WIN32 Window is not repainting - c++

Question

I am coding win32 app, which takes print screen after print screen key pressed. It shows print screen, then after two mouse clicks cut rectangular area between them and copy it to clipboard. I have a problem repainting window. When I click, program calls code in WM_PAINT message but nothing changes on screen. I can see in debugger, that program enters if statement. It is my first win32 program, so I could misunderstood how it works. Please, be forgiving ;)
I am using Win 8.1 and VS 2015.
And here is the code:
// MyPrintScreen2.cpp : Defines the entry point for the application.
//
#include "stdafx.h"
#include "MyPrintScreen2.h"
#include <windowsx.h>
#define MAX_LOADSTRING 100
// Global Variables:
HINSTANCE hInst; // current instance
WCHAR szTitle[MAX_LOADSTRING]; // The title bar text
WCHAR szWindowClass[MAX_LOADSTRING]; // the main window class name
//HWND hWnd;
HBITMAP hBitmap=NULL, outBitmap=NULL;
// Forward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
ATOM hotkey;
bool clickedOnce=false;
bool clickedTwice=false;
int x1, y1, x2, y2,xa,ya;
bool Crop(RECT cropArea);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);
int resx = GetSystemMetrics(SM_CXSCREEN);
int resy = GetSystemMetrics(SM_CYSCREEN);
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
// TODO: Place code here.
// Initialize global strings
LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadStringW(hInstance, IDC_MYPRINTSCREEN2, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_MYPRINTSCREEN2));
MSG msg;
while (GetMessage(&msg, nullptr, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
return (int) msg.wParam;
}
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEXW wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = 0;//CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_MYPRINTSCREEN2));
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = NULL;// MAKEINTRESOURCEW(IDC_MYPRINTSCREEN2);
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassExW(&wcex);
}
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hInst = hInstance; // Store instance handle in our global variable
HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_MAXIMIZE | WS_POPUP,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);
if (!hWnd)
{
return FALSE;
}
//ShowWindow(hWnd, SW_MAXIMIZE);//nCmdShow);
//UpdateWindow(hWnd);
hotkey = GlobalAddAtom((LPWSTR)"PrtScr");
if (hotkey) RegisterHotKey(hWnd, hotkey, NULL, VK_SNAPSHOT);
return TRUE;
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_CREATE:
{
}
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc;
hdc = BeginPaint(hWnd, &ps);
HDC hMemDC = CreateCompatibleDC(hdc);
::SelectObject(hMemDC, hBitmap);
if(!clickedOnce) BitBlt(hdc, 0, 0, resx, resy, hMemDC, 0, 0, SRCCOPY);
Rectangle(hdc,200, 200, 300, 300); //rectangles only for testing with the easiest drawing
if (clickedOnce)
{
Rectangle(hdc, 300, 300, 400, 400);
}
::DeleteDC(hMemDC);
EndPaint(hWnd, &ps);
}
break;
case WM_DESTROY:
DeleteObject(hBitmap);
PostQuitMessage(0);
break;
case WM_HOTKEY:
if (wParam == hotkey)
{
int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
HWND hDesktopWnd = GetDesktopWindow();
HDC hDesktopDC = GetDC(hDesktopWnd);
HDC hCaptureDC = CreateCompatibleDC(hDesktopDC);
hBitmap = CreateCompatibleBitmap(hDesktopDC,
nScreenWidth, nScreenHeight);
SelectObject(hCaptureDC, hBitmap);
BitBlt(hCaptureDC, 0, 0, nScreenWidth, nScreenHeight,
hDesktopDC, 0, 0, SRCCOPY | CAPTUREBLT);
ReleaseDC(hDesktopWnd, hDesktopDC);
DeleteDC(hCaptureDC);
ShowWindow(hWnd, SW_MAXIMIZE);
UpdateWindow(hWnd);
}
break;
case WM_LBUTTONUP:
if (!clickedOnce)
{
x1= GET_X_LPARAM(lParam);
y1= GET_Y_LPARAM(lParam);
clickedOnce = true;
}
else
{
x2 = GET_X_LPARAM(lParam);
y2 = GET_Y_LPARAM(lParam);
clickedTwice = true;
RECT cropArea;
cropArea.top = y1;
cropArea.left = x1;
cropArea.bottom = y2;
cropArea.right = x2;
bool a = Crop(cropArea);
if (OpenClipboard(0))
{
EmptyClipboard();
HANDLE bitmapH = outBitmap;
SetClipboardData(CF_BITMAP, bitmapH);
CloseClipboard();
}
}
RECT rect;
GetClientRect(hWnd, &rect);
//UpdateWindow(hWnd);
RedrawWindow(hWnd,NULL,NULL, RDW_INTERNALPAINT);
break;
case WM_MOUSEMOVE:
if (clickedOnce)
{
xa = GET_X_LPARAM(lParam);
ya = GET_Y_LPARAM(lParam);
//RedrawWindow(hWnd, NULL, NULL, RDW_INTERNALPAINT);
}
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
bool Crop(RECT cropArea)
{
HDC hSrc = CreateCompatibleDC(NULL);
SelectObject(hSrc, hBitmap);
HDC hNew = CreateCompatibleDC(hSrc);
HBITMAP hBmp = CreateCompatibleBitmap(hSrc, cropArea.right - cropArea.left, cropArea.bottom - cropArea.top);
HBITMAP hOld = (HBITMAP)SelectObject(hNew, hBmp);
bool retVal = (BitBlt(hNew, 0, 0, cropArea.right - cropArea.left, cropArea.bottom - cropArea.top, hSrc, cropArea.left, cropArea.top, SRCCOPY)) ? true : false;
SelectObject(hNew, hOld);
DeleteDC(hSrc);
DeleteDC(hNew);
DeleteObject(outBitmap);
outBitmap = hBmp;
return retVal;
}