feat: finish ghostty pane backend integration

1 files changed, 105 insertions, 0 deletions

diff --git a/vendor/libghostty-vt/src/lib/struct.zig b/vendor/libghostty-vt/src/lib/struct.zig
new file mode 100644
index 00000000..bbf07ece
--- /dev/null
+++ b/vendor/libghostty-vt/src/lib/struct.zig
@@ -0,0 +1,105 @@
+const std = @import("std");
+const testing = std.testing;
+const Target = @import("target.zig").Target;
+
+/// Create a struct type that is C ABI compatible from a Zig struct type.
+///
+/// When the target is `.zig`, the original struct type is returned as-is.
+/// When the target is `.c`, the struct is recreated with an `extern` layout,
+/// ensuring a stable, C-compatible memory layout.
+///
+/// This handles packed structs by resolving zero alignments to the natural
+/// alignment of each field's type, since extern structs require explicit
+/// alignment. This means packed struct fields like `bool` will take up
+/// their full size (1 byte) rather than being bit-packed.
+pub fn Struct(
+    comptime target: Target,
+    comptime Zig: type,
+) type {
+    return switch (target) {
+        .zig => Zig,
+        .c => c: {
+            const info = @typeInfo(Zig).@"struct";
+            var fields: [info.fields.len]std.builtin.Type.StructField = undefined;
+            for (info.fields, 0..) |field, i| {
+                fields[i] = .{
+                    .name = field.name,
+                    .type = field.type,
+                    .default_value_ptr = field.default_value_ptr,
+                    .is_comptime = field.is_comptime,
+                    .alignment = if (field.alignment > 0) field.alignment else @alignOf(field.type),
+                };
+            }
+
+            break :c @Type(.{ .@"struct" = .{
+                .layout = .@"extern",
+                .fields = &fields,
+                .decls = &.{},
+                .is_tuple = info.is_tuple,
+            } });
+        },
+    };
+}
+
+/// Returns true if a struct of type `T` with size `size` can set
+/// field `field` (if it fits within the size). This is used for ABI
+/// compatibility for structs that have an explicit size field.
+pub fn sizedFieldFits(
+    comptime T: type,
+    size: usize,
+    comptime field: []const u8,
+) bool {
+    const offset = @offsetOf(T, field);
+    const field_size = @sizeOf(@FieldType(T, field));
+    return size >= offset + field_size;
+}
+
+test "sizedFieldFits boundary checks" {
+    const Sized = extern struct {
+        size: usize,
+        a: u8,
+        b: u32,
+    };
+
+    const size_required = @offsetOf(Sized, "size") + @sizeOf(@FieldType(Sized, "size"));
+    const a_required = @offsetOf(Sized, "a") + @sizeOf(@FieldType(Sized, "a"));
+    const b_required = @offsetOf(Sized, "b") + @sizeOf(@FieldType(Sized, "b"));
+
+    try testing.expect(sizedFieldFits(Sized, size_required, "size"));
+    try testing.expect(!sizedFieldFits(Sized, size_required - 1, "size"));
+
+    try testing.expect(sizedFieldFits(Sized, a_required, "a"));
+    try testing.expect(!sizedFieldFits(Sized, a_required - 1, "a"));
+
+    try testing.expect(sizedFieldFits(Sized, b_required, "b"));
+    try testing.expect(!sizedFieldFits(Sized, b_required - 1, "b"));
+}
+
+test "sizedFieldFits respects alignment padding" {
+    const Sized = extern struct {
+        size: usize,
+        a: u8,
+        b: u32,
+    };
+
+    const up_to_padding = @offsetOf(Sized, "b");
+    try testing.expect(sizedFieldFits(Sized, up_to_padding, "a"));
+    try testing.expect(!sizedFieldFits(Sized, up_to_padding, "b"));
+}
+
+test "packed struct converts to extern with full-size bools" {
+    const Packed = packed struct {
+        flag1: bool,
+        flag2: bool,
+        value: u8,
+    };
+
+    const C = Struct(.c, Packed);
+    const info = @typeInfo(C).@"struct";
+
+    try testing.expectEqual(.@"extern", info.layout);
+    try testing.expectEqual(@as(usize, 1), @sizeOf(@FieldType(C, "flag1")));
+    try testing.expectEqual(@as(usize, 1), @sizeOf(@FieldType(C, "flag2")));
+    try testing.expectEqual(@as(usize, 1), @sizeOf(@FieldType(C, "value")));
+    try testing.expectEqual(@as(usize, 3), @sizeOf(C));
+}