Allow tasks to be subprioritized by drag-and-drop

Summary:
Like the title says, similar to Facebook Tasks.

Not sure how I really feel about this, but I guess it's kind of OK? I never used
this feature in Facebook Tasks but I think some people like it.

The drag-and-drop to repri across priorities feels okayish.

Because subpriority is a double and we just split the difference when
reprioritizing, you lose ~a bit of precision every time you repri two tasks
against each other and so you can break it by swapping the priorities of two
tasks ~50 times. This case is pretty silly and pathological. We can add some
code to deal with this at some point if necessary.

I think this also fixes the whacky task layout widths once and for all.

(There are a couple of minor UI glitches like headers not vanishing and header
counts not updating that I'm not fixing because I am lazy.)

Test Plan: Dragged and dropped tasks around.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley, mgummelt

Maniphest Tasks: T859

Differential Revision: https://secure.phabricator.com/D1731

resources/sql/patches/124.subpriority.sql

@@ -0,0 +1,11 @@
+ALTER TABLE phabricator_maniphest.maniphest_task
+  ADD subpriority DOUBLE NOT NULL;
+
+ALTER TABLE phabricator_maniphest.maniphest_task
+  ADD KEY (priority, subpriority);
+
+/* Seed the subpriority column with reasonable values that keep order stable. */
+UPDATE phabricator_maniphest.maniphest_task
+  SET subpriority = dateModified;
+
+

src/__celerity_resource_map__.php

@@ -776,6 +776,21 @@ celerity_register_resource_map(array(
     ),
     'disk' => '/rsrc/js/application/maniphest/behavior-project-create.js',
   ),
+  'javelin-behavior-maniphest-subpriority-editor' =>
+  array(
+    'uri' => '/res/7d669df7/rsrc/js/application/maniphest/behavior-subpriorityeditor.js',
+    'type' => 'js',
+    'requires' =>
+    array(
+      0 => 'javelin-behavior',
+      1 => 'javelin-magical-init',
+      2 => 'javelin-dom',
+      3 => 'javelin-vector',
+      4 => 'javelin-stratcom',
+      5 => 'javelin-workflow',
+    ),
+    'disk' => '/rsrc/js/application/maniphest/behavior-subpriorityeditor.js',
+  ),
   'javelin-behavior-maniphest-transaction-controls' =>
   array(
     'uri' => '/res/62465554/rsrc/js/application/maniphest/behavior-transaction-controls.js',
@@ -1436,7 +1451,7 @@ celerity_register_resource_map(array(
   ),
   'maniphest-task-summary-css' =>
   array(
-    'uri' => '/res/ddb926e4/rsrc/css/application/maniphest/task-summary.css',
+    'uri' => '/res/d03e96a4/rsrc/css/application/maniphest/task-summary.css',
     'type' => 'css',
     'requires' =>
     array(
@@ -2133,7 +2148,7 @@ celerity_register_resource_map(array(
       'uri' => '/res/pkg/4fbae2af/javelin.pkg.js',
       'type' => 'js',
     ),
-    '8315b569' =>
+    '826b7ac2' =>
     array(
       'name' => 'maniphest.pkg.css',
       'symbols' =>
@@ -2143,7 +2158,7 @@ celerity_register_resource_map(array(
         2 => 'maniphest-task-detail-css',
         3 => 'aphront-attached-file-view-css',
       ),
-      'uri' => '/res/pkg/8315b569/maniphest.pkg.css',
+      'uri' => '/res/pkg/826b7ac2/maniphest.pkg.css',
       'type' => 'css',
     ),
     '86fc0b0c' =>
@@ -2178,7 +2193,7 @@ celerity_register_resource_map(array(
   ),
   'reverse' =>
   array(
-    'aphront-attached-file-view-css' => '8315b569',
+    'aphront-attached-file-view-css' => '826b7ac2',
     'aphront-crumbs-view-css' => '61493db4',
     'aphront-dialog-view-css' => '61493db4',
     'aphront-form-view-css' => '61493db4',
@@ -2244,9 +2259,9 @@ celerity_register_resource_map(array(
     'javelin-util' => '4fbae2af',
     'javelin-vector' => '4fbae2af',
     'javelin-workflow' => '21d01ed8',
-    'maniphest-task-detail-css' => '8315b569',
-    'maniphest-task-summary-css' => '8315b569',
-    'maniphest-transaction-detail-css' => '8315b569',
+    'maniphest-task-detail-css' => '826b7ac2',
+    'maniphest-task-summary-css' => '826b7ac2',
+    'maniphest-transaction-detail-css' => '826b7ac2',
     'phabricator-app-buttons-css' => '61493db4',
     'phabricator-content-source-view-css' => '18be02e0',
     'phabricator-core-buttons-css' => '61493db4',

src/__phutil_library_map__.php

@@ -443,6 +443,7 @@ phutil_register_library_map(array(
     'ManiphestExportController' => 'applications/maniphest/controller/export',
     'ManiphestReplyHandler' => 'applications/maniphest/replyhandler',
     'ManiphestReportController' => 'applications/maniphest/controller/report',
+    'ManiphestSubpriorityController' => 'applications/maniphest/controller/subpriority',
     'ManiphestTask' => 'applications/maniphest/storage/task',
     'ManiphestTaskAuxiliaryStorage' => 'applications/maniphest/storage/auxiliary',
     'ManiphestTaskDescriptionChangeController' => 'applications/maniphest/controller/descriptionchange',
@@ -1301,6 +1302,7 @@ phutil_register_library_map(array(
     'ManiphestExportController' => 'ManiphestController',
     'ManiphestReplyHandler' => 'PhabricatorMailReplyHandler',
     'ManiphestReportController' => 'ManiphestController',
+    'ManiphestSubpriorityController' => 'ManiphestController',
     'ManiphestTask' => 'ManiphestDAO',
     'ManiphestTaskAuxiliaryStorage' => 'ManiphestDAO',
     'ManiphestTaskDescriptionChangeController' => 'ManiphestController',

src/aphront/default/configuration/AphrontDefaultApplicationConfiguration.php

@@ -206,6 +206,7 @@ class AphrontDefaultApplicationConfiguration
           'preview/(?P<id>\d+)/' => 'ManiphestTransactionPreviewController',
         ),
         'export/(?P<key>[^/]+)/' => 'ManiphestExportController',
+        'subpriority/' => 'ManiphestSubpriorityController',
       ),
 
       '/T(?P<id>\d+)' => 'ManiphestTaskDetailController',

src/applications/maniphest/controller/subpriority/ManiphestSubpriorityController.php

@@ -0,0 +1,79 @@
+<?php
+
+/*
+ * Copyright 2012 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @group maniphest
+ */
+final class ManiphestSubpriorityController extends ManiphestController {
+
+  public function processRequest() {
+    $request = $this->getRequest();
+
+    if (!$request->validateCSRF()) {
+      return new Aphront403Response();
+    }
+
+    $task = id(new ManiphestTask())->load($request->getInt('task'));
+    if (!$task) {
+      return new Aphront404Response();
+    }
+
+    if ($request->getInt('after')) {
+      $after_task = id(new ManiphestTask())->load($request->getInt('after'));
+      if (!$after_task) {
+        return new Aphront404Response();
+      }
+      $after_pri = $after_task->getPriority();
+      $after_sub = $after_task->getSubpriority();
+    } else {
+      $after_pri = $request->getInt('priority');
+      $after_sub = null;
+    }
+
+    $new_sub = ManiphestTransactionEditor::getNextSubpriority(
+      $after_pri,
+      $after_sub);
+
+    if ($after_pri != $task->getPriority()) {
+      $xaction = new ManiphestTransaction();
+      $xaction->setAuthorPHID($request->getUser()->getPHID());
+
+      // TODO: Content source?
+
+      $xaction->setTransactionType(ManiphestTransactionType::TYPE_PRIORITY);
+      $xaction->setNewValue($after_pri);
+
+      $editor = new ManiphestTransactionEditor();
+      $editor->applyTransactions($task, array($xaction));
+    }
+
+    $task->setSubpriority($new_sub);
+    $task->save();
+
+    $pri_class = ManiphestTaskSummaryView::getPriorityClass(
+      $task->getPriority());
+    $class = 'maniphest-task-handle maniphest-active-handle '.$pri_class;
+
+    $response = array(
+      'className' => $class,
+    );
+
+    return id(new AphrontAjaxResponse())->setContent($response);
+  }
+
+}

src/applications/maniphest/controller/subpriority/__init__.php

@@ -0,0 +1,22 @@
+<?php
+/**
+ * This file is automatically generated. Lint this module to rebuild it.
+ * @generated
+ */
+
+
+
+phutil_require_module('phabricator', 'aphront/response/403');
+phutil_require_module('phabricator', 'aphront/response/404');
+phutil_require_module('phabricator', 'aphront/response/ajax');
+phutil_require_module('phabricator', 'applications/maniphest/constants/transactiontype');
+phutil_require_module('phabricator', 'applications/maniphest/controller/base');
+phutil_require_module('phabricator', 'applications/maniphest/editor/transaction');
+phutil_require_module('phabricator', 'applications/maniphest/storage/task');
+phutil_require_module('phabricator', 'applications/maniphest/storage/transaction');
+phutil_require_module('phabricator', 'applications/maniphest/view/tasksummary');
+
+phutil_require_module('phutil', 'utils');
+
+
+phutil_require_source('ManiphestSubpriorityController.php');

src/applications/maniphest/controller/tasklist/ManiphestTaskListController.php

@@ -260,34 +260,65 @@ final class ManiphestTaskListController extends ManiphestController {
 
       $selector = new AphrontNullView();
 
+      $group = $query->getParameter('group');
+      $order = $query->getParameter('order');
+      $is_draggable =
+        ($group == 'priority') ||
+        ($group == 'none' && $order == 'priority');
+
+      $lists = new AphrontNullView();
+      $lists->appendChild('<div style="padding: 0em 1em;">');
       foreach ($tasks as $group => $list) {
         $task_list = new ManiphestTaskListView();
         $task_list->setShowBatchControls(true);
+        if ($is_draggable) {
+          $task_list->setShowSubpriorityControls(true);
+        }
         $task_list->setUser($user);
         $task_list->setTasks($list);
         $task_list->setHandles($handles);
 
         $count = number_format(count($list));
-        $selector->appendChild(
-          '<h1 class="maniphest-task-group-header">'.
-            phutil_escape_html($group).' ('.$count.')'.
-          '</h1>');
-        $selector->appendChild($task_list);
+
+        $lists->appendChild(
+          javelin_render_tag(
+            'h1',
+            array(
+              'class' => 'maniphest-task-group-header',
+              'sigil' => 'task-group',
+              'meta'  => array(
+                'priority' => head($list)->getPriority(),
+              ),
+            ),
+            phutil_escape_html($group).' ('.$count.')'));
+
+        $lists->appendChild($task_list);
       }
+      $lists->appendChild('</div>');
+      $selector->appendChild($lists);
 
 
       $selector->appendChild($this->renderBatchEditor($query));
 
+      $form_id = celerity_generate_unique_node_id();
       $selector = phabricator_render_form(
         $user,
         array(
           'method' => 'POST',
           'action' => '/maniphest/batch/',
+          'id'     => $form_id,
         ),
         $selector->render());
 
       $list_container->appendChild($selector);
       $list_container->appendChild($pager);
+
+      Javelin::initBehavior(
+        'maniphest-subpriority-editor',
+        array(
+          'root'  => $form_id,
+          'uri'   =>  '/maniphest/subpriority/',
+        ));
     }
 
     $list_container->appendChild('</div>');

src/applications/maniphest/editor/transaction/ManiphestTransactionEditor.php

@@ -41,6 +41,8 @@ final class ManiphestTransactionEditor {
     $email_to = array();
     $email_to[] = $task->getOwnerPHID();
 
+    $pri_changed = $this->isCreate($transactions);
+
     foreach ($transactions as $key => $transaction) {
       $type = $transaction->getTransactionType();
       $new = $transaction->getNewValue();
@@ -151,6 +153,7 @@ final class ManiphestTransactionEditor {
             break;
           case ManiphestTransactionType::TYPE_PRIORITY:
             $task->setPriority($new);
+            $pri_changed = true;
             break;
           case ManiphestTransactionType::TYPE_ATTACH:
             $task->setAttached($new);
@@ -178,6 +181,13 @@ final class ManiphestTransactionEditor {
 
     }
 
+    if ($pri_changed) {
+      $subpriority = ManiphestTransactionEditor::getNextSubpriority(
+        $task->getPriority(),
+        null);
+      $task->setSubpriority($subpriority);
+    }
+
     $task->save();
     foreach ($transactions as $transaction) {
       $transaction->setTaskID($task->getID());
@@ -383,4 +393,27 @@ final class ManiphestTransactionEditor {
     return array_unique($tags);
   }
 
+  public static function getNextSubpriority($pri, $sub) {
+
+    if ($sub === null) {
+      $next = id(new ManiphestTask())->loadOneWhere(
+        'priority = %d ORDER BY subpriority ASC LIMIT 1',
+        $pri);
+      if ($next) {
+        return $next->getSubpriority() - ((double)(2 << 16));
+      }
+    } else {
+      $next = id(new ManiphestTask())->loadOneWhere(
+        'priority = %d AND subpriority > %s ORDER BY subpriority ASC LIMIT 1',
+        $pri,
+        $sub);
+      if ($next) {
+        return ($sub + $next->getSubpriority()) / 2;
+      }
+    }
+
+    return (double)(2 << 32);
+  }
+
+
 }

src/applications/maniphest/editor/transaction/__init__.php

@@ -11,6 +11,7 @@ phutil_require_module('phabricator', 'applications/feed/publisher');
 phutil_require_module('phabricator', 'applications/maniphest/constants/action');
 phutil_require_module('phabricator', 'applications/maniphest/constants/status');
 phutil_require_module('phabricator', 'applications/maniphest/constants/transactiontype');
+phutil_require_module('phabricator', 'applications/maniphest/storage/task');
 phutil_require_module('phabricator', 'applications/maniphest/view/transactiondetail');
 phutil_require_module('phabricator', 'applications/metamta/constants/notificationtype');
 phutil_require_module('phabricator', 'applications/metamta/storage/mail');

src/applications/maniphest/query/ManiphestTaskQuery.php

@@ -443,6 +443,7 @@ final class ManiphestTaskQuery {
     switch ($this->orderBy) {
       case self::ORDER_PRIORITY:
         $order[] = 'priority';
+        $order[] = 'subpriority';
         $order[] = 'dateModified';
         break;
       case self::ORDER_CREATED:
@@ -463,6 +464,7 @@ final class ManiphestTaskQuery {
 
     foreach ($order as $k => $column) {
       switch ($column) {
+        case 'subpriority':
         case 'ownerOrdering':
           $order[$k] = "task.{$column} ASC";
           break;

src/applications/maniphest/storage/task/ManiphestTask.php

@@ -28,6 +28,7 @@ final class ManiphestTask extends ManiphestDAO {
 
   protected $status;
   protected $priority;
+  protected $subpriority;
 
   protected $title;
   protected $description;

src/applications/maniphest/view/tasklist/ManiphestTaskListView.php

@@ -25,6 +25,7 @@ final class ManiphestTaskListView extends ManiphestView {
   private $handles;
   private $user;
   private $showBatchControls;
+  private $showSubpriorityControls;
 
   public function setTasks(array $tasks) {
     $this->tasks = $tasks;
@@ -46,6 +47,11 @@ final class ManiphestTaskListView extends ManiphestView {
     return $this;
   }
 
+  public function setShowSubpriorityControls($show_subpriority_controls) {
+    $this->showSubpriorityControls = $show_subpriority_controls;
+    return $this;
+  }
+
   public function render() {
 
     $views = array();
@@ -53,6 +59,7 @@ final class ManiphestTaskListView extends ManiphestView {
       $view = new ManiphestTaskSummaryView();
       $view->setTask($task);
       $view->setShowBatchControls($this->showBatchControls);
+      $view->setShowSubpriorityControls($this->showSubpriorityControls);
       $view->setUser($this->user);
       $view->setHandles($this->handles);
       $views[] = $view->render();

src/applications/maniphest/view/tasksummary/ManiphestTaskSummaryView.php

@@ -25,6 +25,7 @@ final class ManiphestTaskSummaryView extends ManiphestView {
   private $handles;
   private $user;
   private $showBatchControls;
+  private $showSubpriorityControls;
 
   public function setTask(ManiphestTask $task) {
     $this->task = $task;
@@ -46,6 +47,24 @@ final class ManiphestTaskSummaryView extends ManiphestView {
     return $this;
   }
 
+  public function setShowSubpriorityControls($show_subpriority_controls) {
+    $this->showSubpriorityControls = $show_subpriority_controls;
+    return $this;
+  }
+
+  public static function getPriorityClass($priority) {
+    $classes = array(
+      ManiphestTaskPriority::PRIORITY_UNBREAK_NOW => 'pri-unbreak',
+      ManiphestTaskPriority::PRIORITY_TRIAGE => 'pri-triage',
+      ManiphestTaskPriority::PRIORITY_HIGH => 'pri-high',
+      ManiphestTaskPriority::PRIORITY_NORMAL => 'pri-normal',
+      ManiphestTaskPriority::PRIORITY_LOW => 'pri-low',
+      ManiphestTaskPriority::PRIORITY_WISH => 'pri-wish',
+    );
+
+    return idx($classes, $priority);
+  }
+
   public function render() {
 
     if (!$this->user) {
@@ -57,16 +76,7 @@ final class ManiphestTaskSummaryView extends ManiphestView {
 
     require_celerity_resource('maniphest-task-summary-css');
 
-    $classes = array(
-      ManiphestTaskPriority::PRIORITY_UNBREAK_NOW => 'pri-unbreak',
-      ManiphestTaskPriority::PRIORITY_TRIAGE => 'pri-triage',
-      ManiphestTaskPriority::PRIORITY_HIGH => 'pri-high',
-      ManiphestTaskPriority::PRIORITY_NORMAL => 'pri-normal',
-      ManiphestTaskPriority::PRIORITY_LOW => 'pri-low',
-      ManiphestTaskPriority::PRIORITY_WISH => 'pri-wish',
-    );
-
-    $pri_class = idx($classes, $task->getPriority());
+    $pri_class = self::getPriorityClass($task->getPriority());
     $status_map = ManiphestTaskStatus::getTaskStatusMap();
 
     $batch = null;
@@ -91,15 +101,32 @@ final class ManiphestTaskSummaryView extends ManiphestView {
         $this->handles,
         $task->getProjectPHIDs()));
 
+    $control_class = null;
+    $control_sigil = null;
+    if ($this->showSubpriorityControls) {
+      $control_class = 'maniphest-active-handle';
+      $control_sigil = 'maniphest-task-handle';
+    }
+
+    $handle = javelin_render_tag(
+      'td',
+      array(
+        'class' => 'maniphest-task-handle '.$pri_class.' '.$control_class,
+        'sigil' => $control_sigil,
+      ),
+      '');
+
     return javelin_render_tag(
       'table',
       array(
         'class' => 'maniphest-task-summary',
         'sigil' => 'maniphest-task',
+        'meta'  => array(
+          'taskID' => $task->getID(),
+        ),
       ),
       '<tr>'.
-        '<td class="maniphest-task-handle '.$pri_class.'">'.
-        '</td>'.
+        $handle.
         $batch.
         '<td class="maniphest-task-number">'.
           'T'.$task->getID().

webroot/rsrc/css/application/maniphest/task-summary.css

@@ -5,7 +5,7 @@
 .maniphest-task-summary {
   width: 100%;
   margin: 4px 0;
-  border-collapse: collapse;
+  border-collapse: separate;
 
   font-size: 12px;
   color: #222222;
@@ -42,6 +42,7 @@
   padding-right: 0px;
   width: 16px;
   text-align: center;
+  overflow: hidden;
 }
 
 .maniphest-task-summary td.maniphest-task-batch,
@@ -70,9 +71,9 @@
 }
 
 .maniphest-task-summary td.maniphest-task-name {
-  overflow: hidden;
   font-weight: bold;
   white-space: normal;
+  overflow: hidden;
 }
 
 .maniphest-task-summary td.maniphest-task-projects {
@@ -95,32 +96,32 @@
 
 .maniphest-task-summary .pri-unbreak {
   border-color: #ff0000;
-  background: #ff0000;
+  background-color: #ff0000;
 }
 
 .maniphest-task-summary .pri-triage {
   border-color: #ee00ee;
-  background: #ee00ee;
+  background-color: #ee00ee;
 }
 
 .maniphest-task-summary .pri-high {
   border-color: #ff6622;
-  background: #ff6622;
+  background-color: #ff6622;
 }
 
 .maniphest-task-summary .pri-normal {
   border-color: #ffaa66;
-  background: #ffaa66;
+  background-color: #ffaa66;
 }
 
 .maniphest-task-summary .pri-low {
   border-color: #eecc66;
-  background: #eecc66;
+  background-color: #eecc66;
 }
 
 .maniphest-task-summary .pri-wish {
   border-color: #0099ff;
-  background: #0099ff;
+  background-color: #0099ff;
 }
 
 .maniphest-task-group-header {
@@ -178,3 +179,26 @@
 .maniphest-list-container {
   padding: 0 1em;
 }
+
+td.maniphest-active-handle {
+  cursor: move;
+  background-image: url('/rsrc/image/grippy_texture.png');
+  background-position: 3px 0px;
+  background-repeat: repeat-y;
+}
+
+.maniphest-subpriority-target {
+  position: relative;
+  border: 1px dashed #aaaaaa;
+  background: #f9f9f9;
+}
+
+.maniphest-task-loading {
+  opacity: 0.5;
+}
+
+.maniphest-task-dragging {
+  position: relative;
+  opacity: 0.5;
+  z-index: 5;
+}

webroot/rsrc/js/application/maniphest/behavior-subpriorityeditor.js

@@ -0,0 +1,203 @@
+/**
+ * @provides javelin-behavior-maniphest-subpriority-editor
+ * @requires javelin-behavior
+ *           javelin-magical-init
+ *           javelin-dom
+ *           javelin-vector
+ *           javelin-stratcom
+ *           javelin-workflow
+ */
+
+JX.behavior('maniphest-subpriority-editor', function(config) {
+
+  var dragging = null;
+  var sending  = null;
+  var origin   = null;
+  var targets  = null;
+  var target   = null;
+  var droptarget = JX.$N('div', {className: 'maniphest-subpriority-target'});
+
+  var ondrag = function(e) {
+    if (dragging || sending) {
+      return;
+    }
+
+    dragging = e.getNode('maniphest-task');
+    origin = JX.$V(e);
+
+    var tasks = JX.DOM.scry(JX.$(config.root), 'table', 'maniphest-task');
+    var heads = JX.DOM.scry(JX.$(config.root), 'h1',  'task-group');
+
+    var nodes = tasks.concat(heads);
+
+    targets = [];
+    for (var ii = 0; ii < nodes.length; ii++) {
+      targets.push({
+        node: nodes[ii],
+        y: JX.$V(nodes[ii]).y + (JX.Vector.getDim(nodes[ii]).y / 2)
+      });
+    }
+    targets.sort(function(u, v) { return v.y - u.y; });
+
+    JX.DOM.alterClass(dragging, 'maniphest-task-dragging', true);
+
+    droptarget.style.height = JX.Vector.getDim(dragging).y + 'px';
+
+    e.kill();
+  };
+
+  var onmove = function(e) {
+    if (!dragging) {
+      return;
+    }
+
+    var p = JX.$V(e);
+
+    // Compute the size and position of the drop target indicator, because we
+    // need to update our static position computations to account for it.
+
+    var adjust_h = JX.Vector.getDim(droptarget).y;
+    var adjust_y = JX.$V(droptarget).y;
+
+    // Find the node we're dragging the task underneath. This is the first
+    // node in the list that's above the cursor. If that node is the node
+    // we're dragging or its predecessor, don't select a target, because the
+    // operation would be a no-op.
+
+    var cur_target = null;
+    for (var ii = 0; ii < targets.length; ii++) {
+
+      // If the drop target indicator is above the target, we need to adjust
+      // the target's trigger height down accordingly. This makes dragging
+      // items down the list smoother, because the target doesn't jump to the
+      // next item while the cursor is over it.
+
+      var trigger = targets[ii].y;
+      if (adjust_y <= trigger) {
+        trigger += adjust_h;
+      }
+
+      // If the cursor is above this target, we aren't dropping underneath it.
+
+      if (trigger >= p.y) {
+        continue;
+      }
+
+      // Don't choose the dragged row or its predecessor as targets.
+
+      cur_target = targets[ii].node;
+      if (cur_target == dragging) {
+        cur_target = null;
+      }
+      if (targets[ii - 1] && targets[ii - 1].node == dragging) {
+        cur_target = null;
+      }
+
+      break;
+    }
+
+    // If we've selected a new target, update the UI to show where we're
+    // going to drop the row.
+
+    if (cur_target != target) {
+
+      if (target) {
+        JX.DOM.remove(droptarget);
+      }
+
+      if (cur_target) {
+        if (cur_target.nextSibling) {
+          cur_target.parentNode.insertBefore(
+            droptarget,
+            cur_target.nextSibling);
+        } else {
+          cur_target.parentNode.appendChild(droptarget);
+        }
+      }
+
+      target = cur_target;
+
+      if (target) {
+
+        // If we've changed where the droptarget is, update the adjustments
+        // so we accurately reflect document state when we tweak things below.
+        // This avoids a flash of bad state as the mouse is dragged upward
+        // across the document.
+
+        adjust_h = JX.Vector.getDim(droptarget).y;
+        adjust_y = JX.$V(droptarget).y;
+      }
+    }
+
+    // If the drop target indicator is above the cursor in the document, adjust
+    // the cursor position for the change in node document position. Do this
+    // before choosing a new target to avoid a flash of nonsense.
+
+    if (target) {
+      if (adjust_y <= origin.y) {
+        p.y -= adjust_h;
+      }
+    }
+
+    p.x = 0;
+    p.y -= origin.y;
+    p.setPos(dragging);
+
+    e.kill();
+  };
+
+  var ondrop = function(e) {
+    if (!dragging) {
+      return;
+    }
+
+    JX.DOM.alterClass(dragging, 'maniphest-task-dragging', false);
+    JX.$V(0, 0).setPos(dragging);
+
+    if (!target) {
+      dragging = null;
+      return;
+    }
+
+    var data = {
+      task: JX.Stratcom.getData(dragging).taskID
+    };
+
+    if (JX.DOM.isType(target, 'h1')) {
+      data.priority = JX.Stratcom.getData(target).priority;
+    } else {
+      data.after = JX.Stratcom.getData(target).taskID;
+    }
+
+    target = null;
+
+    JX.DOM.remove(dragging);
+    JX.DOM.replace(droptarget, dragging);
+
+    sending = dragging;
+    dragging = null;
+
+    JX.DOM.alterClass(sending, 'maniphest-task-loading', true);
+
+    var onresponse = function(r) {
+      JX.DOM.alterClass(sending, 'maniphest-task-loading', false);
+      var handle = JX.DOM.find(sending, 'td', 'maniphest-task-handle');
+      handle.className = r.className;
+      sending = null;
+    };
+
+    new JX.Workflow(config.uri, data)
+      .setHandler(onresponse)
+      .start();
+
+    e.kill();
+  };
+
+  // NOTE: Javelin does not dispatch mousemove by default.
+  JX.enableDispatch(document.body, 'mousemove');
+
+  JX.Stratcom.listen('mousedown', 'maniphest-task-handle',  ondrag);
+  JX.Stratcom.listen('mousemove', null,                     onmove);
+  JX.Stratcom.listen('mouseup',   null,                     ondrop);
+
+});