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digitalmars.D.learn - How to call a GDI+ function from D ?

reply Vinod K Chandran <kcvinu82 gmail.com> writes:
Hi all,
I want to call the Bitmap function from gdi+. This is the syntax 
of the function in C++.
```c++
void Bitmap(
   [in] const WCHAR *filename,
   [in] BOOL        useEmbeddedColorManagement
);
```
And this is the mangled name which I got from goldbolt compiler.
`?Bitmap  YAXPEB_WH Z `

Now, this is my declaration in D.
```d
extern (C++, "Bitmap") void * Bitmap(const(wchar)* file, BOOL 
useClr);
```
And this is my call site.
```d
auto imgPath = toUTF16z(r"C:\Users\AcerLap\Pictures\Saved 
Pictures\d3.png") ;
auto pBmp = Bitmap(imgPath, FALSE);
```
But I got this error message.
```
app.obj : error LNK2019: unresolved external symbol "void * 
__cdecl Bitmap::Bitmap(char16_t const *,int)" 
(?Bitmap 0 YAPAXPB_SH Z) referenced in function 
__D4wing9imagelist9ImageList8addImageMFAyaZv
app.exe : fatal error LNK1120: 1 unresolved externals
Error: linker exited with status 1120
```
You see, the mangled names are different.
 From D - `?Bitmap 0 YAPAXPB_SH Z`
 From C++ - `?Bitmap  YAXPEB_WH Z`
How to fix this ?
Jun 05 2022
parent reply rikki cattermole <rikki cattermole.co.nz> writes:
Bitmap is a class, not a namespace.

The function you want is actually a constructor.

https://github.com/Alexpux/mingw-w64/blob/master/mingw-w64-headers/include/gdiplus/gdiplusheaders.h#L179
Jun 05 2022
parent reply Vinod K Chandran <kcvinu82 gmail.com> writes:
On Sunday, 5 June 2022 at 10:57:16 UTC, rikki cattermole wrote:

 Bitmap is a class, not a namespace.

 The function you want is actually a constructor.

 https://github.com/Alexpux/mingw-w64/blob/master/mingw-w64-headers/include/gdiplus/gdiplusheaders.h#L179


Thank you for the reply. Well, I know that it is a CTOR. But I 
thought this is the D way to call it.
Jun 05 2022
parent Vinod K Chandran <kcvinu82 gmail.com> writes:
On Sunday, 5 June 2022 at 11:33:14 UTC, Vinod K Chandran wrote:


For future readers of this thread, rikki cattermole helped me to 
findthe solution to this problem. I Do not need the C++ classes 
or their methods for this. There is a set of C functions in 
gdiplus.dll. Check this link. 
https://docs.microsoft.com/en-us/windows/win32/gdiplus/-gdiplus-flatapi-flat



 Jun 05 2022