DocumentController — ParentElement RichTextKit

Constructor

public DocumentController(DocumentSettings config, IClipboardHandler clipboard)

Parameter	Type	Description
config	DocumentSettings	Initial page layout and default text style. See DocumentSettings.
clipboard	IClipboardHandler	Platform clipboard implementation. Provide `AvaloniaClipboardHandler` in Avalonia apps.

Avalonia Usage In Avalonia applications, DocumentController is created automatically by RichTextEditor during OnLoaded(). Access it via Editor.DocumentController.

Platform Callbacks

Wire these properties in your UI layer to connect the controller to your rendering and cursor systems.

Callback Action? RequestRedraw { get; set; }

Invoke this callback when the document needs to be repainted. Set to your control's invalidation method (e.g., () => InvalidateVisual()). Called internally by MoveCaret(), ScrollTo(), ScrollBy(), and OnDocumentDidChange().

Callback Action<EditorCursor>? RequestCursorUpdate { get; set; }

Called when the cursor shape should change — for example when hovering over a resize handle. Receives a platform-agnostic EditorCursor value; map it to native cursor types in your UI layer.

Events

Event event Action<NavigationInfo>? OnNavigation

Fired whenever the caret position or selection changes, and whenever the style at the caret changes. Use this to synchronize toolbar toggle states (bold, italic, etc.) and alignment selectors.

controller.OnNavigation += (info) =>
{
    // info.StyleAtCaret — IStyle at the caret
    // info.SelectionInfo — alignment, list type, list level, line spacing
    // info.Selection    — TextRange of the current selection
    UpdateToolbar(info);
};

Event event Action<DocumentInfo>? OnContentSizeChanged

Fired when the overall document height or width changes — use this to update scrollbar ranges. DocumentInfo carries the total Width, Height, and current ScrollOffset.

Properties

Property	Type	Description
Settings	DocumentSettings	Current document configuration (read-only; update via `ApplyDocumentSettings()`)
Shortcuts	ShortcutHandler	Map custom keyboard shortcuts to editor actions
SelectionColor	SKColor	Background color for selected text (default: LightGray)
BackgroundColor	SKColor	Document page background color
VisibleBounds	Rectangle	Current viewport dimensions — set when the control is resized
HasFocus	bool	Set to `true` when the editor control gains keyboard focus; `false` when it loses focus
ReadOnly	bool	When `true`, all editing operations are suppressed
DocumentHeight	float	Total document height minus visible height (max scroll extent in Y)
PageWidth	float	Document page width in pixels
ScrollScale	float	Mouse wheel scroll speed multiplier (default: 20)

Text Styling

All style methods are async Task. They apply to the current selection if one exists, or set the style at the caret (affecting subsequent typing) if no text is selected.

Method Task ApplyBold()

Toggles bold. Font weight alternates between 400 (normal) and 700 (bold).

Method Task ApplyItalic()

Toggles italic.

Method Task ApplyUnderline()

Toggles underline. Cycles between UnderlineStyle.Solid and UnderlineStyle.None.

Method Task ApplyStrikethrough()

Toggles strikethrough. Cycles between StrikeThroughStyle.Solid and StrikeThroughStyle.None.

Method Task ApplySubscript()

Toggles subscript (FontVariant.SubScript). Clears superscript if active.

Method Task ApplySuperscript()

Toggles superscript (FontVariant.SuperScript). Clears subscript if active.

Method Task ApplyFontColor(SKColor color)

Sets the foreground text color of the selection or caret.

Method Task ApplyBackgroundColor(SKColor color)

Sets the background highlight color of the selection or caret.

Method Task ApplyFontFamily(string fontFamily)

Sets the font family by name (e.g., "Arial", "Times New Roman").

Method Task ApplyFontSize(int fontSize)

Sets the font size in points.

Method Task ApplyStyle(IStyle style)

Applies an IStyle overlay to the selection. Only non-null properties of style are applied.

Method void ReplaceStyle(IStyle style)

Replaces the entire style of the selection with the given style (non-async; used internally for bulk import).

Paragraph Formatting

Method Task ApplyAlignment(TextAlignment alignment)

Sets the horizontal alignment of the paragraph containing the caret or selection. TextAlignment values: Left, Center, Right, Justified, Auto.

Method void SetBlockIndent(float value)

Sets the block (left) indent of the current paragraph to an absolute pixel value.

Method void AdjustParagraphIndent(float amount)

Increases or decreases the block indent by amount pixels. Pass positive values to indent, negative to unindent.

Method void AdjustLineSpacing(float amount)

Adjusts the line spacing multiplier for the current paragraph. Common values: 1.0, 1.15, 1.5, 2.0.

Method void ToggleFirstLineIndent()

Toggles first-line indent (20 px) on the current paragraph.

Lists

Method void ToggleBulletList()

Turns bullet list on for the current paragraph, or removes the list formatting if it is already a bullet list.

Method void ToggleNumberedList()

Same as above, for numbered (ordered) lists.

Method void ChangeListLevel(int delta)

Changes the nesting level of the current list item. Pass +1 to indent (increase level) or -1 to unindent. Also triggered by Tab / Shift+Tab inside a list item.

Method void ApplyListFormat(ListType type, int level)

Directly sets the list type and level. Primarily used by importers.

Editing & Clipboard

Method void Insert(string text)

Inserts text at the current caret position, replacing the selection if one exists. Respects overtype mode.

Method async Task Cut()

Copies the selection to the clipboard then deletes it.

Method async Task<bool> Copy()

Copies the selection to the clipboard. Returns true on success.

Method async Task Paste()

Pastes from the clipboard. Handles both plain text and bitmap images. Images are inserted as inline objects.

Method Task Undo()

Undoes the last editing operation. Undo history is maintained by the underlying RTK document.

Method Task Redo()

Redoes the last undone operation.

Navigation & Pointer Input

Method Task SelectAll()

Selects the entire document content.

Method void SelectNone()

Collapses the selection to the caret (no selection).

Method void Click(Point point)

Handle a mouse click (primary button down). Moves the caret to the clicked position. If an inline image is at the click point, it is auto-selected and resize handles appear. Point must be in document (canvas) coordinates, not screen coordinates.

Method void DragTo(Point point)

Handle mouse drag while primary button is held. If dragging from a text area: extends the text selection. If dragging a resize handle on a selected image: resizes the image live.

Method void HoverAt(Point point)

Handle mouse movement with no button held. Updates the cursor shape by calling RequestCursorUpdate when hovering over resize handles.

Method void PointerReleased(Point point)

Handle primary button release. Commits any in-progress image resize as an undoable operation and re-selects the image.

Method void ScrollBy(float x, float y)

Scrolls the viewport by a delta, scaled by ScrollScale. Used for mouse wheel events.

Method void ScrollTo(float x, float y)

Scrolls to an absolute position. Used to synchronize external scrollbars.

Method async Task<bool> OnKeyEvent(KeyInfo key)

Dispatches a key event through the ShortcutHandler. Returns true if the key was consumed. Call this from your platform key-down handler after converting native key codes to KeyInfo.

Inline Images

Method void InsertInlineImage(SKImage image, float displayWidth, float displayHeight)

Inserts an inline image at the current caret position. The display dimensions are automatically clamped so the image does not exceed the available content width. The image flows with the text and can be resized interactively using resize handles after clicking on it.

// Load from file (example)
using var data = SKData.Create("photo.png");
var img = SKImage.FromEncodedData(data);
controller.InsertInlineImage(img, 400f, 300f);

Document Configuration & Rendering

Method void ApplyDocumentSettings(DocumentSettings settings)

Updates the document's page width, margins, and background color. Triggers a re-layout. See DocumentSettings for all configurable values.

Method DocumentReader GetContentReader()

Returns a DocumentReader that iterates the document's paragraphs, runs, and styles. Use this with the Export library to save the document to HTML, RTF, or DOCX format.

Method void Draw(SKCanvas canvas)

Renders the document to the provided Skia canvas. Called automatically by the Avalonia platform layer. You would only call this directly if implementing a custom renderer.

Full Usage Example

// 1. Configure the document
var settings = new DocumentSettings
{
    PageWidth = 800f,
    DocumentBackgroundColor = SKColors.White,
    DocumentMargins = new DocumentMargins(80, 80, 60, 60),
    TextStyle = new Style { FontFamily = "Segoe UI", FontSize = 14 },
    Alignment = TextAlignment.Left
};

// 2. Create controller (Avalonia does this for you in RichTextEditor)
var clipboard = new AvaloniaClipboardHandler(this);
var controller = new DocumentController(settings, clipboard);

// 3. Listen for selection/style changes
controller.OnNavigation += (info) =>
{
    boldButton.IsChecked = info.StyleAtCaret.FontWeight == 700;
    italicButton.IsChecked = info.StyleAtCaret.FontItalic == true;
};

// 4. Listen for size changes (to update scrollbars)
controller.OnContentSizeChanged += (info) =>
{
    vScrollBar.Maximum = info.Height;
};

// 5. Wire redraw
controller.RequestRedraw = () => myCanvas.InvalidateVisual();

// 6. Apply formatting
await controller.ApplyBold();
await controller.ApplyFontSize(18);