Auto repositioning/resizing of child controls (using C++ templates)

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Originally published at Internet.com

Yet, another method to reposition/resize child windows within their parent framework. Although the subject received a lot of attention, including this web site, I invite you to look at the following method as it presents certain advantages over the others I already know.

First of all this is not a library. There is no associated DLL or LIB to link to. Secondly, it is not a class hierarchy. You don't have to derive your classes from classes exposing this functionality. Often, you already have a hierarchy of classes designed for a certain behavior. This behavior does not include repositioning/resizing of child controls, but you want to add it. Since the MFC doesn't let you use multiple inheritance when it comes to windows, you might wonder what is the solution. Well, the solution is templates. GEOMETRY is actually a collection of templates designed to make your windows to resize gracefully.

The interface to GEOMETRY is a single class template CGeometryWnd. You can use this class template with all your window classes including dialogs, forms, property sheets/property pages and splitter windows. Being a template library, GEOMETRY is contained in a single file Geometry.h. All you have to do is to include this file, to use CGeometryWnd and possibly a series of macros, in relation with your classes.

For example to make a dialog resizeable you need to: 1. make your dialog in resource editor resizeable (replace the dialog frame with a resizeable border) 2. specify the rules to apply to child controls (either in the resource editor or in the source code) 3. include in dialog's source code Geometry.h 4. use the template CGeometryWnd over your dialog's class

Ex: #include Geometry.h USE_GEOMETRY_TEMPLATES; ///////////////////////////////////////////////////////////////////////////// // CAboutDlg dialog used for App About class CAboutDlg : public CDialog { DECLARE_GEOMETRY_RTSUPPORT() public: CAboutDlg(); // Dialog Data //{{AFX_DATA(CAboutDlg) enum { IDD = IDD_ABOUTBOX }; //}}AFX_DATA virtual BOOL OnInitDialog(); //{{AFX_VIRTUAL(CAboutDlg) protected: virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support //}}AFX_VIRTUAL // Implementation protected: //{{AFX_MSG(CAboutDlg) // No message handlers //}}AFX_MSG DECLARE_MESSAGE_MAP() }; CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD) { //{{AFX_DATA_INIT(CAboutDlg) //}}AFX_DATA_INIT } void CAboutDlg::DoDataExchange(CDataExchange* pDX) { CDialog::DoDataExchange(pDX); //{{AFX_DATA_MAP(CAboutDlg) //}}AFX_DATA_MAP } BEGIN_MESSAGE_MAP(CAboutDlg, CDialog) //{{AFX_MSG_MAP(CAboutDlg) // No message handlers //}}AFX_MSG_MAP END_MESSAGE_MAP() BOOL CAboutDlg::OnInitDialog() { CDialog::OnInitDialog(); AddConstraint(IDOK,CConstraint("X")); return TRUE; } // App command to run the dialog void CTestPSGeoApp::OnAppAbout() { CGeometryWnd aboutDlg; aboutDlg.DoModal(); } The constraints added to child windows, control their behavior in case the parent resizes. The constraints can be added at design time (aka in resource editor, see note) or at runtime using the DECLARE_GEOMETRY_RTSUPPORT() macro and AddConstraint()function. The constraint object has two important constructors: CConstraint(LPCSTR lpOptions) and CConstraint(float x,float y=0,float cx=0,float cy=0) In the first case you can specify the repositioning/resizing of the control by using a control string (see table for details). Basically the string format is:

Option1[value]+Option2[value]+Â…

Where Optionx (see table below) controls the position/size of the control and [value] ([] are not optional) is an optional parameter specifying the amount (between 0 and 1 as a float number) with which the control will repossition/resize from the total amount of the parent resize value.

Option Meaning Comment

X

Reposition on x axis

Control will move on the x axis

Y

Reposition on y axis

Control will move on the y axis

CX

Resize on x axis

Control will resize its width

CY

Resize on y axis

Control will resize its height

x

Stay on x axis center

Equivalent with X[0.5]

y

Stay on y axis center

Equivalent with Y[0.5]

cx

Equivalent with CX[0.5]

cy

Equivalent with CY[0.5]

MX

Maintain aspect on x axis

Preserves the X/CXParent ratio

MY

Maintain aspect on y axis

Preserves the Y/CYParent ratio

MCX

Maintain aspect on the width

Preserves the CX/CXParent ratio

MCY

Maintain aspect on the height

Preserves the CY/CYParent ratio

Note:

To add the constraints at design time directly in resource editor you' ll gonna surround the controls sharing the same constraint options with invisible group boxes having the caption in the form " $Geometry:Option1[value]+Option2[value]+Â…" w/o the quotes. Please note the $Geometry in front of the options string, this is not optional. Be careful with the capital/minor letters as they have different significance. Using this form of constraints specification you don't need DECLARE_GEOMETRY_RTSUPPORT() and AddConstraint() as previously displayed.

Using the second constructor you will specify the values between 0 and 1 that will be multiplied with the total resize amount of