc/riverctl.1.scd
index 746593e..d8f8bca 100644
--- a/doc/riverctl.1.scd
+++ b/doc/riverctl.1.scd
@@ -139,6 +139,10 @@ are ignored by river.
 	will be assigned the tags 000010001. If no tags would remain after
 	filtering, the _tagmask_ is ignored.
 
+*focus-previous-tags*
+	Sets tags to their previous value on the currently focused output,
+	allowing jumping back and forth between 2 tag setups.
+
 ## MAPPINGS
 
 Mappings are modal in river. Each mapping is associated with a mode and is
diff --git a/river/Output.zig b/river/Output.zig
index 11f3381..5d4449d 100644
--- a/river/Output.zig
+++ b/river/Output.zig
@@ -72,6 +72,9 @@ views: ViewStack(View) = .{},
 current: State = State{ .tags = 1 << 0 },
 pending: State = State{ .tags = 1 << 0 },
 
+/// Remembered version of tags (from last run)
+previous_tags: u32 = 1 << 0,
+
 /// The currently active LayoutDemand
 layout_demand: ?LayoutDemand = null,
 
diff --git a/river/command.zig b/river/command.zig
index b4f1097..315d300 100644
--- a/river/command.zig
+++ b/river/command.zig
@@ -83,6 +83,7 @@ const str_to_impl_fn = [_]struct {
     .{ .name = "toggle-focused-tags",    .impl = @import("command/tags.zig").toggleFocusedTags },
     .{ .name = "toggle-fullscreen",      .impl = @import("command/toggle_fullscreen.zig").toggleFullscreen },
     .{ .name = "toggle-view-tags",       .impl = @import("command/tags.zig").toggleViewTags },
+    .{ .name = "focus-previous-tags",    .impl = @import("command/tags.zig").focusPreviousTags },
     .{ .name = "unmap",                  .impl = @import("command/map.zig").unmap },
     .{ .name = "unmap-pointer",          .impl = @import("command/map.zig").unmapPointer },
     .{ .name = "xcursor-theme",          .impl = @import("command/xcursor_theme.zig").xcursorTheme },
diff --git a/river/command/tags.zig b/river/command/tags.zig
index 308dc2a..b9c223c 100644
--- a/river/command/tags.zig
+++ b/river/command/tags.zig
@@ -31,6 +31,7 @@ pub fn setFocusedTags(
 ) Error!void {
     const tags = try parseTags(allocator, args, out);
     if (seat.focused_output.pending.tags != tags) {
+        seat.focused_output.previous_tags = seat.focused_output.pending.tags;
         seat.focused_output.pending.tags = tags;
         seat.focused_output.arrangeViews();
         seat.focus(null);
@@ -76,6 +77,7 @@ pub fn toggleFocusedTags(
     const output = seat.focused_output;
     const new_focused_tags = output.pending.tags ^ tags;
     if (new_focused_tags != 0) {
+        output.previous_tags = output.pending.tags;
         output.pending.tags = new_focused_tags;
         output.arrangeViews();
         seat.focus(null);
@@ -102,6 +104,23 @@ pub fn toggleViewTags(
     }
 }
 
+/// Switch focus to tags that were selected previously
+pub fn focusPreviousTags(
+    allocator: *std.mem.Allocator,
+    seat: *Seat,
+    args: []const []const u8,
+    out: *?[]const u8,
+) Error!void {
+    const previous_tags = seat.focused_output.previous_tags;
+    if (seat.focused_output.pending.tags != previous_tags) {
+        seat.focused_output.previous_tags = seat.focused_output.pending.tags;
+        seat.focused_output.pending.tags = previous_tags;
+        seat.focused_output.arrangeViews();
+        seat.focus(null);
+        server.root.startTransaction();
+    }
+}
+
 fn parseTags(
     allocator: *std.mem.Allocator,
     args: []const [:0]const u8,