Semi-transparent overlay to show user that window is blocked

overlay.cpp

#include <windows.h>
#include <hbapi.h>
#include <vector>
#include <map>
#include <cstdlib>

typedef std::vector<HWND> HWND_ARRAY;
std::map<HWND, HWND_ARRAY*> arrOverlays;
std::map<HWND, HBRUSH> overlaysBrushes;

HWND WIN32_CreateOverlay(HINSTANCE hInstance, HWND hwndParent, BYTE cRed, BYTE cGreen, BYTE cBlue, BYTE cAlpha);
void WIN32_VanishOverlay(HWND hWndParent, BOOL isShow);
void WIN32_UpdateOverlay(HWND hWndParent);

static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
static void MakeWindowTransparent(HWND hWnd, BYTE level);
static void SetBackgroundColor(HWND hWnd, BYTE red, BYTE green, BYTE blue);
static RECT GetWorkingArea(HWND hwnd);
static void AdjustParentCords(HWND hWnd, HWND hwndParent);

HB_FUNC( OVERLAYCREATE ) // hWnd -> pDisp
{
   HINSTANCE hInstance = GetModuleHandle(NULL);
   HWND hWnd = (HWND) hb_parnl( 1 );
   BYTE colRed = (BYTE) hb_parni( 2 );
   BYTE colGreen = (BYTE) hb_parni( 3 );
   BYTE colBlue = (BYTE) hb_parni( 4 );
   BYTE alpha = (BYTE) hb_parni( 5 );
   HWND hOverlay = WIN32_CreateOverlay(hInstance, hWnd, colRed, colGreen, colBlue, alpha);

   if (!arrOverlays.count(hWnd)) arrOverlays[hWnd] = new HWND_ARRAY();
   arrOverlays[hWnd]->push_back(hOverlay);
}

HB_FUNC( OVERLAYCLOSE ) 
{
   HWND hWndParent = (HWND) hb_parnl( 1 );

   if (!arrOverlays.count(hWndParent)) return;
   HWND_ARRAY *array = arrOverlays[hWndParent];
   for(std::vector<int>::size_type i = 0; i != array->size(); i++) {
	   HWND hWnd = array->at(i);
	   DestroyWindow( hWnd );
	   if (overlaysBrushes.count(hWnd) > 0) {
		   HBRUSH hBrush = overlaysBrushes[hWnd];
		   DeleteObject(hBrush);
	   }
   }
   array->clear();
   delete arrOverlays[hWndParent];
   arrOverlays.erase(hWndParent);
}
  
HB_FUNC ( OVERLAYWNDPROC)
{
	HWND hWnd = (HWND) hb_parnl( 1 );
	long message = hb_parnl( 2 );
	long wParam = hb_parnl( 3 );
    long lParam = hb_parnl( 4 );

	switch (message) {
		case WM_MOVE:
		{
			WIN32_UpdateOverlay(hWnd);								
		}
		case WM_SIZE:
		{
			WIN32_UpdateOverlay(hWnd);	
		}		
	}
}

HB_FUNC( OVERLAYUPDATE ) 
{
   HWND hWndParent = (HWND) hb_parnl( 1 );
   WIN32_UpdateOverlay(hWndParent);
}

HB_FUNC( OVERLAYVANISH)
{
   HWND hWndParent = (HWND) hb_parnl( 1 );
   BOOL isShow = hb_parl( 2 );
   WIN32_VanishOverlay(hWndParent, isShow);
}

void WIN32_UpdateOverlay(HWND hWndParent) {
   if (!arrOverlays.count(hWndParent)) return;
   HWND_ARRAY *array = arrOverlays[hWndParent];
   for(std::vector<int>::size_type i = 0; i != array->size(); i++) {
	   AdjustParentCords( array->at(i), hWndParent );
   }
}

void WIN32_VanishOverlay(HWND hWndParent, BOOL isShow) {
   if (!arrOverlays.count(hWndParent)) return;
   HWND_ARRAY *array = arrOverlays[hWndParent];
   for(std::vector<int>::size_type i = 0; i != array->size(); i++) {
	   ShowWindow(array->at(i), isShow ? SW_SHOW : SW_HIDE );
   }
}

HWND WIN32_CreateOverlay(HINSTANCE hInstance, HWND hwndParent, BYTE cRed, BYTE cGreen, BYTE cBlue, BYTE cAlpha)
{
	WNDCLASS wc;
	RECT lpRect;
	int X, Y, Width, Height;
	HWND hWnd;

	char class_name[255];
	sprintf(class_name, "OverlayWindow");
	//sprintf(class_name, "OverlayWindow_%d", rand());

	memset(&wc, 0, sizeof(WNDCLASS));
	wc.lpszClassName = class_name;
	wc.hInstance = hInstance;
	wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
	wc.hCursor = LoadCursor(0, IDC_ARROW);
	wc.lpfnWndProc = WndProc;

	lpRect = GetWorkingArea(hwndParent);

	X = lpRect.left;
	Y = lpRect.top;
	Width = lpRect.right - X;
	Height = lpRect.bottom - Y;

	RegisterClass(&wc);
	hWnd = CreateWindowEx(WS_EX_TOOLWINDOW /* | WS_EX_TOPMOST*/, wc.lpszClassName, TEXT(""),
		WS_VISIBLE, X, Y, Width, Height, NULL/*hwndParent*/, NULL, hInstance, NULL);

	//AdjustParentCords(hWnd, hwndParent);
	SetWindowLong(hWnd, GWL_STYLE, 0);	  	
	SetBackgroundColor(hWnd, cRed, cGreen, cBlue);
	// Окно будет всегда ренедерится поверх другого
	SetWindowLong(hWnd, GWL_HWNDPARENT, (long)hwndParent);
	// А вот это засунет окно внутри родительского
	//SetParent(hWnd, hwndParent);
	MakeWindowTransparent(hWnd, cAlpha);
	ShowWindow(hWnd, SW_SHOWNORMAL);
	// Отключаем окно оверлея, чтобы на него нельзя было установить фокус
	EnableWindow(hWnd, FALSE);	
	return hWnd;
}

static void AdjustParentCords(HWND hWnd, HWND hwndParent) {
	int X, Y, Width, Height;
	RECT lpRect;

	lpRect = GetWorkingArea(hwndParent);
	X = lpRect.left;
	Y = lpRect.top;
	Width = lpRect.right - X;
	Height = lpRect.bottom - Y;
	//HWND_NOTOPMOST
	SetWindowPos(hWnd, hwndParent, X, Y, Width, Height, SWP_NOZORDER);
}

static RECT GetWorkingArea(HWND hwnd)
{
	RECT rc;
	GetClientRect(hwnd, &rc);
	MapWindowPoints(hwnd, NULL, (POINT*)&rc, 2);
	//MapWindowPoints(hwnd, nullptr, reinterpret_cast<POINT*>(&rc), 2);
	return rc;
}

static void SetBackgroundColor(HWND hWnd, BYTE red, BYTE green, BYTE blue)
{
	HBRUSH brush = CreateSolidBrush(RGB(red, green, blue));
	overlaysBrushes[hWnd] = brush;

	HDC hdc = GetDC(hWnd);
	SetBkColor(hdc, RGB(255, 0, 0));
	ReleaseDC(hWnd, hdc);
	//SetClassLongPtr(hWnd, GCLP_HBRBACKGROUND, (LONG)brush);
}

static void MakeWindowTransparent(HWND hWnd, BYTE level)
{
	SetWindowLong(hWnd, GWL_EXSTYLE,
		GetWindowLong(hWnd, GWL_EXSTYLE) | WS_EX_LAYERED);
	SetLayeredWindowAttributes(hWnd, 0, level, LWA_ALPHA);
}

static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_PAINT:
		{	
		RECT rect;
    	PAINTSTRUCT ps; 
		HDC hdc;
		GetClientRect(hWnd, &rect);		
		hdc = BeginPaint(hWnd, &ps);
		FillRect(hdc, &rect, overlaysBrushes[hWnd]);
		EndPaint(hWnd, &ps); 		
		}
		break;
	case WM_CLOSE:
		PostQuitMessage(0);
		return 0;
	default:
		break;
	}
	return DefWindowProc(hWnd, message, wParam, lParam);
}