From 2d1232878d9ddbf0b67cfd5d059af08ed4fe1e80 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Tue, 29 Jul 2025 14:40:23 -0700
Subject: [PATCH] apprt/gtk-ng: goto_tab

---
 src/apprt/gtk-ng/class/application.zig | 29 ++++++++++++-
 src/apprt/gtk-ng/class/window.zig      | 57 ++++++++++++++++++++++++++
 2 files changed, 85 insertions(+), 1 deletion(-)

diff --git a/src/apprt/gtk-ng/class/application.zig b/src/apprt/gtk-ng/class/application.zig
index 0d5f34237..2efd6e211 100644
--- a/src/apprt/gtk-ng/class/application.zig
+++ b/src/apprt/gtk-ng/class/application.zig
@@ -497,6 +497,8 @@ pub const Application = extern struct {
                 value.config,
             ),
 
+            .goto_tab => return Action.gotoTab(target, value),
+
             .mouse_over_link => Action.mouseOverLink(target, value),
             .mouse_shape => Action.mouseShape(target, value),
             .mouse_visibility => Action.mouseVisibility(target, value),
@@ -535,7 +537,6 @@ pub const Application = extern struct {
             .toggle_fullscreen => Action.toggleFullscreen(target),
 
             // Unimplemented but todo on gtk-ng branch
-            .goto_tab,
             .move_tab,
             .new_split,
             .resize_split,
@@ -1216,6 +1217,32 @@ const Action = struct {
         }
     }
 
+    pub fn gotoTab(
+        target: apprt.Target,
+        tab: apprt.action.GotoTab,
+    ) bool {
+        switch (target) {
+            .app => return false,
+            .surface => |core| {
+                const surface = core.rt_surface.surface;
+                const window = ext.getAncestor(
+                    Window,
+                    surface.as(gtk.Widget),
+                ) orelse {
+                    log.warn("surface is not in a window, ignoring new_tab", .{});
+                    return false;
+                };
+
+                return window.selectTab(switch (tab) {
+                    .previous => .previous,
+                    .next => .next,
+                    .last => .last,
+                    else => .{ .n = @intCast(@intFromEnum(tab)) },
+                });
+            },
+        }
+    }
+
     pub fn mouseOverLink(
         target: apprt.Target,
         value: apprt.action.MouseOverLink,
diff --git a/src/apprt/gtk-ng/class/window.zig b/src/apprt/gtk-ng/class/window.zig
index 70594f53a..8b5074968 100644
--- a/src/apprt/gtk-ng/class/window.zig
+++ b/src/apprt/gtk-ng/class/window.zig
@@ -350,6 +350,63 @@ pub const Window = extern struct {
         return page;
     }
 
+    pub const SelectTab = union(enum) {
+        previous,
+        next,
+        last,
+        n: usize,
+    };
+
+    /// Select the tab as requested. Returns true if the tab selection
+    /// changed.
+    pub fn selectTab(self: *Self, n: SelectTab) bool {
+        const priv = self.private();
+        const tab_view = priv.tab_view;
+
+        // Get our current tab numeric position
+        const selected = tab_view.getSelectedPage() orelse return false;
+        const current = tab_view.getPagePosition(selected);
+
+        // Get our total
+        const total = tab_view.getNPages();
+
+        const goto: c_int = switch (n) {
+            .previous => if (current > 0)
+                current - 1
+            else
+                total - 1,
+
+            .next => if (current < total - 1)
+                current + 1
+            else
+                0,
+
+            .last => total - 1,
+
+            .n => |v| n: {
+                // 1-indexed
+                if (v == 0) return false;
+
+                const n_int = std.math.cast(
+                    c_int,
+                    v,
+                ) orelse return false;
+                break :n @min(n_int - 1, total - 1);
+            },
+        };
+        assert(goto >= 0);
+        assert(goto < total);
+
+        // If our target is the same as our current then we do nothing.
+        if (goto == current) return false;
+
+        // Add the page and select it
+        const page = tab_view.getNthPage(goto);
+        tab_view.setSelectedPage(page);
+
+        return true;
+    }
+
     /// Updates various appearance properties. This should always be safe
     /// to call multiple times. This should be called whenever a change
     /// happens that might affect how the window appears (config change,