Customizing Appearance and Behavior of TAdvExplorerTreeviewTAdvExplorerTreeview (part of TMS Components for Delphi/C++Builder) is a feature-rich treeview control designed to recreate and surpass the look-and-feel of Windows Explorer’s navigation pane. It blends native Explorer aesthetics with extended customization, making it suitable for apps that need a polished, modern hierarchical browser. This article walks through practical ways to customize both the appearance and runtime behavior of TAdvExplorerTreeview so you can adapt it to your app’s UX, branding, and performance needs.
Overview: What makes TAdvExplorerTreeview special
TAdvExplorerTreeview extends standard tree controls with:
- Advanced visual styling (Windows Explorer themes, custom icons, colors, gradients).
- Item-level controls (checkboxes, buttons, inline editing).
- Built-in drag-and-drop, multi-selection, and virtualization-friendly handling for large node sets.
- Events and properties that let you shape selection, expansion, hot-tracking, and keyboard behavior.
The combination of style options and runtime hooks makes it straightforward to match an application’s look while keeping responsive behavior when dealing with many nodes.
Key appearance-customization areas
Below are the common appearance facets you’ll want to change, and how to approach each.
- Icons and images
- Use an ImageList to assign icons to nodes. Each node’s ImageIndex and SelectedIndex control normal and selected icons.
- For per-node custom drawing, handle the OnDrawItem (or similar) event to paint bespoke icons or overlays (e.g., sync status badges).
- Support high-DPI: provide multiple-size image lists or use vector/scaleable icons if available.
- Fonts, colors, and gradients
- Change the control’s Font property for global text appearance.
- Node-level font/color: some properties or owner-draw allow you to apply different fonts/colors per node (useful for grouping or denoting status).
- Backgrounds: TAdvExplorerTreeview supports themed backgrounds or custom fill. Use the Background and Gradient properties (if present) to set subtle gradients that match your app chrome.
- Selection color: customize SelectedFontColor and SelectedColor to match application palette.
- Lines, connectors, and indentation
- Control visibility and style of lines between nodes with LineStyle/LinesVisible properties.
- Indentation and check box alignment can be tuned via Indent and CheckBoxIndent properties to fit dense UIs.
- Node templates and sub-controls
- TAdvExplorerTreeview supports embedding small controls (e.g., buttons or checkboxes) inline with a node. Use node templates or OnCreateNodeControl to add interactive elements.
- Use these for actions like quick rename, context toggles, or inline status indicators.
- Hot-tracking, hover effects, and tooltips
- Toggle hot-tracking to highlight nodes under the mouse.
- Configure ToolTip properties or handle OnGetHint to show dynamic node tooltips (full path, metadata).
- Hover effects can be implemented with owner-draw if you need richer visuals (shadow, subtle scale).
- Multi-column or additional details
- If you need multi-column layout, consider pairing TAdvExplorerTreeview with a grid or using the control’s details view (if provided). Some variants of advanced treeviews include per-node detail columns or right-side panes for metadata.
Behavior customizations: selection, expansion, editing, and interaction
- Selection modes and multi-select
- Control selection behavior with MultiSelect property. For single-selection UIs, disable it; for file-manager-like behavior enable multi-select with Ctrl/Shift handling.
- Use events like OnNodeClick, OnSelectionChange, or OnMultiSelectChange to react to selection changes and update other UI components.
- Expansion and lazy-loading (virtualization)
- For large data sets, avoid pre-populating all nodes. Use OnExpanding (or OnGetChildren/OnCreateChild) to lazy-load children when a node is expanded.
- Use a virtual mode (if supported) so the tree only creates UI nodes for visible items — this improves memory and performance.
- Drag-and-drop and reordering
- Enable built-in drag-and-drop properties for internal rearrangement or to accept external drops.
- Handle OnDragOver and OnDrop to validate drops (forbidden targets, cycle prevention) and to implement copy vs. move logic.
- Provide visual drop cues (insertion lines, highlight target) using the control’s DragImage or custom drawing.
- Inline editing and validation
- Allow label editing via ReadOnly/CanEdit and handle OnEditing/OnEdited to validate names, prevent reserved characters, or auto-apply formatting rules.
- For more complex edits, launch a modal/editor pane on double-click rather than inline editing.
- Keyboard handling and accessibility
- Customize keyboard behavior (Enter to open, F2 to rename, arrows to navigate) by handling KeyDown/KeyPress and preventing default behavior when needed.
- Ensure accessibility: make tree items navigable by keyboard, expose hints for screen readers if your application supports accessibility APIs.
- Context menus and command integration
- Use OnContextPopup or OnContextMenu to show context-sensitive actions for the clicked node(s). Populate menus based on node type or state (file vs. folder, read-only, etc.).
- Integrate commands with an action list so keyboard shortcuts and UI menu items remain consistent.
Practical examples and snippets
Below are conceptual examples showing common customizations (Delphi/C++Builder pseudocode style—adapt to your exact TMS version/API).
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Lazy-load children when a node expands:
procedure TForm1.AdvExplorerTreeView1Expanding(Sender: TObject; Node: TTreeNode; var Allow: Boolean); begin if Node.HasChildren = False then begin // Populate children from data source LoadChildrenFor(Node); end; end; -
Custom drawing for status badges:
procedure TForm1.AdvExplorerTreeView1DrawItem(Sender: TObject; Node: TTreeNode; Rect: TRect; State: TAdvancedDrawState); begin // draw node text normally DrawNodeText(Node, Rect); // draw small status circle aligned right if Node.DataAsRecord.Status = syncPending then Canvas.Brush.Color := clOrange else Canvas.Brush.Color := clGreen; Canvas.Ellipse(Rect.Right - 14, Rect.Top + 4, Rect.Right - 4, Rect.Top + 14); end; -
Validate rename input: “`pascal procedure TForm1.AdvExplorerTreeView1Editing(Sender: TObject; Node: TTreeNode; var Allow: Boolean); begin // prevent editing root nodes Allow := not Node.IsRoot; end;
procedure TForm1.AdvExplorerTreeView1Edited(Sender: TObject; Node: TTreeNode; var S: string); begin if ContainsInvalidChars(S) then begin
ShowMessage('Name contains invalid characters.'); S := Node.Text; // revert end; end; “`
Performance tips for large trees
- Use virtualization/owner-data modes when available to avoid creating VCL objects for all nodes.
- Lazy-load children during expansion rather than preloading entire hierarchies.
- Batch UI updates: when inserting many nodes, call BeginUpdate/EndUpdate (or Lock/Unlock) to prevent repeated repaints.
- Minimize owner-draw complexity during rapid operations; cache measurements or images.
- Use light-weight node data (avoid large objects attached to node.Data).
Theming and consistency with application UX
- Match control colors and fonts to your app’s theme. If you support light/dark modes, switch the tree’s colors, icons, and selection colors accordingly.
- Consider iconography scale across DPI: provide multiple image sizes or vector icons.
- Keep interactive affordances consistent (e.g., hover behavior, double-click actions) across the app so users transfer expectations smoothly.
Testing and version compatibility
- Test customization on different Windows versions and with different VCL themes (Windows classic, Aero, dark themes). –
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