Support readonly values in ParametersView

Author: jsantell

src/app/elements/ParametersViewElement.js

@@ -62,7 +62,7 @@ function propsToElements(entity, elements, props, entities) {
       </accordion-view>`);
       continue;
     } else {
-      const { name, type, prop: propName, enumType, default: def } = prop;
+      const { name, type, prop: propName, enumType, default: def, readonly } = prop;
 
       let value = propByString(entity, propName);
       if (value === undefined) {
@@ -94,6 +94,7 @@ function propsToElements(entity, elements, props, entities) {
           .max="${max}"
           .step="${step}"
           .precision="${precision}"
+          .readonly="${readonly === true}"
           .data="${associatedData}"
           >
         </key-value>`);

src/app/elements/values/KeyValueElement.js

@@ -17,6 +17,7 @@ export default class KeyValueElement extends LitElement {
       type: { type: String, reflect: true },
       enumType: { type: String, reflect: true, attribute: 'enum-type' },
       property: { type: String, reflect: true },
+      readonly: { type: Boolean },
       // For number types only
       min: { type: Number, reflect: true },
       max: { type: Number, reflect: true },
@@ -61,6 +62,8 @@ export default class KeyValueElement extends LitElement {
 
     if (this.value == null) {
       valueElement = html``;
+    } else if (this.readonly) {
+      valueElement = this.value;
     } else {
       switch (this.type) {
         case 'array':