From ef4879ab42d9aa310cab8c42bc86b9852890baa2 Mon Sep 17 00:00:00 2001
From: sibiraj-s <dev.sibiraj@outlook.com>
Date: Wed, 9 Dec 2020 10:50:45 +0530
Subject: [PATCH] feat: allow placeholder to be set via component

---
 src/lib/editor.component.ts | 19 +++++++++++++++++--
 src/plugins/placeholder.ts  | 15 +++++++++++++--
 2 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/src/lib/editor.component.ts b/src/lib/editor.component.ts
index c6eff2bd..ad3ea4dc 100644
--- a/src/lib/editor.component.ts
+++ b/src/lib/editor.component.ts
@@ -1,7 +1,8 @@
 import {
   Component, ViewChild, ElementRef,
   forwardRef, OnDestroy, ViewEncapsulation, OnInit,
-  Output, EventEmitter, Input, TemplateRef
+  Output, EventEmitter, Input, TemplateRef,
+  OnChanges, SimpleChanges
 } from '@angular/core';
 import { NG_VALUE_ACCESSOR, ControlValueAccessor } from '@angular/forms';
 
@@ -23,7 +24,7 @@ import { NgxEditorService, NgxEditorServiceConfig } from './editor.service';
   encapsulation: ViewEncapsulation.None
 })
 
-export class NgxEditorComponent implements ControlValueAccessor, OnInit, OnDestroy {
+export class NgxEditorComponent implements ControlValueAccessor, OnInit, OnDestroy, OnChanges {
   @ViewChild('ngxEditor', { static: true }) ngxEditor: ElementRef;
 
   view: EditorView;
@@ -33,6 +34,7 @@ export class NgxEditorComponent implements ControlValueAccessor, OnInit, OnDestr
   config: NgxEditorServiceConfig;
 
   @Input() customMenuRef: TemplateRef<any>;
+  @Input() placeholder: string;
   @Output() init = new EventEmitter<EditorView>();
   @Output() focusOut = new EventEmitter<void>();
   @Output() focusIn = new EventEmitter<void>();
@@ -150,11 +152,24 @@ export class NgxEditorComponent implements ControlValueAccessor, OnInit, OnDestr
     this.editorInitialized = true;
   }
 
+  setPlaceholder(newPlaceholder?: string): void {
+    const { dispatch, state: { tr } } = this.view;
+    const placeholder = newPlaceholder ?? this.placeholder;
+    dispatch(tr.setMeta('UPDATE_PLACEHOLDER', placeholder));
+  }
+
   ngOnInit(): void {
     this.createEditor();
+    this.setPlaceholder();
   }
 
   ngOnDestroy(): void {
     this.view.destroy();
   }
+
+  ngOnChanges(changes: SimpleChanges): void {
+    if (changes?.placeholder && !changes.placeholder.isFirstChange()) {
+      this.setPlaceholder(changes.placeholder.currentValue);
+    }
+  }
 }
diff --git a/src/plugins/placeholder.ts b/src/plugins/placeholder.ts
index 67506781..82673731 100644
--- a/src/plugins/placeholder.ts
+++ b/src/plugins/placeholder.ts
@@ -1,4 +1,4 @@
-import { Plugin, EditorState, PluginKey } from 'prosemirror-state';
+import { Plugin, EditorState, PluginKey, Transaction } from 'prosemirror-state';
 import { DecorationSet, Decoration } from 'prosemirror-view';
 
 const DEFAULT_PLACEHOLDER = 'Type Here...';
@@ -7,14 +7,25 @@ const PLACEHOLDER_CLASSNAME = 'NgxEditor__Placeholder';
 const placeholderPlugin = (text: string = DEFAULT_PLACEHOLDER): Plugin => {
   return new Plugin({
     key: new PluginKey('placeholder'),
+    state: {
+      init(): string {
+        return text;
+      },
+      apply(tr: Transaction, previousVal: string): string {
+        const placeholder = tr.getMeta('UPDATE_PLACEHOLDER') ?? previousVal;
+        return placeholder;
+      }
+    },
     props: {
       decorations(state: EditorState): DecorationSet {
         const doc = state.doc;
 
+        const placeholder = this.getState(state);
+
         if (doc.childCount === 1 && doc?.firstChild?.isTextblock && doc.firstChild.content.size === 0) {
           const placeHolderEl = document.createElement('span');
           placeHolderEl.classList.add(PLACEHOLDER_CLASSNAME);
-          placeHolderEl.textContent = text;
+          placeHolderEl.textContent = placeholder;
           return DecorationSet.create(doc, [Decoration.widget(1, placeHolderEl)]);
         }