theme function

src/plugins/expressions/common/expression_functions/specs/font.ts

@@ -64,21 +64,22 @@ export const font: ExpressionFunctionFont = {
   inputTypes: ['null'],
   args: {
     align: {
-      default: 'left',
+      default: '{ theme "font.align" default="left" }',
       help: i18n.translate('expressions.functions.font.args.alignHelpText', {
         defaultMessage: 'The horizontal text alignment.',
       }),
       options: Object.values(TextAlignment),
       types: ['string'],
     },
     color: {
+      default: `{ theme "font.color" }`,
       help: i18n.translate('expressions.functions.font.args.colorHelpText', {
         defaultMessage: 'The text color.',
       }),
       types: ['string'],
     },
     family: {
-      default: `"${openSans.value}"`,
+      default: `{ theme "font.family" default="${openSans.value}" }`,
       help: i18n.translate('expressions.functions.font.args.familyHelpText', {
         defaultMessage: 'An acceptable {css} web font string',
         values: {
@@ -88,38 +89,38 @@ export const font: ExpressionFunctionFont = {
       types: ['string'],
     },
     italic: {
-      default: false,
+      default: `{ theme "font.italic" default=false }`,
       help: i18n.translate('expressions.functions.font.args.italicHelpText', {
         defaultMessage: 'Italicize the text?',
       }),
       options: [true, false],
       types: ['boolean'],
     },
     lHeight: {
-      default: null,
+      default: `{ theme "font.lHeight" }`,
       aliases: ['lineHeight'],
       help: i18n.translate('expressions.functions.font.args.lHeightHelpText', {
         defaultMessage: 'The line height in pixels',
       }),
       types: ['number', 'null'],
     },
     size: {
-      default: 14,
+      default: `{ theme "font.size" default=14 }`,
       help: i18n.translate('expressions.functions.font.args.sizeHelpText', {
         defaultMessage: 'The font size in pixels',
       }),
       types: ['number'],
     },
     underline: {
-      default: false,
+      default: `{ theme "font.underline" default=false }`,
       help: i18n.translate('expressions.functions.font.args.underlineHelpText', {
         defaultMessage: 'Underline the text?',
       }),
       options: [true, false],
       types: ['boolean'],
     },
     weight: {
-      default: 'normal',
+      default: `{ theme "font.weight" default="normal" }`,
       help: i18n.translate('expressions.functions.font.args.weightHelpText', {
         defaultMessage: 'The font weight. For example, {list}, or {end}.',
         values: {

src/plugins/expressions/common/expression_functions/specs/index.ts

@@ -24,6 +24,7 @@ import { kibanaContextFunction } from './kibana_context';
 import { variableSet } from './var_set';
 import { variable } from './var';
 import { AnyExpressionFunctionDefinition } from '../types';
+import { theme } from './theme';
 
 export const functionSpecs: AnyExpressionFunctionDefinition[] = [
   clog,
@@ -32,6 +33,7 @@ export const functionSpecs: AnyExpressionFunctionDefinition[] = [
   kibanaContextFunction,
   variableSet,
   variable,
+  theme,
 ];
 
 export * from './clog';
@@ -40,3 +42,4 @@ export * from './kibana';
 export * from './kibana_context';
 export * from './var_set';
 export * from './var';
+export * from './theme';

src/plugins/expressions/common/expression_functions/specs/theme.ts

@@ -0,0 +1,66 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import { i18n } from '@kbn/i18n';
+import { get } from 'lodash';
+import { ExpressionFunctionDefinition } from '../types';
+
+interface Arguments {
+  variable: string;
+  default: string | number | boolean;
+}
+
+type Output = string | number | boolean | undefined;
+
+export type ExpressionFunctionTheme = ExpressionFunctionDefinition<
+  'theme',
+  null,
+  Arguments,
+  Output
+>;
+
+export const theme: ExpressionFunctionTheme = {
+  name: 'theme',
+  aliases: [],
+  help: i18n.translate('expressions.functions.themeHelpText', {
+    defaultMessage: 'Reads a theme setting.',
+  }),
+  inputTypes: ['null'],
+  args: {
+    variable: {
+      aliases: ['_'],
+      help: i18n.translate('expressions.functions.theme.args.variableHelpText', {
+        defaultMessage: 'theme variable to read.',
+      }),
+      required: true,
+      types: ['string'],
+    },
+    default: {
+      help: i18n.translate('expressions.functions.font.args.defaultHelpText', {
+        defaultMessage: 'default value in case theming info is not available.',
+      }),
+      types: ['string', 'number'],
+    },
+  },
+  fn: (input, args, handlers) => {
+    // currently we use variable `theme`, but external theme service would be preferable
+    const vars = handlers.variables.theme || {};
+    return get(vars, args.variable, args.default);
+  },
+};