Using glColor* with OpenGL version 4.4 - windows

Question

I am in the process of updating our ancient OpenGL code. It is a Windows system and I am using GLEW. The OpenGL version is 4.4 (previously, the way the context was created limited us to 1.1). The code base is large and so I want to update it in stages (i.e. get everything working now on a version higher than 1.1 with minimal work). So far, I found only one break. Transparency no longer works. I suspect this may be due to glColor* or glTexEnv* being deprecated. I tried to request a specific version of OpenGL but was not successful. Can you tell me what I am doing wrong in context creation or what changes I can make to the draw code to get transparency to work? (Other help appreciated of course.)
Here is the context creation code (error checking removed for readability):
PIXELFORMATDESCRIPTOR pfd = {
/*WORD nSize*/ sizeof(PIXELFORMATDESCRIPTOR),
/*WORD nVersion*/ 1,
/*DWORD dwFlags*/ PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL,
/*BYTE iPixelType*/ PFD_TYPE_RGBA,
/*BYTE cColorBits*/ 24,
/*BYTE cRedBits*/ 0,
/*BYTE cRedShift*/ 0,
/*BYTE cGreenBits*/ 0,
/*BYTE cGreenShift*/ 0,
/*BYTE cBlueBits*/ 0,
/*BYTE cBlueShift*/ 0,
/*BYTE cAlphaBits*/ 8,
/*BYTE cAlphaShift*/ 0,
/*BYTE cAccumBits*/ 0,
/*BYTE cAccumRedBits*/ 0,
/*BYTE cAccumGreenBits*/ 0,
/*BYTE cAccumBlueBits*/ 0,
/*BYTE cAccumAlphaBits*/ 0,
/*BYTE cDepthBits*/ 16,
/*BYTE cStencilBits*/ 0,
/*BYTE cAuxBuffers*/ 0,
/*BYTE iLayerType*/ PFD_MAIN_PLANE,
/*BYTE bReserved*/ 0,
/*DWORD dwLayerMask*/ 0,
/*DWORD dwVisibleMask*/ 0,
/*DWORD dwDamageMask*/ 0
};
int nPixelFormat = ChoosePixelFormat(hDC, &pfd);
SetPixelFormat(hDC, nPixelFormat, &pfd);
hRC_ = wglCreateContext(hDC);
wglMakeCurrent(hDC, hRC_);
MsgUtil::TraceWin("version: %s", glGetString(GL_VERSION)); // Output: version: 4.4.0
glewInit();
GLint attribs[] = {
WGL_CONTEXT_MAJOR_VERSION_ARB, 3,
WGL_CONTEXT_MINOR_VERSION_ARB, 0,
WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB,
0
};
HGLRC CompHRC = wglCreateContextAttribsARB(hDC, 0, attribs);
if (CompHRC && wglMakeCurrent(hDC, CompHRC)){
hRC_ = CompHRC;
}
MsgUtil::TraceWin("version: %s", glGetString(GL_VERSION)); // Output: version: 4.4.0
Even after requesting version 3.0, glGetString(GL_VERSION) returns 4.4.0. I draw to a framebuffer and then use glReadPixels() to write to a bitmap (though I don't think that is especially relevant here).
Here is the framebuffer code (stays bound for lifetime of context):
glGenFramebuffers(1, &defaultFramebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
glGenRenderbuffers(1, &colorRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA, framebufferWidth, framebufferHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderbuffer);
glGenRenderbuffers(1, &depthRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, framebufferWidth, framebufferHeight);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);
Here is the draw code:
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glColor4f(1.0f, 1.0f, 1.0f, alpha);
glBindTexture(GL_TEXTURE_2D, texture_id);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
// Turn theImage (a CImage) into a texture
HBITMAP hbitmap = NewCreateDib24(*window_dc_, MAX_DELTA, MAX_DELTA);
CBitmap* bitmap = CBitmap::FromHandle(hbitmap);
CDC* memDC = new CDC();
memDC->CreateCompatibleDC(window_dc_);
CBitmap* pOldBitmap = memDC->SelectObject(bitmap);
theImage.StretchBlt(*memDC, 0, 0, MAX_DELTA, MAX_DELTA, SRCCOPY);
LPBYTE tempbitsMem = new BYTE[bm_info.bmiHeader.biSizeImage];
bitmap->GetBitmapBits(bm_info.bmiHeader.biSizeImage, (LPVOID)tempbitsMem);
glTexImage2D(GL_TEXTURE_2D, 0, 3, MAX_DELTA, MAX_DELTA, 0, GL_BGR, GL_UNSIGNED_BYTE, tempbitsMem);
// Draw texture
glBegin(GL_QUADS);
glTexCoord2d(tx.x_, 1.0 - tx.y_);
glVertex2d(px.x_, px.y_);
glTexCoord2d(t0.x_, 1.0 - t0.y_);
glVertex2d(p0.x_, p0.y_ );
glTexCoord2d(ty.x_, 1.0 - ty.y_);
glVertex2d(py.x_, py.y_);
glTexCoord2d(txy.x_, 1.0 - txy.y_);
glVertex2d(pxy.x_, pxy.y_);
glEnd();
The texture is now applied with full opacity, regardless of the alpha value sent to glColor4f(). However, if I change the RGB values, then that is still reflected in the output.

Answer 1

You should ask for a compatibility profile instead of a core profile.