reactos操作系统实现(198)

为了测试2位颜色位图装载到设备是否出错，编写了下面这段测试代码，如下：

#001  /* test with 2 bits color depth, not likely to succeed */

#002      hbmp = CreateBitmap(16, 16, 1, 2, bits);

#003      ok( hbmp != NULL, "CreateBitmap returns %p/n", hbmp);

#004      oldhbmp = SelectObject( hdcmem, hbmp);

#005      if( bitspixel != 2)

#006          ok( !oldhbmp, "SelectObject of a bitmap with 2 bits/pixel should return  NULL/n");

从这段代码可以看到，当内存DC不是两位颜色时，选择加载2位颜色的位图，就需要返回空句柄，否则就是这个SelectObject的API函数实现有问题。在没有修改这个BUG之前，这个函数返回是成功的加载位图了。因此需要修改这个函数的代码如下：

#001  HBITMAP

#002  APIENTRY

#003  NtGdiSelectBitmap(

#004      IN HDC hDC,

#005      IN HBITMAP hBmp)

#006  {

#007      PDC pDC;

#008      PDC_ATTR pdcattr;

#009      HBITMAP hOrgBmp;

#010      PSURFACE psurfBmp, psurfOld;

#011      HRGN hVisRgn;

#012 

#013      if (hDC == NULL || hBmp == NULL) return NULL;

#014 

#015      pDC = DC_LockDc(hDC);

#016      if (!pDC)

#017      {

#018          return NULL;

#019      }

#020      pdcattr = pDC->pdcattr;

#021 

#022      /* must be memory dc to select bitmap */

#023      if (pDC->dctype != DC_TYPE_MEMORY)

#024      {

#025          DC_UnlockDc(pDC);

#026          return NULL;

#027      }

#028 

#029      psurfBmp = SURFACE_LockSurface(hBmp);

#030      if (!psurfBmp)

#031      {

#032          DC_UnlockDc(pDC);

#033          return NULL;

#034      }

#035 

#036       //判断位图颜色数目是否与设备的颜色数目一样。

#037       if (pDC->ppdev)

#038       {            

#039              if (BitsPerFormat(psurfBmp->SurfObj.iBitmapFormat) == 4)

#040              {

#041                     //

#042                     DPRINT1("BitsPerFormat %d/n",BitsPerFormat(psurfBmp->SurfObj.iBitmapFormat));

#043                     DPRINT1("pDC->ppdev->gdiinfo.cBitsPixel %d/n",pDC->ppdev->gdiinfo.cBitsPixel);

#044 

#045                     if ( BitsPerFormat(psurfBmp->SurfObj.iBitmapFormat) !=

#046                            pDC->ppdev->gdiinfo.cBitsPixel)

#047                     {

#048                            SURFACE_UnlockSurface(psurfBmp);

#049 

#050                            DC_UnlockDc(pDC);

#051                            return NULL;

#052                     }

#053              }

#054       }

#055      

 

从36行代码开始，就是添加来解决这个BUG的，最后运行测试代码，成功地返回NULL句柄。