"Lights off" effect of the main application window - c++

Question

How to make a "Lights off" effect for the main application window? I mean this:
lights on:
lights off:
UPDATE-1:
I made my own "lights-off" window implementation.
The algorithm is as follows:
Create a new hidden child window (darkened window)
Creating a screenshot of the main window
Fill the darkened window with black brush and copy onto it HDC the screenshot using AlphaBlend() function with a certain transparency value
Show the darkened window.
And it works great. But there is one drawback - when show and hide the darkened window then all child controls of the main window are painted in its color (darkened window color) for a short time:
This:
Here is description from .rc-file:
mainWindow DIALOGEX 0, 0, 309, 177
STYLE DS_SETFONT | DS_MODALFRAME | DS_FIXEDSYS | DS_CENTER | WS_MINIMIZEBOX | WS_POPUP | WS_CLIPCHILDREN | WS_CAPTION | WS_SYSMENU
CAPTION "Dialog"
FONT 8, "MS Shell Dlg", 400, 0, 0x1
BEGIN
DEFPUSHBUTTON "OK",IDOK,198,156,50,14,WS_CLIPSIBLINGS
PUSHBUTTON "Cancel",IDCANCEL,252,156,50,14,WS_CLIPSIBLINGS
CONTROL "",IDC_TAB1,"SysTabControl32",0x0,7,4,204,111,WS_CLIPSIBLINGS
PUSHBUTTON "Button1",IDC_BUTTON1,228,18,22,17,WS_CLIPSIBLINGS
PUSHBUTTON "Button2",IDC_BUTTON2,262,43,32,19,WS_CLIPSIBLINGS
EDITTEXT IDC_EDIT1,216,46,35,15,ES_AUTOHSCROLL | WS_CLIPSIBLINGS
LTEXT "Static",IDC_STATIC1,223,86,59,11,WS_CLIPSIBLINGS
LTEXT "Static",IDC_STATIC2,7,119,36,13,WS_CLIPSIBLINGS
CONTROL "Check1",IDC_CHECK1,"Button",BS_AUTOCHECKBOX | WS_CLIPSIBLINGS | WS_TABSTOP,45,121,56,8
CONTROL "Check2",IDC_CHECK2,"Button",BS_AUTOCHECKBOX | WS_CLIPSIBLINGS | WS_TABSTOP,110,119,36,13
CONTROL "Check3",IDC_CHECK3,"Button",BS_AUTOCHECKBOX | WS_CLIPSIBLINGS | WS_TABSTOP,127,137,44,11
PUSHBUTTON "Button3",IDC_BUTTON3,110,154,55,16,WS_CLIPSIBLINGS
EDITTEXT IDC_EDIT2,232,72,40,14,ES_AUTOHSCROLL|WS_CLIPSIBLINGS
CONTROL "",IDC_SLIDER1,"msctls_trackbar32",TBS_BOTH | TBS_NOTICKS | WS_TABSTOP | WS_CLIPSIBLINGS,220,106,69,15
CONTROL "Radio1",IDC_RADIO1,"Button",BS_AUTORADIOBUTTON|WS_CLIPSIBLINGS,21,136,38,10
CONTROL "",IDC_SPIN1,"msctls_updown32",UDS_ARROWKEYS|WS_CLIPSIBLINGS,100,137,11,14
PUSHBUTTON "Button4",IDC_BUTTON4,17,149,50,14,WS_CLIPSIBLINGS
CONTROL "Check4",IDC_CHECK4,"Button",BS_AUTOCHECKBOX | WS_TABSTOP | WS_CLIPSIBLINGS,203,131,35,11
END
And now question is - how to fix this?

Answer 1

I wrote for you the first approach mentioned by Remy Lebeau:
LightLayer.h
#pragma once
#include <Windows.h>
class LightLayer
{
public:
/**
* darkness [0-255]
* 0: light
* 255: dark
*/
LightLayer(HWND attachedWindow, int darkness = 180);
bool isValid() const;
void turnLightOn();
void turnLightOff();
void setDarkness(int darkness);
void onWindowPosChanged(LPARAM lParam);
void onShowWindow(WPARAM wParam);
private:
bool mValid;
bool mMustShow;
bool mWinPosChanged;
HWND mLayer;
HWND mAttachedWin;
WNDPROC mDefProc;
void setVisibility(bool visibility);
void updatePos();
static INT_PTR CALLBACK LightsLayerProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
};
LightLayer.cpp
#include "LightLayer.h"
LightLayer::LightLayer(HWND attachedWindow, int darkness)
{
mValid = false;
mMustShow = false;
mWinPosChanged = false;
mAttachedWin = NULL;
mLayer = CreateWindowEx(
WS_EX_LAYERED,
L"STATIC",
NULL,
WS_POPUP,
0, 0, 0, 0,
attachedWindow,
NULL, NULL, NULL);
if (mLayer)
{
mValid = true;
mAttachedWin = attachedWindow;
SetWindowLongPtr(mLayer, GWLP_USERDATA, (LONG_PTR) this);
mDefProc = (WNDPROC) SetWindowLongPtr(mLayer, GWLP_WNDPROC, (LONG_PTR) LightsLayerProc);
setDarkness(darkness);
}
}
bool LightLayer::isValid() const
{
return mValid;
}
void LightLayer::turnLightOn()
{
setVisibility(false);
}
void LightLayer::turnLightOff()
{
setVisibility(true);
}
void LightLayer::setDarkness(int darkness)
{
if(mValid)
SetLayeredWindowAttributes(mLayer, 0, darkness, LWA_ALPHA);
}
void LightLayer::setVisibility(bool visibility)
{
if (!mValid)
return;
mMustShow = visibility;
if (visibility)
updatePos();
ShowWindow(mLayer, visibility ? SW_SHOW : SW_HIDE);
SetFocus(mAttachedWin);
}
void LightLayer::updatePos()
{
if (!mValid)
return;
RECT rc;
GetClientRect(mAttachedWin, &rc);
MapWindowPoints(mAttachedWin, GetParent(mAttachedWin), (LPPOINT)&rc, 2);
SetWindowPos(mLayer, HWND_NOTOPMOST,
rc.left,
rc.top,
rc.right - rc.left,
rc.bottom - rc.top,
0);
OutputDebugStringA("\nupdatePos");
}
void LightLayer::onWindowPosChanged(LPARAM lParam)
{
if (!mValid)
return;
if (mMustShow)
{
updatePos();
mWinPosChanged = false;
}
else
mWinPosChanged = true;
}
void LightLayer::onShowWindow(WPARAM wParam)
{
setVisibility(wParam && mMustShow);
}
INT_PTR CALLBACK LightLayer::LightsLayerProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
LightLayer* caller = reinterpret_cast<LightLayer*>(GetWindowLongPtr(hWnd, GWLP_USERDATA));
switch (uMsg)
{
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
FillRect(hdc, &ps.rcPaint, GetSysColorBrush(COLOR_BACKGROUND));
EndPaint(hWnd, &ps);
}
break;
}
return caller->mDefProc(hWnd, uMsg, wParam, lParam);
}
And now add this to your dialog procedure:
LightLayer* lightLyr = nullptr;
INT_PTR CALLBACK DlgProc(HWND hDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_INITDIALOG:
{
lightLyr = new LightLayer(hDlg, 180);
// Check if it's valid (e.g. no errors upon window creation)
if (! lightLyr->isValid())
{
delete lightLyr;
lightLyr = nullptr;
}
}
break;
case WM_COMMAND:
{
switch (LOWORD(wParam))
{
case IDC_OFF:
{
if(lightLyr)
{
lightLyr->turnLightOff();
SendDlgItemMessage(hDlg, IDC_ON, BM_SETCHECK, BST_UNCHECKED, 0);
}
break;
}
case IDC_ON:
{
if(lightLyr)
{
lightLyr->turnLightOn();
SendDlgItemMessage(hDlg, IDC_OFF, BM_SETCHECK, BST_UNCHECKED, 0);
}
break;
}
}
break;
case WM_WINDOWPOSCHANGED:
if(lightLyr)
lightLyr->onWindowPosChanged(lParam);
break;
case WM_SHOWWINDOW:
if(lightLyr)
lightLyr->onShowWindow(wParam);
break;
case WM_DESTROY:
delete lightLyr;
break;
}
return 0;
}
And here's a showcase.