start

pub fn start(rect: Rect.Physical) ?Picture {
        if (rect.empty()) {
            //log.err("Picture.start() was called with an empty rect", .{});
            return null;
        }

        // insert queues to catch stuff like stroke after renders
        const cw = dvui.currentWindow();
        const prev_dr_cmds = cw.defer_render_cmds;
        const prev_dr_cmds_after = cw.defer_render_cmds_after;
        // allocate here to return null before we create a target texture
        const render_cmds = cw.arena().create(std.ArrayList(dvui.RenderCommand)) catch return null;
        const render_cmds_after = cw.arena().create(std.ArrayList(dvui.RenderCommand)) catch return null;
        render_cmds.* = .empty;
        render_cmds_after.* = .empty;

        var r = rect;
        // enlarge texture to pixels boundaries
        const x_start = @floor(r.x);
        const x_end = @ceil(r.x + r.w);
        r.x = x_start;
        r.w = @round(x_end - x_start);

        const y_start = @floor(r.y);
        const y_end = @ceil(r.y + r.h);
        r.y = y_start;
        r.h = @round(y_end - y_start);

        const texture = dvui.textureCreateTarget(.{ .width = @trunc(r.w), .height = @trunc(r.h) }) catch return null;

        const target = dvui.renderTarget(.{ .texture = texture, .offset = r.topLeft() });

        // everything looks good, install our render queues
        cw.defer_render_cmds = render_cmds;
        cw.defer_render_cmds_after = render_cmds_after;

        return .{
            .r = r,
            .texture = texture,
            .prev_target = target,
            .prev_dr_cmds = prev_dr_cmds,
            .prev_dr_cmds_after = prev_dr_cmds_after,
            .render_cmds = render_cmds,
            .render_cmds_after = render_cmds_after,
        };
    }