Direct2D中DWrite文字

DWrite可以高速地呈现文字：

#include "stdafx.h"

class unicode_file
{
    PCWSTR m_view;
    UINT32 m_size;

public:
    unicode_file();
    ~unicode_file();
    PCWSTR text() const;
    UINT32 size() const;
};

struct SampleWindow
    : DesktopWindow
{
    ComPtr m_brush;
    ComPtr m_textLayout;
    float m_offset;
    float m_anchor;

    void CreateDeviceIndependentResources()
    {
        ComPtr factory;
        HR(DWriteCreateFactory(DWRITE_FACTORY_TYPE_SHARED, 
            __uuidof(IDWriteFactory1), 
            reinterpret_cast(factory.GetAddressOf())));
        ComPtr format;
        HR(factory->CreateTextFormat(L"Consolas", 
            nullptr, DWRITE_FONT_WEIGHT_NORMAL, DWRITE_FONT_STYLE_NORMAL, 
            DWRITE_FONT_STRETCH_NORMAL, 12.0f, 
            L"", format.GetAddressOf()));

        unicode_file file;

        ASSERT(!m_textLayout);
        HR(factory->CreateTextLayout(file.text(), file.size(), 
            format.Get(), 100.0f, 100.0f, 
            m_textLayout.GetAddressOf()));

        m_offset = 0.0f;
    }

    LRESULT MouseLeftButtonDownHandler(UINT, WPARAM, LPARAM lparam, BOOL&)
    {
        SetCapture();
        m_anchor = HIWORD(lparam) - m_offset;
        return 0;
    }

    LRESULT MouseLeftButtonUpHandler(UINT, WPARAM, LPARAM, BOOL&)
    {
        ReleaseCapture();
        return 0;
    }

    LRESULT MouseMoveHandler(UINT, WPARAM wparam, LPARAM lparam, BOOL&)
    {
        if (wparam & MK_LBUTTON)
        {
            m_offset = HIWORD(lparam) - m_anchor;
            Invalidate();
        }
        return 0;
    }
    
    void CreateDeviceResources()
    {
        HR(m_target->CreateSolidColorBrush(COLOR_WHITE, m_brush.GetAddressOf()));
    }

    void Draw()
    {
        m_target->Clear(COLOR_BLACK);
        //
        auto size = m_target->GetSize();

        auto margin = 50.0f;
        size.width -= margin * 2.0f;
        size.height -= margin * 2.0f;

        if (m_textLayout->SetMaxWidth(size.width) == S_OK &&
            m_textLayout->SetMaxHeight(size.height) == S_OK)
        {
            auto t = Matrix3x2F::Translation(0.0f, min(0.0f, m_offset));
            m_target->SetTransform(t);
            m_target->DrawTextLayout(Point2F(margin, margin), 
                m_textLayout.Get(), m_brush.Get(), 
                D2D1_DRAW_TEXT_OPTIONS_NONE);
        }
    }
};

int __stdcall wWinMain(HINSTANCE, HINSTANCE, PWSTR, int)
{
    ComInitialize com;
    SampleWindow window;
    return window.Run();
}

unicode_file::unicode_file()
{
    auto file = CreateFile(L"D2DTest.cpp", GENERIC_READ, FILE_SHARE_READ, 
        nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
    ASSERT(file);

    LARGE_INTEGER size;
    VERIFY(GetFileSizeEx(file, &size));

    auto map = CreateFileMapping(file, nullptr, PAGE_READONLY, 0, 0, nullptr);
    ASSERT(map);

    VERIFY(CloseHandle(file));
    

    PSTR ansi = static_cast(MapViewOfFile(map, FILE_MAP_READ, 0, 0, 0));
    m_size = MultiByteToWideChar(CP_ACP, 0, ansi, -1, nullptr, 0);
    PWSTR pwstr = new WCHAR[m_size];
    MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS, ansi, -1, pwstr, m_size);
    m_view = static_cast(pwstr);

    ASSERT(m_view);
    VERIFY(CloseHandle(map));
    VERIFY(UnmapViewOfFile(ansi));
}

unicode_file::~unicode_file()
{
    PWSTR pwstr = const_cast(m_view);
    delete [] pwstr;
}

PCWSTR unicode_file::text() const
{
    ASSERT(m_view);
    return m_view;
}

UINT32 unicode_file::size() const
{
    return m_size;
}