{#
  Shared trip cover: one source of truth for cover resolution + retina
  rendering, used by both the trip-list card (trips.html.twig) and the
  trip-page banner strip (trip-feed-col.html.twig) so the two surfaces
  cannot drift (KTD2).

  Resolution (R7 / R11):
    1. author-selected header.cover_image, when it resolves to page media;
    2. else the first published journal entry's first image;
    3. else nothing.
  A set-but-missing cover_image (deleted/moved file) is `is not defined` in
  page media, so it falls through to the auto-pick rather than rendering a
  broken image (R11). Resolution matches against `media.images` (not all
  media), so a non-image selection — e.g. a `.gpx` from the trip page's own
  media, which the picker used to offer — also falls through instead of
  routing a non-image Medium into cropResize.

  Twig macros can only emit strings — they cannot return a Medium object —
  so resolution and rendering live together in one macro: it emits the
  wrapper + retina <img> when a cover exists, and nothing at all when none
  does (which gives R9/AE4 a clean text-only header for free).

  Rendering (R6 / R14): cropZoom crops-to-fill (cover), so the 1x derivative is
  an actual w×h strip matching the banner/card aspect — NOT cropResize, which
  fits-inside and would hand a portrait source back as a narrow sliver that the
  wrapper's object-fit:cover then upscales into a blur. `alt` is the trip title.

  Retina, all-or-nothing: a 2x derivative (2w×2h) is added to the `srcset` only
  when the source is genuinely wide enough to supply it without upscaling
  (`cover.width >= 2w`); otherwise the srcset is 1x only — no blurry, re-encoded
  upscale, and no odd intermediate widths. Note most imported phone photos are
  ≤1440px wide, so an auto-picked fallback cover is usually 1x-only; the 2x
  kicks in mainly for an explicitly-set wide landscape `cover_image`.
#}
{% macro render(trip_page, alt, w, h, wrapper_class, sizes) %}
{%- set cover = null -%}
{%- if trip_page.header.cover_image and trip_page.media.images[trip_page.header.cover_image] is defined -%}
    {%- set cover = trip_page.media.images[trip_page.header.cover_image] -%}
{%- else -%}
    {%- set dailies_page = grav.pages.find(trip_page.route ~ '/dailies') -%}
    {%- if dailies_page -%}
        {%- set first_entry = dailies_page.children.published()|first -%}
        {%- if first_entry and first_entry.media.images|length > 0 -%}
            {%- set cover = first_entry.media.images|first -%}
        {%- endif -%}
    {%- endif -%}
{%- endif -%}
{%- if cover -%}
<div class="{{ wrapper_class }}">
    <img src="{{ cover.cropZoom(w, h).url }}"
         srcset="{{ cover.cropZoom(w, h).url }} {{ w }}w{% if cover.width >= (w * 2) %}, {{ cover.cropZoom(w * 2, h * 2).url }} {{ (w * 2) }}w{% endif %}"
         sizes="{{ sizes|default('100vw') }}"
         alt="{{ alt }}"
         loading="lazy">
</div>
{%- endif -%}
{% endmacro %}