The LA Fox Developer Newsletter

May 1998

Add a Cascade Function to

Your Window Menu

Use this generic code to give your MDI application a profes-

sional Windows feel.

Most VFP applications are MDI (multiple document interface) in

nature. That means that users can open several forms at the

same time and jump from one to another at will. MDI applica-

tions usually have a Window menu, with options to cascade and

tile the open windows and to select specific windows. VFP has

most of that functionality built in. But there is no Cascade

function. If you want to let your users cascade their forms, you

have to write the code yourself.

What exactly do we mean by cascade? Essentially, it means

that all the open forms will appear on the screen, each offset

slightly to the right and below the one before. If you examine

other MDI applications, you will observe a fairly consistent

behavior.

Specifically, each window (form) is resized so that it occupies

three quarters of the parent window. The first window is then

moved to the top left corner of the parent. Subsequent window

are placed on top of the previous one, offset down and to the

right by an amount equal to the height of the title bar. If a given

window does not fit within the boundaries of the parent, the

sequence starts again from top left corner of the parent.

The code at the end of this article implements this procedure.

As it is generic, it does not know the names of the forms that it

is working with. Instead, it uses _SCREEN to access the forms.

For those who haven’t worked with _SCREEN before, it is

essentially, a device which allows the main VFP window to be

manipulated as if it was itself a form. You can use it to alter the

main window’s title, to assign an icon to the main window (see

the FoxStuff article Do your application icons always show up?),

to move the main window to a particular point on the screen,

and, as in this case, to access the forms currently contained in

the main window. It has around 70 properties and 20 methods,

all of which are described in the VFP Help.

Our Cascade routine uses two properties of_SCREEN: the

Forms property is an array (to be precise, a collection) of the

currently open forms; and FormCount is the number of forms in

this collection. Using these properties, the routine iterates

through the open forms, changing their sizes and positions as it

does so.

There are a couple of points to watch out for. The routine can

only resize a form if its BorderStyle property is 3; other border

styles are non-resizable. So we need to test the BorderStyle

property each time round the loop. But before we do that, we

must check that this property actually exists. That’s because

the Forms collection can also hold floating toolbars, and these

do not have a border style. The Type() fUnction is used to check

that the property exists.

Even if the form is resizable, it might be subject to minimum

and maximum sizes, as stipulated by its MinWidth, MinHeight,

MaxWidth and MaxHeight properties. If any of these properties

is greater than —1, it means that a corresponding limit is in

force. Our routine tests for this before resizing each form.

After the form is resized, the routine moves it to its new posi-

tion. The Sysmetric(9) function, called near the start of the

code, determines the height of the title bar, this being the

amount of the vertical and horizontal offset for each window.

To use the code, cut and paste it to your application. Add a

Cascade prompt to your Window menu, and place a suitable

call (e.g. DO Cascade) in its result field.

PROCEDURE Cascade

local lnHorizOff, lnVertOff, lnNewWidth, InNewHeight, InNewLeft,

lnNewTop, lnFmldx

lnHorizOff = Sysmetric(9) && horizontal offset

InVertOff = Sysmetric(9) && vertical offset

lnNewWidth = 0.75 * _SCREEN.Width && new form width

lnNewHeight = 0.75 * _SCREEN.Height && new form height

lnNewLeft = 0

lnNewTop = 0

FOR lnFmldx =1 TO _SCREEN.FormCount

WiTH _SCREEN.Forms(lnFmldx)

IF Type(”.Border~ty!a”}c>”tJ” AND .BorderS+yle 3

*

form has a resizable border, so adjust its dimensions,

*

subject to its mm/max height and width

.Width = ItF(.MinWidth = -1,lnNewWidth,

Max(InNewWidth,.MinWidth))

.Width = lIF(.MaxWidth = -1,lnNewWldth,

Min(lnNewWidth,.MaxWidth))

.Height = IIF(.MinHeight = -1,lnNewHeight,;

Max(lnNewHeight,.MinHeight))

.Height = ilF(.MaxHeight = -1,lnNewHelght,;

Mmn(innewHeight,.MaxHeight))

ENDIF

*

move the form to its new position

IF (lnNewTop + .Height ‘C _SCREEN.Height);

AND (InNewLeft + .Width <_SCREEN.Width)

*

the form will not overflow the main window,

*

so go ahead and move it

.Move(lnNewLeft,InNewTop)

*

calculate the position of the next form

InNewLeft = InNewLeft + inHorizOff

lnNewlop = lnNewTop + InVertOff

ELSE

*

form does overflow, so go back to top left corner

.Move(0,0)

InNewLeft = InHorlzOffset

lnNewTop = InVertOffset

ENDIF

ENDW1TH

ENDFOR

ENDPROC

(Copyright Mike Lewis Consultants Ltd. 1998.)

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