From 31613d15ef0f4052829bd2d161c2d80acfa5e1d6 Mon Sep 17 00:00:00 2001
From: Campbell Barton <campbell@blender.org>
Date: Tue, 13 Jun 2023 14:36:55 +1000
Subject: [PATCH] ImBuf: WIN32 UNC support for path to URI conversion

Correct the drive letter check & support UNC paths.
---
 source/blender/imbuf/intern/thumbs.cc | 28 +++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/source/blender/imbuf/intern/thumbs.cc b/source/blender/imbuf/intern/thumbs.cc
index d599a4a9fb7..88db853f943 100644
--- a/source/blender/imbuf/intern/thumbs.cc
+++ b/source/blender/imbuf/intern/thumbs.cc
@@ -218,13 +218,29 @@ static bool uri_from_filename(const char *path, char *uri)
   char orig_uri[URI_MAX];
 
 #ifdef WIN32
-  if (strlen(path) < 2 && path[1] != ':') {
-    /* Not a correct absolute path. */
-    return 0;
+  bool path_is_unc = BLI_path_is_unc(path);
+  char path_unc_normalized[FILE_MAX];
+  if (path_is_unc) {
+    STRNCPY(path_unc_normalized, path);
+    BLI_path_normalize_unc(path_unc_normalized, sizeof(path_unc_normalized));
+    path = path_unc_normalized;
+    /* Assign again because a normalized UNC path may resolve to a drive letter. */
+    path_is_unc = BLI_path_is_unc(path);
+  }
+
+  if (path_is_unc) {
+    /* Skip over the `\\` prefix, it's not needed for a URI. */
+    SNPRINTF(orig_uri, "file://%s", BLI_path_slash_skip(path));
+  }
+  else if (BLI_path_is_win32_drive(path)) {
+    SNPRINTF(orig_uri, "file:///%s", path);
+    /* Always use an uppercase drive/volume letter in the URI. */
+    orig_uri[8] = char(toupper(orig_uri[8]));
+  }
+  else {
+    /* Not a correct absolute path with a drive letter or UNC prefix. */
+    return false;
   }
-  SNPRINTF(orig_uri, "file:///%s", path);
-  /* Always use an uppercase drive/volume letter in the URI. */
-  orig_uri[8] = char(toupper(orig_uri[8]));
   BLI_str_replace_char(orig_uri, '\\', '/');
 #else
   SNPRINTF(orig_uri, "file://%s", path);