LayoutEngine.Layout(Object, LayoutEventArgs) Method
Definition
Important
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Requests that the layout engine perform a layout operation.
public:
virtual bool Layout(System::Object ^ container, System::Windows::Forms::LayoutEventArgs ^ layoutEventArgs);public virtual bool Layout (object container, System.Windows.Forms.LayoutEventArgs layoutEventArgs);abstract member Layout : obj * System.Windows.Forms.LayoutEventArgs -> bool
override this.Layout : obj * System.Windows.Forms.LayoutEventArgs -> boolPublic Overridable Function Layout (container As Object, layoutEventArgs As LayoutEventArgs) As BooleanParameters
- container
- Object
The container on which the layout engine will operate.
- layoutEventArgs
- LayoutEventArgs
An event argument from a Layout event.
Returns
true if layout should be performed again by the parent of container; otherwise, false.
Exceptions
container is not a type on which LayoutEngine can perform layout.
Examples
The following code example demonstrates the use of the Layout method to implement custom layout behavior. This code example is part of a larger example provided for the LayoutEngine class.
public:
virtual bool Layout(Object^ container,
LayoutEventArgs^ layoutEventArgs) override
{
Control^ parent = nullptr;
try
{
parent = (Control ^) container;
}
catch (InvalidCastException^ ex)
{
throw gcnew ArgumentException(
"The parameter 'container' must be a control", "container", ex);
}
// Use DisplayRectangle so that parent.Padding is honored.
Rectangle parentDisplayRectangle = parent->DisplayRectangle;
Point nextControlLocation = parentDisplayRectangle.Location;
for each (Control^ currentControl in parent->Controls)
{
// Only apply layout to visible controls.
if (!currentControl->Visible)
{
continue;
}
// Respect the margin of the control:
// shift over the left and the top.
nextControlLocation.Offset(currentControl->Margin.Left,
currentControl->Margin.Top);
// Set the location of the control.
currentControl->Location = nextControlLocation;
// Set the autosized controls to their
// autosized heights.
if (currentControl->AutoSize)
{
currentControl->Size = currentControl->GetPreferredSize(
parentDisplayRectangle.Size);
}
// Move X back to the display rectangle origin.
nextControlLocation.X = parentDisplayRectangle.X;
// Increment Y by the height of the control
// and the bottom margin.
nextControlLocation.Y += currentControl->Height +
currentControl->Margin.Bottom;
}
// Optional: Return whether or not the container's
// parent should perform layout as a result of this
// layout. Some layout engines return the value of
// the container's AutoSize property.
return false;
}
public override bool Layout(
object container,
LayoutEventArgs layoutEventArgs)
{
Control parent = container as Control;
// Use DisplayRectangle so that parent.Padding is honored.
Rectangle parentDisplayRectangle = parent.DisplayRectangle;
Point nextControlLocation = parentDisplayRectangle.Location;
foreach (Control c in parent.Controls)
{
// Only apply layout to visible controls.
if (!c.Visible)
{
continue;
}
// Respect the margin of the control:
// shift over the left and the top.
nextControlLocation.Offset(c.Margin.Left, c.Margin.Top);
// Set the location of the control.
c.Location = nextControlLocation;
// Set the autosized controls to their
// autosized heights.
if (c.AutoSize)
{
c.Size = c.GetPreferredSize(parentDisplayRectangle.Size);
}
// Move X back to the display rectangle origin.
nextControlLocation.X = parentDisplayRectangle.X;
// Increment Y by the height of the control
// and the bottom margin.
nextControlLocation.Y += c.Height + c.Margin.Bottom;
}
// Optional: Return whether or not the container's
// parent should perform layout as a result of this
// layout. Some layout engines return the value of
// the container's AutoSize property.
return false;
}
Public Overrides Function Layout( _
ByVal container As Object, _
ByVal layoutEventArgs As LayoutEventArgs) As Boolean
Dim parent As Control = container
' Use DisplayRectangle so that parent.Padding is honored.
Dim parentDisplayRectangle As Rectangle = parent.DisplayRectangle
Dim nextControlLocation As Point = parentDisplayRectangle.Location
Dim c As Control
For Each c In parent.Controls
' Only apply layout to visible controls.
If c.Visible <> True Then
Continue For
End If
' Respect the margin of the control:
' shift over the left and the top.
nextControlLocation.Offset(c.Margin.Left, c.Margin.Top)
' Set the location of the control.
c.Location = nextControlLocation
' Set the autosized controls to their
' autosized heights.
If c.AutoSize Then
c.Size = c.GetPreferredSize(parentDisplayRectangle.Size)
End If
' Move X back to the display rectangle origin.
nextControlLocation.X = parentDisplayRectangle.X
' Increment Y by the height of the control
' and the bottom margin.
nextControlLocation.Y += c.Height + c.Margin.Bottom
Next c
' Optional: Return whether or not the container's
' parent should perform layout as a result of this
' layout. Some layout engines return the value of
' the container's AutoSize property.
Return False
End Function
Remarks
This method is called when the layout engine is to perform a layout operation on the container parameter. You can check the value of the AffectedProperty, AffectedComponent, and AffectedControl properties on layoutEventArgs to decide if a layout operation is necessary.
Notes to Inheritors
Override the Layout(Object, LayoutEventArgs) method to provide your custom layout behavior.
When laying out the contents of the container parameter, be sure to check the Visible property of each child control.
Return true if your layout engine logic determines that layout should be performed again by the parent of the container. This might occur, for example, when the layout engine resizes child controls and determines that the container must be increased in size to accommodate the new layout.
