LayoutCollector class
LayoutCollector class
This class allows to compute page numbers of document nodes.
To learn more, visit the Converting to Fixed-page Format documentation article.
Remarks
When you create a LayoutCollector and specify a Document document object to attach to, the collector will record mapping of document nodes to layout objects when the document is formatted into pages.
You will be able to find out on which page a particular document node (e.g. run, paragraph or table cell) is located by using the LayoutCollector.get_start_page_index(), LayoutCollector.get_end_page_index() and LayoutCollector.get_num_pages_spanned() methods. These methods automatically build page layout model of the document and update fields if required.
When you no longer need to collect layout information, it is best to set the LayoutCollector.document property to None
to avoid unnecessary collection of more layout mappings.
Constructors
| Name | Description |
|---|---|
| LayoutCollector(doc) | Initializes an instance of this class. |
Properties
| Name | Description |
|---|---|
| document | Gets or sets the document this collector instance is attached to. |
Methods
| Name | Description |
|---|---|
| clear() | Clears all collected layout data. Call this method after document was manually updated, or layout was rebuilt. |
| get_end_page_index(node) | Gets 1-based index of the page where node ends. Returns 0 if node cannot be mapped to a page. |
| get_num_pages_spanned(node) | Gets number of pages the specified node spans. 0 if node is within a single page. This is the same as LayoutCollector.get_end_page_index() - LayoutCollector.get_start_page_index(). |
| get_start_page_index(node) | Gets 1-based index of the page where node begins. Returns 0 if node cannot be mapped to a page. |
Examples
Shows how to see the the ranges of pages that a node spans.
doc = aw.Document()
layout_collector = aw.layout.LayoutCollector(doc)
# Call the "GetNumPagesSpanned" method to count how many pages the content of our document spans.
# Since the document is empty, that number of pages is currently zero.
self.assertEqual(doc, layout_collector.document)
self.assertEqual(0, layout_collector.get_num_pages_spanned(doc))
# Populate the document with 5 pages of content.
builder = aw.DocumentBuilder(doc=doc)
builder.write('Section 1')
builder.insert_break(aw.BreakType.PAGE_BREAK)
builder.insert_break(aw.BreakType.PAGE_BREAK)
builder.insert_break(aw.BreakType.SECTION_BREAK_EVEN_PAGE)
builder.write('Section 2')
builder.insert_break(aw.BreakType.PAGE_BREAK)
builder.insert_break(aw.BreakType.PAGE_BREAK)
# Before the layout collector, we need to call the "UpdatePageLayout" method to give us
# an accurate figure for any layout-related metric, such as the page count.
self.assertEqual(0, layout_collector.get_num_pages_spanned(doc))
layout_collector.clear()
doc.update_page_layout()
self.assertEqual(5, layout_collector.get_num_pages_spanned(doc))
# We can see the numbers of the start and end pages of any node and their overall page spans.
nodes = doc.get_child_nodes(aw.NodeType.ANY, True)
for node in nodes:
print(f'-> NodeType.{node.node_type}: ')
print(f'\tStarts on page {layout_collector.get_start_page_index(node)}, ends on page {layout_collector.get_end_page_index(node)},' + f' spanning {layout_collector.get_num_pages_spanned(node)} pages.')
# We can iterate over the layout entities using a LayoutEnumerator.
layout_enumerator = aw.layout.LayoutEnumerator(doc)
self.assertEqual(aw.layout.LayoutEntityType.PAGE, layout_enumerator.type)
# The LayoutEnumerator can traverse the collection of layout entities like a tree.
# We can also apply it to any node's corresponding layout entity.
layout_enumerator.set_current(layout_collector, doc.get_child(aw.NodeType.PARAGRAPH, 1, True))
self.assertEqual(aw.layout.LayoutEntityType.SPAN, layout_enumerator.type)
self.assertEqual('¶', layout_enumerator.text)
See Also
- module aspose.words.layout