Allow quoting hypertext attribute values (#14550)

doc/lua_api.md

@@ -3535,10 +3535,12 @@ Markup language used in `hypertext[]` elements uses tags that look like HTML tag
 The markup language is currently unstable and subject to change. Use with caution.
 Some tags can enclose text, they open with `<tagname>` and close with `</tagname>`.
 Tags can have attributes, in that case, attributes are in the opening tag in
-form of a key/value separated with equal signs. Attribute values should not be quoted.
+form of a key/value separated with equal signs.
+Attribute values should be quoted using either " or '.
 
-If you want to insert a literal greater-than sign or a backslash into the text,
-you must escape it by preceding it with a backslash.
+If you want to insert a literal greater-than, less-than, or a backslash into the text,
+you must escape it by preceding it with a backslash. In a quoted attribute value, you
+can insert a literal quote mark by preceding it with a backslash.
 
 These are the technically basic tags but see below for usual tags. Base tags are:
 

games/devtest/mods/testformspec/formspec.lua

@@ -69,9 +69,9 @@ local hypertext_basic = [[A hypertext element
 This is a normal text.
 
 <bigger><mono>style</mono> test</bigger>
-<style color=#FFFF00>Yellow text.</style> <style color=#FF0000>Red text.</style>
-<style size=24>Size 24.</style> <style size=16>Size 16</style>. <style size=12>Size 12.</style>
-<style font=normal>Normal font.</style> <style font=mono>Mono font.</style>
+<style color="#FFFF00">Yellow text.</style> <style color='#FF0000'>Red text.</style>
+<style size="24">Size 24.</style> <style size=16>Size 16</style>. <style size=12>Size 12.</style>
+<style font="normal">Normal font.</style> <style font=mono>Mono font.</style>
 
 <bigger>Tag test</bigger>
 <normal>normal</normal>
@@ -88,20 +88,20 @@ This is a normal text.
 
 <bigger>Custom tag test</bigger>
 <tag name=t_green color=green>
-<tag name=t_hover hovercolor=yellow>
-<tag name=t_size size=24>
-<tag name=t_mono font=mono>
-<tag name=t_multi color=green font=mono size=24>
+<tag name="t_hover" hovercolor=yellow>
+<tag name="t_size" size=24>
+<tag name="t_mono" font=mono>
+<tag name="t_multi" color=green font=mono size=24>
 <t_green>color=green</t_green>
-Action: <action name=color><t_green>color=green</t_green></action>
-Action: <action name=hovercolor><t_hover>hovercolor=yellow</t_hover></action>
-Action URL: <action name=open url=https://example.com/?a=b#c>open URL</action>
+Action: <action name="color"><t_green>color=green</t_green></action>
+Action: <action name="hovercolor"><t_hover>hovercolor=yellow</t_hover></action>
+Action URL: <action name="open" url="https://example.com/?a=b#c">open URL</action>
 <t_size>size=24</t_size>
 <t_mono>font=mono</t_mono>
 <t_multi>color=green font=mono size=24</t_multi>
 
 <bigger><mono>action</mono> test</bigger>
-<action name=action_test>action</action>
+<action name="action_test">action</action>
 
 <bigger><mono>img</mono> test</bigger>
 Normal:

src/gui/guiHyperText.cpp

@@ -421,43 +421,68 @@ u32 ParsedText::parseTag(const wchar_t *text, u32 cursor)
 	AttrsList attrs;
 	while (c != L'>') {
 		std::string attr_name = "";
-		core::stringw attr_val = L"";
+		std::wstring attr_val = L"";
 
+		// Consume whitespace
 		while (c == ' ') {
 			c = text[++cursor];
 			if (c == L'\0' || c == L'=')
 				return 0;
 		}
 
+		// Read attribute name
 		while (c != L' ' && c != L'=') {
 			attr_name += (char)c;
 			c = text[++cursor];
 			if (c == L'\0' || c == L'>')
 				return 0;
 		}
 
+		// Consume whitespace
 		while (c == L' ') {
 			c = text[++cursor];
 			if (c == L'\0' || c == L'>')
 				return 0;
 		}
 
+		// Skip equals
 		if (c != L'=')
 			return 0;
-
 		c = text[++cursor];
-
 		if (c == L'\0')
 			return 0;
 
-		while (c != L'>' && c != L' ') {
-			attr_val += c;
+		// Read optional quote
+		wchar_t quote_used = 0;
+		if (c == L'"' || c == L'\'') {
+			quote_used = c;
 			c = text[++cursor];
 			if (c == L'\0')
 				return 0;
 		}
 
-		attrs[attr_name] = stringw_to_utf8(attr_val);
+		// Read attribute value
+		bool escape = false;
+		while (escape || (quote_used && c != quote_used) || (!quote_used && c != L'>' && c != L' ')) {
+			if (quote_used && !escape && c == L'\\') {
+				escape = true;
+			} else {
+				escape = false;
+				attr_val += c;
+			}
+			c = text[++cursor];
+			if (c == L'\0')
+				return 0;
+		}
+
+		// Remove quote
+		if (quote_used) {
+			if (c != quote_used)
+				return 0;
+			c = text[++cursor];
+		}
+
+		attrs[attr_name] = wide_to_utf8(attr_val);
 	}
 
 	++cursor; // Last ">"