core: introduce new markdown input

To fix
* Avoid blinking in preview
* Don't insert stupid space on empty textarea

core/static/core/simplemde/simplemde.min.css

+/**
+ * simplemde v1.11.2
+ * Copyright Next Step Webs, Inc.
+ * @link https://github.com/NextStepWebs/simplemde-markdown-editor
+ * @license MIT
+ */
+.CodeMirror{color:#000}.CodeMirror-lines{padding:4px 0}.CodeMirror pre{padding:0 4px}.CodeMirror-gutter-filler,.CodeMirror-scrollbar-filler{background-color:#fff}.CodeMirror-gutters{border-right:1px solid #ddd;background-color:#f7f7f7;white-space:nowrap}.CodeMirror-linenumber{padding:0 3px 0 5px;min-width:20px;text-align:right;color:#999;white-space:nowrap}.CodeMirror-guttermarker{color:#000}.CodeMirror-guttermarker-subtle{color:#999}.CodeMirror-cursor{border-left:1px solid #000;border-right:none;width:0}.CodeMirror div.CodeMirror-secondarycursor{border-left:1px solid silver}.cm-fat-cursor .CodeMirror-cursor{width:auto;border:0!important;background:#7e7}.cm-fat-cursor div.CodeMirror-cursors{z-index:1}.cm-animate-fat-cursor{width:auto;border:0;-webkit-animation:blink 1.06s steps(1) infinite;-moz-animation:blink 1.06s steps(1) infinite;animation:blink 1.06s steps(1) infinite;background-color:#7e7}@-moz-keyframes blink{50%{background-color:transparent}}@-webkit-keyframes blink{50%{background-color:transparent}}@keyframes blink{50%{background-color:transparent}}.cm-tab{display:inline-block;text-decoration:inherit}.CodeMirror-ruler{border-left:1px solid #ccc;position:absolute}.cm-s-default .cm-header{color:#00f}.cm-s-default .cm-quote{color:#090}.cm-negative{color:#d44}.cm-positive{color:#292}.cm-header,.cm-strong{font-weight:700}.cm-em{font-style:italic}.cm-link{text-decoration:underline}.cm-strikethrough{text-decoration:line-through}.cm-s-default .cm-keyword{color:#708}.cm-s-default .cm-atom{color:#219}.cm-s-default .cm-number{color:#164}.cm-s-default .cm-def{color:#00f}.cm-s-default .cm-variable-2{color:#05a}.cm-s-default .cm-variable-3{color:#085}.cm-s-default .cm-comment{color:#a50}.cm-s-default .cm-string{color:#a11}.cm-s-default .cm-string-2{color:#f50}.cm-s-default .cm-meta,.cm-s-default .cm-qualifier{color:#555}.cm-s-default .cm-builtin{color:#30a}.cm-s-default .cm-bracket{color:#997}.cm-s-default .cm-tag{color:#170}.cm-s-default .cm-attribute{color:#00c}.cm-s-default .cm-hr{color:#999}.cm-s-default .cm-link{color:#00c}.cm-invalidchar,.cm-s-default .cm-error{color:red}.CodeMirror-composing{border-bottom:2px solid}div.CodeMirror span.CodeMirror-matchingbracket{color:#0f0}div.CodeMirror span.CodeMirror-nonmatchingbracket{color:#f22}.CodeMirror-matchingtag{background:rgba(255,150,0,.3)}.CodeMirror-activeline-background{background:#e8f2ff}.CodeMirror{position:relative;overflow:hidden;background:#fff}.CodeMirror-scroll{overflow:scroll!important;margin-bottom:-30px;margin-right:-30px;padding-bottom:30px;height:100%;outline:0;position:relative}.CodeMirror-sizer{position:relative;border-right:30px solid transparent}.CodeMirror-gutter-filler,.CodeMirror-hscrollbar,.CodeMirror-scrollbar-filler,.CodeMirror-vscrollbar{position:absolute;z-index:6;display:none}.CodeMirror-vscrollbar{right:0;top:0;overflow-x:hidden;overflow-y:scroll}.CodeMirror-hscrollbar{bottom:0;left:0;overflow-y:hidden;overflow-x:scroll}.CodeMirror-scrollbar-filler{right:0;bottom:0}.CodeMirror-gutter-filler{left:0;bottom:0}.CodeMirror-gutters{position:absolute;left:0;top:0;min-height:100%;z-index:3}.CodeMirror-gutter{white-space:normal;height:100%;display:inline-block;vertical-align:top;margin-bottom:-30px}.CodeMirror-gutter-wrapper{position:absolute;z-index:4;background:0 0!important;border:none!important;-webkit-user-select:none;-moz-user-select:none;user-select:none}.CodeMirror-gutter-background{position:absolute;top:0;bottom:0;z-index:4}.CodeMirror-gutter-elt{position:absolute;cursor:default;z-index:4}.CodeMirror-lines{cursor:text;min-height:1px}.CodeMirror pre{-moz-border-radius:0;-webkit-border-radius:0;border-radius:0;border-width:0;background:0 0;font-family:inherit;font-size:inherit;margin:0;white-space:pre;word-wrap:normal;line-height:inherit;color:inherit;z-index:2;position:relative;overflow:visible;-webkit-tap-highlight-color:transparent;-webkit-font-variant-ligatures:none;font-variant-ligatures:none}.CodeMirror-wrap pre{word-wrap:break-word;white-space:pre-wrap;word-break:normal}.CodeMirror-linebackground{position:absolute;left:0;right:0;top:0;bottom:0;z-index:0}.CodeMirror-linewidget{position:relative;z-index:2;overflow:auto}.CodeMirror-code{outline:0}.CodeMirror-gutter,.CodeMirror-gutters,.CodeMirror-linenumber,.CodeMirror-scroll,.CodeMirror-sizer{-moz-box-sizing:content-box;box-sizing:content-box}.CodeMirror-measure{position:absolute;width:100%;height:0;overflow:hidden;visibility:hidden}.CodeMirror-cursor{position:absolute}.CodeMirror-measure pre{position:static}div.CodeMirror-cursors{visibility:hidden;position:relative;z-index:3}.CodeMirror-focused div.CodeMirror-cursors,div.CodeMirror-dragcursors{visibility:visible}.CodeMirror-selected{background:#d9d9d9}.CodeMirror-focused .CodeMirror-selected,.CodeMirror-line::selection,.CodeMirror-line>span::selection,.CodeMirror-line>span>span::selection{background:#d7d4f0}.CodeMirror-crosshair{cursor:crosshair}.CodeMirror-line::-moz-selection,.CodeMirror-line>span::-moz-selection,.CodeMirror-line>span>span::-moz-selection{background:#d7d4f0}.cm-searching{background:#ffa;background:rgba(255,255,0,.4)}.cm-force-border{padding-right:.1px}@media print{.CodeMirror div.CodeMirror-cursors{visibility:hidden}}.cm-tab-wrap-hack:after{content:''}span.CodeMirror-selectedtext{background:0 0}.CodeMirror{height:auto;min-height:300px;border:1px solid #ddd;border-bottom-left-radius:4px;border-bottom-right-radius:4px;padding:10px;font:inherit;z-index:1}.CodeMirror-scroll{min-height:300px}.CodeMirror-fullscreen{background:#fff;position:fixed!important;top:50px;left:0;right:0;bottom:0;height:auto;z-index:9}.CodeMirror-sided{width:50%!important}.editor-toolbar{position:relative;opacity:.6;-webkit-user-select:none;-moz-user-select:none;-ms-user-select:none;-o-user-select:none;user-select:none;padding:0 10px;border-top:1px solid #bbb;border-left:1px solid #bbb;border-right:1px solid #bbb;border-top-left-radius:4px;border-top-right-radius:4px}.editor-toolbar:after,.editor-toolbar:before{display:block;content:' ';height:1px}.editor-toolbar:before{margin-bottom:8px}.editor-toolbar:after{margin-top:8px}.editor-toolbar:hover,.editor-wrapper input.title:focus,.editor-wrapper input.title:hover{opacity:.8}.editor-toolbar.fullscreen{width:100%;height:50px;overflow-x:auto;overflow-y:hidden;white-space:nowrap;padding-top:10px;padding-bottom:10px;box-sizing:border-box;background:#fff;border:0;position:fixed;top:0;left:0;opacity:1;z-index:9}.editor-toolbar.fullscreen::before{width:20px;height:50px;background:-moz-linear-gradient(left,rgba(255,255,255,1) 0,rgba(255,255,255,0) 100%);background:-webkit-gradient(linear,left top,right top,color-stop(0,rgba(255,255,255,1)),color-stop(100%,rgba(255,255,255,0)));background:-webkit-linear-gradient(left,rgba(255,255,255,1) 0,rgba(255,255,255,0) 100%);background:-o-linear-gradient(left,rgba(255,255,255,1) 0,rgba(255,255,255,0) 100%);background:-ms-linear-gradient(left,rgba(255,255,255,1) 0,rgba(255,255,255,0) 100%);background:linear-gradient(to right,rgba(255,255,255,1) 0,rgba(255,255,255,0) 100%);position:fixed;top:0;left:0;margin:0;padding:0}.editor-toolbar.fullscreen::after{width:20px;height:50px;background:-moz-linear-gradient(left,rgba(255,255,255,0) 0,rgba(255,255,255,1) 100%);background:-webkit-gradient(linear,left top,right top,color-stop(0,rgba(255,255,255,0)),color-stop(100%,rgba(255,255,255,1)));background:-webkit-linear-gradient(left,rgba(255,255,255,0) 0,rgba(255,255,255,1) 100%);background:-o-linear-gradient(left,rgba(255,255,255,0) 0,rgba(255,255,255,1) 100%);background:-ms-linear-gradient(left,rgba(255,255,255,0) 0,rgba(255,255,255,1) 100%);background:linear-gradient(to right,rgba(255,255,255,0) 0,rgba(255,255,255,1) 100%);position:fixed;top:0;right:0;margin:0;padding:0}.editor-toolbar a{display:inline-block;text-align:center;text-decoration:none!important;color:#2c3e50!important;width:30px;height:30px;margin:0;border:1px solid transparent;border-radius:3px;cursor:pointer}.editor-toolbar a.active,.editor-toolbar a:hover{background:#fcfcfc;border-color:#95a5a6}.editor-toolbar a:before{line-height:30px}.editor-toolbar i.separator{display:inline-block;width:0;border-left:1px solid #d9d9d9;border-right:1px solid #fff;color:transparent;text-indent:-10px;margin:0 6px}.editor-toolbar a.fa-header-x:after{font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;font-size:65%;vertical-align:text-bottom;position:relative;top:2px}.editor-toolbar a.fa-header-1:after{content:"1"}.editor-toolbar a.fa-header-2:after{content:"2"}.editor-toolbar a.fa-header-3:after{content:"3"}.editor-toolbar a.fa-header-bigger:after{content:"▲"}.editor-toolbar a.fa-header-smaller:after{content:"▼"}.editor-toolbar.disabled-for-preview a:not(.no-disable){pointer-events:none;background:#fff;border-color:transparent;text-shadow:inherit}@media only screen and (max-width:700px){.editor-toolbar a.no-mobile{display:none}}.editor-statusbar{padding:8px 10px;font-size:12px;color:#959694;text-align:right}.editor-statusbar span{display:inline-block;min-width:4em;margin-left:1em}.editor-preview,.editor-preview-side{padding:10px;background:#fafafa;overflow:auto;display:none;box-sizing:border-box}.editor-statusbar .lines:before{content:'lines: '}.editor-statusbar .words:before{content:'words: '}.editor-statusbar .characters:before{content:'characters: '}.editor-preview{position:absolute;width:100%;height:100%;top:0;left:0;z-index:7}.editor-preview-side{position:fixed;bottom:0;width:50%;top:50px;right:0;z-index:9;border:1px solid #ddd}.editor-preview-active,.editor-preview-active-side{display:block}.editor-preview-side>p,.editor-preview>p{margin-top:0}.editor-preview pre,.editor-preview-side pre{background:#eee;margin-bottom:10px}.editor-preview table td,.editor-preview table th,.editor-preview-side table td,.editor-preview-side table th{border:1px solid #ddd;padding:5px}.CodeMirror .CodeMirror-code .cm-tag{color:#63a35c}.CodeMirror .CodeMirror-code .cm-attribute{color:#795da3}.CodeMirror .CodeMirror-code .cm-string{color:#183691}.CodeMirror .CodeMirror-selected{background:#d9d9d9}.CodeMirror .CodeMirror-code .cm-header-1{font-size:200%;line-height:200%}.CodeMirror .CodeMirror-code .cm-header-2{font-size:160%;line-height:160%}.CodeMirror .CodeMirror-code .cm-header-3{font-size:125%;line-height:125%}.CodeMirror .CodeMirror-code .cm-header-4{font-size:110%;line-height:110%}.CodeMirror .CodeMirror-code .cm-comment{background:rgba(0,0,0,.05);border-radius:2px}.CodeMirror .CodeMirror-code .cm-link{color:#7f8c8d}.CodeMirror .CodeMirror-code .cm-url{color:#aab2b3}.CodeMirror .CodeMirror-code .cm-strikethrough{text-decoration:line-through}.CodeMirror .CodeMirror-placeholder{opacity:.5}.CodeMirror .cm-spell-error:not(.cm-url):not(.cm-comment):not(.cm-tag):not(.cm-word){background:rgba(255,0,0,.15)}
\ No newline at end of file

core/templates/core/markdown_textarea.jinja

+<div>
+	<textarea name="{{ widget.name }}"{% include "django/forms/widgets/attrs.html" %}>
+	{% if widget.value %}{{ widget.value }}{% endif %}</textarea>
+
+	{# The simplemde script can be included twice, it's safe in the code #}
+	<script src="{{ statics.js }}"> </script>
+	<script type="text/javascript">
+		var css = "{{ statics.css }}";
+
+		// Only import the css once
+		if (!document.head.innerHTML.includes(css)){
+			document.head.innerHTML += '<link rel="stylesheet" href="' + css + '">';
+		}
+
+		// You can't get the csrf token from the template in a widget
+		// We get it from a cookie as a workaround, see this link
+		// https://docs.djangoproject.com/en/2.0/ref/csrf/#ajax
+		function getCookie(name) {
+			var cookieValue = null;
+			if (document.cookie && document.cookie !== '') {
+				var cookies = document.cookie.split(';');
+				for (var i = 0; i < cookies.length; i++) {
+					var cookie = jQuery.trim(cookies[i]);
+					// Does this cookie string begin with the name we want?
+					if (cookie.substring(0, name.length + 1) === (name + '=')) {
+						cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
+						break;
+					}
+				}
+			}
+			return cookieValue;
+		}
+
+
+		// Custom markdown parser
+		function customMarkdownParser(plainText, preview) {
+			// Wait for jquery to load
+			var waitForJquery = setInterval(function () {
+				if (typeof $ != 'undefined'){
+					clearInterval(waitForJquery)
+					$.ajax({
+						url: "{{ markdown_api_url }}",
+						method: "POST",
+						data: { text: plainText, csrfmiddlewaretoken: getCookie('csrftoken') },
+					}).done(function (msg) {
+						preview.innerHTML = msg;
+					});
+				}
+			}, 10);
+		}
+
+		// Pretty markdown input
+		var simplemde = new SimpleMDE({
+			element: document.getElementById("{{ widget.attrs.id }}"),
+			spellChecker: false,
+			previewRender: function(plainText, preview){ // Async method
+				customMarkdownParser(plainText, preview);
+			}
+		});
+
+	</script>
+</div>
\ No newline at end of file

core/views/forms.py

@@ -26,6 +26,8 @@ from django.contrib.auth.forms import UserCreationForm, AuthenticationForm
 from django import forms
 from django.conf import settings
 from django.db import transaction
+from django.templatetags.static import static
+from django.core.urlresolvers import reverse
 from django.core.exceptions import ValidationError
 from django.forms import (
     CheckboxSelectMultiple,
@@ -90,19 +92,17 @@ class SelectDate(DateInput):
 
 
 class MarkdownInput(Textarea):
-    def render(self, name, value, attrs=None):
-        output = (
-            '<p><a href="%(syntax_url)s">%(help_text)s</a></p>'
-            '<div class="markdown_editor">%(content)s</div>'
-            % {
-                "syntax_url": Page.get_page_by_full_name(
-                    settings.SITH_CORE_PAGE_SYNTAX
-                ).get_absolute_url(),
-                "help_text": _("Help on the syntax"),
-                "content": super(MarkdownInput, self).render(name, value, attrs),
-            }
-        )
-        return output
+    template_name = "core/markdown_textarea.jinja"
+
+    def get_context(self, name, value, attrs):
+        context = super(MarkdownInput, self).get_context(name, value, attrs)
+
+        context["statics"] = {
+            "js": static("core/simplemde/simplemde.min.js"),
+            "css": static("core/simplemde/simplemde.min.css"),
+        }
+        context["markdown_api_url"] = reverse("api:api_markdown")
+        return context
 
 
 class SelectFile(TextInput):