GDI+ and Fat API

[mmscg]

I am trying to figure out how to call a GDI+ Flat Api function, but cannot get anything working.

Here is my code:

#include <windows.h>
#include <objidl.h>
#include <gdiplus.h>
#include <GdiplusFlat.h>
using namespace Gdiplus;
#pragma comment (lib,"Gdiplus.lib")

VOID OnPaint(HDC hdc)
{
	Graphics graphics(hdc);
	Pen      pen(Color(255, 0, 0, 255));
	//graphics.DrawLine(&pen, 0, 0, 200, 100);
	GdipDrawLine(&graphics, &pen, 0, 0, 200, 0); //Flat Api version
}

Here I am trying to call only one flat function GdipDrawLine.

Any suggestions?

[ovidiucucu]

• Once included Gdiplus, use DllExports namespace i.e. DllExports::GdipDrawLine.
• First two arguments of DllExports::GdipDrawLine are not of type Gdilpus::Graphics and Gdiplus::Pen, but GpGraphics and GpPen.
  

  GpStatus WINGDIPAPI
  GdipDrawLine(GpGraphics *graphics, GpPen *pen, REAL x1, REAL y1,
                        REAL x2, REAL y2);

  None has implicit conversion from one to another.
• It has no sense in a C++ program to directly use flat GDI+ APIs.
  Generally, GDI+ classes methods are simple inline wrappers, e.g.
  

      Status DrawLine(IN const Pen* pen,
                      IN INT x1,
                      IN INT y1,
                      IN INT x2,
                      IN INT y2)
      {
          return SetStatus(DllExports::GdipDrawLineI(nativeGraphics,
                                                     pen->nativePen,
                                                     x1,
                                                     y1,
                                                     x2,
                                                     y2));
      }

• Given the above points, you have to choose one of two:
  
  1. Use only GDI+ classes, recommended in C++ code;
  2. Use GDI+ flat API only in C code (as well as in other languages, except C++).

[mmscg]

So are you are saying the Flat Api functions cannot be used in C++,
or just that using the wrapper method is easier?

I added

using namespace Gdiplus:: DllExports;

to my code and I now get this error:

error C2664: 'Gdiplus:llExports::GdipDrawLine' : cannot convert parameter 1 from 'Gdiplus::Graphics *__w64 ' to 'Gdiplus::GpGraphics *'

[ovidiucucu]

So are you are saying the Flat Api functions cannot be used in C++,
or just that using the wrapper method is easier?

I have never said "cannot". You can use flat GDI+ API in C++ code but it's like scratching with the foot.
Yes, the (wrapper) C++ classes are easier to use in C++ code. For that purpose they have been designed.

I added

using namespace Gdiplus:: DllExports;

to my code and I now get this error:

error C2664: 'Gdiplus:llExports::GdipDrawLine' : cannot convert parameter 1 from 'Gdiplus::Graphics *__w64 ' to 'Gdiplus::GpGraphics *'

Have you ever read this?

• First two arguments of DllExports::GdipDrawLine are not of type Gdilpus::Graphics and Gdiplus::Pen, but GpGraphics and GpPen.
  

  GpStatus WINGDIPAPI
  GdipDrawLine(GpGraphics *graphics, GpPen *pen, REAL x1, REAL y1,
                        REAL x2, REAL y2);

  None has implicit conversion from one to another.
  ...

[mmscg]

Yes, I had read that, but still being fairly new to C++ I find this very confusing.

Can one type be cast to another then?

I have been using GDI+ in my VB6 projects for the last year, and have become fairly proficient with the Flat Apis.

As I continue to learn C++, and start to port some of my projects from VB6 to C++,
I thought it might be easier for me to continue to use the Flat Api methodology for the GDI+ conversion.

Also now, even for just curiosity sake, I would like to see how to draw a line in C++ using flat GDI+ api.

[ovidiucucu]

Well, here is an example of using GDI+ flat API.

   using namespace DllExports;

   GpPen* pen = NULL;
   GpGraphics* graphics = NULL;
   ARGB color = 255 << ALPHA_SHIFT | 255 << BLUE_SHIFT;
   GpUnit unit = UnitPixel;
   REAL width = 1.0;

   GdipCreatePen1(color, width, unit, &pen);
   GdipCreateFromHDC(hdc, &graphics);
   GdipDrawLine(graphics, pen, 0, 0, 100, 50);
   // ...
   GdipDeletePen(pen);
   GdipDeleteGraphics(graphics);

Resources

• [MSDN] GDI+ Flat API

[mmscg]

Thank you... you C++ guys are amazing!!

This works perfectly for me, and should be enough to get me on my way.
(I'm sure I'll hit a few stumbling blocks, and might have to ask more questions).