mod: replace Layout.content with Layout.render

The App.Renderer is used for the new `Layout.render` method. Each layout
renders itself now with corresponding renderers which might only update
parts of the screen, etc.

src/layout/Framing.zig

@@ -11,32 +11,28 @@ const Key = terminal.Key;
 
 const log = std.log.scoped(.layout_framing);
 
-pub fn Layout(comptime Event: type) type {
+pub fn Layout(comptime Event: type, comptime Renderer: type) type {
     if (!isTaggedUnion(Event)) {
         @compileError("Provided user event `Event` for `Layout(comptime Event: type)` is not of type `union(enum)`.");
     }
     const Element = union(enum) {
-        layout: @import("../layout.zig").Layout(Event),
+        layout: @import("../layout.zig").Layout(Event, Renderer),
         widget: @import("../widget.zig").Widget(Event),
     };
     const Events = std.ArrayList(Event);
-    const Contents = std.ArrayList(u8);
     return struct {
         size: terminal.Size = undefined,
-        contents: Contents = undefined,
         element: Element = undefined,
         events: Events = undefined,
 
         pub fn init(allocator: std.mem.Allocator, element: Element) @This() {
             return .{
-                .contents = Contents.init(allocator),
                 .element = element,
                 .events = Events.init(allocator),
             };
         }
 
         pub fn deinit(this: *@This()) void {
-            this.contents.deinit();
             this.events.deinit();
             switch ((&this.element).*) {
                 .layout => |*layout| {
@@ -85,19 +81,18 @@ pub fn Layout(comptime Event: type) type {
             return &this.events;
         }
 
-        pub fn content(this: *@This()) !*Contents {
-            this.contents.clearRetainingCapacity();
+        pub fn render(this: *@This(), renderer: Renderer) !void {
             // TODO: padding contents accordingly
             switch ((&this.element).*) {
                 .layout => |*layout| {
-                    const layout_content = try layout.content();
-                    try this.contents.appendSlice(layout_content.items);
+                    try layout.render(renderer);
                 },
                 .widget => |*widget| {
-                    try this.contents.appendSlice(try widget.content());
+                    const content = try widget.content();
+                    // TODO: use renderer
+                    _ = try terminal.write(content);
                 },
             }
-            return &this.contents;
         }
     };
 }