From 5608428dc856451bc7c1afc0b5fce3dce0f9792f Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Thu, 9 Dec 2021 20:29:00 +0100
Subject: [PATCH] Backport PR #21890: Drop retina images when building PDF docs

---
 doc/conf.py | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/doc/conf.py b/doc/conf.py
index 669957fe3ef4..018255694033 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -167,6 +167,21 @@ def _check_dependencies():
 
 # Sphinx gallery configuration
 
+def matplotlib_reduced_latex_scraper(block, block_vars, gallery_conf,
+                                     **kwargs):
+    """
+    Reduce srcset when creating a PDF.
+
+    Because sphinx-gallery runs *very* early, we cannot modify this even in the
+    earliest builder-inited signal. Thus we do it at scraping time.
+    """
+    from sphinx_gallery.scrapers import matplotlib_scraper
+
+    if gallery_conf['builder_name'] == 'latex':
+        gallery_conf['image_srcset'] = []
+    return matplotlib_scraper(block, block_vars, gallery_conf, **kwargs)
+
+
 sphinx_gallery_conf = {
     'examples_dirs': ['../examples', '../tutorials', '../plot_types'],
     'filename_pattern': '^((?!sgskip).)*$',
@@ -183,6 +198,7 @@ def _check_dependencies():
     'remove_config_comments': True,
     'min_reported_time': 1,
     'thumbnail_size': (320, 224),
+    'image_scrapers': (matplotlib_reduced_latex_scraper, ),
     # Compression is a significant effort that we skip for local and CI builds.
     'compress_images': ('thumbnails', 'images') if is_release_build else (),
     'matplotlib_animations': True,