SelectObject函数是将对象选定到指定的设备场境中。具体实现代码如下：

#001 HGdioBJ

#002 WINAPI

#003 SelectObject(HDC hDC,

#004 HGdioBJ hGdiobj)

#005 {

#006 PDC_ATTR pDc_Attr;

#007 HGdioBJ hOldObj = NULL;

#008 UINT uType;

#009 // PTEB pTeb;

#010

获取这个HDC相关的属性。

#011 if(!GdiGetHandleUserData(hDC,GDI_OBJECT_TYPE_DC,(PVOID)&pDc_Attr))

#012 {

#013 SetLastError(ERROR_INVALID_HANDLE);

#014 return NULL;

#015 }

#016

获取选择DC的对象正确的句柄。

#017 hGdiobj = GdiFixUpHandle(hGdiobj);

#018 if (!GdiIsHandleValid(hGdiobj))

#019 {

#020 return NULL;

#021 }

#022

获取这个对象的类型。

#023 uType = GDI_HANDLE_GET_TYPE(hGdiobj);

#024

根据不同的类型调用合适的函数把对象设置到DC里。

#025 switch (uType)

#026 {

#027 case GDI_OBJECT_TYPE_REGION:

#028 return (HGdioBJ)ExtSelectClipRgn(hDC,hGdiobj,RGN_COPY);

#029

#030 case GDI_OBJECT_TYPE_BITMAP:

#031 return NtGdiSelectBitmap(hDC,hGdiobj);

#032

#033 case GDI_OBJECT_TYPE_BRUSH:

#034 hOldObj = pDc_Attr->hbrush;

#035 pDc_Attr->ulDirty_ |= DC_BRUSH_DIRTY;

#036 pDc_Attr->hbrush = hGdiobj;

#037 return hOldObj;

#038 // return NtGdiSelectBrush(hDC,hGdiobj);

#039

#040 case GDI_OBJECT_TYPE_PEN:

#041 case GDI_OBJECT_TYPE_EXTPEN:

#042 hOldObj = pDc_Attr->hpen;

#043 pDc_Attr->ulDirty_ |= DC_PEN_DIRTY;

#044 pDc_Attr->hpen = hGdiobj;

#045 return hOldObj;

#046 // return NtGdiSelectPen(hDC,hGdiobj);

#047

#048 case GDI_OBJECT_TYPE_FONT:

#049 hOldObj = pDc_Attr->hlfntNew;

#050 if (hOldObj == hGdiobj) return hOldObj;

#051 #if 0

#052 pDc_Attr->ulDirty_ &= ~SLOW_WIDTHS;

#053 pDc_Attr->ulDirty_ |= DIRTY_CHARSET;

#054 pDc_Attr->hlfntNew = hGdiobj;

#055 pTeb = NtCurrentTeb();

#056 if (((pTeb->GdiTebBatch.HDC == 0) ||

#057 (pTeb->GdiTebBatch.HDC == hDC)) &&

#058 ((pTeb->GdiTebBatch.Offset + sizeof(GDIBSOBJECT)) <= GDIBATCHBUFSIZE) &&

#059 (!(pDc_Attr->ulDirty_ & DC_DIBSECTION)))

#060 {

#061 PGDIBSOBJECT pgO = (PGDIBSOBJECT)(&pTeb->GdiTebBatch.Buffer[0] +

#062 pTeb->GdiTebBatch.Offset);

#063 pgO->gbHdr.Cmd = GdiBCSelObj;

#064 pgO->gbHdr.Size = sizeof(GDIBSOBJECT);

#065 pgO->hgdiobj = hGdiobj;

#066

#067 pTeb->GdiTebBatch.Offset += sizeof(GDIBSOBJECT);

#068 pTeb->GdiTebBatch.HDC = hDC;

#069 pTeb->GdiBatchCount++;

#070 if (pTeb->GdiBatchCount >= GDI_BatchLimit) NtGdiFlush();

#071 return hOldObj;

#072 }

#073 #endif

#074 // default for select object font

#075 return NtGdiSelectFont(hDC,hGdiobj);

#076

#077 #if 0

#078 case GDI_OBJECT_TYPE_MetaDC:

#079 return MFDRV_SelectObject( hDC,hGdiobj);

#080 case GDI_OBJECT_TYPE_EMF:

#081 PLDC pLDC = GdiGetLDC(hDC);

#082 if ( !pLDC ) return NULL;

#083 return EMFDRV_SelectObject( hDC,hGdiobj);

#084 #endif

#085 case GDI_OBJECT_TYPE_COLORSPACE:

#086 SetColorSpace(hDC,(HCOLORSPACE) hGdiobj);

#087 return NULL;

#088

#089 case GDI_OBJECT_TYPE_PALETTE:

#090 default:

#091 SetLastError(ERROR_INVALID_FUNCTION);

#092 return NULL;

#093 }

#094

#095 return NULL;

#096 }

#097

原文链接：https://www.f2er.com/react/308327.html