Win32 C++: Using a openfilename and displaying a bitmap file - c++

Question

I'm new here, I'm more adapted in C# then in C++.
Therefore, I require the assistance of C++ experts for this dilemnia I am currently having.
What is listed down below is just the code snippet that i think is necessary to complete, nevertheless, i believe there are still more to be achieved.
#include "stdafx.h"
#include "winmain.h"
#include "Resource.h"
#include <stdio.h>
#include <CommDlg.h>
#include <windows.h>
OPENFILENAME ofn;
TCHAR szFile[260];
switch (message)
{
case WM_COMMAND:
wmId = LOWORD(wParam);
wmEvent = HIWORD(wParam);
// Parse the menu selections:
switch (wmId)
{
case ID_FILE_LOADBITMAP:
bBitmap = !bBitmap;
InvalidateRect(hWnd,0,TRUE);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
case WM_PAINT:
hdc = BeginPaint(hWnd, &ps);
// TODO: Add any drawing code here...
if(bBitmap)
{
ZeroMemory(&ofn, sizeof(ofn));
ofn.lStructSize = sizeof(ofn);
ofn.hwndOwner = hWnd;
ofn.lpstrFile = szFile;
//
// Set lpstrFile[0] to '\0' so that GetOpenFileName does not
// use the contents of szFile to initialize itself.
//
ofn.lpstrFile[0] = '\0';
ofn.nMaxFile = sizeof(szFile);
ofn.nFilterIndex = 1;
ofn.lpstrFileTitle = NULL;
ofn.nMaxFileTitle = 0;
ofn.lpstrInitialDir = NULL;
ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
// Display the Open dialog box.
if (GetOpenFileName(&ofn)==TRUE)
hf = CreateFile(ofn.lpstrFile, GENERIC_READ,
0, (LPSECURITY_ATTRIBUTES) NULL,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
(HANDLE) NULL);
LoadBitmap(__T("F-35C.bmp"), hdc);
EndPaint(hWnd, &ps);
break;
}
As you can see, as i click my case menu: LoadBitmap
It just loads the openfiledialog and choose the file that i want without showing in the Windows, that is all. What i actually want to do is to load the filepath into the LoadBitmap function instead of hardcoding it in the function ("F-35C.bmp).
I also do know that ofn.lpStrFile has the file path, but I am unable to load the Bitmap file despite replacing __T("F-35C.bmp") with ofn.lpStrFile.
As below shows the function of the LoadBitMap Function.
bool LoadBitmap(LPCWSTR szFileName, HDC hWinDC)
{
// Load the bitmap image file
HBITMAP hBitmap;
hBitmap = (HBITMAP)::LoadImage(NULL, szFileName, IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE);
// Verify that the image was loaded
if (hBitmap == NULL) {
::MessageBox(NULL, __T("LoadImage Failed"), __T("Error"), MB_OK);
return false;
}
// Create a device context that is compatible with the window
HDC hLocalDC;
hLocalDC = ::CreateCompatibleDC(hWinDC);
// Verify that the device context was created
if (hLocalDC == NULL) {
::MessageBox(NULL, __T("CreateCompatibleDC Failed"), __T("Error"), MB_OK);
return false;
}
// Get the bitmap's parameters and verify the get
BITMAP qBitmap;
int iReturn = GetObject(reinterpret_cast<HGDIOBJ>(hBitmap), sizeof(BITMAP),
reinterpret_cast<LPVOID>(&qBitmap));
if (!iReturn) {
::MessageBox(NULL, __T("GetObject Failed"), __T("Error"), MB_OK);
return false;
}
// Select the loaded bitmap into the device context
HBITMAP hOldBmp = (HBITMAP)::SelectObject(hLocalDC, hBitmap);
if (hOldBmp == NULL) {
::MessageBox(NULL, __T("SelectObject Failed"), __T("Error"), MB_OK);
return false;
}
// Blit the dc which holds the bitmap onto the window's dc
BOOL qRetBlit = ::BitBlt(hWinDC, 0, 0, qBitmap.bmWidth, qBitmap.bmHeight,
hLocalDC, 0, 0, SRCCOPY);
if (!qRetBlit) {
::MessageBox(NULL, __T("Blit Failed"), __T("Error"), MB_OK);
return false;
}
// Unitialize and deallocate resources
::SelectObject(hLocalDC, hOldBmp);
::DeleteDC(hLocalDC);
::DeleteObject(hBitmap);
return true;
}
To add on, I am using Microsoft Visual Studio 2010 Developer Version with Win32 Application ( Not Console ).

Answer 1

You've got your LoadBitmap() parameters backwards. This is from MSDN:
HBITMAP LoadBitmap(
__in HINSTANCE hInstance,
__in LPCTSTR lpBitmapName
);
I'm also fairly certain that you don't need to wrap your filename in __T() macro for function calls.

Answer 2

I see a problem in the fact that you are opening the file right after the GetOpenFileName call, the dwShareMode parameter in CreateFile is set to 0 ( no sharing is allowed ) and you do not close or use the obtained handle( hf ). This will result in the failure of the LoadImage call, because the file is still open with no sharing at the time of the call.
Solution: Either remove the CreateFile call, because it's useless in this code, or close the handle before calling LoadBitmap.

Answer 3

Do not do all of this inside WM_PAINT, which will be called many MANY times during the execution of your program.
Load the bitmap once, and keep the HBITMAP around. The painting code should then start with that HBITMAP.