patch 9.0.0632: calling a function from an "expr" option has overhead
Problem: Calling a function from an "expr" option has too much overhead.
Solution: Add call_simple_func() and use it for 'foldexpr'
diff --git a/runtime/doc/fold.txt b/runtime/doc/fold.txt
index 93efcbb..f11ca08 100644
--- a/runtime/doc/fold.txt
+++ b/runtime/doc/fold.txt
@@ -74,8 +74,6 @@
of a line. Examples:
This will create a fold for all consecutive lines that start with a tab: >
:set foldexpr=getline(v:lnum)[0]==\"\\t\"
-This will call a function to compute the fold level: >
- :set foldexpr=MyFoldLevel(v:lnum)
This will make a fold out of paragraphs separated by blank lines: >
:set foldexpr=getline(v:lnum)=~'^\\s*$'&&getline(v:lnum+1)=~'\\S'?'<1':1
This does the same: >
@@ -84,6 +82,10 @@
Note that backslashes must be used to escape characters that ":set" handles
differently (space, backslash, double quote, etc., see |option-backslash|).
+The most efficient is to call a compiled function without arguments: >
+ :set foldexpr=MyFoldLevel()
+The function must use v:lnum. See |expr-option-function|.
+
These are the conditions with which the expression is evaluated:
- The current buffer and window are set for the line.
- The variable "v:lnum" is set to the line number.
diff --git a/runtime/doc/vim9.txt b/runtime/doc/vim9.txt
index b73011a..15e9a70 100644
--- a/runtime/doc/vim9.txt
+++ b/runtime/doc/vim9.txt
@@ -1410,6 +1410,21 @@
'three'
]
+
+Calling a function in an expr option ~
+ *expr-option-function*
+A few options, such as 'foldexpr', are an expresison that is evaluated to get
+a value. The evaluation can have quite a bit of overhead. One way to
+minimize the overhead, and also to keep the option value very simple, is to
+defined a compiled function and set the option to call it without arguments.
+Example: >
+ vim9script
+ def MyFoldFunc(): any
+ ... compute fold level for line v:lnum
+ return level
+ enddef
+ set foldexpr=s:MyFoldFunc()
+
==============================================================================
4. Types *vim9-types*