Use renderable arrays instead of the array of strings we used to.

...  Arrays of strings are still supported... Just not encouraged.

includes/utilities.inc

@@ -865,3 +865,38 @@ function islandora_deprecated($release, $solution = NULL) {
   }
   return $message;
 }
+
+/**
+ * Transform recursively-merged array of strings to renderable arrays.
+ *
+ * Previously, functions/hooks like islandora_view_object would return an
+ * associative array with string values containing markup. These values were
+ * then imploded into one large piece of markup. Here, we transform this older
+ * structure which was generated into a renderable array, because renderable
+ * arrays are awesome!
+ *
+ * @param array $markup_array
+ *   An associative array of which the values are either a string or an array
+ *   of strings, which we transform to renderable markup elements (by
+ *   reference).
+ */
+function islandora_array_of_markup_to_renderable_array(&$markup_array) {
+  foreach ($markup_array as &$value) {
+    if (!is_array($value)) {
+      $value = array(
+        '#markup' => $value,
+      );
+    }
+    else {
+      foreach ($value as &$inner) {
+        if (!is_array($inner)) {
+          $inner = array(
+            '#markup' => $inner,
+          );
+        }
+      }
+      unset($inner);
+    }
+  }
+  unset($value);
+}

islandora.module

@@ -624,6 +624,7 @@ function islandora_manage_overview_object(AbstractObject $object) {
   $output = array();
   foreach (islandora_build_hook_list(ISLANDORA_OVERVIEW_HOOK, $object->models) as $hook) {
     $temp = module_invoke_all($hook, $object);
+    islandora_array_of_markup_to_renderable_array($temp);
     if (!empty($temp)) {
       $output = array_merge_recursive($output, $temp);
     }
@@ -634,7 +635,7 @@ function islandora_manage_overview_object(AbstractObject $object) {
   }
   arsort($output);
   drupal_alter(ISLANDORA_OVERVIEW_HOOK, $object, $output);
-  return implode('', $output);
+  return $output;
 }
 
 /**
@@ -649,7 +650,9 @@ function islandora_manage_overview_object(AbstractObject $object) {
  */
 function islandora_default_islandora_manage_overview_object(AbstractObject $object) {
   $output = theme('islandora_default_overview', array('islandora_object' => $object));
-  return array('Default overview output' => $output);
+  return array('Default overview output' => array(
+    '#markup' => $output,
+  ));
 }
 
 /**
@@ -675,6 +678,7 @@ function islandora_edit_object(AbstractObject $object) {
   $output = array();
   foreach (islandora_build_hook_list(ISLANDORA_EDIT_HOOK, $object->models) as $hook) {
     $temp = module_invoke_all($hook, $object);
+    islandora_array_of_markup_to_renderable_array($temp);
     if (!empty($temp)) {
       $output = array_merge_recursive($output, $temp);
     }
@@ -685,7 +689,7 @@ function islandora_edit_object(AbstractObject $object) {
   }
   arsort($output);
   drupal_alter(ISLANDORA_EDIT_HOOK, $object, $output);
-  return implode('', $output);
+  return $output;
 }
 
 /**
@@ -700,7 +704,9 @@ function islandora_edit_object(AbstractObject $object) {
  */
 function islandora_default_islandora_edit_object(AbstractObject $object) {
   $output = theme('islandora_default_edit', array('islandora_object' => $object));
-  return array('Default Edit output' => $output);
+  return array('Default Edit output' => array(
+    '#markup' => $output,
+  ));
 }
 
 /**
@@ -743,6 +749,7 @@ function islandora_view_object(AbstractObject $object) {
     // @todo Remove page number and size from this hook, implementers of the
     // hook should use drupal page handling directly.
     $temp = module_invoke_all($hook, $object, $page_number, $page_size);
+    islandora_array_of_markup_to_renderable_array($temp);
     if (!empty($temp)) {
       $output = array_merge_recursive($output, $temp);
     }
@@ -753,7 +760,7 @@ function islandora_view_object(AbstractObject $object) {
   }
   arsort($output);
   drupal_alter($hooks, $object, $output);
-  return implode('', $output);
+  return $output;
 }
 
 
@@ -786,7 +793,9 @@ function islandora_drupal_title(AbstractObject $object) {
  */
 function islandora_default_islandora_view_object($object) {
   $output = theme('islandora_default', array('islandora_object' => $object));
-  return array('Default output' => $output);
+  return array('Default output' => array(
+    '#markup' => $output,
+  ));
 }
 
 /**