split: add auto as split option

Add an `auto` split direction which splits along the larger direction.

src/Surface.zig

@@ -3195,7 +3195,17 @@ pub fn performBindingAction(self: *Surface, action: input.Binding.Action) !bool
 
         .new_split => |direction| {
             if (@hasDecl(apprt.Surface, "newSplit")) {
-                try self.rt_surface.newSplit(direction);
+                const resolved_direction: input.SplitDirection = switch (direction) {
+                    .right => .right,
+                    .down => .down,
+                    .auto => auto: {
+                        const size = self.screen_size;
+                        if (size.width > size.height) {
+                            break :auto .right;
+                        } else break :auto .down;
+                    },
+                };
+                try self.rt_surface.newSplit(resolved_direction);
             } else log.warn("runtime doesn't implement newSplit", .{});
         },
 

src/input.zig

@@ -10,10 +10,16 @@ pub const Binding = @import("input/Binding.zig");
 pub const Link = @import("input/Link.zig");
 pub const KeyEncoder = @import("input/KeyEncoder.zig");
 pub const InspectorMode = Binding.Action.InspectorMode;
-pub const SplitDirection = Binding.Action.SplitDirection;
 pub const SplitFocusDirection = Binding.Action.SplitFocusDirection;
 pub const SplitResizeDirection = Binding.Action.SplitResizeDirection;
 
+// This is made extern (c_int) to make interop easier with our embedded
+// runtime. The small size cost doesn't make a difference in our union.
+pub const SplitDirection = enum(c_int) {
+    right,
+    down,
+};
+
 // Keymap is only available on macOS right now. We could implement it
 // in theory for XKB too on Linux but we don't need it right now.
 pub const Keymap = switch (builtin.os.tag) {

src/input/Binding.zig

@@ -256,11 +256,11 @@ pub const Action = union(enum) {
         application: []const u8,
     };
 
-    // This is made extern (c_int) to make interop easier with our embedded
+    pub const SplitDirection = enum {
-    // runtime. The small size cost doesn't make a difference in our union.
-    pub const SplitDirection = enum(c_int) {
         right,
         down,
+        // splits along the larger direction
+        auto,
 
         // Note: we don't support top or left yet
     };