Walkthrough: Adding a D2D Object to an MFC Project

Bài viết
08/03/2021

This walkthrough teaches how to add a basic Direct2D (D2D) object to a Visual C++, Microsoft Foundation Class Library (MFC) project, and then build the project into an application that prints "Hello, World!" on a gradient background.

The walkthrough shows how to accomplish these tasks:

Create an MFC application.
Create a solid-color brush and a linear-gradient brush.
Modify the gradient brush so that it will change appropriately when the window is resized.
Implement a D2D drawing handler.
Verify the results.

Note

Your computer might show different names or locations for some of the Visual Studio user interface elements in the following instructions. The Visual Studio edition that you have and the settings that you use determine these elements. For more information, see Personalizing the IDE.

Prerequisites

To complete this walkthrough, you must have Visual Studio installed with the Desktop development with C++ workload and the optional Visual C++ MFC for x86 and x64 component.

To create an MFC application

Use the MFC Application Wizard to create an MFC application. See Walkthrough: Using the New MFC Shell Controls for instructions on how to open the wizard for your version of Visual Studio.
In the Name box, type MFCD2DWalkthrough. Choose OK.
In the MFC Application Wizard, choose Finish without changing any settings.

To create a solid-color brush and a linear-gradient brush

In Solution Explorer, in the MFCD2DWalkthrough project, in the Header Files folder, open MFCD2DWalkthroughView.h. Add this code to the CMFCD2DWalkthroughView class to create three data variables:
```
CD2DTextFormat* m_pTextFormat;
CD2DSolidColorBrush* m_pBlackBrush;
CD2DLinearGradientBrush* m_pLinearGradientBrush;
```
Save the file and close it.

In the Source Files folder, open MFCD2DWalkthroughView.cpp. In the constructor for the CMFCD2DWalkthroughView class, add this code:

// Enable D2D support for this window:
EnableD2DSupport();

// Initialize D2D resources:
m_pBlackBrush = new CD2DSolidColorBrush(
    GetRenderTarget(),
    D2D1::ColorF(D2D1::ColorF::Black));

m_pTextFormat = new CD2DTextFormat(
    GetRenderTarget(),
    _T("Verdana"),
    50);

m_pTextFormat->Get()->SetTextAlignment(
    DWRITE_TEXT_ALIGNMENT_CENTER);

m_pTextFormat->Get()->SetParagraphAlignment(
    DWRITE_PARAGRAPH_ALIGNMENT_CENTER);

D2D1_GRADIENT_STOP gradientStops[2];

gradientStops[0].color =
    D2D1::ColorF(D2D1::ColorF::White);

gradientStops[0].position = 0.f;
gradientStops[1].color =
    D2D1::ColorF(D2D1::ColorF::Indigo);

gradientStops[1].position = 1.f;

m_pLinearGradientBrush = new CD2DLinearGradientBrush(
    GetRenderTarget(),
    gradientStops,
    ARRAYSIZE(gradientStops),
    D2D1::LinearGradientBrushProperties(
        D2D1::Point2F(0,0),
        D2D1::Point2F(0,0)));

Save the file and close it.

To modify the gradient brush so that it will change appropriately when the window is resized

On the Project menu, choose Class Wizard.
In the MFC Class Wizard, under Class name, select CMFCD2DWalkthroughView.
On the Messages tab, in the Messages box, select WM_SIZE and then choose Add Handler. This action adds the OnSize message handler to the CMFCD2DWalkthroughView class.
In the Existing handlers box, select OnSize. Choose Edit Code to display the CMFCD2DWalkthroughView::OnSize method. At the end of the method, add the following code.
```
m_pLinearGradientBrush->SetEndPoint(CPoint(cx, cy));
```
Save the file and close it.

To implement a D2D drawing handler

On the Project menu, choose Class Wizard.
In the MFC Class Wizard, under Class name, select CMFCD2DWalkthroughView.
On the Messages tab, choose Add Custom Message.
In the Add Custom Message dialog box, in the Custom Windows Message box, type AFX_WM_DRAW2D. In the Message handler name box, type OnDraw2D. Select the Registered Message option and then choose OK. This action adds a message handler for the AFX_WM_DRAW2D message to the CMFCD2DWalkthroughView class.

In the Existing handlers box, select OnDraw2D. Choose Edit Code to display the CMFCD2DWalkthroughView::OnDraw2D method. Use this code for the CMFCD2DWalkthroughView::OnDrawD2D method:

afx_msg LRESULT CMFCD2DWalkthroughView::OnDraw2D(
    WPARAM wParam,
    LPARAM lParam)
{
    CHwndRenderTarget* pRenderTarget = (CHwndRenderTarget*)lParam;
    ASSERT_VALID(pRenderTarget);

    CRect rect;
    GetClientRect(rect);

    pRenderTarget->FillRectangle(rect, m_pLinearGradientBrush);

    pRenderTarget->DrawText(
        _T("Hello, World!"),
        rect,
        m_pBlackBrush,
        m_pTextFormat);

    return TRUE;
}

Save the file and close it.

To verify the results

Build and run the application. It should have a gradient rectangle that changes when you resize the window. "Hello World!" should be displayed in the center of the rectangle.

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