1. Introduction to MFC CRgn

One may come across plenty of Non-Rectangular window or user interaction dialog in their experience. Many of MP3 players in the market produce a non-rectangular fancy UI. In this example, we will create a round-shaped dialog with a username and password fields in it. The technique is very simple. Perform your drawing as usual and then use the CRgn class to create a region from your drawing. Then you can ask the window to have the boundaries defined by the MFC

CRgn

 object.

2. Dialog Controls & Region

First, we create a dialog-based MFC application and name it as RoundWind. Once the dialog is ready, we resize it to 247×129. Then position the controls in the dialog as shown below:

We will display the controls in this dialog in such a way that they live in an elliptical area. Once the dialog-based application is ready with the controls, we can define the path for the region. We can create a region in multiple ways, and in this example, we will create a region from a path. Now we move to the coding part of this.

3. Displaying The Dialog in Elliptical Shape

First, we will switch to ‘Class View’. We will make modification on the MFC created dialog class so it will show itself as a round window. In our example, the dialog class is CRoundWndDlg. The below picture shows this:

3.1 Declare CRgn & CClientDC Members

In the Header file of the CRoundWindDlg we add two members. One is for the client device context

CClientDC

and another one is to specify the region MFC

CRgn

 using the client device context. These declarations are below:

3.2 BeginPath & EndPath to Define MFC CRgn’s Path

In the

OnInitDialog

of the dialog class, we define the path using the

CClientDC

supplied drawing function. The drawing function which we call between the

BeginPath

and

EndPath

defines the path for the region.  To make the example simple, we use the

ellipse

function. Since it is enclosed by the

BeginPath

&

EndPath

, the ellipse is the path for our example, and we feed this to MFC

CRgn

later. But one can use the

MoveTo

,

LineTo

, and

ArcTo

 etc., to define a complex path for the region. Remember, one should place all these drawing functions within the Begin and End path pair. The code below defines an elliptical path:

3.3 CRgn’s Path and Elliptical MFC Dialog Window

Note that the drawing function

Ellipse

was enclosed in between

BeginPath

and

EndPath

. The drawing that is enclosed between begin & end pair will form the path for defining the Region.

CreateFromPath

function of the

CRgn

will generate the region out of the path defined by the Client Device Context. The below code defines a Region using MFC

CRgn

 and region path:

In our example, we created the region from the path which available through the

CClientDC

. The

CreateFromPath

takes the device context object and extracts the path specified in it. Once a region is ready, we can set that to any Window. In our example, we want to display the dialog as a round window and hence we are calling the

SetWindowRgn

function. As the function expects a Window Handle to a Region, we extracted it from the

CRgn

instance using the ‘

(HRGN) m_rgn

’ in-built casting operator. The second parameter TRUE specifies that we want to redraw the dialog instance.

When we execute the code, the output looks like the below one:

Source Code (From Google Drive): Download MFC Round Dialog Example

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Categories: MFC

Tags: BeginPath, CreateFromPath, CRgn, EndPath, SetWindowRgn

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