Question

I am following a tutorial. And I am trying to draw a .bmp file to the screen. It builds with no errors but no image appears. according to the book, I should see the image pop up in random places. Below is my code. The author doesnt recommend this technique for drawing objects, he is just doing for demostration. In case your wondering.

The image is a 25×25 square red square.

#include <windows.h>
#include <iostream>
#include <time.h>

using namespace std;

const string APPTITLE = "Game Loop";
HWND window;
HDC device;
bool gameover = false;


void DrawBitmap(char *filename, int x, int y)
{
 //load the bitmap image
 HBITMAP image = (HBITMAP)LoadImage(0,"c.bmp", IMAGE_BITMAP,0,0, LR_LOADFROMFILE);

 BITMAP bm;
 GetObject(image, sizeof(BITMAP), &bm);

 HDC hdcImage = CreateCompatibleDC(device);
 SelectObject(hdcImage,image);

 BitBlt(
  device,
  x,y,
  bm.bmWidth, bm.bmHeight,
  hdcImage,
  0,0,
  SRCCOPY);

 //deletec the device context and bitmap
 DeleteDC(hdcImage);
 DeleteObject((HBITMAP)image);
}

bool Game_Init()
{
 srand(time(NULL));
 return 1;
}

void Game_Run()
{
 if(gameover == true) return;

 RECT rect;
 GetClientRect(window, &rect);

 //draw bitmap at random location
 int x = rand() % (rect.right - rect.left);
 int y = rand() % (rect.bottom - rect.top);

 DrawBitmap("c.bmp",x,y);
}

void Game_End()
{
 //free the device
 ReleaseDC(window,device);
}

LRESULT CALLBACK WinProc(HWND hWnd, UINT message, WPARAM WParam, LPARAM lparam)
{
 switch(message)
 {
  case WM_DESTROY:
   gameover = true;
   PostQuitMessage(0);
  break;
 }

 return DefWindowProc(hWnd, message, WParam, lparam);
}

ATOM MyRegisterClass(HINSTANCE hInstance)
{
 //set the new windows properties

 WNDCLASSEX wc;

 wc.cbSize  = sizeof(WNDCLASSEX);
 wc.style  = CS_HREDRAW | CS_VREDRAW;
 wc.lpfnWndProc = (WNDPROC) WinProc;
 wc.cbClsExtra = 0;
 wc.cbWndExtra = 0;
 wc.hInstance = hInstance;
 wc.hIcon  = NULL;
 wc.hCursor  = LoadCursor(NULL, IDC_ARROW);
 wc.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
 wc.lpszMenuName = NULL;
 wc.lpszClassName= APPTITLE.c_str();
 wc.hIconSm  = NULL;

 return RegisterClassEx(&wc);
}

bool InitInstance(HINSTANCE hInstance, int nCmdShow)
{
 //create a  new window
 window = CreateWindow(
  APPTITLE.c_str(),
  APPTITLE.c_str(),
  WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT, CW_USEDEFAULT,
  640,480,
  NULL,
  NULL,
  hInstance,
  NULL);

 //was there an error creating the window ?
 if(window == 0) return 0;

 //display the window 
 ShowWindow(window, nCmdShow);
 UpdateWindow(window);
 device = GetDC(window);

 return 1;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
      LPSTR lpCmdLine, int nCmdShow)
{
 //declare variables
 MSG msg;

 //register the class
 MyRegisterClass(hInstance);

 //initialize application
 if(!InitInstance(hInstance, nCmdShow)) return 0;

 //initilize the game
 if(!Game_Init()) return 0;

 //main message loop
 while(!gameover)
 {
  if(PeekMessage(&msg,NULL, 0, 0,PM_REMOVE))
  {
   TranslateMessage(&msg);
   DispatchMessage(&msg);
  }
  Game_Run();
 }

 Game_End();

 return msg.wParam;
}

I am not sure if its because I have the image in the wrong location. but if that was the case. I figure it would throw a error. I have the image placed at the root of my source folder.

[EDIT]

Also , when I rebuild, I get a warning which might be a cause but here is the warning

1>------ Rebuild All started: Project: Begin, Configuration: Debug Win32 ------
1>Deleting intermediate and output files for project 'Begin', configuration 'Debug|Win32'
1>Compiling...
1>main.cpp
1>c:\users\numerical25\documents\visual studio 2008\projects\begin\begin\main.cpp(39) : warning C4244: 'argument' : conversion from 'time_t' to 'unsigned int', possible loss of data
1>Compiling manifest to resources...
1>Microsoft (R) Windows (R) Resource Compiler Version 6.1.6723.1
1>Copyright (C) Microsoft Corporation.  All rights reserved.
1>Linking...
1>LINK : C:\Users\numerical25\Documents\Visual Studio 2008\Projects\Begin\Debug\Begin.exe not found or not built by the last incremental link; performing full link
1>Embedding manifest...
1>Microsoft (R) Windows (R) Resource Compiler Version 6.1.6723.1
1>Copyright (C) Microsoft Corporation.  All rights reserved.
1>Build log was saved at "file://c:\Users\numerical25\Documents\Visual Studio 2008\Projects\Begin\Begin\Debug\BuildLog.htm"
1>Begin - 0 error(s), 1 warning(s)
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========

Answer 1

The code does work, you just forgot to put your c.bmp in the right location. Put it in the project output folder (i.e. bin/Debug) if you’re launching the program from Explorer or to the project folder if you’re lanching the program from Visual Studio.