I'd like to be able to render with OpenGL to a RECT as part of a plugin. But it needs to be offscreen so it doesn't affect the main application. But I'm running into an issue where I can't create a rendering context, maybe you can find my error. Here is the original sample code:

uint16 nsPluginInstance::HandleEvent(void* aEvent)
{
  NPEvent * event = (NPEvent *)aEvent;
  switch (event->event) {
    case WM_PAINT: 
    {
      if(!mWindow)
        break;

      // get the dirty rectangle to update or repaint the whole window
      RECT * drc = (RECT *)event->lParam;
      if(drc)
        FillRect((HDC)event->wParam, drc, (HBRUSH)(COLOR_ACTIVECAPTION+1));
      else {
        RECT rc;
        rc.bottom = mWindow->y + mWindow->height;
        rc.left   = mWindow->x;
        rc.right  = mWindow->x + mWindow->width;
        rc.top    = mWindow->y;
        FillRect((HDC)event->wParam, &rc, (HBRUSH)(COLOR_ACTIVECAPTION+1));
      }
      break;
    }
    case WM_KEYDOWN:
    {
      Beep(1000,100);
      break;
    }
    default:
      return 0;
  }
  return 1;
}

And here, I'm trying to create a rendering context without creating a window. But the message box comes up with "Can't Create A GL Rendering Context."...

uint16 nsPluginInstance::HandleEvent(void* aEvent)
{
  NPEvent * event = (NPEvent *)aEvent;
  switch (event->event) {
    case WM_PAINT: 
    {
      if(!mWindow)
        break;

      // get the dirty rectangle to update or repaint the whole window
      RECT * drc = (RECT *)event->lParam;
      if(drc)
        FillRect((HDC)event->wParam, drc, (HBRUSH)(COLOR_ACTIVECAPTION+1));
      else {
        RECT rc;
        rc.bottom = mWindow->y + mWindow->height;
        rc.left   = mWindow->x;
        rc.right  = mWindow->x + mWindow->width;
        rc.top    = mWindow->y;

        //FillRect((HDC)event->wParam, &rc, (HBRUSH)(COLOR_ACTIVECAPTION+1));

	  HWND hWND=(HWND)mWindow->window;
	  if (!hWND)
		  MessageBox(NULL,"Can't get the window handle.","ERROR",MB_OK|MB_ICONEXCLAMATION);
	  else
	  {
		  char message[50] = {0};
		  wsprintf(message, "Found Window Handle: %hu", hWND);
		  MessageBox(NULL,message,"ERROR",MB_OK|MB_ICONEXCLAMATION);
	  }

	  HDC hDC = GetDC(hWND);
	  if (!hDC)
		  MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
	  else
	  {
		  char message[50] = {0};
		  wsprintf(message, "Found GL Device Context: %hu", hDC);
		  MessageBox(NULL,message,"ERROR",MB_OK|MB_ICONEXCLAMATION);
	  }

        HGLRC hRC = wglCreateContext(hDC);
        if(!hRC)
          MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);

        if(!wglMakeCurrent(hDC,hRC))
          MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
      }
      break;
    }
    case WM_KEYDOWN:
    {
      Beep(1000,100);
      break;
    }
    default:
      return 0;
  }
  return 1;
}

[Edited by - tgraupmann on March 19, 2005 7:35:10 PM]

I'm tempted to just create a hidden window.

why not to create child window with same size as rect and then create your contex

This isn't the best solution, but I have Firefox creating a visible window.

I just had to add the following lines to [plugin.cpp].

#include "lesson2.h" // Nehe example 2

extern bool	fullscreen;NPBool nsPluginInstance::init(NPWindow* aWindow){	// I think we'll need a hidden window to render to	fullscreen=FALSE; // will always be windowed in browser		// Create Our OpenGL Window	if (!CreateGLWindow("NeHe's First Polygon Tutorial",640,480,16,fullscreen))	{		return FALSE; // Quit If Window Was Not Created	}		// no GUI to init in windowless case	mInitialized = TRUE;	return TRUE;}

void nsPluginInstance::shut(){	// Shutdown	KillGLWindow(); // Kill the OpenGL Window		// no GUI to shut in windowless case	mInitialized = FALSE;}

extern HDC hDC;uint16 nsPluginInstance::HandleEvent(void* aEvent){  NPEvent * event = (NPEvent *)aEvent;  switch (event->event) {    case WM_PAINT:     {      if(!mWindow)        break;	  // get the dirty rectangle to update or repaint the whole window      RECT * drc = (RECT *)event->lParam;      if(drc)	  {		  FillRect((HDC)event->wParam, drc, (HBRUSH)(COLOR_ACTIVECAPTION+1));		  DrawGLScene();		  SwapBuffers(hDC);	  }      else {        RECT rc;        rc.bottom = mWindow->y + mWindow->height;        rc.left   = mWindow->x;        rc.right  = mWindow->x + mWindow->width;        rc.top    = mWindow->y;        FillRect((HDC)event->wParam, &rc, (HBRUSH)(COLOR_ACTIVECAPTION+1));		DrawGLScene();		SwapBuffers(hDC);      }      break;    }    case WM_KEYDOWN:    {      Beep(1000,100);      break;    }    default:      return 0;  }  return 1;}

Quote: Original post by shadowwz
why not to create child window with same size as rect and then create your contex

Good suggestion. I'll give that a shot.

also the problem was in the pixelformat,you used default wich maybe can be used for opengl contex

What's the command you use to draw a BITMAP on a RECT?

	  // get the dirty rectangle to update or repaint the whole window      RECT * drc = (RECT *)event->lParam;      if(drc)	  {		  DrawGLScene();		  SwapBuffers(hDC);		  //FillRect((HDC)event->wParam, drc, (HBRUSH)(COLOR_ACTIVECAPTION+1));		  HDC hdcDest = CreateCompatibleDC(hDC);		  HBITMAP hBitmap = CreateCompatibleBitmap(hDC,childRect.right,childRect.bottom);		  HGDIOBJ oldObj = SelectObject(hdcDest,hBitmap);		  BitBlt(hdcDest,0,0,childRect.right,childRect.bottom,				hDC,0,0,SRCCOPY);		  // Draw the bitmap on the RECT called drc		  SelectObject(hDC,oldObj);		  DeleteDC(hdcDest);		  DeleteObject(hBitmap);	  }

if your opengl window is hidden,it may not work with device contex.
- you can draw scene to texture, wich can be saved to bitmap - or using glReadPixel to save scene to bitmap.

Quote: Original post by tgraupmann
This isn't the best solution, but I have Firefox creating a visible window.

I just had to add the following lines to [plugin.cpp].

#include "lesson2.h" // Nehe example 2

extern bool	fullscreen;NPBool nsPluginInstance::init(NPWindow* aWindow){	// I think we'll need a hidden window to render to	fullscreen=FALSE; // will always be windowed in browser		// Create Our OpenGL Window	if (!CreateGLWindow("NeHe's First Polygon Tutorial",640,480,16,fullscreen))	{		return FALSE; // Quit If Window Was Not Created	}		// no GUI to init in windowless case	mInitialized = TRUE;	return TRUE;}

don't you need to update window handle of aWindow,with new created one ?

Quote:

extern HDC hDC;uint16 nsPluginInstance::HandleEvent(void* aEvent){  NPEvent * event = (NPEvent *)aEvent;  switch (event->event) {    case WM_PAINT:     {      if(!mWindow)        break;	  // get the dirty rectangle to update or repaint the whole window      RECT * drc = (RECT *)event->lParam;      if(drc)	  {		  FillRect((HDC)event->wParam, drc, (HBRUSH)(COLOR_ACTIVECAPTION+1));		  DrawGLScene();		  SwapBuffers(hDC);	  }      else {        RECT rc;        rc.bottom = mWindow->y + mWindow->height;        rc.left   = mWindow->x;        rc.right  = mWindow->x + mWindow->width;        rc.top    = mWindow->y;        FillRect((HDC)event->wParam, &rc, (HBRUSH)(COLOR_ACTIVECAPTION+1));		DrawGLScene();		SwapBuffers(hDC);      }      break;    }

why you using "FillRect((HDC)event->wParam,&rc,(HBRUSH)(COLOR_ACTIVECAPTION+1));"
if you using "DrawGLScene(); SwapBuffers(hDC);" ?

also maybe you should change the name of "extern HDC hDC;" to something else,you may be not initialized it.

You could take a look at pBuffers or RENDER_TO_TEXTURE extensions. They are quite easy to create, and designed for offscreen rendering.

If you need some help i could explain some more, but i think you can find all you need using google. If not, let me know.

[edit]Don't know if firefox supports these features though[/edit]