// WhatColor.c
// Shows the position and color of the point under the cursor.
// To use, click on the window and drag the cursor around the screen.
// Dbl-click to close (or single-click on notification-area icon).

#include <windows.h>

#define SIZEX 92
#define SIZEY 42
#define POSX 0
#define POSY 0
#define COLOR_BACK RGB(0,0,0)
#define COLOR_FORE RGB(0,200,200)
#define ID_TASKBAR_ICON 1
#define MYWM_NOTIFYICON WM_USER

LRESULT CALLBACK windowProc (HWND hwnd, UINT msg, WPARAM wp, LPARAM lp)
{
static HDC hdcDisp;
static int x, y;
static COLORREF color;

switch (msg) {

case WM_CREATE:
hdcDisp = CreateDC ("DISPLAY", NULL, NULL, NULL);
break;

case WM_PAINT:
{
HDC hdc;
PAINTSTRUCT ps;
char txt[32];

hdc = BeginPaint (hwnd, &ps);
SetBkColor (hdc, COLOR_BACK);
SetTextColor (hdc, COLOR_FORE);
TextOut (hdc, 5, 5, txt, wsprintf (txt, "(%d, %d)", x, y));
TextOut (hdc, 5, 23, txt, wsprintf (txt, "%02x %02x %02x",
GetRValue (color), GetGValue (color), GetBValue (color)));
EndPaint (hwnd, &ps);
}
break;

case WM_LBUTTONDOWN:
SetCapture (hwnd);
SendMessage (hwnd, WM_MOUSEMOVE, wp, lp);
break;

case WM_MOUSEMOVE:
if (GetCapture() != hwnd) break;
// The extra stuff here is to make it work properly
// when the window is not positioned at 0,0.
x = POSX + (SHORT) LOWORD (lp);
y = POSY + (SHORT) HIWORD (lp);
color = GetPixel (hdcDisp, x, y);
InvalidateRect (hwnd, NULL, TRUE);
break;

case WM_LBUTTONUP:
ReleaseCapture();
break;

case MYWM_NOTIFYICON:
switch (wp) {
case ID_TASKBAR_ICON:
switch (lp) {
// Reacting to the button-down message seems to pass
// the button-up to the next icon (after closing this one)
// so instead, react to the button-up message.
case WM_LBUTTONUP:
PostMessage (hwnd, WM_DESTROY, 0, 0);
break;
}
break;
}
break;

case WM_LBUTTONDBLCLK:
case WM_DESTROY:
DeleteDC (hdcDisp);
PostQuitMessage (0);
break;

default:
return DefWindowProc (hwnd, msg, wp, lp);
}
return 0;
}

BOOL taskbarAddIcon (HWND hwnd, UINT id, HICON hicon)
{
NOTIFYICONDATA nid = { sizeof (NOTIFYICONDATA) };
nid.hWnd = hwnd;
nid.uID = id;
nid.uFlags = NIF_MESSAGE | NIF_ICON;
nid.hIcon = hicon;
nid.uCallbackMessage = MYWM_NOTIFYICON;
return Shell_NotifyIcon (NIM_ADD, &nid);
}

BOOL taskbarDeleteIcon (HWND hwnd, UINT id)
{
NOTIFYICONDATA nid = { sizeof (NOTIFYICONDATA) };
nid.hWnd = hwnd;
nid.uID = id;
return Shell_NotifyIcon (NIM_DELETE, &nid);
}

void registerWindow (HINSTANCE hinst, char *appName,
HBRUSH hbrBackground, WNDPROC wndproc)
{
WNDCLASSEX wc = { sizeof (wc) };
wc.style = CS_DBLCLKS;
wc.lpfnWndProc = wndproc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hinst;
wc.hIcon = LoadIcon (hinst, appName);
wc.hCursor = LoadCursor (NULL, IDC_ARROW);
wc.hbrBackground = hbrBackground;
wc.lpszMenuName = NULL;
wc.lpszClassName = appName;
wc.hIconSm = LoadIcon (hinst, appName);
RegisterClassEx (&wc);
}

int WINAPI WinMain (HINSTANCE hinst, HINSTANCE unused, PSTR cmd, int show)
{
char *appName = "WhatColor";
MSG msg;
HWND hwnd;
HBRUSH hbrBackground;
HICON hIcon;

hbrBackground = (HBRUSH) CreateSolidBrush (COLOR_BACK);
registerWindow (hinst, appName, hbrBackground, windowProc);

// Create invisible parent to keep the actual window out of the taskbar.
hwnd = CreateWindow (appName, 0, 0, 0, 0, 0, 0, 0, 0, hinst, 0);
hwnd = CreateWindow (appName, appName, WS_POPUP|WS_VISIBLE,
POSX, POSY, SIZEX, SIZEY, hwnd, // The invisible parent
0, hinst, 0);

hIcon = (HICON) LoadImage (hinst, appName, IMAGE_ICON,
16, 16, LR_DEFAULTCOLOR);
taskbarAddIcon (hwnd, ID_TASKBAR_ICON, hIcon);
DestroyIcon (hIcon);

while (GetMessage (&msg, 0, 0, 0))
DispatchMessage (&msg);

taskbarDeleteIcon (hwnd, ID_TASKBAR_ICON);
DeleteObject (hbrBackground);
return msg.wParam;
}