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POBackground changes after images are drawn on the screen
 

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  1. POBackground changes after images are drawn on the screen
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    <p>We are learning about windows raw touch events in class using Visual Studios 2012 in C++. I got my demo working and it does exactly what it is supposed to, which is drawing circles beneath your fingertips to detect that a touch event has been raised. But after a certain time has passed and if you are still pressing on the screen with the circles drawn the screen turns blue! The circles still show but they are blue as well with black contours and I can still move them around. I showed the professor and he can't seem to figure it out which is why I came here. Can anyone take a look at my code to let me know what seems to be the cause of it?</p> <pre><code>// GT_HelloWorldWin32.cpp // compile with: /D_UNICODE /DUNICODE /DWIN32 /D_WINDOWS /c #ifndef WINVER // Specifies that the minimum required platform is Windows 7. #define WINVER 0x0601 // Change this to the appropriate value to target other versions of Windows. #endif #ifndef _WIN32_WINNT // Specifies that the minimum required platform is Windows 7. #define _WIN32_WINNT 0x0601 // Change this to the appropriate value to target other versions of Windows. #endif #include &lt;windows.h&gt; // for windows touch #include &lt;windowsx.h&gt; // included for point conversion #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;tchar.h&gt; #include "wtypes.h" #include &lt;iostream&gt; using namespace std; // The main window class name. TCHAR szWindowClass[] = _T("win32app"); // The string that appears in the application's title bar. TCHAR szTitle[] = _T("Hello World!"); //Instancing the handler HINSTANCE hInst; LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); //Maximum ammount of touches allowed #define MAXPOINTS 10 // You will use this array to track touch points int points[MAXPOINTS][2]; // You will use this array to switch the color / track ids int idLookup[MAXPOINTS]; // You can make the touch points larger // by changing this radius value static int radius = 30; // There should be at least as many colors // as there can be touch points so that you // can have different colors for each point COLORREF colors[] = { RGB(153,255,51), RGB(153,0,0), RGB(0,153,0), RGB(255,255,0), RGB(255,51,204), RGB(0,0,0), RGB(0,153,0), RGB(153, 255, 255), RGB(153,153,255), RGB(0,51,153) }; int wmId, wmEvent, i, x, y, index; UINT cInputs; PTOUCHINPUT pInputs; POINT ptInput; // This function is used to return an index given an ID int GetContactIndex(int dwID){ for (int i=0; i &lt; MAXPOINTS; i++){ if (idLookup[i] == -1){ idLookup[i] = dwID; return i; }else{ if (idLookup[i] == dwID){ return i; } } } // Out of contacts return -1; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASSEX wcex; int width = 0, height = 0; // Screen resolution GetScreenResolution(width, height); wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 0; wcex.hInstance = hInstance; wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_APPLICATION)); wcex.hCursor = LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wcex.lpszMenuName = NULL; wcex.lpszClassName = szWindowClass; wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_APPLICATION)); if (!RegisterClassEx(&amp;wcex)) { MessageBox(NULL, _T("Call to RegisterClassEx failed!"), _T("Win32 Guided Tour"), NULL); return 1; } hInst = hInstance; // Store instance handle in our global variable // The parameters to CreateWindow explained: // szWindowClass: the name of the application // szTitle: the text that appears in the title bar // WS_OVERLAPPEDWINDOW: the type of window to create // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y) // 500, 100: initial size (width, length) // NULL: the parent of this window // NULL: this application does not have a menu bar // hInstance: the first parameter from WinMain // NULL: not used in this application HWND hWnd = CreateWindow( szWindowClass, szTitle, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 800, 600, NULL, NULL, hInstance, NULL ); if (!hWnd) { MessageBox(NULL, _T("Call to CreateWindow failed!"), _T("Win32 Guided Tour"), NULL); return 1; } // register the window for touch instead of gestures RegisterTouchWindow(hWnd, 0); // the following code initializes the points for (int i=0; i&lt; MAXPOINTS; i++){ points[i][0] = -1; points[i][1] = -1; idLookup[i] = -1; } ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); // Main message loop: MSG msg; while (GetMessage(&amp;msg, NULL, 0, 0)) { TranslateMessage(&amp;msg); DispatchMessage(&amp;msg); } return (int) msg.wParam; } // // FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM) // // PURPOSE: Processes touch messages for the main window. // // WM_TOUCH - handles WM_TOUCH messages in the application // WM_DESTROY - post a quit message and return // LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { // For double buffering static HDC memDC = 0; static HBITMAP hMemBmp = 0; HBITMAP hOldBmp = 0; //For drawing / fills PAINTSTRUCT ps; HDC hdc; switch (message) { case WM_TOUCH: //LOWORD(wParam) = number of touch points in this message //HIWORD(wParam) = reserved for future use //lParam = handle for use with GetTouchInputInfo cInputs = LOWORD(wParam); pInputs = new TOUCHINPUT[ cInputs ]; if(pInputs) { if( GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, pInputs, sizeof(TOUCHINPUT)) ) { for (int i=0; i &lt; static_cast&lt;INT&gt;(cInputs); i++) { TOUCHINPUT ti = pInputs[i]; index = GetContactIndex(ti.dwID); if(ti.dwID != 0 &amp;&amp; index &lt; MAXPOINTS ) { //get screen corrdinates of touch ptInput.x = TOUCH_COORD_TO_PIXEL(ti.x); ptInput.y = TOUCH_COORD_TO_PIXEL(ti.y); //get coordinates relative to the top left of the application window ScreenToClient(hWnd, &amp;ptInput); if(ti.dwFlags &amp; TOUCHEVENTF_UP) { points[index][0] = -1; points[index][1] = -1; } else { points[index][0] = ptInput.x; points[index][1] = ptInput.y; } } } } CloseTouchInputHandle((HTOUCHINPUT)lParam); delete [] pInputs; } InvalidateRect(hWnd, NULL, FALSE); break; case WM_PAINT: hdc = BeginPaint(hWnd, &amp;ps); RECT client; GetClientRect(hWnd, &amp;client); //START DOUBLE BUFFERING if (!memDC) { memDC = CreateCompatibleDC(hdc); } hMemBmp = CreateCompatibleBitmap(hdc, client.right, client.bottom); hOldBmp = (HBITMAP)SelectObject(memDC, hMemBmp); FillRect(memDC, &amp;client, CreateSolidBrush(RGB(255,255,255))); //Draw Touched Points for (i=0; i &lt; MAXPOINTS; i++) { SelectObject( memDC, CreateSolidBrush(colors[i])); x = points[i][0]; y = points[i][1]; if (x &gt;0 &amp;&amp; y&gt;0) { Ellipse(memDC, x - radius, y - radius, x + radius, y + radius); } } BitBlt(hdc, 0,0, client.right, client.bottom, memDC, 0,0, SRCCOPY); EndPaint(hWnd, &amp;ps); ReleaseDC(hWnd, hdc); //DeleteObject(hMemBmp); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } return 0; } </code></pre>
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    1. USManuel Mangual
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    1. This table or related slice is empty.
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      1. POBackground changes after images are drawn on the screen
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      1. VTUpMod
    1. COOne thing I notice - you should not call `ReleaseDC(hWnd, hdc)` after `EndPaint` and you should probably call `DeleteDC(memDC)` somewhere.
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      1. POBackground changes after images are drawn on the screen
      1. USRoger Rowland
    2. COso, just rearrange the order as in EndPaint then ReleaseDC(...)?
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      1. POBackground changes after images are drawn on the screen
      1. USManuel Mangual
    3. CONo, you should not call `ReleaseDC` at all ! That's one of the things that `EndPaint` will do for you.
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      1. POBackground changes after images are drawn on the screen
      1. USRoger Rowland
 

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