Problem

${image} does nothing on the Wayland backend (fixes #2158). Configs that use images for panels, frames or weather icons silently lose all graphics on a Wayland session, and imlib2 floods stderr:

***** Imlib2 Developer Warning ***** :
	This program is calling the Imlib call:
		imlib_image_clear();
	With the parameter:
		image
	being NULL. Please fix your program.

Cause

cimlib_render() renders through imlib2, which can only paint into an X11 drawable, and it sizes its temporary buffer from window.geometry / window.drawable — both are populated by the X11 output only. On Wayland they are still empty, so imlib_create_image(0, 0) returns NULL, every queued image is dropped, and the calls above run against a null image.

Approach

Ask the active output what it draws into instead of assuming a drawable:

• display_output_base::drawing_context() returns the cairo context the output composites into, or nullptr for outputs that keep drawing to an X11 drawable.
• display_output_wayland implements it with the context of its own surface, and creates an imlib2 context that is not bound to a drawable (cimlib_init_cpu()), since it has none.
• cimlib_render_cairo() walks the same image list, converts imlib2's unpremultiplied ARGB data into cairo's premultiplied ARGB32 (respecting draw_blended, which now means "composite as opaque") and paints each image at text_start + (cur->x, cur->y) scaled to the -WxH size — i.e. the same position and the same stacking order (images behind text) as the X11 path. Cache flushing (imlib_cache_flush_interval, -f, -h) is unchanged.

draw_stuff() only dispatches: X11 keeps calling cimlib_render() because drawing_context() is null there. No config settings were added, and the X11 path is untouched.

Verification

GNOME 46 / mutter (Wayland), conky at 319260b7, built with -DBUILD_WAYLAND=ON -DBUILD_IMLIB2=ON.

Because mutter has no wlr-layer-shell, conky falls back to an xdg-toplevel, which is enough to render. Both binaries were run against the same config and the surface was dumped with cairo_surface_write_to_png() from a debugger (no screenshot tool needed on GNOME):

conky.config = {
  background = false,
  output_backend = 'wayland',
  own_window = true,
  minimum_width = 420, minimum_height = 300,
  update_interval = 2,
}
conky.text = [[
WAYLAND IMLIB2 PATCH
${image /path/to/temperature.png -p 330,10 -s 64x64}
${image /path/to/humidity.png    -p 10,80 -s 64x64}
${image /path/to/frame-01.png    -p 90,80 -s 320x180}
]]

• unpatched: text only, no icons, imlib2 null-image warnings every frame
• patched: text and the three images; zero imlib2 warnings, zero unable to load image
• the composited result was compared against an independent reference composite built with ImageMagick: compare -metric AE → 0.99 % differing pixels, i.e. only resampling-filter noise (cairo FILTER_GOOD vs ImageMagick's default), so colours, alpha and scaling line up.

Happy to attach the before/after screenshot (I could not upload it from the CLI).

Notes / limits

• Like the X11 path, images are re-loaded and re-composited every update. The conversion is O(w*h) per image per frame; if that matters it could cache the converted cairo_surface_t per image_list_s.
• ${image ... -i}/-p/-s/-f/-h all work since they share image_list_s.