How to find out DC's dimensions?

Let's say I have a handle to device context (na开发者_如何学JAVAturally, in Windows environment):

HDC hdc;

How can I get the width and height of it?

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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

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

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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;

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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

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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.

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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;
    }
}