Force Win32 common controls to draw on `ID2D1HwndRenderTarget`?

If you want to share a device context (HDC) between GDI and Direct2D, you can use a ID2D1DCRenderTarget and Bind to this HDC when you want to render on it.

This is demonstrated in this official sample : GDI/Direct2D Interoperability Sample

Note, as is, it doesn't compile/work with today's Visual Studio. So, here is a similar code here with a simple button and textbox:

#include <windows.h>
#include <stdlib.h>
#include <math.h>
#include <d2d1.h>

template<class Interface>
inline void
SafeRelease(Interface** ppInterfaceToRelease)
{
    if (*ppInterfaceToRelease != NULL)
    {
        (*ppInterfaceToRelease)->Release();
        (*ppInterfaceToRelease) = NULL;
    }
}

EXTERN_C IMAGE_DOS_HEADER __ImageBase;

class DemoApp
{
public:
    DemoApp();
    ~DemoApp();

    HRESULT Initialize();

private:
    HRESULT CreateDeviceIndependentResources();
    HRESULT CreateDeviceResources();
    void DiscardDeviceResources();
    HRESULT OnRender(const PAINTSTRUCT& ps);
    static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

private:
    HWND m_hwnd;
    ID2D1Factory* m_pD2DFactory;
    ID2D1DCRenderTarget* m_pDCRT;
    ID2D1SolidColorBrush* m_pBlackBrush;
};

int WINAPI WinMain(HINSTANCE /*hInstance*/, HINSTANCE /*hPrevInstance*/, LPSTR /*lpCmdLine*/, int /*nCmdShow*/)
{
    if (SUCCEEDED(CoInitialize(NULL)))
    {
        DemoApp app;
        if (SUCCEEDED(app.Initialize()))
        {
            MSG msg;
            while (GetMessage(&msg, NULL, 0, 0))
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
        }
        CoUninitialize();
    }
    return 0;
}

DemoApp::DemoApp() :
    m_hwnd(NULL),
    m_pD2DFactory(NULL),
    m_pDCRT(NULL),
    m_pBlackBrush(NULL)
{
}

DemoApp::~DemoApp()
{
    SafeRelease(&m_pD2DFactory);
    SafeRelease(&m_pDCRT);
    SafeRelease(&m_pBlackBrush);
}

HRESULT DemoApp::Initialize()
{
    HRESULT hr;

    hr = CreateDeviceIndependentResources();
    if (SUCCEEDED(hr))
    {
        // Register the window class.
        WNDCLASSEX wcex = { sizeof(WNDCLASSEX) };
        wcex.style = CS_HREDRAW | CS_VREDRAW;
        wcex.lpfnWndProc = DemoApp::WndProc;
        wcex.cbClsExtra = 0;
        wcex.cbWndExtra = sizeof(LONG_PTR);
        wcex.hInstance = (HINSTANCE)&__ImageBase;
        wcex.hbrBackground = NULL;
        wcex.lpszMenuName = NULL;
        wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
        wcex.lpszClassName = L"D2DDemoApp";
        RegisterClassEx(&wcex);

        // Create the application window.
        // Because the CreateWindow function takes its size in pixels, we obtain the system DPI and use it to scale the window size.
        FLOAT dpiX, dpiY;
        m_pD2DFactory->GetDesktopDpi(&dpiX, &dpiY);

        m_hwnd = CreateWindow(
            L"D2DDemoApp",
            L"Direct2D Demo App",
            WS_OVERLAPPEDWINDOW,
            CW_USEDEFAULT,
            CW_USEDEFAULT,
            static_cast<UINT>(ceil(640.f * dpiX / 96.f)),
            static_cast<UINT>(ceil(480.f * dpiY / 96.f)),
            NULL,
            NULL,
            (HINSTANCE)&__ImageBase,
            this
        );

        hr = m_hwnd ? S_OK : E_FAIL;
        if (SUCCEEDED(hr))
        {
            ShowWindow(m_hwnd, SW_SHOWNORMAL);

            UpdateWindow(m_hwnd);
        }
    }

    return hr;
}

HRESULT DemoApp::CreateDeviceIndependentResources()
{
    // Create D2D factory
    return D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED, &m_pD2DFactory);
}

HRESULT DemoApp::CreateDeviceResources()
{
    HRESULT hr = S_OK;
    if (!m_pDCRT)
    {
        // Create a DC render target.
        D2D1_RENDER_TARGET_PROPERTIES props = D2D1::RenderTargetProperties(
            D2D1_RENDER_TARGET_TYPE_DEFAULT,
            D2D1::PixelFormat(
                DXGI_FORMAT_B8G8R8A8_UNORM,
                D2D1_ALPHA_MODE_IGNORE),
            0,
            0,
            D2D1_RENDER_TARGET_USAGE_NONE,
            D2D1_FEATURE_LEVEL_DEFAULT
        );

        hr = m_pD2DFactory->CreateDCRenderTarget(&props, &m_pDCRT);
        if (SUCCEEDED(hr))
        {
            // Create a black brush.
            hr = m_pDCRT->CreateSolidColorBrush(D2D1::ColorF(D2D1::ColorF::Black), &m_pBlackBrush);
        }
    }

    return hr;
}

void DemoApp::DiscardDeviceResources()
{
    SafeRelease(&m_pDCRT);
    SafeRelease(&m_pBlackBrush);
}

HRESULT DemoApp::OnRender(const PAINTSTRUCT& ps)
{
    HRESULT hr;
    RECT rc;

    // Get the dimensions of the client drawing area.
    GetClientRect(m_hwnd, &rc);

    // Draw the pie chart with Direct2D.

    // Create the DC render target.
    hr = CreateDeviceResources();

    if (SUCCEEDED(hr))
    {
        // Bind the DC to the DC render target.
        hr = m_pDCRT->BindDC(ps.hdc, &rc);

        m_pDCRT->BeginDraw();
        m_pDCRT->SetTransform(D2D1::Matrix3x2F::Identity());
        m_pDCRT->Clear(D2D1::ColorF(D2D1::ColorF::White));

        m_pDCRT->DrawEllipse(D2D1::Ellipse(D2D1::Point2F(150.0f, 150.0f), 100.0f, 100.0f), m_pBlackBrush, 3.0);

        m_pDCRT->DrawLine(
            D2D1::Point2F(150.0f, 150.0f),
            D2D1::Point2F((150.0f + 100.0f * 0.15425f), (150.0f - 100.0f * 0.988f)), m_pBlackBrush, 3.0
        );

        m_pDCRT->DrawLine(
            D2D1::Point2F(150.0f, 150.0f),
            D2D1::Point2F((150.0f + 100.0f * 0.525f), (150.0f + 100.0f * 0.8509f)), m_pBlackBrush, 3.0
        );

        m_pDCRT->DrawLine(
            D2D1::Point2F(150.0f, 150.0f),
            D2D1::Point2F((150.0f - 100.0f * 0.988f), (150.0f - 100.0f * 0.15425f)), m_pBlackBrush, 3.0
        );

        hr = m_pDCRT->EndDraw();

        if (SUCCEEDED(hr))
        {
            // Draw the pie chart with GDI.

            // Save the original object.
            HGDIOBJ original = NULL;
            original = SelectObject(ps.hdc, GetStockObject(DC_PEN));

            HPEN blackPen = CreatePen(PS_SOLID, 3, 0);
            SelectObject(ps.hdc, blackPen);

            Ellipse(ps.hdc, 300, 50, 500, 250);

            POINT pntArray1[2];
            pntArray1[0].x = 400;
            pntArray1[0].y = 150;
            pntArray1[1].x = static_cast<LONG>(400 + 100 * 0.15425);
            pntArray1[1].y = static_cast<LONG>(150 - 100 * 0.9885);

            POINT pntArray2[2];
            pntArray2[0].x = 400;
            pntArray2[0].y = 150;
            pntArray2[1].x = static_cast<LONG>(400 + 100 * 0.525);
            pntArray2[1].y = static_cast<LONG>(150 + 100 * 0.8509);


            POINT pntArray3[2];
            pntArray3[0].x = 400;
            pntArray3[0].y = 150;
            pntArray3[1].x = static_cast<LONG>(400 - 100 * 0.988);
            pntArray3[1].y = static_cast<LONG>(150 - 100 * 0.15425);

            Polyline(ps.hdc, pntArray1, 2);
            Polyline(ps.hdc, pntArray2, 2);
            Polyline(ps.hdc, pntArray3, 2);

            DeleteObject(blackPen);

            // Restore the original object.
            SelectObject(ps.hdc, original);
        }
    }

    if (hr == D2DERR_RECREATE_TARGET)
    {
        hr = S_OK;
        DiscardDeviceResources();
    }

    return hr;
}

LRESULT CALLBACK DemoApp::WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if (message == WM_CREATE)
    {
        LPCREATESTRUCT pcs = (LPCREATESTRUCT)lParam;
        SetWindowLongPtr(hwnd, GWLP_USERDATA, (LONG_PTR)pcs->lpCreateParams);

        auto button = CreateWindowExW(0, L"button", L"Send", WS_CHILD | WS_VISIBLE, 10, 10, 120, 30, hwnd, (HMENU)1, (HINSTANCE)&__ImageBase, 0); // win32 control
        auto edit = CreateWindowExW(0, L"edit", L"Edit", WS_CHILD | WS_VISIBLE, 10, 50, 120, 30, hwnd, (HMENU)2, (HINSTANCE)&__ImageBase, 0); // win32 control
        return 1;
    }

    LRESULT result = 0;
    DemoApp* pDemoApp = (DemoApp*)(GetWindowLongPtr(hwnd, GWLP_USERDATA));
    bool wasHandled = false;
    if (pDemoApp)
    {
        switch (message)
        {
        case WM_PAINT:
        case WM_DISPLAYCHANGE:
        {
            PAINTSTRUCT ps;
            BeginPaint(hwnd, &ps);
            pDemoApp->OnRender(ps);
            EndPaint(hwnd, &ps);
        }
        result = 0;
        wasHandled = true;
        break;

        case WM_DESTROY:
        {
            PostQuitMessage(0);
        }
        result = 1;
        wasHandled = true;
        break;
        }
    }

    if (!wasHandled)
    {
        result = DefWindowProc(hwnd, message, wParam, lParam);
    }

    return result;
}

And here is how it renders (left circle is Direct2D, right is aliased GDI):

How to force Win32 controls to draw onto my ID2D1Bitmap1? Is that even possible?

Yes. You can write GDI content to a Direct2D GDI-compatible render target. This approach is useful for applications that primarily render with Direct2D but have an extensibility model or other legacy content that requires the ability to render with GDI.

Step:

To render GDI content to a Direct2D GDI-compatible render target, use an ID2D1GdiInteropRenderTarget, which provides access to a device context that can accept GDI draw calls. Unlike other interfaces, an ID2D1GdiInteropRenderTarget object is not created directly. Instead, use the QueryInterface method of an existing render target instance.

Refer: Draw GDI Content to a Direct2D GDI-Compatible Render Target