Traverse the content tree

Traversing the content tree, or, visiting every node or page in a hierarchical data structure makes the content tree stay inspectable until you paginate. This allows you to generate content first and decide its style afterwards which is useful for applying rules that depend on the finished document, such as banding every second row or restyling every heading.

Iterate children

GetContentNodeIterator returns an iterator over the direct children of a node. Every child is a ContentElement.

C#

for (ContentNodeIterator itr = node.GetContentNodeIterator(); itr.HasNext(); itr.Next())
{
    ContentElement el = itr.Current();
    // ... inspect el ...
}

C++

for (ContentNodeIterator itr = node.GetContentNodeIterator(); itr.HasNext(); itr.Next())
{
    ContentElement el = itr.Current();
    // ... inspect el ...
}

Go

for itr := node.GetContentNodeIterator(); itr.HasNext(); itr.Next() {
    el := itr.Current()
    // ... inspect el ...
}

Java

for (ContentNodeIterator itr = node.getContentNodeIterator(); itr.hasNext(); itr.next()) {
    ContentElement el = itr.current();
    // ... inspect el ...
}

JavaScript

const itr = await node.getContentNodeIterator();
while (await itr.hasNext()) {
    const el = await itr.current();
    await itr.next();
    // ... inspect el ...
}

Obj-C

PTContentNodeIterator* itr = [node GetContentNodeIterator];
for (; [itr HasNext]; [itr Next])
{
    PTContentElement* el = [itr Current];
    // ... inspect el ...
}

PHP

for ($itr = $node->GetContentNodeIterator(); $itr->HasNext(); $itr->Next()) {
    $el = $itr->Current();
    // ... inspect el ...
}

Python

itr = node.GetContentNodeIterator()
while itr.HasNext():
    el = itr.Current()
    # ... inspect el ...
    itr.Next()

Ruby

itr = node.GetContentNodeIterator()
while itr.HasNext()
  el = itr.Current()
  # ... inspect el ...
  itr.Next()
end

Identify elements

A content element exposes one conversion method per concrete type. In C++, these return an ElementRef, which supports the safe-bool idiom and is dereferenced with ->. In the other languages, they return the object itself, or a null value when the element is not of that type.

C#

Paragraph para = el.AsParagraph();
if (para != null)
    para.GetTextStyledElement().SetFontSize(11);

C++

if (ElementRef<Paragraph> para = el.AsParagraph())
    para->GetTextStyledElement().SetFontSize(11);

Go

para := el.AsParagraph()
if para.Swigcptr() != 0 {
    para.GetTextStyledElement().SetFontSize(11)
}

Java

Paragraph para = el.asParagraph();
if (para != null)
    para.getTextStyledElement().setFontSize(11);

JavaScript

const para = await el.asParagraph();
if (para !== null) {
    (await para.getTextStyledElement()).setFontSize(11);
}

Obj-C

PTParagraph* para = [el AsParagraph];
if (para != nil)
    [[para GetTextStyledElement] SetFontSize:11];

PHP

$para = $el->AsParagraph();
if ($para != null)
    $para->GetTextStyledElement()->SetFontSize(11);

Python

para = el.AsParagraph()
if para is not None:
    para.GetTextStyledElement().SetFontSize(11)

Ruby

para = el.AsParagraph()
if !para.nil?
  para.GetTextStyledElement().SetFontSize(11)
end

Method	Converts to
AsContentNode	Any node that has children
AsParagraph	Paragraph
AsTextRun	TextRun
AsPageNumber	PageNumber
AsTable, AsTableRow, AsTableCell	Table elements
AsList, AsListItem	List elements
AsShape, AsChart, AsFloat	Shape, chart and float

Info

In C++, dereferencing an invalid ElementRef throws an error. Always test it first.

Walk the whole tree

Recursing through AsContentNode visits every element in the document, whatever its nesting depth - including content inside table cells, list items, shape text boxes and floats.

C#

// Highlight every second text run and outline every table cell.
static bool RestyleContentTree(ContentNode node, bool highlight)
{
    for (ContentNodeIterator itr = node.GetContentNodeIterator(); itr.HasNext(); itr.Next())
    {
        ContentElement el = itr.Current();

        TextRun textRun = el.AsTextRun();
        if (textRun != null)
        {
            if (highlight)
            {
                TextStyledElement style = textRun.GetTextStyledElement();
                style.SetBold(true);
                style.SetBackgroundColor(255, 245, 180);
            }
            highlight = !highlight;
            continue;
        }

        TableCell cell = el.AsTableCell();
        if (cell != null)
            cell.SetBorder(0.5, 150, 150, 150);

        ContentNode child = el.AsContentNode();
        if (child != null)
            highlight = RestyleContentTree(child, highlight);
    }
    return highlight;
}

RestyleContentTree(doc, false);

C++

// Highlight every second text run and outline every table cell.
void RestyleContentTree(ContentNode node, bool& highlight)
{
    for (ContentNodeIterator itr = node.GetContentNodeIterator(); itr.HasNext(); itr.Next())
    {
        ContentElement el = itr.Current();

        if (ElementRef<TextRun> text_run = el.AsTextRun())
        {
            if (highlight)
            {
                TextStyledElement style = text_run->GetTextStyledElement();
                style.SetBold(true);
                style.SetBackgroundColor(255, 245, 180);
            }
            highlight = !highlight;
            continue;
        }

        if (ElementRef<TableCell> cell = el.AsTableCell())
            cell->SetBorder(0.5, 150, 150, 150);

        if (ElementRef<ContentNode> child = el.AsContentNode())
            RestyleContentTree(*child, highlight);
    }
}

bool highlight = false;
RestyleContentTree(doc, highlight);

Go

// Highlight every second text run and outline every table cell.
func restyleContentTree(node ContentNode, highlight bool) bool {
    for itr := node.GetContentNodeIterator(); itr.HasNext(); itr.Next() {
        el := itr.Current()

        if textRun := el.AsTextRun(); textRun.Swigcptr() != 0 {
            if highlight {
                style := textRun.GetTextStyledElement()
                style.SetBold(true)
                style.SetBackgroundColor(255, 245, 180)
            }
            highlight = !highlight
            continue
        }

        if cell := el.AsTableCell(); cell.Swigcptr() != 0 {
            cell.SetBorder(0.5, 150, 150, 150)
        }

        if child := el.AsContentNode(); child.Swigcptr() != 0 {
            highlight = restyleContentTree(child, highlight)
        }
    }
    return highlight
}

restyleContentTree(doc, false)

Java

// Highlight every second text run and outline every table cell.
static boolean restyleContentTree(ContentNode node, boolean highlight) throws PDFNetException {
    for (ContentNodeIterator itr = node.getContentNodeIterator(); itr.hasNext(); itr.next()) {
        ContentElement el = itr.current();

        TextRun textRun = el.asTextRun();
        if (textRun != null) {
            if (highlight) {
                TextStyledElement style = textRun.getTextStyledElement();
                style.setBold(true);
                style.setBackgroundColor(255, 245, 180);
            }
            highlight = !highlight;
            continue;
        }

        TableCell cell = el.asTableCell();
        if (cell != null)
            cell.setBorder(0.5, 150, 150, 150);

        ContentNode child = el.asContentNode();
        if (child != null)
            highlight = restyleContentTree(child, highlight);
    }
    return highlight;
}

restyleContentTree(doc, false);

JavaScript

// Highlight every second text run and outline every table cell.
const restyleContentTree = async (node, highlight) => {
    const itr = await node.getContentNodeIterator();
    while (await itr.hasNext()) {
        const el = await itr.current();
        await itr.next();

        const textRun = await el.asTextRun();
        if (textRun !== null) {
            if (highlight) {
                const style = await textRun.getTextStyledElement();
                style.setBold(true);
                style.setBackgroundColor(255, 245, 180);
            }
            highlight = !highlight;
            continue;
        }

        const cell = await el.asTableCell();
        if (cell !== null) {
            cell.setBorder(0.5, 150, 150, 150);
        }

        const child = await el.asContentNode();
        if (child !== null) {
            highlight = await restyleContentTree(child, highlight);
        }
    }
    return highlight;
};

await restyleContentTree(doc, false);

Obj-C

// Highlight every second text run and outline every table cell.
BOOL RestyleContentTree(PTContentNode* node, BOOL highlight)
{
    PTContentNodeIterator* itr = [node GetContentNodeIterator];
    for (; [itr HasNext]; [itr Next])
    {
        PTContentElement* el = [itr Current];

        PTTextRun* text_run = [el AsTextRun];
        if (text_run != nil)
        {
            if (highlight)
            {
                PTTextStyledElement* style = [text_run GetTextStyledElement];
                [style SetBold:YES];
                [style SetBackgroundColor:255 green:245 blue:180];
            }
            highlight = !highlight;
            continue;
        }

        PTTableCell* cell = [el AsTableCell];
        if (cell != nil)
            [cell SetBorder:0.5 red:150 green:150 blue:150];

        PTContentNode* child = [el AsContentNode];
        if (child != nil)
            highlight = RestyleContentTree(child, highlight);
    }
    return highlight;
}

RestyleContentTree(doc, NO);

PHP

// Highlight every second text run and outline every table cell.
function RestyleContentTree($node, $highlight)
{
    for ($itr = $node->GetContentNodeIterator(); $itr->HasNext(); $itr->Next()) {
        $el = $itr->Current();

        $text_run = $el->AsTextRun();
        if ($text_run != null) {
            if ($highlight) {
                $style = $text_run->GetTextStyledElement();
                $style->SetBold(true);
                $style->SetBackgroundColor(255, 245, 180);
            }
            $highlight = !$highlight;
            continue;
        }

        $cell = $el->AsTableCell();
        if ($cell != null)
            $cell->SetBorder(0.5, 150, 150, 150);

        $child = $el->AsContentNode();
        if ($child != null)
            $highlight = RestyleContentTree($child, $highlight);
    }
    return $highlight;
}

RestyleContentTree($doc, false);

Python

# Highlight every second text run and outline every table cell.
def restyle_content_tree(node, highlight):
    itr = node.GetContentNodeIterator()
    while itr.HasNext():
        el = itr.Current()
        itr.Next()

        text_run = el.AsTextRun()
        if text_run is not None:
            if highlight:
                style = text_run.GetTextStyledElement()
                style.SetBold(True)
                style.SetBackgroundColor(255, 245, 180)
            highlight = not highlight
            continue

        cell = el.AsTableCell()
        if cell is not None:
            cell.SetBorder(0.5, 150, 150, 150)

        child = el.AsContentNode()
        if child is not None:
            highlight = restyle_content_tree(child, highlight)
    return highlight

restyle_content_tree(doc, False)

Ruby

# Highlight every second text run and outline every table cell.
def restyle_content_tree(node, highlight)
  itr = node.GetContentNodeIterator()
  while itr.HasNext()
    el = itr.Current()
    itr.Next()

    text_run = el.AsTextRun()
    if !text_run.nil?
      if highlight
        style = text_run.GetTextStyledElement()
        style.SetBold(true)
        style.SetBackgroundColor(255, 245, 180)
      end
      highlight = !highlight
      next
    end

    cell = el.AsTableCell()
    cell.SetBorder(0.5, 150, 150, 150) if !cell.nil?

    child = el.AsContentNode()
    highlight = restyle_content_tree(child, highlight) if !child.nil?
  end
  highlight
end

restyle_content_tree(doc, false)

A FlowDocument is itself a ContentNode, so passing the document walks the entire tree.

Restyle just-created content

Traversal is also handy for a narrow scope, such as recoloring the header row you have only just built.

C#

// Make every paragraph in the header row white.
for (ContentNodeIterator cellItr = headerRow.GetContentNodeIterator();
        cellItr.HasNext(); cellItr.Next())
{
    TableCell cell = cellItr.Current().AsTableCell();
    if (cell == null) continue;

    for (ContentNodeIterator paraItr = cell.GetContentNodeIterator();
            paraItr.HasNext(); paraItr.Next())
    {
        Paragraph para = paraItr.Current().AsParagraph();
        if (para != null)
            para.GetTextStyledElement().SetTextColor(255, 255, 255);
    }
}

C++

// Make every paragraph in the header row white.
for (ContentNodeIterator cell_itr = header_row.GetContentNodeIterator();
        cell_itr.HasNext(); cell_itr.Next())
{
    if (ElementRef<TableCell> cell = cell_itr.Current().AsTableCell())
    {
        for (ContentNodeIterator para_itr = cell->GetContentNodeIterator();
                para_itr.HasNext(); para_itr.Next())
        {
            if (ElementRef<Paragraph> para = para_itr.Current().AsParagraph())
                para->GetTextStyledElement().SetTextColor(255, 255, 255);
        }
    }
}

Go

// Make every paragraph in the header row white.
for cellItr := headerRow.GetContentNodeIterator(); cellItr.HasNext(); cellItr.Next() {
    cell := cellItr.Current().AsTableCell()
    if cell.Swigcptr() == 0 {
        continue
    }

    for paraItr := cell.GetContentNodeIterator(); paraItr.HasNext(); paraItr.Next() {
        para := paraItr.Current().AsParagraph()
        if para.Swigcptr() != 0 {
            para.GetTextStyledElement().SetTextColor(255, 255, 255)
        }
    }
}

Java

// Make every paragraph in the header row white.
for (ContentNodeIterator cellItr = headerRow.getContentNodeIterator();
        cellItr.hasNext(); cellItr.next()) {
    TableCell cell = cellItr.current().asTableCell();
    if (cell == null) continue;

    for (ContentNodeIterator paraItr = cell.getContentNodeIterator();
            paraItr.hasNext(); paraItr.next()) {
        Paragraph para = paraItr.current().asParagraph();
        if (para != null)
            para.getTextStyledElement().setTextColor(255, 255, 255);
    }
}

JavaScript

// Make every paragraph in the header row white.
const cellItr = await headerRow.getContentNodeIterator();
while (await cellItr.hasNext()) {
    const cell = await (await cellItr.current()).asTableCell();
    if (cell !== null) {
        const paraItr = await cell.getContentNodeIterator();
        while (await paraItr.hasNext()) {
            const para = await (await paraItr.current()).asParagraph();
            if (para !== null) {
                (await para.getTextStyledElement()).setTextColor(255, 255, 255);
            }
            await paraItr.next();
        }
    }
    await cellItr.next();
}

Obj-C

// Make every paragraph in the header row white.
PTContentNodeIterator* cell_itr = [header_row GetContentNodeIterator];
for (; [cell_itr HasNext]; [cell_itr Next])
{
    PTTableCell* cell = [[cell_itr Current] AsTableCell];
    if (cell == nil) continue;

    PTContentNodeIterator* para_itr = [cell GetContentNodeIterator];
    for (; [para_itr HasNext]; [para_itr Next])
    {
        PTParagraph* para = [[para_itr Current] AsParagraph];
        if (para != nil)
            [[para GetTextStyledElement] SetTextColor:255 green:255 blue:255];
    }
}

PHP

// Make every paragraph in the header row white.
for ($cell_itr = $header_row->GetContentNodeIterator();
        $cell_itr->HasNext(); $cell_itr->Next()) {
    $cell = $cell_itr->Current()->AsTableCell();
    if ($cell == null) continue;

    for ($para_itr = $cell->GetContentNodeIterator();
            $para_itr->HasNext(); $para_itr->Next()) {
        $para = $para_itr->Current()->AsParagraph();
        if ($para != null)
            $para->GetTextStyledElement()->SetTextColor(255, 255, 255);
    }
}

Python

# Make every paragraph in the header row white.
cell_itr = header_row.GetContentNodeIterator()
while cell_itr.HasNext():
    cell = cell_itr.Current().AsTableCell()
    cell_itr.Next()
    if cell is None:
        continue

    para_itr = cell.GetContentNodeIterator()
    while para_itr.HasNext():
        para = para_itr.Current().AsParagraph()
        if para is not None:
            para.GetTextStyledElement().SetTextColor(255, 255, 255)
        para_itr.Next()

Ruby

# Make every paragraph in the header row white.
cell_itr = header_row.GetContentNodeIterator()
while cell_itr.HasNext()
  cell = cell_itr.Current().AsTableCell()
  cell_itr.Next()
  next if cell.nil?

  para_itr = cell.GetContentNodeIterator()
  while para_itr.HasNext()
    para = para_itr.Current().AsParagraph()
    para.GetTextStyledElement().SetTextColor(255, 255, 255) if !para.nil?
    para_itr.Next()
  end
end

Read content back

Traversal is not only for styling. The getters on text runs, tables, and sections let you inspect a document you have assembled, to compute a summary, run a validation pass, or log its structure.

Notes

• Traversal reflects the tree as built. Line breaks, page breaks and page numbers are resolved during pagination and are not visible beforehand.

• Iterators visit direct children only; recurse through AsContentNode to go deeper.

Further Reading

• Tables for the table elements most often restyled after the fact.

• Paragraphs and text for the style properties available on runs and paragraphs.