core: add zoom keybinding for splits

include/ghostty.h

@@ -262,6 +262,7 @@ typedef void (*ghostty_runtime_new_tab_cb)(void *, ghostty_surface_config_s);
 typedef void (*ghostty_runtime_new_window_cb)(void *, ghostty_surface_config_s);
 typedef void (*ghostty_runtime_close_surface_cb)(void *, bool);
 typedef void (*ghostty_runtime_focus_split_cb)(void *, ghostty_split_focus_direction_e);
+typedef void (*ghostty_runtime_zoom_split_cb)(void *);
 typedef void (*ghostty_runtime_goto_tab_cb)(void *, int32_t);
 typedef void (*ghostty_runtime_toggle_fullscreen_cb)(void *, ghostty_non_native_fullscreen_e);
 
@@ -278,6 +279,7 @@ typedef struct {
     ghostty_runtime_new_window_cb new_window_cb;
     ghostty_runtime_close_surface_cb close_surface_cb;
     ghostty_runtime_focus_split_cb focus_split_cb;
+    ghostty_runtime_zoom_split_cb zoom_split_cb;
     ghostty_runtime_goto_tab_cb goto_tab_cb;
     ghostty_runtime_toggle_fullscreen_cb toggle_fullscreen_cb;
 } ghostty_runtime_config_s;

src/Surface.zig

@@ -2118,6 +2118,13 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !void
             } else log.warn("runtime doesn't implement gotoSplit", .{});
         },
 
+        .zoom_split => {
+            log.warn("ZOOM ZOOM", .{});
+            if (@hasDecl(apprt.Surface, "zoomSplit")) {
+                self.rt_surface.zoomSplit();
+            } else log.warn("runtime doesn't implement zoomSplit", .{});
+        },
+
         .toggle_fullscreen => {
             if (@hasDecl(apprt.Surface, "toggleFullscreen")) {
                 self.rt_surface.toggleFullscreen(self.config.macos_non_native_fullscreen);

src/apprt/embedded.zig

@@ -72,6 +72,9 @@ pub const App = struct {
         /// Focus the previous/next split (if any).
         focus_split: ?*const fn (SurfaceUD, input.SplitFocusDirection) callconv(.C) void = null,
 
+        /// Zoom the current split.
+        zoom_split: ?*const fn (SurfaceUD) callconv(.C) void = null,
+
         /// Goto tab
         goto_tab: ?*const fn (SurfaceUD, usize) callconv(.C) void = null,
 
@@ -270,6 +273,15 @@ pub const Surface = struct {
         func(self.opts.userdata, direction);
     }
 
+    pub fn zoomSplit(self: *const Surface) void {
+        const func = self.app.opts.zoom_split orelse {
+            log.info("runtime embedder does not support zoom split", .{});
+            return;
+        };
+
+        func(self.opts.userdata);
+    }
+
     pub fn getContentScale(self: *const Surface) !apprt.ContentScale {
         return self.content_scale;
     }

src/config.zig

@@ -682,6 +682,12 @@ pub const Config = struct {
                 .{ .key = .right, .mods = .{ .super = true, .alt = true } },
                 .{ .goto_split = .right },
             );
+
+            try result.keybind.set.put(
+                alloc,
+                .{ .key = .equal, .mods = .{ .super = true, .shift = true } },
+                .{ .zoom_split = {} },
+            );
         }
 
         return result;

src/input/Binding.zig

@@ -158,6 +158,9 @@ pub const Action = union(enum) {
     /// Focus on a split in a given direction.
     goto_split: SplitFocusDirection,
 
+    /// Zoom and unzoom the current split.
+    zoom_split: void,
+
     /// Reload the configuration. The exact meaning depends on the app runtime
     /// in use but this usually involves re-reading the configuration file
     /// and applying any changes. Note that not all changes can be applied at