Knowledge Base

PRB: Line Drawn with Line Method Is Behind Form's Objects

Article ID: 142399

Article Last Modified on 9/30/2003

APPLIES TO

This article was previously published under Q142399

SYMPTOMS

Using the form's Line method to draw a line over an object during the form's initialization causes the line to be behind the object.

CAUSE

If the Line method is called from either the form's Init event, or any other event that fires when the form is initially started, the line will actually be drawn prior to the placement of the form's objects. On slower computers, this can be easily visualized. Because the line that is produced by using the Line method of a form is not an object and therefore lacks any properties that can be manipulated, it is not possible to force it to the front of the object.

WORKAROUND

Following are three possible workarounds, in order of preference:

  • Use either a Line or Shape object. These objects have properties that can be manipulated at either design time or run time. -or-

  • Create a new property of the form to contain a logical false value: For example, zLineDraw. Within the GotFocus Event of the first object in the form's tab order, check the value of zLineDraw. If it is false, call the form's Line method. Then set the zLineDraw property to true as in the following example: 
       IF !ThisForm.zLineDraw
      ThisForm.Line(<nXCoord2>, <nYCoord2>)
      ThisForm.zLineDraw = .T.
   ENDIF
    -or-

  • Use a Timer to call the Line method of the form. In this case, the Interval can be set initially to 500 (milliseconds) and the Timer Event that calls the form's Line method should reset the Interval to 0 so that it is triggered only once.

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

  1. Create a new form, and use the Form Controls toolbar to place a Shape on the form and create a large rectangular area.
  2. Set the DrawWidth property of the form to 10. This will cause the line width to be large enough to fully visualize the affect.
  3. With the Shape as the selected object on the form, change its BackColor property to red (255,0,0).
  4. In the form's Init event, add the following code: 
       * The following code determines the x and y coordinates
   * of the Shape1 object.
   xLeft = This.Shape1.Left
   yTop = This.Shape1.Top
   xRight = This.Shape1.Left + This.Shape1.Width
   yBottom = This.Shape1.Top + This.Shape1.Height

   * The following code draws an "X" in the area of the Shape1 object.
   ThisForm.Line(xLeft,yTop,xRight,yBottom)
   ThisForm.Line(xRight,yTop,xLeft,yBottom)
  5. Save the form as linetest. Then close the form, and use the DO FORM command to run it. Depending on the speed of the computer running the form, it may be possible to see that the X appears before the red shape. The DrawWidth property of 10 should result in a portion of the X protruding from each of the shape's four corners.

Additional query words: VFoxWin

Keywords: KB142399


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