Thread: opengl DC question

Hi every1;

Ok, im done on reviewing vector math.

now im reading this code in this book"game programming with opengl". i have 3 questions for three parts.

i broke the parts in 3 sections.

Code:

HDC  g_HDC                //global  DC

question 1:is this device context similar in concept to the hdc memory context that we create in win API to write onto (like in
DDB bitmap functions , bitblt ,,stretchblt)?

Code:

HGLRC  hRC;
HDC  hdc;
////////////

case WM_CREATE:

hdc = GetDC(hwnd);
g_HDC = hdc;
SetupPixelFormat(hdc);


hRC = wglCreateContext(hdc);
wglMakeCurrent(hdc, hRC);

return 0;
break;

question 2: why there is no ReleaseDC(hwnd, hdc); function
in the above code. as its routily done in win API?


then in the body of opengl code during rendering phase we have:

Code:

//////////////
glTranslatef(,,,,,,,,,,,,,);
glRotatef(,,,,,,,,,,,,,,,,,);
glColor3f(,,,,,,,,,,,,,,,,,,);
glBegin(GL_TRIANGLE);
glVertex3f(,,,,,,,,,,,,,,,,)

glVertex3f(,,,,,,,,,,,,,,,,)

glVertex3f(,,,,,,,,,,,,,,,,)

glEnd();

SwapBuffers(g_HDC);       //bring back buffer to forground

TranslateMessage(&msg);
DispatchMessage(&msg);

///////////////////////////

*if answer to question 1 is yes disregard this one.

question 3: why couldnt we simply make hdc global like;

HDC hdc;

and use it throuout the program so we dont need a second copy of it as g_HDC .? is it because we have to have 2 different device context , one for window procedure and one for opengl calls
.so how come they are identical?

why there is no ReleaseDC function for g_HDC neither?


thanks
silver or travis should know these.