SetLayer()

[Untoter]

hey,

http://www.amyuni.com/WebHelp/Amyuni_Do ... verter.htm

Code: Select all

void SetLayer( HDC hDC, LPWSTR LayerInfo )
{
switch ( ExtEscape( hDC, ESCAPE_SETLAYER, (int)((wcslen(LayerInfo) + 1)* sizeof(LayerInfo[0])),(LPCSTR)LayerInfo, 0, NULL ) )

i changed it a bit to

Code: Select all

bool SetLayer( HDC hDC, std::wstring sTest )
{
	auto iRet = ExtEscape( hDC, ESCAPE_SETLAYER, (int) ((wcslen( sTest.c_str( ) ) + 1)	* sizeof( sTest.c_str( ) )), (LPCSTR)sTest.c_str( ), 0, NULL );

My Question is, why u cast (LPCSTR). U receive a wchar_t and c cast it to ANSI? Most times this cant work.

[Alexandre]

Hello,

From MSDN documentation of ExtEscape we have:

int ExtEscape(
_In_ HDC hdc,
_In_ int nEscape,
_In_ int cbInput,
_In_ LPCSTR lpszInData,
_In_ int cbOutput,
_Out_ LPSTR lpszOutData
);

Where lpszInData is defined as:

lpszInData [in]
A pointer to the input structure required for the specified escape.

As you can see lpszInData is actually a pointer to raw data, not to an ANSI string. In this particular case, the "input structure required for the specified escape", happens to be a wide string, but it could have been something else, a pointer to a struct for example.