refactor: move column selector from form to table

This commit changes the way the `column_selector` is set up. Up until
now, it was a simple select input, that could only be used in
conjunction with an existing form. That meant, that the colums selector
had to be places at a position away from the actual table.
Now the column selector is its own form, therefore it can be places
whereever we want it. Also it is not a templatetag anymore, but a simple
partial template that has to be included with {% include ... %}.
The downside is, that we might now have multiple forms sending get
parameters - this is where the new "form_get_hidden.html" template comes
in. It adds existing get parameters to hidden fields in the form, that
way multiple forms don't get in each others way.

Closes: #173

apis_core/apis_metainfo/templates/generic_list.html

@@ -52,14 +52,8 @@ <h3 style="margin-bottom:15px;">
 
             <!--Search mask-->
             {% load django_tables2 crispy_forms_tags %}
-            <form action="." class="uniForm" method="get">
-
-              {% if togglable_colums %}
-                <legend>Select additional columns</legend>
-                {% column_selector %}
-              {% endif %}
-
-              <br />
+            <form class="uniForm">
+              {% include "partials/form_get_hidden.html" with request=request exclude_fields=filter.form.fields %}
               {% crispy filter.form filter.form.helper %}
             </form>
 
@@ -118,14 +112,26 @@ <h1>{{ data.title }}</h1>
               {% endif %}
 
             {% endblock %}
+
           </div>
         </div>
       </div>
       <div class="col-md-8" id="results">
         <div class="card">
           <div class="card-body">
             {% with table.paginator.count as total %}
-              <legend>Result: {{ total }} items</legend>
+              <div class="row">
+                <div class="col">
+                  <h3>Result: {{ total }} items</h3>
+                </div>
+                <div class="col">
+
+                  {% if togglable_colums %}
+                    {% include "partials/column_selector.html" with togglable_columns=togglable_colums request=request %}
+                  {% endif %}
+
+                </div>
+              </div>
 
               {% if conf_items %}
                 <div class="dropdown">

apis_core/apis_metainfo/templatetags/apis_metainfo_extras.py

@@ -14,12 +14,3 @@ def class_definition(context):
         print(e)
         pass
     return values
-
-
-@register.inclusion_tag("apis_metainfo/tags/column_selector.html", takes_context=True)
-def column_selector(context):
-    try:
-        return {"columns": context["togglable_colums"]}
-    except Exception as e:
-        print(e)
-        return {"columns": None}

apis_core/core/templates/partials/column_selector.html

@@ -0,0 +1,20 @@
+{% if togglable_columns %}
+  <form class="form-inline float-right">
+    <select class="selectpicker"
+            multiple
+            data-selected-text-format="count > 2"
+            name="columns"
+            id="column_selector">
+      {% for col in togglable_columns %}<option value="{{ col }}">{{ col|title }}</option>{% endfor %}
+    </select>
+    {% include "partials/form_get_hidden.html" with request=request exclude_fields="columns" %}
+    <button type="submit" class="form-control">Show</button>
+    <script>
+    $('#column_selector').on('loaded.bs.select', function (e) {
+        var url = new URL(window.location.href);
+        var columns = url.searchParams.getAll("columns");
+        $('#column_selector').selectpicker('val', columns);
+    });
+    </script>
+  </form>
+{% endif %}

apis_core/core/templates/partials/form_get_hidden.html

@@ -0,0 +1,11 @@
+{# this template is meant to be used in forms #}
+{# it add exisiting GET parameters to the form as hidden input fields #}
+{# it requires the request as argument `request` as well as an `exclude_fields` list #}
+{# this should be the list of fields of the form itself #}
+{% for field, values in request.GET.lists %}
+
+  {% if field not in exclude_fields %}
+    {% for value in values %}<input type="hidden" name="{{ field }}" value="{{ value }}" />{% endfor %}
+  {% endif %}
+
+{% endfor %}