I have this strange issue when using Gdiplus in my C++ Windows app. I put a picture into the main window and it stays there. However when I load a file into my program the Gdi+ graphics are wiped when I move the main window outside the screen edge. I put the image in an "img" directory in the project solution directory and load it from WM_PAINT sub function. What is strange is at first the graphics stay there at first but it gets corrupted right after loading a file. This is very specific but strange.
// OpenFileTest1.cpp : Defines the entry point for the application.
//
#include "framework.h"
#include "OpenFileTest1.h"
#define _WIN32_DCOM
#include <Commdlg.h>
#include <comdef.h>
#include <Wbemidl.h>
#include <gdiplus.h>
#include <commctrl.h>
#pragma comment (lib,"gdiplus.lib")
#pragma comment(lib, "wbemuuid.lib")
#pragma comment(lib, "comctl32.lib")
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")
using namespace Gdiplus;
#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;
HWND loadButton;
HWND labelText1;
BOOL initialFileOpen = true;
HANDLE hFile;
OPENFILENAME ofn;
wchar_t szFileName[MAX_PATH] = L"";
DWORD dwFileSize;
BYTE* loadedFilePointer;
// Forward declarations of functions included in this code module:
ATOM MyRegisterClass(HINSTANCE hInstance);
BOOL InitInstance(HINSTANCE, int);
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM);
void openFile();
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.
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
// Initialize global strings
LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
LoadStringW(hInstance, IDC_OPENFILETEST1, szWindowClass, MAX_LOADSTRING);
MyRegisterClass(hInstance);
// Perform application initialization:
if (!InitInstance (hInstance, nCmdShow))
{
return FALSE;
}
HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_OPENFILETEST1));
MSG msg;
// Main message loop:
while (GetMessage(&msg, nullptr, 0, 0))
{
if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
GdiplusShutdown(gdiplusToken);
return (int) msg.wParam;
}
//
// FUNCTION: MyRegisterClass()
//
// PURPOSE: Registers the window class.
//
ATOM MyRegisterClass(HINSTANCE hInstance)
{
WNDCLASSEXW wcex;
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_OPENFILETEST1));
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = MAKEINTRESOURCEW(IDC_OPENFILETEST1);
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));
return RegisterClassExW(&wcex);
}
//
// FUNCTION: InitInstance(HINSTANCE, int)
//
// PURPOSE: Saves instance handle and creates main window
//
// COMMENTS:
//
// In this function, we save the instance handle in a global variable and
// create and display the main program window.
//
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hInst = hInstance; // Store instance handle in our global variable
hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);
InitCommonControls();
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
return TRUE;
}
//
// FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
//
// PURPOSE: Processes messages for the main window.
//
// WM_COMMAND - process the application menu
// WM_PAINT - Paint the main window
// WM_DESTROY - post a quit message and return
//
//
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_CREATE:
loadButton = CreateWindowW(L"Button", L"Load file", WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON | BS_MULTILINE | WS_TABSTOP, 10, 30, 100, 50, hWnd, (HMENU)LOADBUTTON, NULL, NULL);
labelText1 = CreateWindowW(L"Static", L"Click Load button", WS_VISIBLE | WS_CHILD | WS_BORDER, 10, 100, 390, 24, hWnd, NULL, NULL, NULL);
break;
case WM_COMMAND:
{
int wmId = LOWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case IDM_ABOUT:
DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
break;
case IDM_EXIT:
DestroyWindow(hWnd);
break;
case LOADBUTTON:
openFile();
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
}
break;
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc here...
Graphics graphics(hdc);
Image image(L"img\\sample1.png");
// Draw the original source image.
//graphics.DrawImage(&image, 10, 10);
// Create a Rect object that specifies the destination of the image.
Rect destRect(0, 0, 600, 450);
// Draw the rectangle that bounds the image.
//graphics.DrawRectangle(&pen, destRect);
// Draw the image.
graphics.DrawImage(&image, destRect);
EndPaint(hWnd, &ps);
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
// Message handler for about box.
INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
UNREFERENCED_PARAMETER(lParam);
switch (message)
{
case WM_INITDIALOG:
return (INT_PTR)TRUE;
case WM_COMMAND:
if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
{
EndDialog(hDlg, LOWORD(wParam));
return (INT_PTR)TRUE;
}
break;
}
return (INT_PTR)FALSE;
}
void openFile()
{
ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(OPENFILENAME);
ofn.hwndOwner = hWnd;
ofn.lpstrFilter = L"All Files (*.*)\0*.*\0";
ofn.lpstrFile = szFileName;
ofn.nMaxFile = MAX_PATH;
ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY;
if (GetOpenFileNameW(&ofn))
{
hFile = CreateFileW(szFileName, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL);
if (hFile != INVALID_HANDLE_VALUE)
{
dwFileSize = GetFileSize(hFile, NULL);
if (dwFileSize != 0xFFFFFFFF)
{
if (initialFileOpen)
{
initialFileOpen = false;
}
else
{
delete[] loadedFilePointer;
}
loadedFilePointer = new BYTE[dwFileSize];
DWORD NoBytesReadToFile;
if (ReadFile(hFile, loadedFilePointer, dwFileSize, &NoBytesReadToFile, NULL) == false)
{
MessageBoxW(hWnd, _T("Error: cannot read file."), _T("Error reading file"), MB_OK | MB_ICONERROR);
}
SetWindowTextW(labelText1, szFileName);
}
}
CloseHandle(hFile);
}
}
I also put a button handle inside "Resource.h"
#define LOADBUTTON 1501
Anyone knows what is happening? What could the possible reason be here?
I figured it out: the image location in the code was relative and Windows open file dialog changes current directory depending on where you load a file from so the solution is to make the program image file location constant:
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code that uses hdc here...
Graphics graphics(hdc);
wchar_t exePath[MAX_PATH];
GetModuleFileNameW(NULL,exePath,MAX_PATH);
wchar_t imgPath[20] = L"\\img\\sample1.png";
wchar_t *exeNamePtr = wcsrchr(exePath, L'\\');
wcsncpy_s(exeNamePtr,17,imgPath,16);
Image image(exePath);
// Draw the original source image.
//graphics.DrawImage(&image, 10, 10);
// Create a Rect object that specifies the destination of the image.
Rect destRect(0, 0, 600, 450);
// Draw the rectangle that bounds the image.
//graphics.DrawRectangle(&pen, destRect);
// Draw the image.
graphics.DrawImage(&image, destRect);
EndPaint(hWnd, &ps);
}
break;