From 83ee363cb4c19246ac977f55e46439dd8a1508ba Mon Sep 17 00:00:00 2001
From: "jeremy@jermolene.com" <jeremy@jermolene.com>
Date: Tue, 22 Jun 2021 21:52:00 +0100
Subject: [PATCH] Add charcode operator to make it easier to generate strings
 containing control characters

Avoids some confusing hacks. @saqimtiaz I'm guessing you might have already done something like this?
---
 core/modules/filters/strings.js                 | 10 ++++++++++
 editions/test/tiddlers/tests/test-filters.js    |  6 ++++++
 editions/tw5.com/tiddlers/filters/charcode.tid  | 17 +++++++++++++++++
 .../tiddlers/filters/examples/charcode.tid      |  7 +++++++
 4 files changed, 40 insertions(+)
 create mode 100644 editions/tw5.com/tiddlers/filters/charcode.tid
 create mode 100644 editions/tw5.com/tiddlers/filters/examples/charcode.tid

diff --git a/core/modules/filters/strings.js b/core/modules/filters/strings.js
index 286907dca..6fd64df08 100644
--- a/core/modules/filters/strings.js
+++ b/core/modules/filters/strings.js
@@ -172,4 +172,14 @@ exports.pad = function(source,operator,options) {
 	return results;
 }
 
+exports.charcode = function(source,operator,options) {
+	var chars = [];
+	$tw.utils.each(operator.operands,function(operand) {
+		if(operand !== "") {
+			chars.push(String.fromCharCode($tw.utils.parseInt(operand)));
+		}
+	});
+	return [chars.join("")];
+};
+
 })();
diff --git a/editions/test/tiddlers/tests/test-filters.js b/editions/test/tiddlers/tests/test-filters.js
index ee428b1a0..9b8c2bd44 100644
--- a/editions/test/tiddlers/tests/test-filters.js
+++ b/editions/test/tiddlers/tests/test-filters.js
@@ -818,6 +818,12 @@ function runTests(wiki) {
 	it("should handle the deserializers operator", function() {
 	expect(wiki.filterTiddlers("[deserializers[]]").join(",")).toBe("application/javascript,application/json,application/x-tiddler,application/x-tiddler-html-div,application/x-tiddlers,text/css,text/html,text/plain");
 	});
+	
+	it("should handle the charcode operator", function() {
+		expect(wiki.filterTiddlers("[charcode[9]]").join(" ")).toBe(String.fromCharCode(9));
+		expect(wiki.filterTiddlers("[charcode[9],[10]]").join(" ")).toBe(String.fromCharCode(9) + String.fromCharCode(10));
+		expect(wiki.filterTiddlers("[charcode[]]").join(" ")).toBe("");
+	});
 
 }
 
diff --git a/editions/tw5.com/tiddlers/filters/charcode.tid b/editions/tw5.com/tiddlers/filters/charcode.tid
new file mode 100644
index 000000000..85d70111e
--- /dev/null
+++ b/editions/tw5.com/tiddlers/filters/charcode.tid
@@ -0,0 +1,17 @@
+caption: charcode
+created: 20210622214425635
+modified: 20210622214425635
+op-input: ignored
+op-output: a string formed from concatenating the characters specified by the numeric codes given in the operand(s)
+op-parameter: numeric character code
+op-parameter-name: C
+op-purpose: generates string characters from their numeric character codes
+tags: [[Filter Operators]]
+title: charcode Operator
+type: text/vnd.tiddlywiki
+
+<<.from-version "5.1.24">>
+
+This operator returns a string formed from concatenating the characters specified by the numeric codes given in one or more operands. It is useful for generating special characters such as tab (`charcode[9]`) or new line (`charcode[13],[10]`).
+
+<<.operator-examples "charcode">>
diff --git a/editions/tw5.com/tiddlers/filters/examples/charcode.tid b/editions/tw5.com/tiddlers/filters/examples/charcode.tid
new file mode 100644
index 000000000..f68d23952
--- /dev/null
+++ b/editions/tw5.com/tiddlers/filters/examples/charcode.tid
@@ -0,0 +1,7 @@
+created: 20210622214849214
+modified: 20210622214849214
+tags: [[charcode Operator]] [[Operator Examples]]
+title: charcode Operator (Examples)
+type: text/vnd.tiddlywiki
+
+<<.operator-example 1 "[charcode[65]match[A]]">>