LibHTML+Browser: Add a simple DOM inspector popup window

LibHTML now provides a DOMTreeModel which can be used to view a given
Document's DOM tree. :^)

Libraries/LibHTML/DOMTreeModel.cpp

@@ -0,0 +1,110 @@
+#include "DOMTreeModel.h"
+#include <AK/StringBuilder.h>
+#include <LibHTML/DOM/Document.h>
+#include <LibHTML/DOM/Text.h>
+#include <ctype.h>
+#include <stdio.h>
+
+DOMTreeModel::DOMTreeModel(Document& document)
+    : m_document(document)
+{
+    m_element_icon.set_bitmap_for_size(16, GraphicsBitmap::load_from_file("/res/icons/16x16/inspector-object.png"));
+    m_text_icon.set_bitmap_for_size(16, GraphicsBitmap::load_from_file("/res/icons/16x16/filetype-unknown.png"));
+}
+
+DOMTreeModel::~DOMTreeModel()
+{
+}
+
+GModelIndex DOMTreeModel::index(int row, int column, const GModelIndex& parent) const
+{
+    if (!parent.is_valid()) {
+        return create_index(row, column, &m_document);
+    }
+    auto& parent_node = *static_cast<Node*>(parent.internal_data());
+    return create_index(row, column, parent_node.child_at_index(row));
+}
+
+GModelIndex DOMTreeModel::parent_index(const GModelIndex& index) const
+{
+    if (!index.is_valid())
+        return {};
+    auto& node = *static_cast<Node*>(index.internal_data());
+    if (!node.parent())
+        return {};
+
+    // No grandparent? Parent is the document!
+    if (!node.parent()->parent()) {
+        return create_index(0, 0, &m_document);
+    }
+
+    // Walk the grandparent's children to find the index of node's parent in its parent.
+    // (This is needed to produce the row number of the GModelIndex corresponding to node's parent.)
+    int grandparent_child_index = 0;
+    for (auto* grandparent_child = node.parent()->parent()->first_child(); grandparent_child; grandparent_child = grandparent_child->next_sibling()) {
+        if (grandparent_child == node.parent())
+            return create_index(grandparent_child_index, 0, node.parent());
+        ++grandparent_child_index;
+    }
+
+    ASSERT_NOT_REACHED();
+    return {};
+}
+
+int DOMTreeModel::row_count(const GModelIndex& index) const
+{
+    if (!index.is_valid())
+        return 1;
+    auto& node = *static_cast<Node*>(index.internal_data());
+    return node.child_count();
+}
+
+int DOMTreeModel::column_count(const GModelIndex&) const
+{
+    return 1;
+}
+
+static String with_whitespace_collapsed(const StringView& string)
+{
+    StringBuilder builder;
+    for (int i = 0; i < string.length(); ++i) {
+        if (isspace(string[i])) {
+            builder.append(' ');
+            while (i < string.length()) {
+                if (isspace(string[i])) {
+                    ++i;
+                    continue;
+                }
+                builder.append(string[i]);
+                break;
+            }
+            continue;
+        }
+        builder.append(string[i]);
+    }
+    return builder.to_string();
+}
+
+GVariant DOMTreeModel::data(const GModelIndex& index, Role role) const
+{
+    auto* node = static_cast<Node*>(index.internal_data());
+    if (role == Role::Icon) {
+        if (node->is_element())
+            return m_element_icon;
+        // FIXME: More node type icons?
+        return m_text_icon;
+    }
+    if (role == Role::Display) {
+        if (node->is_text()) {
+
+            return String::format("%s", with_whitespace_collapsed(to<Text>(*node).data()).characters());
+        }
+        return String::format("<%s>", node->tag_name().characters());
+    }
+    return {};
+}
+
+void DOMTreeModel::update()
+{
+    did_update();
+}