From ca05f248737c9af46907cb395b448d378cc0e19e Mon Sep 17 00:00:00 2001
From: CJ van den Berg <cj@vdbonline.com>
Date: Fri, 24 Oct 2025 16:19:48 +0200
Subject: [PATCH] feat: add renderer.Layer

---
 src/renderer/vaxis/Layer.zig    | 117 ++++++++++++++++++++++++++++++++
 src/renderer/vaxis/renderer.zig |   1 +
 2 files changed, 118 insertions(+)
 create mode 100644 src/renderer/vaxis/Layer.zig

diff --git a/src/renderer/vaxis/Layer.zig b/src/renderer/vaxis/Layer.zig
new file mode 100644
index 0000000..f43d827
--- /dev/null
+++ b/src/renderer/vaxis/Layer.zig
@@ -0,0 +1,117 @@
+const std = @import("std");
+const vaxis = @import("vaxis");
+
+pub const Plane = @import("Plane.zig");
+
+const Layer = @This();
+
+view: View,
+y_off: i32 = 0,
+x_off: i32 = 0,
+plane_: Plane,
+
+const View = struct {
+    allocator: std.mem.Allocator,
+    screen: vaxis.Screen,
+    unicode: *const vaxis.Unicode,
+
+    pub const Config = struct {
+        h: u16,
+        w: u16,
+    };
+
+    pub fn init(allocator: std.mem.Allocator, unicode: *const vaxis.Unicode, config: Config) std.mem.Allocator.Error!View {
+        return .{
+            .allocator = allocator,
+            .screen = try vaxis.Screen.init(allocator, .{
+                .rows = config.h,
+                .cols = config.w,
+                .x_pixel = 0,
+                .y_pixel = 0,
+            }),
+            .unicode = unicode,
+        };
+    }
+
+    pub fn deinit(self: *View) void {
+        self.screen.deinit(self.allocator);
+    }
+};
+
+pub const Options = struct {
+    y: i32 = 0,
+    x: i32 = 0,
+    h: u16 = 0,
+    w: u16 = 0,
+};
+
+pub fn init(allocator: std.mem.Allocator, unicode: *const vaxis.Unicode, opts: Options) std.mem.Allocator.Error!*Layer {
+    const self = try allocator.create(Layer);
+    self.* = .{
+        .view = try View.init(allocator, unicode, .{
+            .h = opts.h,
+            .w = opts.w,
+        }),
+        .y_off = opts.y,
+        .x_off = opts.x,
+        .plane_ = undefined,
+    };
+    const name = "layer";
+    self.plane_ = .{
+        .window = self.window(),
+        .name_buf = undefined,
+        .name_len = name.len,
+    };
+    @memcpy(self.plane_.name_buf[0..name.len], name);
+    return self;
+}
+
+pub fn deinit(self: *Layer) void {
+    const allocator = self.view.allocator;
+    self.view.deinit();
+    allocator.destroy(self);
+}
+
+fn window(self: *Layer) vaxis.Window {
+    return .{
+        .x_off = 0,
+        .y_off = 0,
+        .parent_x_off = 0,
+        .parent_y_off = 0,
+        .width = self.view.screen.width,
+        .height = self.view.screen.height,
+        .screen = &self.view.screen,
+        .unicode = self.view.unicode,
+    };
+}
+
+pub fn plane(self: *Layer) *Plane {
+    return &self.plane_;
+}
+
+pub fn draw(self: *const Layer, plane_: Plane) void {
+    if (self.x_off >= plane_.window.width) return;
+    if (self.y_off >= plane_.window.height) return;
+
+    const src_y = 0;
+    const src_x = 0;
+    const src_h: usize = self.view.screen.height;
+    const src_w = self.view.screen.width;
+
+    const dst_dim_y: i32 = @intCast(plane_.dim_y());
+    const dst_dim_x: i32 = @intCast(plane_.dim_x());
+    const dst_y = self.y_off;
+    const dst_x = self.x_off;
+    const dst_w = @min(src_w, dst_dim_x - dst_x);
+
+    for (src_y..src_h) |src_row_| {
+        const src_row: i32 = @intCast(src_row_);
+        const src_row_offset = src_row * src_w;
+        const dst_row_offset = (dst_y + src_row) * plane_.window.screen.width;
+        if (dst_y + src_row > dst_dim_y) return;
+        @memcpy(
+            plane_.window.screen.buf[@intCast(dst_row_offset + dst_x)..@intCast(dst_row_offset + dst_x + dst_w)],
+            self.view.screen.buf[@intCast(src_row_offset + src_x)..@intCast(src_row_offset + dst_w)],
+        );
+    }
+}
diff --git a/src/renderer/vaxis/renderer.zig b/src/renderer/vaxis/renderer.zig
index 7ecf83d..b71767c 100644
--- a/src/renderer/vaxis/renderer.zig
+++ b/src/renderer/vaxis/renderer.zig
@@ -9,6 +9,7 @@ const builtin = @import("builtin");
 const RGB = @import("color").RGB;
 
 pub const Plane = @import("Plane.zig");
+pub const Layer = @import("Layer.zig");
 pub const Cell = @import("Cell.zig");
 pub const CursorShape = vaxis.Cell.CursorShape;