Render proper "Show Context" links in DocumentEngine diffs, not just bullets

Summary:
Ref T13513. Currently, viewing a Jupyter document, hidden context just gets a plain "* * *" facade with no way to expand it.

Support click-to-expand, like source changes.

Test Plan:
  - Clicked to expand various Jupyter diffs.
  - Clicked to expand normal source changes.

Maniphest Tasks: T13513

Differential Revision: https://secure.phabricator.com/D21243

src/applications/differential/parser/DifferentialChangesetParser.php

@@ -1084,6 +1084,22 @@ final class DifferentialChangesetParser extends Phobject {
         $vs = $id;
       }
 
+      if ($mask_force) {
+        $engine_blocks->setRevealedIndexes(array_keys($mask_force));
+      }
+
+      if ($range_start !== null || $range_len !== null) {
+        $range_min = $range_start;
+
+        if ($range_len === null) {
+          $range_max = null;
+        } else {
+          $range_max = (int)$range_start + (int)$range_len;
+        }
+
+        $engine_blocks->setRange($range_min, $range_max);
+      }
+
       $renderer
         ->setDocumentEngine($engine)
         ->setDocumentEngineBlocks($engine_blocks);

src/applications/differential/render/DifferentialChangesetHTMLRenderer.php

@@ -496,7 +496,12 @@ abstract class DifferentialChangesetHTMLRenderer
    * @param int Total number of lines in the changeset.
    * @return markup Rendered links.
    */
-  protected function renderShowContextLinks($top, $len, $changeset_length) {
+  protected function renderShowContextLinks(
+    $top,
+    $len,
+    $changeset_length,
+    $is_blocks = false) {
+
     $block_size = 20;
     $end = ($top + $len) - $block_size;
 
@@ -509,12 +514,22 @@ abstract class DifferentialChangesetHTMLRenderer
 
     $links = array();
 
+    $block_display = new PhutilNumber($block_size);
+
     if ($is_large_block) {
       $is_first_block = ($top == 0);
       if ($is_first_block) {
-        $text = pht('Show First %d Line(s)', $block_size);
+        if ($is_blocks) {
+          $text = pht('Show First %s Block(s)', $block_display);
         } else {
-        $text = pht("\xE2\x96\xB2 Show %d Line(s)", $block_size);
+          $text = pht('Show First %s Line(s)', $block_display);
+        }
+      } else {
+        if ($is_blocks) {
+          $text = pht("\xE2\x96\xB2 Show %s Block(s)", $block_display);
+        } else {
+          $text = pht("\xE2\x96\xB2 Show %s Line(s)", $block_display);
+        }
       }
 
       $links[] = $this->renderShowContextLink(
@@ -523,17 +538,31 @@ abstract class DifferentialChangesetHTMLRenderer
         $text);
     }
 
+    if ($is_blocks) {
+      $text = pht('Show All %s Block(s)', new PhutilNumber($len));
+    } else {
+      $text = pht('Show All %s Line(s)', new PhutilNumber($len));
+    }
+
     $links[] = $this->renderShowContextLink(
       true,
       "{$top}-{$len}/{$top}-{$len}",
-      pht('Show All %d Line(s)', $len));
+      $text);
 
     if ($is_large_block) {
       $is_last_block = (($top + $len) >= $changeset_length);
       if ($is_last_block) {
-        $text = pht('Show Last %d Line(s)', $block_size);
+        if ($is_blocks) {
+          $text = pht('Show Last %s Block(s)', $block_display);
         } else {
-        $text = "\xE2\x96\xBC ".pht('Show %d Line(s)', $block_size);
+          $text = pht('Show Last %s Line(s)', $block_display);
+        }
+      } else {
+        if ($is_blocks) {
+          $text = pht("\xE2\x96\xBC Show %s Block(s)", $block_display);
+        } else {
+          $text = pht("\xE2\x96\xBC Show %s Line(s)", $block_display);
+        }
       }
 
       $links[] = $this->renderShowContextLink(

src/applications/differential/render/DifferentialChangesetTwoUpRenderer.php

@@ -381,22 +381,17 @@ final class DifferentialChangesetTwoUpRenderer
     $old_comments = $this->getOldComments();
     $new_comments = $this->getNewComments();
 
-    $gap_view = javelin_tag(
-      'tr',
-      array(
-        'sigil' => 'context-target',
-      ),
-      phutil_tag(
-        'td',
-        array(
-          'colspan' => 6,
-          'class' => 'show-more',
-        ),
-        pht("\xE2\x80\xA2 \xE2\x80\xA2 \xE2\x80\xA2")));
-
     $rows = array();
+    $gap = array();
     $in_gap = false;
-    foreach ($block_list->newTwoUpLayout() as $row) {
+
+    // NOTE: The generated layout is affected by range constraints, and may
+    // represent only a slice of the document.
+
+    $layout = $block_list->newTwoUpLayout();
+    $available_count = $block_list->getLayoutAvailableRowCount();
+
+    foreach ($layout as $idx => $row) {
       list($old, $new) = $row;
 
       if ($old) {
@@ -416,13 +411,17 @@ final class DifferentialChangesetTwoUpRenderer
       if (!$is_visible) {
         if (!$in_gap) {
           $in_gap = true;
-          $rows[] = $gap_view;
         }
+        $gap[$idx] = $row;
         continue;
       }
 
       if ($in_gap) {
         $in_gap = false;
+        $rows[] = $this->renderDocumentEngineGap(
+          $gap,
+          $available_count);
+        $gap = array();
       }
 
       if ($old) {
@@ -577,6 +576,12 @@ final class DifferentialChangesetTwoUpRenderer
       );
     }
 
+    if ($in_gap) {
+      $rows[] = $this->renderDocumentEngineGap(
+        $gap,
+        $available_count);
+    }
+
     $output = $this->wrapChangeInTable($rows);
 
     return $this->renderChangesetTable($output);
@@ -616,4 +621,25 @@ final class DifferentialChangesetTwoUpRenderer
     );
   }
 
+  private function renderDocumentEngineGap(array $gap, $available_count) {
+    $content = $this->renderShowContextLinks(
+      head_key($gap),
+      count($gap),
+      $available_count,
+      $is_blocks = true);
+
+    return javelin_tag(
+      'tr',
+      array(
+        'sigil' => 'context-target',
+      ),
+      phutil_tag(
+        'td',
+        array(
+          'colspan' => 6,
+          'class' => 'show-more',
+        ),
+        $content));
+  }
+
 }

src/applications/files/diff/PhabricatorDocumentEngineBlocks.php

@@ -5,6 +5,29 @@ final class PhabricatorDocumentEngineBlocks
 
   private $lists = array();
   private $messages = array();
+  private $rangeMin;
+  private $rangeMax;
+  private $revealedIndexes;
+  private $layoutAvailableRowCount;
+
+  public function setRange($min, $max) {
+    $this->rangeMin = $min;
+    $this->rangeMax = $max;
+    return $this;
+  }
+
+  public function setRevealedIndexes(array $indexes) {
+    $this->revealedIndexes = $indexes;
+    return $this;
+  }
+
+  public function getLayoutAvailableRowCount() {
+    if ($this->layoutAvailableRowCount === null) {
+      throw new PhutilInvalidStateException('new...Layout');
+    }
+
+    return $this->layoutAvailableRowCount;
+  }
 
   public function addMessage($message) {
     $this->messages[] = $message;
@@ -115,6 +138,11 @@ final class PhabricatorDocumentEngineBlocks
       );
     }
 
+    $this->layoutAvailableRowCount = count($rows);
+
+    $rows = $this->revealIndexes($rows, true);
+    $rows = $this->sliceRows($rows);
+
     return $rows;
   }
 
@@ -147,6 +175,11 @@ final class PhabricatorDocumentEngineBlocks
       $idx++;
     }
 
+    $this->layoutAvailableRowCount = count($rows);
+
+    $rows = $this->revealIndexes($rows, false);
+    $rows = $this->sliceRows($rows);
+
     return $rows;
   }
 
@@ -172,4 +205,47 @@ final class PhabricatorDocumentEngineBlocks
     );
   }
 
+  private function sliceRows(array $rows) {
+    $min = $this->rangeMin;
+    $max = $this->rangeMax;
+
+    if ($min === null && $max === null) {
+      return $rows;
+    }
+
+    if ($max === null) {
+      return array_slice($rows, $min, null, true);
+    }
+
+    if ($min === null) {
+      $min = 0;
+    }
+
+    return array_slice($rows, $min, $max - $min, true);
+  }
+
+  private function revealIndexes(array $rows, $is_vector) {
+    if ($this->revealedIndexes === null) {
+      return $rows;
+    }
+
+    foreach ($this->revealedIndexes as $index) {
+      if (!isset($rows[$index])) {
+        continue;
+      }
+
+      if ($is_vector) {
+        foreach ($rows[$index] as $block) {
+          if ($block !== null) {
+            $block->setIsVisible(true);
+          }
+        }
+      } else {
+        $rows[$index]->setIsVisible(true);
+      }
+    }
+
+    return $rows;
+  }
+
 }

src/infrastructure/internationalization/translation/PhabricatorUSEnglishTranslation.php

@@ -1069,29 +1069,54 @@ final class PhabricatorUSEnglishTranslation
         ),
       ),
 
-      'Show First %d Line(s)' => array(
+      'Show First %s Line(s)' => array(
         'Show First Line',
-        'Show First %d Lines',
+        'Show First %s Lines',
       ),
 
-      "\xE2\x96\xB2 Show %d Line(s)" => array(
+      'Show First %s Block(s)' => array(
+        'Show First Block',
+        'Show First %s Blocks',
+      ),
+
+      "\xE2\x96\xB2 Show %s Line(s)" => array(
         "\xE2\x96\xB2 Show Line",
-        "\xE2\x96\xB2 Show %d Lines",
+        "\xE2\x96\xB2 Show %s Lines",
       ),
 
-      'Show All %d Line(s)' => array(
+      "\xE2\x96\xB2 Show %s Block(s)" => array(
+        "\xE2\x96\xB2 Show Block",
+        "\xE2\x96\xB2 Show %s Blocks",
+      ),
+
+      'Show All %s Line(s)' => array(
         'Show Line',
-        'Show All %d Lines',
+        'Show All %s Lines',
       ),
 
-      "\xE2\x96\xBC Show %d Line(s)" => array(
+      'Show All %s Block(s)' => array(
+        'Show Block',
+        'Show All %s Blocks',
+      ),
+
+      "\xE2\x96\xBC Show %s Line(s)" => array(
         "\xE2\x96\xBC Show Line",
-        "\xE2\x96\xBC Show %d Lines",
+        "\xE2\x96\xBC Show %s Lines",
       ),
 
-      'Show Last %d Line(s)' => array(
+      "\xE2\x96\xBC Show %s Block(s)" => array(
+        "\xE2\x96\xBC Show Block",
+        "\xE2\x96\xBC Show %s Blocks",
+      ),
+
+      'Show Last %s Line(s)' => array(
         'Show Last Line',
-        'Show Last %d Lines',
+        'Show Last %s Lines',
+      ),
+
+      'Show Last %s Block(s)' => array(
+        'Show Last Block',
+        'Show Last %s Blocks',
       ),
 
       '%s marked %s inline comment(s) as done and %s inline comment(s) as '.