Coordinate systems need not start at zero. Sca1eLeftis the minimum value an Xcoordinate can assume. ScaleLeft and ScaleTop are the coordinates of the upper-left comer of the control in a user-defined system of coordinates. You can also assign values to these properties, in which case you’re automatically switching to a userdefined coordinate system (the ScaleMode property is reset to zero). Where the Xcoordinate of the control’s middle point in the previous coor~inate system ~a!? 1,440, it’s now one. If you change the FoI’Q1’scoordinate. system to inches the control won’t be resized, bulits ScaleWidth and ScaleHeight properties will become two (inches). Its Width and Height properties are 2,880. 1 Form that’s 2,R80 twin wide and 2,880 rwips tall is approximatelv tvvo mches WId” and two inches tall. Changing the coordinate system doesn’tchange the size of the control, but it does change the number of units that can fit along the tW6 axes of the control.
These two properties are the control’s inner dimensions in units of the current coordinate system. Conversely, if v.iu set the Sca.lcWidth and/or Scalefieight properties, the ScaleMode property is reset to O. If you set this property to 0 (User), you must also set the ScaleWidth and ScaleHeight properties. Set this property to one of the values shown in Table 6.1 to establish a new coordinate system. The ScnleMode property sets (or returns) the-control’s current coordinate system. They also change value if you change the container’s coordinate system to reflect the control’s position in the new coordinate system. If you change their values, the control is repositioned. The Left and Top properties are the coordinates of the control’s upper-left comer, / and they are expressed in the container’s coordinate system. These properties will also change value if you change the container’s coordinate system to reflect the control’s dimensions in the new coordinate system. If you resize the control on the Form by dragging its handles with the mouse, the Width and Height properties will change value to reflect the new size of the control. If you change the control’s coordinate system, the values of these two properties won’t change. The Width and Height properties of the Picture Box control are expressed in twips. Suppose you’re placing a PictureBox control on a Form whose coordinate system is the default, twips. These two properties determine the actual dimensions of the control and are ways expressed in the units of the container of the control. There are two groups of properties: those that control the size and position of the control and those that affect (and are affected by) the choice of coordinate system. and methods that relate to the control’s position and the coordinate system.
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