Mouse-over (rollover) effect in a Windows GUI program

// show mouse-over (rollover) action on a label
// BCX created code modified for Pelles C and Dev C++
// (invalid conversions of lpfnOldProc solved by proper casting)

#include <windows.h>  // in turn includes winuser.h

#define ID_Form1 0
#define ID_Label1 1

static HINSTANCE BCX_hInstance;
static int     BCX_ScaleX;
static int     BCX_ScaleY;
static char    BCX_ClassName[2048];
static HWND    Form1;
static HWND    Label1;
static int     Focus;

#define Show(Window)  RedrawWindow(Window,0,0,0);ShowWindow(Window,SW_SHOW);

HWND    BCX_Form(char*,int=0,int=0,int=250,int=150,int=0,int=0);
HWND    BCX_Label(char*,HWND,int=0,int=0,int=0,int=0,int=0,int=0,int=0);
LRESULT Set_Color (int,int,int,int);

void    FormLoad (void);
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK LabelProc (HWND, UINT, WPARAM, LPARAM);


// standard main for windows GUI programs
int WINAPI WinMain(HINSTANCE hInst,HINSTANCE hPrev,LPSTR CmdLine,int CmdShow)
{
 WNDCLASS Wc;
 MSG      Msg;
 // *****************************
 strcpy(BCX_ClassName,"MouseOverLabel1");
 // ***************************************
 // Programmer has selected to use pixels
 // adjust scaling accordingly
 // ***************************************
 BCX_ScaleX       = 1;
 BCX_ScaleY       = 1;
 BCX_hInstance    =  hInst;
 // ******************************************************
 Wc.style         =  CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
 Wc.lpfnWndProc   =  WndProc;
 Wc.cbClsExtra    =  0;
 Wc.cbWndExtra    =  0;
 Wc.hInstance     =  hInst;
 Wc.hIcon         =  LoadIcon(NULL,IDI_WINLOGO);
 Wc.hCursor       =  LoadCursor(NULL,IDC_ARROW);
 Wc.hbrBackground =  (HBRUSH)(COLOR_BTNFACE+1);
 Wc.lpszMenuName  =  NULL;
 Wc.lpszClassName =  BCX_ClassName;
 RegisterClass(&Wc);

 FormLoad();
 while(GetMessage(&Msg,NULL,0,0))
 {
   HWND hActiveWindow = GetActiveWindow();
   if (!IsWindow(hActiveWindow) || !IsDialogMessage(hActiveWindow,&Msg))
   {
     TranslateMessage(&Msg);
     DispatchMessage(&Msg);
   }
 }
 return Msg.wParam;
}


// create the windows form
HWND BCX_Form(char *Caption, int X, int Y, int W, int H, int Style, int Exstyle)
{
  HWND  A;
  // assign default style
  if (!Style)
  {
    Style= WS_MINIMIZEBOX  |
    WS_SIZEBOX      |
    WS_CAPTION      |
    WS_MAXIMIZEBOX  |
    WS_POPUP        |
    WS_SYSMENU;
  }
  A = CreateWindowEx(Exstyle,BCX_ClassName,Caption,
    Style,
    X*BCX_ScaleX,
    Y*BCX_ScaleY,
    (4+W)*BCX_ScaleX,
    (12+H)*BCX_ScaleY,
    NULL,(HMENU)NULL,BCX_hInstance,NULL);
  SendMessage(A,(UINT)WM_SETFONT,(WPARAM)GetStockObject(DEFAULT_GUI_FONT),
    (LPARAM)MAKELPARAM(FALSE,0));
  return A;
}


// create a label
HWND BCX_Label
(char* Text,HWND hWnd,int id,int X,int Y,int W,int H,int Style,int Exstyle)
{
  HWND  A;
  // assign default style
  if (!Style)
  {
    Style=WS_CHILD | SS_NOTIFY | SS_LEFT | WS_VISIBLE;
  }
  A = CreateWindowEx(Exstyle,"static",Text,Style,X*BCX_ScaleX, Y*BCX_ScaleY, 
    W*BCX_ScaleX, H*BCX_ScaleY,hWnd,(HMENU)id,BCX_hInstance,NULL);
  SendMessage(A,(UINT)WM_SETFONT,(WPARAM)GetStockObject(DEFAULT_GUI_FONT),
    (LPARAM)MAKELPARAM(FALSE,0));
  if (W==0)
  {
    HDC  hdc=GetDC(A);
    SIZE  size;
    GetTextExtentPoint32(hdc,Text,strlen(Text),&size);
    ReleaseDC(A,hdc);
    MoveWindow(A,X*BCX_ScaleX,Y*BCX_ScaleY,size.cx,size.cy,TRUE);
  }
  return A;
}


LRESULT Set_Color (int TxtColr,int BkColr,int wParam,int lParam)
{
  static HBRUSH  ReUsableBrush;
  SetTextColor((HDC)wParam,TxtColr);
  if (BkColr==-1)
  {
    BkColr=GetClassLong(GetParent((HWND)lParam),GCL_HBRBACKGROUND);
    if (BkColr>31)
    { 
	    SetBkMode((HDC)wParam,TRANSPARENT); 
	    return BkColr; 
	  }
    else
      BkColr=GetSysColor(BkColr-1);
  }
  DeleteObject(ReUsableBrush);
  ReUsableBrush=CreateSolidBrush(BkColr);
  SetBkColor((HDC)wParam,BkColr);
  return (LRESULT)ReUsableBrush;
}


// details like corner coordinates, width, height ...
void FormLoad (void)
  {
    Form1=BCX_Form("Mouse-over Label ...",80,88,320,102);
    Label1=BCX_Label("Move the mouse over me!",Form1,ID_Label1,32,24,250,28);
    //  setup callback functions 
    SetProp(Label1,"oldproc",(HANDLE)GetWindowLong(Label1,GWL_WNDPROC));
    SetWindowLong(Label1,GWL_WNDPROC,(DWORD)LabelProc);
    Show(Form1);
  }


// standard windows message handler
LRESULT CALLBACK WndProc (HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
  while(1)
  {
  if (Msg==WM_MOUSEMOVE)
  {
    if (Focus)
    {
      Focus=FALSE;
      InvalidateRect(Label1,0,TRUE);
    }
    break;
  }
  if (Msg==WM_CTLCOLORSTATIC)
  {
    static int      cFG;
    memset(&cFG,0,sizeof(cFG));
    static int      cBG;
    memset(&cBG,0,sizeof(cBG));
    if ((HANDLE)lParam==Label1)
    {
      if (Focus)
      {
        cFG=RGB(0,0,0);       // black text
        cBG=RGB(255,255,0);   // label bg = yellow
      }
      else
      {
        cFG=RGB(255,255,255); // white text
        cBG=RGB(0,0,255);     // label bg = blue
      }
      if ((HWND)lParam==Label1 && Msg==WM_CTLCOLORSTATIC)
        return Set_Color(cFG,cBG,wParam,lParam);
    }
    break;
  }
  if (Msg==WM_CLOSE)
  {
    DestroyWindow(Form1);
    return 0;
  }
  break;
  }
  // clean up and exit program
  if (Msg==WM_DESTROY)
  {
    UnregisterClass(BCX_ClassName,BCX_hInstance);
    PostQuitMessage(0);
  }
  return DefWindowProc(hWnd,Msg,wParam,lParam);
}


// the label events
LRESULT CALLBACK LabelProc (HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
  static  FARPROC  lpfnOldProc;
  memset(&lpfnOldProc,0,sizeof(lpfnOldProc));
  static  LRESULT  lResult;
  memset(&lResult,0,sizeof(lResult));
  lpfnOldProc=(FARPROC)GetProp(hWnd,"oldproc");  // cast to FARPROC
  while(1)
  {
    if (Msg==WM_MOUSEMOVE)
    {
      if (!Focus)
      {
        Focus=TRUE;
        InvalidateRect(Label1,0,TRUE);
      }
      break;
    }
    // clean up
    if (Msg==WM_DESTROY)
    {
      SetWindowLong(hWnd,GWL_WNDPROC,(DWORD)GetProp(hWnd,"oldproc"));
      RemoveProp(hWnd,"oldproc");
      // cast to WNDPROC
      return CallWindowProc((WNDPROC)lpfnOldProc,hWnd,Msg,wParam,lParam);
    }
    break;
  }
  // cast to WNDPROC
  return CallWindowProc((WNDPROC)lpfnOldProc,hWnd,Msg,wParam,lParam);
}