Added gnuplot scripts syntax highlighting (SpartanJ/ecode#613).

Fixed: trying to open images triggered binary file popup.
Added a minor explanation on how to enable the spell checker from the editor context menu.

src/modules/languages-syntax-highlighting/src/eepp/ui/doc/languages/gnuplot.cpp

@@ -0,0 +1,249 @@
+#include <eepp/ui/doc/languages/gnuplot.hpp>
+#include <eepp/ui/doc/syntaxdefinitionmanager.hpp>
+
+namespace EE { namespace UI { namespace Doc { namespace Language {
+
+SyntaxDefinition& addGnuplot() {
+
+	// Direct conversion from https://github.com/mammothb/vscode-gnuplot (MIT License)
+
+	return SyntaxDefinitionManager::instance()
+		->add(
+
+			{ "gnuplot",
+			  { "%.gp$", "%.gnuplot$", "%.gnu$", "%.plot$", "%.plt$" },
+			  {
+				  { { "include", "#number" }, "normal", "", SyntaxPatternMatchType::LuaPattern },
+				  { { "include", "#string_single" },
+					"normal",
+					"",
+					SyntaxPatternMatchType::LuaPattern },
+				  { { "include", "#string_double" },
+					"normal",
+					"",
+					SyntaxPatternMatchType::LuaPattern },
+				  { { "\\b(for)\\b\\s*(\\[)", "\\]" },
+					{ "normal", "keyword", "operator" },
+					{ "operator" },
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "#number" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { "include", "#operator" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { "include", "#string_double" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { "include", "#string_single" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { ":" }, "operator", "", SyntaxPatternMatchType::RegEx },
+						{ { "\\b([a-zA-Z]\\w*)\\b\\s*(=|in)" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::RegEx },
+
+					} },
+				  { { "\\[", "\\]" },
+					{ "operator" },
+					{ "operator" },
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "#number" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { "include", "#operator" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+						{ { ":" }, "operator", "", SyntaxPatternMatchType::RegEx },
+
+					} },
+				  { { "\\\\." }, "string", "", SyntaxPatternMatchType::RegEx },
+				  { { "(?<!\\$)(#)(?!\\{).*$\\n?" }, "comment", "", SyntaxPatternMatchType::RegEx },
+				  { { "for" }, "keyword", "", SyntaxPatternMatchType::RegEx },
+				  { { "\\b(angles|arrow|autoscale|bind|bmargin|border|boxwidth|color|colorsequence|"
+					  "clabel|clip|cntrlabel|cntrparam|colorbox|colornames|contour|dashtype|"
+					  "datastyle|datafile|decimalsign|dgrid3d|dummy|encoding|errorbars|fit|"
+					  "fontpath|format|functionstyle|functions|grid|hidden3d|historysize|history|"
+					  "isosamples|jitter|key|label|linetype|link|lmargin|loadpath|locale|logscale|"
+					  "macros|mapping|margin|micro|minussign|monochrome|mouse|mttics|multiplot|"
+					  "mx2tics|mxtics|my2tics|mytics|mztics|nonlinear|object|offsets|origin|output|"
+					  "parametric|paxis|plot|pm3d|palette|pointintervalbox|pointsize|polar|print|"
+					  "psdir|raxis|rgbmax|rlabel|rmargin|rrange|rtics|samples|size|style|surface|"
+					  "table|terminal|termoption|theta|tics|ticslevel|ticscale|timestamp|timefmt|"
+					  "title|tmargin|trange|ttics|urange|variables|version|view|vrange|x2data|"
+					  "x2dtics|x2label|x2mtics|x2range|x2tics|x2zeroaxis|xdata|xdtics|xlabel|xl|"
+					  "xmtics|xrange|xr|xtics|xyplane|xzeroaxis|y2data|y2dtics|y2label|y2mtics|"
+					  "y2range|y2tics|y2zeroaxis|ydata|ydtics|ylabel|yl|ymtics|yrange|yr|ytics|"
+					  "yzeroaxis|zdata|zdtics|zzeroaxis|cbdata|cbdtics|zero|zeroaxis|zlabel|zl|"
+					  "zmtics|zrange|zr|ztics|cblabel|cbl|cbmtics|cbrange|cbr|cbtics)\\b" },
+					"keyword",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(break|cd|call|clear|continue|do|evaluate|exit|fit|help|history|if|for|"
+					  "import|load|lower|pause|plot|print|printerr|pwd|quit|raise|refresh|replot|"
+					  "reread|reset|save|set|show|shell|splot|stats|syste|test|toggle|undefine|"
+					  "unset|update|while|FIT_LIMIT|FIT_MAXITER|FIT_START_LAMBDA|FIT_LAMBDA_FACTOR|"
+					  "FIT_LOG|FIT_SCRIPT|!|functions|var)\\b" },
+					"keyword",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(abs|acos|acosh|arg|asin|asinh|atan|atan2|atanh|besj0|besj1|besy0|besy1|"
+					  "ceil|cos|cosh|erf|erfc|exp|floor|gamma|ibeta|igamma|imag|int|inverf|invnorm|"
+					  "lambertw|lgamma|log|log10|norm|rand|real|sgn|sin|sinh|sqrt|tan|tanh)\\b" },
+					"function",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(gprintf|sprintf|strlen|strstrt|substr|system|word|words)\\b" },
+					"function",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(on|off|default|inside|outside|lmargin|rmargin|tmargin|bmargin|at|left|"
+					  "right|center|top|bottom|center|vertical|horizontal|Left|Right|noreverse|"
+					  "noinvert|samplen|spacing|width|height|noautotitle|columnheader|title|"
+					  "noenhanced|nobox|linestyle|ls|linetype|lt|linewidth|lw)\\b" },
+					"literal",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(aed512|aed767|aifm|aqua|bitgraph|canvas|cgm|corel|dumb|dxf|eepic|emf|"
+					  "emtex|eps|epslatex|epson_180dpi|epson_60dpi|epson_lx800|fig|gif|gpic|"
+					  "hp2623A|hp2648|hp500c|hpdj|hpgl|hpljii|hppj|imagen|jpeg|kc_tek40xx|km_"
+					  "tek40xx|latex|mf|mif|mp|nec_cp6|okidata|pbm|pcl5|pdf|png|pngcairo|"
+					  "postscript|pslatex|pstex|pstricks|qms|regis|selanar|starc|svg|tandy_60dpi|"
+					  "tek40xx|tek410x|texdraw|tgif|tkcanvas|tpic|unknown|vttek)\\b" },
+					"literal",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(u(sing)?|t(it(le)?)?|notit(le)?|w(i(th)?)?|steps|fs(teps)?|notitle|l(i("
+					  "nes)?)?|linespoints|via)\\b" },
+					"keyword",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "(?x:\n\t\t\t\t        \\b                      # Start with a word "
+					  "boundary\n\t\t\t\t        (?=\\b[\\w$]*(\\(|.*=|\\s))\t# Look-ahead for a "
+					  "bracket or equals or a white space\n\t\t\t\t        (?![^(]*\\))\t          "
+					  "  # negative look ahead for a closing bracket without an opening one. This "
+					  "stops a from matching in f(a)\n\t\t\t\t        (\t\t\t\t\t              # "
+					  "Group variable name\n\t\t\t\t\t        [A-Za-z] \t\t\t        # A "
+					  "letter\n\t\t\t\t\t        [\\w$]*\t \t\t          # Any alphanumeric or "
+					  "$\n\t\t\t\t        )\t\t\t\t\t              # That is it for the "
+					  "name.\n\t\t\t        )" },
+					"normal",
+					"",
+					SyntaxPatternMatchType::RegEx },
+				  { { "\\b(if)\\b" }, "keyword", "", SyntaxPatternMatchType::RegEx },
+				  { { "\\b(show)\\b", "(?!\\#)($\\n?)" },
+					{ "keyword" },
+					{},
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "$self" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+
+					} },
+				  { { "\\b(set)\\b\\s*\\b(terminal)\\b", "(?!\\#)($\\n?)" },
+					{ "keyword", "keyword", "keyword" },
+					{},
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "$self" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+
+					} },
+				  { { "\\b(set)\\b\\s*\\b(key)\\b", "(?!\\#)($\\n?)" },
+					{ "keyword", "keyword", "keyword" },
+					{},
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "$self" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+
+					} },
+				  { { "\\b(set)\\b\\s*(?!\\b(terminal|key|for)\\b)", "(?!\\#)($\\n?)" },
+					{ "keyword", "keyword", "keyword" },
+					{},
+					"",
+					SyntaxPatternMatchType::RegEx,
+					{
+						{ { "include", "$self" },
+						  "normal",
+						  "",
+						  SyntaxPatternMatchType::LuaPattern },
+
+					} },
+
+			  },
+			  {
+
+			  },
+			  "",
+			  {}
+
+			} )
+		.addRepositories( {
+
+			{ "string_single",
+			  {
+				  { { "'", "'" }, { "string" }, { "string" }, "", SyntaxPatternMatchType::RegEx },
+
+			  } },
+			{ "string_double",
+			  {
+				  { { "\"", "\"", "\\\\[\\$`\"\\\\\\n]" },
+					{ "string" },
+					{ "string" },
+					"",
+					SyntaxPatternMatchType::RegEx },
+
+			  } },
+			{ "operator",
+			  {
+				  { { "\\s*(==|~=|>|>=|<|<=|&|&&|:|\\||\\|\\||\\+|-|\\*|\\.\\*|/|\\./"
+					  "|\\\\|\\.\\\\|\\^|\\.\\^)\\s*" },
+					"operator",
+					"",
+					SyntaxPatternMatchType::RegEx },
+
+			  } },
+			{ "number",
+			  {
+				  { { "(?x:         # turn on extended mode\n                -?         # an "
+					  "optional minus\n                (?:\n                  [0-9]    # a 0-9 "
+					  "character\n                  \\d*      # followed by zero or more digits\n  "
+					  "              )\n                (?:\n                  \\.       # a "
+					  "period\n                  \\d+      # followed by one or more digits\n      "
+					  "          )?         # make decimal portion optional\n                (?:\n "
+					  "                 [eE]   # an e character\n                  [+-]?  # "
+					  "followed by an option +/-\n                  \\d+    # followed by one or "
+					  "more digits\n                  (?:\n                    \\.   # a period\n  "
+					  "                  \\d+  # followed by one or more digits\n                  "
+					  ")?     # make decimal in exponent power optional\n                )?       "
+					  "# make exponent optional\n              )" },
+					"number",
+					"",
+					SyntaxPatternMatchType::RegEx },
+
+			  } },
+		} );
+}
+
+}}}} // namespace EE::UI::Doc::Language

src/modules/languages-syntax-highlighting/src/eepp/ui/doc/languages/gnuplot.hpp

@@ -0,0 +1,11 @@
+#ifndef EE_UI_DOC_Gnuplot
+#define EE_UI_DOC_Gnuplot
+#include <eepp/ui/doc/syntaxdefinition.hpp>
+
+namespace EE { namespace UI { namespace Doc { namespace Language {
+
+extern SyntaxDefinition& addGnuplot();
+
+}}}} // namespace EE::UI::Doc::Language
+
+#endif

src/modules/languages-syntax-highlighting/src/eepp/ui/doc/languagessyntaxhighlighting.cpp

@@ -38,6 +38,7 @@
 #include <eepp/ui/doc/languages/gleam.hpp>
 #include <eepp/ui/doc/languages/glsl.hpp>
 #include <eepp/ui/doc/languages/gn.hpp>
+#include <eepp/ui/doc/languages/gnuplot.hpp>
 #include <eepp/ui/doc/languages/go.hpp>
 #include <eepp/ui/doc/languages/graphql.hpp>
 #include <eepp/ui/doc/languages/groovy.hpp>
@@ -354,6 +355,10 @@ void LanguagesSyntaxHighlighting::load() {
 
 	sdm->addPreDefinition( { "GN", []() -> SyntaxDefinition& { return addGn(); }, { "%.gn$" } } );
 
+	sdm->addPreDefinition( { "gnuplot",
+							 []() -> SyntaxDefinition& { return addGnuplot(); },
+							 { "%.gp$", "%.gnuplot$", "%.gnu$", "%.plot$", "%.plt$" } } );
+
 	sdm->addPreDefinition( { "Go", []() -> SyntaxDefinition& { return addGo(); }, { "%.go$" } } );
 
 	sdm->addPreDefinition( {