How to Draw a Custom Window Caption

• Microsoft Windows Software Development Kit (SDK) versions 3.1
• Microsoft Win32 Application Programming Interface (API) included with:

      - Microsoft Windows NT versions 3.5 and 3.51
      - Microsoft Windows 95 version 4.0
  

SUMMARY

Microsoft Windows draws captions in the caption bar (or title bar) for all eligible windows in the system. Applications need to specify only the WS_CAPTION style to take advantage of this facility. The current version of Microsoft Windows, however, imposes three significant restrictions on the captions. An application that does not want to be tied by any of these restrictions may want to draw its own caption. This article lists the restrictions and the steps required to draw a window caption.

These restrictions also apply to Windows NT, but there are a few differences for Windows 95.

It is important to note that an application should not draw its own caption unless it has very good reasons to do so. A window caption is a user interface object, and rendering it in ways different from other windows in the system may obstruct the user's conceptual grasp of the Microsoft Windows user interface.

MORE INFORMATION

Windows and Windows NT

The three important restrictions imposed by Microsoft Windows version 3.1 and Microsoft Windows NT on the caption for a window are:

- It consists of text only; graphics are not allowed. - All text is centered and drawn with the system font. - The length of the displayed caption is limited to 78 characters

  even when there is space on the caption bar to accommodate extra
  characters.

1. Get the current window's rectangle using GetWindowRect(). This includes client plus nonclient areas and is in screen coordinates.

2. Get a device context (DC) to the window using GetWindowDC().

3. Compute the origin and dimensions of the caption bar. One needs to account for the window decorations (frame, border) and window bitmaps (min/max/system boxes). Remember that different window styles will result in different decorations and a different number of min/max/system boxes. Use GetSystemMetrics() to compute the dimensions of the frame, border, and the system bitmap dimensions.

4. Render the caption within the boundaries of the rectangle computed in step 3. Remember that the user can change the caption bar color any time by using the Control Panel. Some components of the caption, particularly text backgrounds, may need to be changed based on the current caption bar color. Use GetSysColor to determine the current color.

Sample Code

   case WM_NCACTIVATE:
      if ((BOOL)wParam == FALSE)
      {
         DefWindowProc( hWnd, message, wParam, lParam );
      // Add code here to draw caption when window is inactive.

         return TRUE;
      }
      // Fall through if wParam == TRUE, i.e., window is active.

      case WM_NCPAINT:
      // Let Windows do what it usually does. Let the window caption
      // be empty to avoid any Windows-initiated caption bar drawing

         DefWindowProc( hWnd, message, wParam, lParam );
         hDC = GetWindowDC( hWnd );
         GetWindowRect( hWnd, (LPRECT)&rc2 );

      // Compute the caption bar's origin. This window has a system box
      // a minimize box, a maximize box, and has a resizeable frame

         x = GetSystemMetrics( SM_CXSIZE ) +
             GetSystemMetrics( SM_CXBORDER ) +
             GetSystemMetrics( SM_CXFRAME );
         y = GetSystemMetrics( SM_CYFRAME );
         rc1.left = x;
         rc1.top = y;

      // 2*x gives twice the bitmap+border+frame size. Since there are
      // only two bitmaps, two borders, and one frame at the end of the
      // caption bar, subtract a frame to account for this.

         rc1.right = rc2.right - rc2.left - 2*x -
                     GetSystemMetrics( SM_CXFRAME );
         rc1.bottom = GetSystemMetrics( SM_CYSIZE );

      // Render the caption. Use the active caption color as the text
      // background.

         SetBkColor( hDC, GetSysColor(COLOR_ACTIVECAPTION) );
         DrawText( hDC, (LPSTR)"Left Justified Caption", -1,
                 (LPRECT)&rc1, DT_LEFT );
        ReleaseDC( hWnd, hDC );
        break;

Windows 95

On Windows 95, the text is not centered and the user can choose the Font. In addition, your application might want to monitor the WM_WININICHANGED message, because the user can change titlebar widths, and so forth, dynamically. When this happens, the application should take the new system metrics into account, and force a window redraw.