BigClock with Transparent Background

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Introduction

This is a transparent desktop clock based on the 7 segment LCD. I published a seven segment LCD article a while ago, and based upon that control, I quickly slapped together a transparent desktop clock. It is with pleasure I am sharing it with The Code Project community.

Background

One of my colleagues walked by and was very impressed with BigClock. He immediately requested a copy for himself, and I see it on his screen all the time.

Using the Code

The 7 segment code worked without modification in a transparent environment. However I added a class interception snippet to erase the CStatic frames at runtime. This way, the controls in the dialog editor can have the 'sunken' style to see how big the controls are and where they are. This makes it easier to design the form for the control. Here is the code that does this:

// Call this when the control is painted the first time
// The interception is archived by `maintaining a class variable called 
// 'firstpaint'

Clcd7::Clcd7()
    {
    .....
    firstpaint = true;
    .....
    }

if(firstpaint)
    {
    //TRACE("firstpaint\r\n");
    firstpaint = false;
      ModifyStyleEx(WS_EX_STATICEDGE | WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE, 0);
    }

One would ask why do this in OnPaint? Well, the CStatic and CWnd based controls do not receive many messages. This way, we are taking advantage of the only message that even static controls cannot avoid: painting.

Features

I added 12/24 hour switch, seconds display on/off switch and small/medium/large size control. I also added AutoStart, OnTop, and window placement persistence.

Screens

Medium size setting on top of the silver theme:

The small setting is ideal for a clock that is always on screen.

This is how BigClock looks like on my development machine, in the upper right corner.

BigClock on large setting with the setup/config dialog:

Points of Interest

The code snippet for creating transparent dialogs is as follows:

// These defines are not in W32 SDKs
#define WS_EX_LAYERED     0x00080000
#define LWA_COLORKEY     1     // Use a color as the transparency color.

// Into the global space or class space insert:

//  Function pointer for the layering API is in User32.dll
typedef BOOL (WINAPI *lpfnSetLayeredWindowAttributes)
            (HWND hWnd, COLORREF cr, BYTE bAlpha, DWORD dwFlags);

lpfnSetLayeredWindowAttributes g_pSetLayeredWindowAttributes = NULL;


HMODULE hUser32 = GetModuleHandle(_T("USER32.DLL"));
    g_pSetLayeredWindowAttributes = (lpfnSetLayeredWindowAttributes)
                        GetProcAddress(hUser32, "SetLayeredWindowAttributes");

// Into the init dialog insert:

    // Set layered style for the dialog
    SetWindowLong(m_hWnd, GWL_EXSTYLE, 
        GetWindowLong(m_hWnd, GWL_EXSTYLE) | WS_EX_LAYERED);

   if(g_pSetLayeredWindowAttributes)
        {
        // Use green (0,255,0) as transparency color
        g_pSetLayeredWindowAttributes(m_hWnd, RGB(0, 255, 0), 0, LWA_COLORKEY);
        }
// After this initialization, anything painted in green will be transparent 

History

• 20th January, 2008: Initial version, added taskbar hiding