CResizableFormView

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Introduction

The inspiration for this coding project was the result of a) Paolo Messina's article on his CResizableDialog code, and b) me mentioning I had adapted a CFormView to use a CResizablePage in an embedded property sheet.

The CResizablePage in a formview was a minor exercise compared to this. What I've come up with is a CResizableFormView. This code is based entirely on Paolo's CResizableDialog code.

If you're not interested in how I did it, Skip to the bottom of this article to see how to implement it yourself.

The Concept

It seemed to me that if a dialog box could benefit from this technique, then so could a formview, because after all, a formview is nothing more than a view that acts like a dialog box. It even uses a resource template like a dialog box.

Initially

The initial coding was fairly straightforward. I created a CFormView-derived class called CResizableFormView. Next, I copied all of the utility functions (functions not contributed by ClassWizard). Then, I evaluated the need/availability of some of the windows messages Paolo's code was using. I ended up only needing to handle the WM_SIZE command. Lastly, I decided that the min/max window size code was not applicable to a formview, so I deleted the code involving that particular aspect of CResizableDialog.

Implementation

After getting the code to compile, I tried deriving a new class based on my new CResizableFormView. After some experimentation, I discovered that I could not use the AddAnchor function until AFTER the InitialUpdate had completed. If I didn't follow this rule, the controls would not resize correctly.

void CFormview2View::OnInitialUpdate()
{
    CResizableFormView::OnInitialUpdate();
    GetParentFrame()->RecalcLayout();
    ResizeParentToFit();

    // put our code AFTER the stuff ClassWizard gave us.

    AddAnchor(IDC_LIST1, TOP_LEFT, BOTTOM_RIGHT);
    AddAnchor(IDC_GROUP1, TOP_LEFT, BOTTOM_LEFT);
}

Minor Issues

After playing around with resizing for a while, I discovered that if I made the view window smaller than the original dialog template, a couple of bad things happened involving the controls that were "anchored".

• The listbox disappeared altogether and would only partially appear as I made the view horizontally larger.

• The groupbox around the radio controls would just keep resizing until nothing was left (of the groupbox).

It was obvious at that point that I had to include some code to restrict the controls from resizing once they reached (or were smaller than) their original size. I also assumed that I had to be mindful of getting the correct original size, meaning I had to determine each control's size before the window was allowed to be resized the first time. Assuming that the programmer could decide to do something other than use a call to MFC's ResizeParentToFit, I had to make sure to get the control's info immediately after the view was created, but before it was resized. I wanted to impact as little of Paolo's original code as I could manage, so the fix was a while coming.

To remedy the situation, I created a CTypedPtrArray that held a new structure. This structure contains the original size and location of each "anchored" control, as well as its HWND and control ID. To support the structure, I had to also write a couple of new functions. Here are the details:

void CResizableFormView::AddResizedControls()

This function is responsible for determining the HWND and window size / location of the specified control, as well as storing its anchor positions. The parameter list is identical to the original AddAnchor function. Once all of this information was gathered, the control was added to the new CTypedPtrArray for safe-keeping.

void CResizableFormView::AnchorControls()

This function actually calls AddAnchor for all of the controls the programmer specified when he/she called the AddResizedControls function. The significance of this will be evident later.

Results

In order to implement the sizing/positioning fix, A new order of execution was required in the CResizableFormView-derived class. The OnInitialUpdate function now looks like this:

void CFormview2View::OnInitialUpdate()
{
    // jms - 11/28/00 - new code starts

    // We do this here because we need to get the *original* size of the 

    // controls *before* the dialog is sized the first time.  I don't know 

    // what will happen if we do it after, but I didn't want to find out.

    //

    // Since we do this here, I decided to pass the parameters needed by 

    // the AddAnchor() function to eliminate the need to call AddAnchor 

    // from this function (after the view had been resized).

    AddResizedControl(IDC_LIST1, TOP_LEFT, BOTTOM_RIGHT);
    AddResizedControl(IDC_GROUP1, TOP_LEFT, BOTTOM_LEFT);
    // jms - 11/28/00 - new code stops


    CResizableFormView::OnInitialUpdate();
    GetParentFrame()->RecalcLayout();
    ResizeParentToFit();

    // Normally, we would put the calls to AddAnchor AFTER we call 

    // ResizeParentToFit().

    //AddAnchor(IDC_LIST1, TOP_LEFT, BOTTOM_RIGHT);

    //AddAnchor(IDC_GROUP1, TOP_LEFT, BOTTOM_LEFT);


    // jms - 11/28/00 - new code starts

    // Now anchor the controls we specified earlier in this function. We call 

    // this function because it cycles thru the list of controls that are to 

    // be resized. This prevents us from having to call AddAnchor (lots of 

    // redundant typing at this point).

    AnchorControls();

}

But what if you wanted the view to NOT resize itself according to the dialog template. That's easy. Just calculate the size of the parent window of the formview, and call MoveWindow before exiting OnInitialUpdate. Here's an example:

void CFormview2View::OnInitialUpdate()
{
    AddResizedControl(IDC_LIST1, TOP_LEFT, BOTTOM_RIGHT);
    AddResizedControl(IDC_GROUP1, TOP_LEFT, BOTTOM_LEFT);
    AddResizedControl(IDC_IPADDRESS1, BOTTOM_RIGHT);

    CResizableFormView::OnInitialUpdate();
    GetParentFrame()->RecalcLayout();

    // Here's where the difference lies.  We don't want to call ResizeParentToFit() until

    // AFTER we calculate the true (initial) size of the parent frame. 

    CRect rectFrame;
    CFrameWnd* pFrame = GetParentFrame();
    ASSERT_VALID(pFrame);
    pFrame->GetWindowRect(rectFrame);
    CSize size = rectFrame.Size();

    // Now, we can call ResizeParentToFit() and anchor the controls.

    ResizeParentToFit(FALSE);
    AnchorControls();

    // Finally, we need to actually resize the frame to its original dimensions.  This

    // allows the anchor code to work  with its existing code.

    pFrame->MoveWindow(rectFrame, TRUE);
}

The Final Word

To implement the CResizableFormView, perform the following steps:

1. Create a CFormView class and its dialog template if necessary.
2. Change the base class of your CFormView-derived class to CResizableFormView.
3. #include "ResizableFormView.h" in your derived formview's header file.
4. If the function isn't already there, use ClassWizard to override the OnInitialUpdate function.
5. Call AddResizedControls for each control that will be resized/repositioned. Do this BEFORE the call to the base class' OnInitialUpdate.
6. Call AnchorControls. Do this AFTER the call to ResizeParentToFit