How to find out DC's dimensions? - c++

Question

Let's say I have a handle to device context (naturally, in Windows environment):
HDC hdc;
How can I get the width and height of it?

Answer 1

A device context (DC) is a structure that defines a set of graphic objects and their associated attributes, and the graphic modes that affect output.
By width and height I'm guessing you are referring to the bitmap painted ?
If so then i guess you can try the following :
BITMAP structBitmapHeader;
memset( &structBitmapHeader, 0, sizeof(BITMAP) );
HGDIOBJ hBitmap = GetCurrentObject(hDC, OBJ_BITMAP);
GetObject(hBitmap, sizeof(BITMAP), &structBitmapHeader);
//structBitmapHeader.bmWidth
//structBitmapHeader.bmHeight

Answer 2

I also know little about GDI, but it seems GetDeviceCaps might do the trick.

Answer 3

This simple piece of code I use always to get the dimensions of the rendering area, when I have only the HDC.
First, you must get a HWND from the HDC - is simple, then you can get the client rect of this HWND:
RECT rcCli;
GetClientRect(WindowFromDC(hdc), &rcCli);
// then you might have:
nWidth = rcCli.right-rcCli.left;
nHeight = rcCli.bottom-rcCli.top;

Answer 4

As a disclaimer, I know nothing about GDI or what you have to work with in your application. I'm just trying to be helpful if possible.
That said, I found a link which seems to suggest that it's appropriate to use GetClientRect to get the size of the drawing area:
RECT clientRect;
GetClientRect(hWnd,&clientRect);
http://www.toymaker.info/Games/html/gdi.html#winsize

Answer 5

You could WindowFromDC(...) to get the DC's window if it's associated with a window. You could then use #KevinK's answer to get the client rect from this.

Answer 6

but if get Calculator' window_dc dimension, it will failed at “GetCurrentObject” or "GetObject", i think maybe the window attribute include "ws_ex_noredirectionbitmap", how to get dismension in this case?
HDC win_dc = ::GetWindowDC(hwnd);
BITMAP bm = { 0 };
HGDIOBJ hBitmap = GetCurrentObject(win_dc, OBJ_BITMAP);
if (hBitmap)
{
if (GetObject(hBitmap, sizeof(BITMAP), &bm))
{
windc_dimension.cx = bm.bmWidth;
windc_dimension.cy = bm.bmHeight;
}
}