Define and use \output macro in Sphinx/MathJax

Update TODOs

doc/conf.py

@@ -185,9 +185,8 @@ def local_inv(name: str, *parts: str) -> Optional[str]:
 
 # See https://github.com/iiasa/message_ix/pull/721#pullrequestreview-1497907368:
 # prefer to write \text{} explicitly
-# TODO read at least some of these from message_ix.models
-# TODO complete list
-# TODO also add these to a LaTeX preamble
+# TODO Populate these by reference to message_ix.models
+# TODO Also add these to a LaTeX preamble for PDF output
 text_macros = """ACT
 STORAGE
 STORAGE_CHARGE
@@ -202,6 +201,10 @@ def local_inv(name: str, *parts: str) -> Optional[str]:
         macros={k.replace("_", ""): r"\text{" + k + "}" for k in text_macros.split()},
     ),
 )
+# Example only for #811
+mathjax3_config["tex"]["macros"].update(
+    output=r"\text{output}_{c h h^D l m n^D n^L t y^A y^V}",
+)
 
 # -- Options for sphinx.ext.napoleon ---------------------------------------------------
 

doc/notation.rst

@@ -7,7 +7,7 @@ This page explains the notation used in this mathematical formulation section of
 
    & \forall \, c, h, \ l \notin L^{\text{RES}} \cup L^{\text{REN}} \cup L^{\text{STOR}}, n = n^D = n^O, y = y^A: \\&
    \sum_{h m n^L t ; y^V \leq y}{\left(
-     \text{output}_{c h h^D l m n^D n^L t y^A y^V}
+     \output
      \cdot \text{duration_time_rel}_{h^1=h^D;h^2=h}
      \cdot \text{ACT}_{h m n^L t y^A y^V}
    \right)} \\&