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/HStack.zig

@@ -11,23 +11,21 @@ const Key = terminal.Key;
 
 const log = std.log.scoped(.layout_hstack);
 
-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 Widget = @import("../widget.zig").Widget(Event);
-    const Lay = @import("../layout.zig").Layout(Event);
+    const Lay = @import("../layout.zig").Layout(Event, Renderer);
     const Element = union(enum) {
         layout: Lay,
         widget: Widget,
     };
     const Elements = std.ArrayList(Element);
     const Events = std.ArrayList(Event);
-    const Contents = std.ArrayList(u8);
     return struct {
         // TODO: current focused `Element`?
         size: terminal.Size = undefined,
-        contents: Contents = undefined,
         elements: Elements = undefined,
         events: Events = undefined,
 
@@ -53,7 +51,6 @@ pub fn Layout(comptime Event: type) type {
                 @compileError("child: " ++ field.name ++ " is not of type " ++ @typeName(Lay) ++ " or " ++ @typeName(Widget) ++ " but " ++ @typeName(ChildType));
             }
             return .{
-                .contents = Contents.init(allocator),
                 .elements = elements,
                 .events = Events.init(allocator),
             };
@@ -61,7 +58,6 @@ pub fn Layout(comptime Event: type) type {
 
         pub fn deinit(this: *@This()) void {
             this.events.deinit();
-            this.contents.deinit();
             for (this.elements.items) |*element| {
                 switch (element.*) {
                     .layout => |*layout| {
@@ -116,21 +112,21 @@ pub fn Layout(comptime Event: type) type {
             return &this.events;
         }
 
-        pub fn content(this: *@This()) !*Contents {
-            this.contents.clearRetainingCapacity();
-            // TODO: concat contents accordingly to create a vertical stack
+        pub fn render(this: *@This(), renderer: Renderer) !void {
+            // TODO: concat contents accordingly to create a horizontal stack
             for (this.elements.items) |*element| {
                 switch (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());
+                        // TODO: clear per widget if necessary (i.e. can I query that?)
+                        // TODO: render using `renderer`
+                        const content = try widget.content();
+                        _ = try terminal.write(content);
                     },
                 }
             }
-            return &this.contents;
         }
     };
 }