[librsvg: 3/45] Desiderata for observability

[Marge Bot <marge-bot src gnome org>]

commit fe81d49621a5b80c8ee4d74203218aaec6da1738
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed May 11 16:01:12 2022 -0500

    Desiderata for observability
    
    Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/731>

 devel-docs/api-observability.md | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
---
diff --git a/devel-docs/api-observability.md b/devel-docs/api-observability.md
index 654494f71..2bb5a923c 100644
--- a/devel-docs/api-observability.md
+++ b/devel-docs/api-observability.md
@@ -33,6 +33,23 @@ Shaved.
 
 ## Desiderata
 
+Know exactly what an application did with librsvg:
+
+* All API calls and their parameters.
+
+* State of the Cairo context at entry.
+
+* "What SVG?" - be careful and explicit about exfiltrating SVG data to the logs.
+
+Internals of the library:
+
+* Regular debug tracing.  We may have options to enable/disable
+  tracing domains: parsing, cascading, referencing elements, temporary
+  surfaces during filtering, render tree, etc.
+
+* Log all points where an error is detected/generated, even if it will
+  be discarded later (e.g. invalid CSS values are silently ignored,
+  per the spec).
 
 ## Stuff to log