Configurable ligature support

Author: MikeChristensen

docs/en_US/images/preferences_sql_editor.png

@@ -421,6 +421,10 @@ Use the fields on the *Editor* panel to change settings of the query editor.
   font should already be installed on your system. If the font is not found,
   the editor will fall back to the default font, Source Code Pro.
 
+* When the *Font ligatures?* switch is set to *True*, ligatures will be
+  enabled in SQL text boxes and editors provided the configured font family
+  supports them.
+
 * Use the *Font size* field to specify the font size that will be used in text
   boxes and editors.
 

docs/en_US/preferences.rst

@@ -14,6 +14,7 @@ export default function cmOverride(theme) {
       height: '100%',
       color: editor.fg,
       backgroundColor: editor.bg,
+      letterSpacing: '0px',
 
       '&.cm-focused': {
         outline: 'none',

web/pgadmin/static/js/Theme/overrides/codemirror.override.js

@@ -305,6 +305,7 @@ export default function Editor({
     newConfigExtn.push(EditorView.theme({
       '& .cm-scroller .cm-content': {
         fontSize: fontSize,
+        fontVariantLigatures: pref.sql_font_ligatures ? 'normal' : 'none',
         fontFamily: `${pref.sql_font_family}, ${theme.typography.fontFamilySourceCode}`,
       },
       '.cm-gutters': {

web/pgadmin/static/js/components/ReactCodeMirror/components/Editor.jsx

@@ -390,6 +390,16 @@ def register_query_tool_preferences(self):
         )
     )
 
+    self.sql_font_ligatures = self.preference.register(
+        'Editor', 'sql_font_ligatures',
+        gettext("Font ligatures?"), 'boolean',
+        False, category_label=PREF_LABEL_DISPLAY,
+        help_str=gettext(
+            'If set to true, ligatures will be enabled in SQL text boxes '
+            'and editors provided the configured font family supports them.'
+        )
+    )
+
     self.sql_font_family = self.preference.register(
         'Editor', 'sql_font_family',
         gettext("Font family"), 'text', 'Source Code Pro',