Provide a farm_map_geofield field widget that uses farmOS-map.

modules/farm/farm_area/farm_area.farm_map.inc

@@ -71,7 +71,7 @@ function farm_area_farm_map_view($name, $element) {
   }
 
   // Show "all areas" layer in geofield maps.
-  if ($name == 'farm_map_geofield') {
+  if (in_array($name,  array('farm_map_geofield', 'farm_map_geofield_widget'))) {
     farm_map_add_behavior('areas_combined', array('zoom' => FALSE));
   }
 }

modules/farm/farm_map/farm_map_geofield/farm_map_geofield.farm_map.inc

@@ -0,0 +1,27 @@
+<?php
+/**
+ * @file
+ * Farm Map hooks implemented by the Farm Map Geofield module.
+ */
+
+/**
+ * Implements hook_farm_map_behaviors().
+ */
+function farm_map_geofield_farm_map_behaviors() {
+  return array(
+    'geofield' => array(
+      'js' => 'js/farmOS.map.behaviors.geofield.js',
+    ),
+  );
+}
+
+/**
+ * Implements hook_farm_map_view().
+ */
+function farm_map_geofield_farm_map_view($name, $element) {
+
+  // Add geofield behavior to the geofield widget map.
+  if ($name == 'farm_map_geofield_widget') {
+    farm_map_add_behavior('geofield');
+  }
+}

modules/farm/farm_map/farm_map_geofield/farm_map_geofield.module

@@ -69,3 +69,69 @@ function farm_map_geofield_field_formatter_view($entity_type, $entity, $field, $
 
   return $element;
 }
+
+/**
+ * Implements hook_field_widget_info().
+ */
+function farm_map_geofield_field_widget_info() {
+  return array(
+    'farm_map_geofield' => array(
+      'label' => t('farmOS Map'),
+      'field types' => array('geofield'),
+      'behaviors' => array(
+        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
+      ),
+    ),
+  );
+}
+
+/**
+ * Implements hook_field_widget_form().
+ */
+function farm_map_geofield_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
+
+  // Start with the Geofield WKT widget.
+  $instance['widget']['type'] = 'geofield_wkt';
+  $element = geofield_field_widget_form($form, $form_state, $field, $instance, $langcode, $items, $delta, $element);
+
+  // Get the geometry (as WKT).
+  $wkt = '';
+  if (!empty($items[$delta]['geom'])) {
+    $wkt = $items[$delta]['geom'];
+  }
+
+  // Add a farmOS map instance with the WKT and drawing controls.
+  $element['map'] = array(
+    '#type' => 'farm_map',
+    '#map_name' => 'farm_map_geofield_widget',
+    '#wkt' => $wkt,
+    '#edit' => TRUE,
+  );
+
+  // Move the geometry field below the map.
+  $element['geom']['#weight'] = 100;
+
+  // Add the element to an array, because it's the format that
+  // FIELD_BEHAVIOR_CUSTOM expects.
+  /**
+   * @todo
+   * This is necessary due to a legacy decision that was made in early farmOS
+   * development, when we were using the OpenLayers module. The farmOS Geofield
+   * (field_farm_geofield) was set up with a cardinality of -1 (allowing
+   * unlimited values), and the OpenLayers Geofield widget was configured to
+   * save all features as a combined geometry. So, even though the field was
+   * configured to allow unlimited values, only one value was ever saved. And
+   * only one value was/is ever needed. So in the future, when we move to Drupal
+   * 8, we should plan to change the cardinality to 1. The decision was made to
+   * leave it as -1 in 7.x-1.x, because changing it would cause a change to the
+   * REST API (which expects an array of geometries, even though only one should
+   * ever be provided).
+   *
+   * Using FIELD_BEHAVIOR_CUSTOM and wrapping the element in an array is the
+   * same approach that the openlayers_geofield module takes.
+   */
+  $full_element = array($element);
+
+  // Return the widget element.
+  return $full_element;
+}

modules/farm/farm_map/farm_map_geofield/js/farmOS.map.behaviors.geofield.js

@@ -0,0 +1,9 @@
+(function ($) {
+  farmOS.map.behaviors.geofield = {
+    attach: function (instance) {
+      instance.edit.wktOn('featurechange', function(wkt) {
+        $('#' + instance.target).parents('.field-widget-farm-map-geofield').find('textarea').val(wkt);
+      });
+    },
+  };
+}(jQuery));