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vxfw: add Center widget
Center widget centers a child widget within itself
+119
+118
src/vxfw/Center.zig
+118
src/vxfw/Center.zig
···
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const std = @import("std");
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const vaxis = @import("../main.zig");
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const Allocator = std.mem.Allocator;
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const vxfw = @import("vxfw.zig");
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const Center = @This();
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child: vxfw.Widget,
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pub fn widget(self: *const Center) vxfw.Widget {
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return .{
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.userdata = @constCast(self),
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.eventHandler = typeErasedEventHandler,
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.drawFn = typeErasedDrawFn,
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};
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}
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fn typeErasedEventHandler(ptr: *anyopaque, ctx: *vxfw.EventContext, event: vxfw.Event) anyerror!void {
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const self: *const Center = @ptrCast(@alignCast(ptr));
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return self.child.handleEvent(ctx, event);
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}
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fn typeErasedDrawFn(ptr: *anyopaque, ctx: vxfw.DrawContext) Allocator.Error!vxfw.Surface {
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const self: *const Center = @ptrCast(@alignCast(ptr));
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return self.draw(ctx);
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}
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/// Cannot have unbounded constraints
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pub fn draw(self: *const Center, ctx: vxfw.DrawContext) Allocator.Error!vxfw.Surface {
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const child_ctx = ctx.withConstraints(.{ .width = 0, .height = 0 }, ctx.max);
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const max_size = ctx.max.size();
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const child = try self.child.draw(child_ctx);
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const x = (max_size.width - child.size.width) / 2;
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const y = (max_size.height - child.size.height) / 2;
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const children = try ctx.arena.alloc(vxfw.SubSurface, 1);
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children[0] = .{
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.origin = .{ .col = x, .row = y },
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.z_index = 0,
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.surface = child,
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};
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return .{
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.size = max_size,
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.widget = self.widget(),
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.buffer = &.{},
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.children = children,
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};
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}
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test Center {
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const Text = @import("Text.zig");
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// Will be height=1, width=3
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const text: Text = .{ .text = "abc" };
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const center: Center = .{ .child = text.widget() };
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var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
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defer arena.deinit();
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const ucd = try vaxis.Unicode.init(arena.allocator());
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vxfw.DrawContext.init(&ucd, .unicode);
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{
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// Center expands to the max size. It must therefore have non-null max width and max height.
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// These values are asserted in draw
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const ctx: vxfw.DrawContext = .{
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.arena = arena.allocator(),
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.min = .{},
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.max = .{ .width = 10, .height = 10 },
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};
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const surface = try center.draw(ctx);
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// Center does not produce any drawable cells
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try std.testing.expectEqual(0, surface.buffer.len);
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// Center has 1 child
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try std.testing.expectEqual(1, surface.children.len);
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// Center is the max size
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try std.testing.expectEqual(surface.size, ctx.max.size());
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const child = surface.children[0];
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// The child is 1x3
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try std.testing.expectEqual(3, child.surface.size.width);
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try std.testing.expectEqual(1, child.surface.size.height);
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// A centered 1x3 in 10x10 should be at origin 3, 4. The bias is toward the top left corner
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try std.testing.expectEqual(4, child.origin.row);
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try std.testing.expectEqual(3, child.origin.col);
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}
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{
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// Center expands to the max size. It must therefore have non-null max width and max height.
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// These values are asserted in draw
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const ctx: vxfw.DrawContext = .{
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.arena = arena.allocator(),
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.min = .{},
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.max = .{ .width = 5, .height = 3 },
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};
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const surface = try center.draw(ctx);
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// Center does not produce any drawable cells
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try std.testing.expectEqual(0, surface.buffer.len);
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// Center has 1 child
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try std.testing.expectEqual(1, surface.children.len);
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// Center is the max size
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try std.testing.expectEqual(surface.size, ctx.max.size());
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const child = surface.children[0];
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// The child is 1x3
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try std.testing.expectEqual(3, child.surface.size.width);
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try std.testing.expectEqual(1, child.surface.size.height);
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// A centered 1x3 in 3x5 should be at origin 1, 1. This is a perfectly centered child
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try std.testing.expectEqual(1, child.origin.row);
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try std.testing.expectEqual(1, child.origin.col);
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}
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}
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test "refAllDecls" {
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std.testing.refAllDecls(@This());
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}