一. 资源管理(Resource management)
和Direct3D一样，Direct2D程序需要处理设备丢失(Device lost)问题。Direct2D中的资源分为设备独立资源(Device independent resource)和设备依赖资源(Device dependent resource)。
设备独立资源包括：
- ID2D1DrawingStateBlock
- ID2D1Factory
- ID2D1Geometry 和由此继承而来的接口
- ID2D1GeometrySink and ID2D1SimplifiedGeometrySink
- ID2D1StrokeStyle
设备依赖资源包括：
- ID2D1Brush 和由此继承而来的接口
- ID2D1Layer
- ID2D1RenderTarget 和由此继承而来的接口
- 其他资源
具体参见：http://msdn.microsoft.com/en-us/library/dd756757(v=VS.85).aspx
二. Direct2D程序的结构
- 在程序初始化函数处创建设备独立资源，如ID2D1Factory，IDWriteFactory等；
- 创建设备依赖资源，如果运行过程中出现设备丢失，需要重新创建；
- 响应WM_PAINT消息，在OnPaint()或OnDraw()等处，用创建的资源Render；
- 响应WM_SIZE消息，在OnSize()处调用ID2D1RenderTarget::Resize();
- 响应WM_ERASEBKGND，在OnEraseBkgnd()处返回FALSE，阻止GDI重绘客户区背景色，设置背景色的工作交给Direct2D在Render时设置，否则在Resize时会出现窗口闪烁的问题；
- 退出程序前，清理资源。
为提高程序的性能，尽量减少资源的创建和销毁操作，将能够重复利用的资源接口变量申明为View类的成员变量。
三. Direct2D demo
一个简单的MFC程序，用于演示Direct2D程序的结构和一些简单绘图操作。
1.Direct2D prerequisite
D2dPrerequisite.h，包含一些编译Direct2D程序所需要用到的头文件，lib库文件，帮助宏和预处理指令：
1: //D2dPrerequisite.h
2: #pragma once
3:
4: //
5: //Header files and lib files for Direct2D and DirectWrite
6: #include <d2d1.h> //Direct2D,for normal rendering task
7: #include <d2d1helper.h>
8: #include <dwrite.h> //DirectWrite,for drawing text
9: #include <wincodec.h> //Windows imaging component,for image decoding
10:
11: #pragma comment(lib,"d2d1.lib")
12: #pragma comment(lib,"dwrite.lib")
13: #pragma comment(lib,"windowscodecs.lib")
14:
15: //
16: //Helper template for resource releasing
17: template<class Interface>
18: inlinevoid SafeRelease(Interface **ppInterfaceToRelease)
19: {
20: if (*ppInterfaceToRelease != NULL)
21: {
22: (*ppInterfaceToRelease)->Release();
23: (*ppInterfaceToRelease) = NULL;
24: }
25: }
26:
27: #ifndef Assert
28: #if defined( DEBUG ) || defined( _DEBUG )
29: #define Assert(b) do {if (!(b)) {OutputDebugStringA("Assert: " #b "\n");}} while(0)
30: #else
31: #define Assert(b)
32: #endif //DEBUG || _DEBUG
33: #endif
34:
35: #ifndef HINST_THISCOMPONENT
36: EXTERN_C IMAGE_DOS_HEADER __ImageBase;
37: #define HINST_THISCOMPONENT ((HINSTANCE)&__ImageBase)
38: #endif
2.View类中的成员变量：
1: //View.h
2: private:
3: //Direct2D interface
4: ID2D1Factory* m_pD2d1Factory;
5: ID2D1HwndRenderTarget* m_pHwndRenderTarget;
6: ID2D1SolidColorBrush* m_pSolidColorBrush;
7: ID2D1LinearGradientBrush* m_pLinearGradientBrush;
8: ID2D1RadialGradientBrush* m_pRadialGradientBrush;
9:
10: //DirectWrite interface
11: IDWriteFactory* m_pDWriteFactory;
12: IDWriteTextFormat* m_pTextFormat;
3.创建设备独立资源
1: //View.cpp
2: BOOL CBasicView::CreateDeviceIndependentResource()
3: {
4: HRESULT hr = D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED,&m_pD2d1Factory);
5: ASSERT(hr == S_OK);
6:
7: if (SUCCEEDED(hr))
8: {
9: hr = DWriteCreateFactory(DWRITE_FACTORY_TYPE_SHARED,
10: __uuidof(m_pDWriteFactory),
11: reinterpret_cast<IUnknown**>(&m_pDWriteFactory));
12: ASSERT(hr == S_OK);
13: }
14:
15: //Create TextFormat object with IDWriteFactory
16: if (SUCCEEDED(hr))
17: {
18: const CString fontName = _T("Verdana");
19: const FLOAT fontSize = 32.0f;
20: hr = m_pDWriteFactory->CreateTextFormat(
21: fontName,
22: NULL,
23: DWRITE_FONT_WEIGHT_NORMAL,
24: DWRITE_FONT_STYLE_NORMAL,
25: DWRITE_FONT_STRETCH_NORMAL,
26: fontSize,
27: L"", //locale
28: &m_pTextFormat
29: );
30: ASSERT(hr == S_OK);
31: if (SUCCEEDED(hr))
32: {
33: //Center alignment vertically and horizontally
34: m_pTextFormat->SetTextAlignment(DWRITE_TEXT_ALIGNMENT_CENTER);
35: m_pTextFormat->SetParagraphAlignment(DWRITE_PARAGRAPH_ALIGNMENT_CENTER);
36: }
37: }
38: return (hr == S_OK);
39: }
4.创建设备依赖资源
1: //View.cpp
2: BOOL CBasicView::CreateDeviceDependentResource()
3: {
4: ASSERT(m_pD2d1Factory != NULL);
5: if (m_pHwndRenderTarget != NULL) //There is no need to create render target
6: return TRUE;
7:
8: RECT rc;
9: GetClientRect(&rc);
10: D2D1_SIZE_U size = SizeU(rc.right-rc.left,rc.bottom-rc.top);
11: HRESULT hr = m_pD2d1Factory->CreateHwndRenderTarget(
12: RenderTargetProperties(),
13: HwndRenderTargetProperties(m_hWnd,size),//Bind the HwndRenderTarget to view window
14: &m_pHwndRenderTarget);
15: ASSERT(hr == S_OK);
16: if (SUCCEEDED(hr))
17: {
18: //Create solid color brush
19: hr = m_pHwndRenderTarget->CreateSolidColorBrush(
20: ColorF(ColorF::LightGreen),
21: &m_pSolidColorBrush);
22: ASSERT(hr == S_OK);
23:
24: //Create gradient stops collection,
25: //used by linear gradient brush or radial gradient brush
26: ID2D1GradientStopCollection* pGradientStops = NULL;
27: D2D1_GRADIENT_STOP stops[2];
28: stops[0].color = ColorF(ColorF::Yellow);
29: stops[0].position = 0.0f;
30: stops[1].color = ColorF(ColorF::Red);
31: stops[1].position = 1.0f;
32: HRESULT hr = m_pHwndRenderTarget->CreateGradientStopCollection(
33: stops,
34: 2,
35: D2D1_GAMMA_2_2,
36: D2D1_EXTEND_MODE_CLAMP,
37: &pGradientStops);
38: ASSERT(hr == S_OK);
39:
40: //Create linear gradient brush
41: hr = m_pHwndRenderTarget->CreateLinearGradientBrush(
42: LinearGradientBrushProperties(Point2F(210,110),Point2F(290,190)),
43: pGradientStops,
44: &m_pLinearGradientBrush);
45: ASSERT(hr == S_OK);
46:
47: //Create radial gradient brush
48: hr = m_pHwndRenderTarget->CreateRadialGradientBrush(
49: RadialGradientBrushProperties(Point2F(350,150),Point2F(0,0),50,50),
50: pGradientStops,
51: &m_pRadialGradientBrush);
52: ASSERT(hr == S_OK);
53:
54: SafeRelease(&pGradientStops);
55: }
56:
57: return (hr == S_OK);
58: }
5.Render
1: //View.cpp
2: void CBasicView::Render()
3: {
4: ASSERT(m_pD2d1Factory != NULL);
5: if (!m_pHwndRenderTarget) //Render target need to be recreated
6: {
7: //Recreate device dependent resource
8: BOOL succeeded = CreateDeviceDependentResource();
9: if (!succeeded)
10: return;
11: }
12:
13: const D2D1_COLOR_F redColor = ColorF(ColorF::Red);
14: const D2D1_COLOR_F greenColor = ColorF(ColorF::Green);
15: const D2D1_COLOR_F blueColor = ColorF(ColorF::Blue);
16: const D2D1_COLOR_F yellowColor = ColorF(ColorF::Yellow);
17: const D2D1_COLOR_F pinkColor = ColorF(ColorF::Pink);
18: const D2D1_COLOR_F lightBlue = ColorF(ColorF::LightBlue);
19: const D2D1_COLOR_F lightGreen = ColorF(ColorF::LightGreen);
20:
21: m_pHwndRenderTarget->BeginDraw();
22: m_pHwndRenderTarget->Clear(ColorF(ColorF::White)); //Clear the background
23:
24: //Draw line
25: //We can set the color and opacity of solid color brush at any time,
26: //so there is no need to create brushes for different colors
27: m_pSolidColorBrush->SetColor(redColor);
28: D2D1_POINT_2F startPoint = Point2F(10,10);
29: D2D1_POINT_2F endPoint = Point2F(90,90);
30: m_pHwndRenderTarget->DrawLine(startPoint,endPoint,m_pSolidColorBrush,5.0);
31:
32: //Draw rectangle
33: m_pSolidColorBrush->SetColor(greenColor);
34: D2D1_RECT_F rect = RectF(110,10,190,90);
35: m_pHwndRenderTarget->DrawRectangle(rect,m_pSolidColorBrush,4.0f);
36:
37: //Draw rounded rectangle
38: m_pSolidColorBrush->SetColor(blueColor);
39: rect = RectF(210,10,290,90);
40: D2D1_ROUNDED_RECT roundedRect = RoundedRect(rect,10,10);
41: m_pHwndRenderTarget->DrawRoundedRectangle(roundedRect,m_pSolidColorBrush,3.0f);
42:
43: //Draw ellipse
44: m_pSolidColorBrush->SetColor(redColor);
45: D2D1_POINT_2F center = D2D1::Point2F(350,50);
46: D2D1_ELLIPSE ellipse = D2D1::Ellipse(center,40,30);
47: m_pHwndRenderTarget->DrawEllipse(ellipse,m_pSolidColorBrush,3.0f);
48:
49: //Fill rectangle
50: m_pSolidColorBrush->SetColor(pinkColor);
51: rect = RectF(10,110,90,190);
52: m_pHwndRenderTarget->FillRectangle(rect,m_pSolidColorBrush);
53:
54: //Fill rounded rectangle
55: m_pSolidColorBrush->SetColor(blueColor);
56: m_pSolidColorBrush->SetOpacity(0.3f);
57: rect = RectF(110,110,190,190);
58: roundedRect = RoundedRect(rect,20,20);
59: m_pHwndRenderTarget->FillRoundedRectangle(roundedRect,m_pSolidColorBrush);
60:
61: //Fill rectangle with linear gradient brush
62: rect = RectF(210,110,290,190);
63: m_pHwndRenderTarget->FillRectangle(rect,m_pLinearGradientBrush);
64:
65: //Fill ellipse with gradient brush
66: ellipse = D2D1::Ellipse(Point2F(350,150),40,40);
67: m_pHwndRenderTarget->FillEllipse(ellipse,m_pRadialGradientBrush);
68:
69: //Draw text with a linear gradient brush
70: const CString text = _T("Text drawed with Direct2D & DWrite!");
71: rect = RectF(20,210,380,290);
72: m_pHwndRenderTarget->DrawTextW(
73: text,
74: text.GetLength(),
75: m_pTextFormat,
76: rect,
77: m_pLinearGradientBrush);
78:
79: HRESULT hr = m_pHwndRenderTarget->EndDraw();
80:
81: if (hr == D2DERR_RECREATE_TARGET) //Render target need to be recreated
82: {
83: //Discard all device dependent resources,
84: //and recreate them in the next render procedure
85: DiscardDeviceDependentResource();
86: }
87: }
6. 销毁设备依赖资源，以备下次Render时再次创建
1: //View.cpp
2: void CBasicView::DiscardDeviceDependentResource()
3: {
4: SafeRelease(&m_pRadialGradientBrush);
5: SafeRelease(&m_pLinearGradientBrush);
6: SafeRelease(&m_pSolidColorBrush);
7: SafeRelease(&m_pHwndRenderTarget);
8: }
7.Resize
1: //View.cpp
2: void CBasicView::Resize(int width,int height)
3: {
4: if (m_pHwndRenderTarget)
5: {
6: m_pHwndRenderTarget->Resize(SizeU(width,height));
7: }
8: }