SkiaのSkBitmap::setPixelsで自分で管理しているメモリをSkBitmapに設定して描画

// Skiaがminmaxを使用するので、Windowsと一緒に使う場合はNOMINMAXを定義
#define NOMINMAX

#include <Windows.h>
#include <tchar.h>

// skia
#include "include/core/SkCanvas.h"
#include "include/core/SkBitmap.h"

// DIB Sectionに設定するピクセルの構造体
struct rgbu_t {
  unsigned char b;
  unsigned char g;
  unsigned char r;
  unsigned char u;// unused
  rgbu_t(unsigned char R, unsigned char G, unsigned char B) :b(B), g(G), r(R) {}
  static const rgbu_t White;
  static const rgbu_t Black;
};

// DIBSectionを作成する関数
void createDIBsection32(
  HBITMAP* hBitmap,
  HDC* hMemDC,
  BITMAPINFO* bmpInfo,
  rgbu_t** m_lpPixel,
  LONG width,
  LONG height)
{
  //DIBの情報を設定する
  bmpInfo->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
  bmpInfo->bmiHeader.biWidth = width;
  bmpInfo->bmiHeader.biHeight = -height; //-を指定しないと上下逆になる
  bmpInfo->bmiHeader.biPlanes = 1;
  bmpInfo->bmiHeader.biBitCount = 32;
  bmpInfo->bmiHeader.biCompression = BI_RGB;

  HDC hdc = CreateDC(_T("DISPLAY"), 0, 0, 0);

  *hBitmap = CreateDIBSection(hdc, bmpInfo, DIB_RGB_COLORS, (void**)m_lpPixel, NULL, 0);
  *hMemDC = CreateCompatibleDC(hdc);

  DeleteDC(hdc);

  SelectObject(*hMemDC, *hBitmap);

}

// DIBSectionを削除する関数
void deleteDIBsection32(HDC hMemDC, HBITMAP hBitmap) {
  DeleteDC(hMemDC);
  DeleteObject(hBitmap);
}

// DIBSectionの情報
HBITMAP dib_hBitmap;
HDC dib_hMemDC;
BITMAPINFO dib_bmpInfo;
rgbu_t* dib_lpPixel;

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {

  HDC hdc;
  RECT rect;
  static int width;
  static int height;

  static SkBitmap skbitmap;

  switch (msg) {
  case WM_CREATE:

    GetClientRect(hwnd, &rect);
    //DIB Sectionを作成（32Bit)
    createDIBsection32(
      &dib_hBitmap,
      &dib_hMemDC,
      &dib_bmpInfo,
      &dib_lpPixel,
      rect.right,
      rect.bottom
    );
    width = rect.right;
    height = rect.bottom;

    // dib_lpPixel 経由でDIBSectionを赤で塗りつぶす
    for (int y = 0; y < height; y++) {
      for (int x = 0; x < width; x++) {
        dib_lpPixel[y * width + x] = rgbu_t(0, 0, 255);
      }
    }
 

    {
      skbitmap.setInfo(SkImageInfo::MakeN32Premul(width, height));
      // SkiaのBitmapにDIBSectionの情報を設定
      skbitmap.setPixels(dib_lpPixel);
      SkCanvas canvas(skbitmap);

      // 図形の描画
      SkPaint paint;
      paint.setStyle(SkPaint::kStroke_Style);
      paint.setStrokeWidth(5);
      paint.setColor(SK_ColorRED);
      canvas.drawCircle(200, 200, 100, paint);
    }

    break;
  case WM_PAINT:
  {

    // 画像を表示
    PAINTSTRUCT ps;
    HDC hDC = BeginPaint(hwnd, &ps);

    BitBlt(hDC, 0, 0, width, height, dib_hMemDC, 0, 0, SRCCOPY);


    EndPaint(hwnd, &ps);

    break;
  }
  case WM_DESTROY:
    deleteDIBsection32(dib_hMemDC, dib_hBitmap);
    PostQuitMessage(0);
    return 0;
  case WM_LBUTTONDOWN:
    hdc = GetDC(hwnd);
    ReleaseDC(hwnd, hdc);
    return 0;
  }
  return DefWindowProc(hwnd, msg, wp, lp);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
  PSTR lpCmdLine, int nCmdShow) {
  HWND hwnd;
  WNDCLASS winc;
  MSG msg;

  winc.style = CS_HREDRAW | CS_VREDRAW;
  winc.lpfnWndProc = WndProc;
  winc.cbClsExtra = winc.cbWndExtra = 0;
  winc.hInstance = hInstance;
  winc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
  winc.hCursor = LoadCursor(NULL, IDC_ARROW);
  winc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
  winc.lpszMenuName = NULL;
  winc.lpszClassName = TEXT("SZL_WINDOW");

  if (!RegisterClass(&winc)) return 0;

  hwnd = CreateWindow(
    TEXT("SZL_WINDOW"), TEXT("szl window"),
    WS_OVERLAPPEDWINDOW | WS_VISIBLE,
    CW_USEDEFAULT, CW_USEDEFAULT,
    600, 400,
    NULL, NULL,
    hInstance, NULL
  );

  if (hwnd == NULL) return 0;

  while (GetMessage(&msg, NULL, 0, 0)) DispatchMessage(&msg);
  return msg.wParam;
}