DockPanelDesigner

Overview

Namespace: TheTechIdea.Beep.Winform.Controls.Design.Server.Docking.Designers
Inheritance: ParentControlDesigner (allows child controls to be dropped onto the panel)
Visibility: internal sealed

DockPanelDesigner provides the design-time experience for individual DockPanel controls. It extends ParentControlDesigner so users can drag child controls onto the panel from the toolbox. It provides 10 designer verbs for docking/manageCommands and intelligent snapping when the panel is moved on the form.

Key Features

• Auto-key generation — On InitializeNewComponent, a unique Key is derived from the component's site name (e.g., "dockPanel1")
• Intelligent move snapping — When dragged, panel snaps to nearest dock edge or stacks with overlapped panels
• Float detection — Dragging outside the host form (>40px boundary) floats the panel
• 10 designer verbs — Dock Left/Right/Top/Bottom/Fill, Stack with Prev/Next, Move Earlier/Later in Stack, Remove
• Smart-tag — DockPanelActionList with position, sizing, and behavior properties
• Resize forwarding — Panel resize delegates to BeepDockingDesignerWiring for proportional recalculation

Designer Verbs (10)

Design-Time Behaviors

Auto-Key on InitializeNewComponent

When a new DockPanel is created (either from the manager's "Add Panel" verb or by drag-dropping), the designer auto-generates a unique Key from the designer host name:

public override void InitializeNewComponent(IDictionary defaultValues)
{
    base.InitializeNewComponent(defaultValues);
    string key = Component.Site?.Name ?? "dockPanel";
    SetPanelProperty("Key", key);
    SetPanelProperty("Title", key);
}

Move Snapping

When the user drags a DockPanel in the designer, the OnDesignerComponentChanged handler detects Bounds/Location/Size changes. For move changes:

1. FindPanelUnderCenter() — Checks if another panel is at the same parent level under the moved panel's center. If yes, stacks them.
2. ShouldFloatPanel() — Checks if the panel center is >40px outside the host form bounds. If yes, floats the panel.
3. ResolveNearestDockPosition() — Calculates the nearest dock edge (Left/Right/Top/Bottom) based on distance from center to host form bounds.

Resize Forwarding

Resize changes are forwarded to BeepDockingDesignerWiring.ResizePanel() for proportional recalculation of adjacent panels.

Selection Tracking

When a DockPanel becomes the primary selection in the designer, BeepDockingDesignerWiring.ActivateDesignPanel() is called to update the docking manager's active panel state.

DockPanelActionList Smart-Tag

Examples

Snap-to-Edge Logic

private DockPosition ResolveNearestDockPosition()
{
    var panel = (DockPanel)Component;
    var hostBounds = panel.Manager?.HostForm?.Bounds
        ?? panel.Parent?.Bounds;
    var center = new Point(
        panel.Bounds.Left + panel.Bounds.Width / 2,
        panel.Bounds.Top + panel.Bounds.Height / 2);

    // Calculate distances to each edge
    int distLeft = center.X - hostBounds.Left;
    int distRight = hostBounds.Right - center.X;
    int distTop = center.Y - hostBounds.Top;
    int distBottom = hostBounds.Bottom - center.Y;

    // Return nearest edge
    int min = Math.Min(Math.Min(distLeft, distRight),
                       Math.Min(distTop, distBottom));
    if (min == distLeft) return DockPosition.Left;
    if (min == distRight) return DockPosition.Right;
    if (min == distTop) return DockPosition.Top;
    return DockPosition.Bottom;
}