zterm/src/layout/Framing.zig

//! Framing layout for a nested `Layout`s or `Widget`s.
//!
//! # Example
//! ...
const std = @import("std");
const terminal = @import("../terminal.zig");

const isTaggedUnion = @import("../event.zig").isTaggedUnion;
const Error = @import("../event.zig").Error;
const Key = terminal.Key;

const log = std.log.scoped(.layout_framing);

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, Renderer),
        widget: @import("../widget.zig").Widget(Event, Renderer),
    };
    const Events = std.ArrayList(Event);
    return struct {
        size: terminal.Size = undefined,
        element: Element = undefined,
        events: Events = undefined,

        pub fn init(allocator: std.mem.Allocator, element: Element) @This() {
            return .{
                .element = element,
                .events = Events.init(allocator),
            };
        }

        pub fn deinit(this: *@This()) void {
            this.events.deinit();
            switch ((&this.element).*) {
                .layout => |*layout| {
                    layout.deinit();
                },
                .widget => |*widget| {
                    widget.deinit();
                },
            }
        }

        pub fn handle(this: *@This(), event: Event) !*Events {
            this.events.clearRetainingCapacity();
            // order is important
            switch (event) {
                .resize => |size| {
                    this.size = size;
                    // adjust size according to the containing elements
                    const sub_event = event;
                    switch ((&this.element).*) {
                        .layout => |*layout| {
                            const events = try layout.handle(sub_event);
                            try this.events.appendSlice(events.items);
                        },
                        .widget => |*widget| {
                            if (widget.handle(sub_event)) |e| {
                                try this.events.append(e);
                            }
                        },
                    }
                },
                else => {
                    switch ((&this.element).*) {
                        .layout => |*layout| {
                            const events = try layout.handle(event);
                            try this.events.appendSlice(events.items);
                        },
                        .widget => |*widget| {
                            if (widget.handle(event)) |e| {
                                try this.events.append(e);
                            }
                        },
                    }
                },
            }
            return &this.events;
        }

        pub fn render(this: *@This(), renderer: Renderer) !void {
            // TODO: padding contents accordingly
            switch ((&this.element).*) {
                .layout => |*layout| {
                    try layout.render(renderer);
                },
                .widget => |*widget| {
                    const content = try widget.content();
                    // TODO: use renderer
                    _ = try terminal.write(content);
                },
            }
        }
    };
}