Renderer.Draw Method

  • Article

Renderer.Draw Method

Draws the Stroke object on the device context whose handle is passed in.

Definition

Visual Basic .NET Public Sub Draw( _
ByVal hdc As IntPtr, _
ByVal stroke As Stroke _
)
C# public void Draw(
IntPtr hdc,
Stroke stroke
);
Managed C++ public: void Draw(
IntPtr *hdc,
Stroke *stroke
);

Parameters

hdc System.IntPtr. The handle of the device context on which to draw.
stroke Microsoft.Ink.Stroke. The Stroke object to draw.

Exceptions

ArgumentNullException Leave Site: The caller does not specify the Stroke object.

Remarks

Important Security InformationSecurity Alert: For managed code, use the appropriate overload that accepts a Graphics Leave Site object instead of the one that accepts an IntPtr Leave Site; otherwise, you need to hold on to the handle in such a way that results in a memory leak. The overloads that accept an hdc parameter are useful if you are using resources that are unmanaged code.

The pen width is adjusted appropriately, based on how you use SetViewTransform method. Specifically, the pen width is multiplied (or scaled) by the square root of the determinant of the view transform.

Note: If you have not set the pen width explicitly, it is 53 by default. You must multiply the pen width by the square root of the determinant to yield the correct bounding box. The height and width of the bounding box are expanded by half this amount in each direction.

For example, consider that the pen width is 53, the square root of the determinant is 50, and the bounding box is (0,0,1000,1000). The pen width adjustment to the bounding box in each direction is calculated as (53*50)/2, and the right and bottom sides are incremented by one. This results in a rendered bounding box of (-1325,-1325,2326,2326).

The Renderer object forces the viewport and window origins to 0,0. Any existing settings are saved and restored, but are not used by the Renderer. To perform scrolling, use the Renderer object's GetViewTransform and GetObjectTransform methods.

Important Security InformationSecurity Alert: If using under partial trust, this method requires SecurityPermissionFlag.UnmanagedCode Leave Site permission in addition to the permissions required by Renderer. See Security And Trust for more information.

Examples

[C#]

This C# example takes the Strokes collection from an Ink object associated with an InkCollector object, theInkCollector, which is attached to a Panel Leave Site, panelForInking. The example then calls the Draw method to draw the strokes onto a device context attached to another Panel Leave Site, panelForDrawing. Only Stroke objects with a height or width greater than 300 HIMETRIC units are drawn.

              using Microsoft.Ink;
...
// Members
private InkCollector theInkCollector;
private System.Windows.Forms.Panel panelForInking;
private System.Windows.Forms.Panel panelForDrawing;
...
// In the constructor...
    // Initialize InkCollector
    theInkCollector = new InkCollector(panelForInking.Handle);
    theInkCollector.Enabled = true;
    theInkCollector.Stroke += new InkCollectorStrokeEventHandler(theInkCollector_Stroke);

    // Paint event handler for drawing panel
    panelForDrawing.Paint += new PaintEventHandler(panelForDrawing_Paint);
...

private void theInkCollector_Stroke(object sender, InkCollectorStrokeEventArgs e)
{
    // Force a repaint on the drawing panel
    panelForDrawing.Refresh();
}

private void panelForDrawing_Paint(object sender, PaintEventArgs e)
{
    // Get the handle to the device context
    IntPtr theHdc = e.Graphics.GetHdc();

    // Draw the InkCollector's strokes
    // using a handle to the device context.
    // Draw only strokes whose size is large enough.
    foreach (Stroke theStroke in theInkCollector.Ink.Strokes)
    {
        Rectangle strokeBounds = theStroke.GetBoundingBox();
        if (strokeBounds.Width > 300 ||
            strokeBounds.Height > 300)
        {
            theInkCollector.Renderer.Draw(theHdc, theStroke);
        }
    }

    // Release the device context handle
    e.Graphics.ReleaseHdc(theHdc);
}

[Visual Basic .NET]

This Microsoft® Visual Basic® .NET example takes the Strokes collection from an Ink object associated with an InkCollector object, theInkCollector, which is attached to a Panel Leave Site, panelForInking. The example then calls the Draw method to draw the strokes onto a device context attached to another Panel Leave Site, panelForDrawing. Only Stroke objects with a height or width greater than 300 HIMETRIC units are drawn.

              Imports Microsoft.Ink
...
    'Initialize InkCollector in the Form's New subroutine
    theInkCollector = New InkCollector(PanelForInking.Handle)
    theInkCollector.Enabled = True
...
Friend WithEvents theInkCollector As InkCollector
Friend WithEvents PanelForInking As System.Windows.Forms.Panel
Friend WithEvents PanelForDrawing As System.Windows.Forms.Panel
...
Private Sub theInkCollector_Stroke(ByVal sender As Object, ByVal e As Microsoft.Ink.InkCollectorStrokeEventArgs) _
Handles theInkCollector.Stroke
    'Force a repaint on the PanelForDrawing
    PanelForDrawing.Refresh()
End Sub

Private Sub PanelForDrawing_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) _
Handles PanelForDrawing.Paint
    ' Get the handle to the device context
    Dim theHdc As IntPtr = e.Graphics.GetHdc()

    ' Draw the InkCollector's strokes if they are large enough
    Dim theStroke As Stroke
    For Each theStroke In theInkCollector.Ink.Strokes
        Dim strokeBounds As Rectangle = theStroke.GetBoundingBox()
        If strokeBounds.Width > 300 Or strokeBounds.Height > 300 Then
            theInkCollector.Renderer.Draw(theHdc, theStroke)
        End If
    Next

    ' Release the device context handle
    e.Graphics.ReleaseHdc(theHdc)
End Sub

See Also