iczelion tut26

Tutorial 26: Splash Screen

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Now that we know how to use a bitmap, we can progress to a more creative use of it. Splash screen. Download the example.

Theory

A splash screen is a window that has no title bar, no system menu box, no border that displays a bitmap for a while and then disappears automatically. It's usually used during program startup, to display the program's logo or to distract the user's attention while the program does some lengthy initialization. We will implement a splash screen in this tutorial.
The first step is to include the bitmap in the resource file. However, if you think of it,  it's a waste of precious memory to load a bitmap that will be used only once and keep it in memory till the program is closed. A better solution is to create a *resource* DLL which contains the bitmap and has the sole purpose of displaying the splash screen. This way, you can load the DLL when you want to display the splash screen and unload it when it's not necessary anymore. So we will have two modules: the main program and the splash DLL. We will put the bitmap into the DLL's resource.
The general scheme is as follows:

1. Put the bitmap into the DLL as a bitmap resource
2. The main program calls LoadLibrary to load the dll into memory
3. The DLL entrypoint function of the DLL is called. It will create a timer and set the length of time that the splash screen will be displayed. Next it  will register and create a window without caption and border and display the bitmap in the client area.
4. When the specified length of time elapsed, the splash screen is removed from the screen and the control is returned to the main program
5. The main program calls FreeLibrary to unload the DLL from memory and then goes on with whatever task it is supposed to do.

We will examine the mechanisms in detail.

Load/Unload DLL

You can dynamically load a DLL with LoadLibrary function which has the following syntax:

LoadLibrary  proto lpDLLName:DWORD

It takes only one parameter: the address of the name of the DLL you want to load into memory. If the call is successful, it returns the module handle of the DLL else it returns NULL.
To unload a DLL, call FreeLibrary:

FreeLibrary  proto  hLib:DWORD

It takes one parameter: the module handle of the DLL you want to unload. Normally, you got that handle from LoadLibrary

How to use a timer

First, you must create a timer first with SetTimer:

SetTimer  proto  hWnd:DWORD, TimerID:DWORD, uElapse:DWORD, lpTimerFunc:DWORD

hWnd is the handle of a window that will receive the timer notification message. This parameter can be NULL to specify that there is no window that's associated with the timer.
TimerID is a user-defined value that is used as the ID of the timer.
uElapse is the time-out value in milliseconds.
lpTimerFunc is the address of a function that will process the timer notification messages. If you pass NULL, the timer messages will be sent to the window specified by hWnd parameter.

SetTimer returns the ID of the timer if successful. Otherwise it returns NULL. So it's best not to use the timer ID of 0.

You can create a timer in two ways:

• If you have a window and you want the timer notification messages to go to that window, you must pass all four parameters to SetTimer (the lpTimerFunc must be NULL)
• If you don't have a window or you don't want to process the timer messages in the window procedure, you must pass NULL to the function in place of a window handle. You must also specify the address of the timer function that will process the timer messages.

We will use the first approach in this example.
When the time-out period elapses, WM_TIMER message is sent to the window that is associated with the timer. For example, if you specify uElapse of 1000, your window will receive WM_TIMER every second.
When you don't need the timer anymore, destroy it with KillTimer:

KillTimer  proto  hWnd:DWORD, TimerID:DWORD

Example:

;-----------------------------------------------------------------------
;                         The main program
;-----------------------------------------------------------------------
.386
.model flat,stdcall
option casemap:none
include masm32includewindows.inc
include masm32includeuser32.inc
include masm32includekernel32.inc
includelib masm32libuser32.lib
includelib masm32libkernel32.lib

WinMain proto :DWORD,:DWORD,:DWORD,:DWORD

.data
ClassName db "SplashDemoWinClass",0
AppName  db "Splash Screen Example",0
Libname db "splash.dll",0

.data?
hInstance HINSTANCE ?
CommandLine LPSTR ?
.code
start:
 invoke LoadLibrary,addr Libname
 .if eax!=NULL
    invoke FreeLibrary,eax
 .endif
 invoke GetModuleHandle, NULL
 mov    hInstance,eax
 invoke GetCommandLine
 mov    CommandLine,eax
 invoke WinMain, hInstance,NULL,CommandLine, SW_SHOWDEFAULT
 invoke ExitProcess,eax

WinMain proc hInst:HINSTANCE,hPrevInst:HINSTANCE,CmdLine:LPSTR,CmdShow:DWORD
 LOCAL wc:WNDCLASSEX
 LOCAL msg:MSG
 LOCAL hwnd:HWND
 mov   wc.cbSize,SIZEOF WNDCLASSEX
 mov   wc.style, CS_HREDRAW or CS_VREDRAW
 mov   wc.lpfnWndProc, OFFSET WndProc
 mov   wc.cbClsExtra,NULL
 mov   wc.cbWndExtra,NULL
 push  hInstance
 pop   wc.hInstance
 mov   wc.hbrBackground,COLOR_WINDOW+1
 mov   wc.lpszMenuName,NULL
 mov   wc.lpszClassName,OFFSET ClassName
 invoke LoadIcon,NULL,IDI_APPLICATION
 mov   wc.hIcon,eax
 mov   wc.hIconSm,eax
 invoke LoadCursor,NULL,IDC_ARROW
 mov   wc.hCursor,eax
 invoke RegisterClassEx, addr wc
 INVOKE CreateWindowEx,NULL,ADDR ClassName,ADDR AppName,
           WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,
           CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,NULL,NULL,
           hInst,NULL
 mov   hwnd,eax
 invoke ShowWindow, hwnd,SW_SHOWNORMAL
 invoke UpdateWindow, hwnd
 .while TRUE
  invoke GetMessage, ADDR msg,NULL,0,0
  .break .if (!eax)
  invoke TranslateMessage, ADDR msg
  invoke DispatchMessage, ADDR msg
 .endw
 mov     eax,msg.wParam
 ret
WinMain endp

WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
 .IF uMsg==WM_DESTROY
  invoke PostQuitMessage,NULL
 .ELSE
  invoke DefWindowProc,hWnd,uMsg,wParam,lParam
  ret
 .ENDIF
 xor eax,eax
 ret
WndProc endp
end start

;--------------------------------------------------------------------
;                         The Bitmap DLL
;--------------------------------------------------------------------
.386
.model flat, stdcall
include masm32includewindows.inc
include masm32includeuser32.inc
include masm32includekernel32.inc
include masm32includegdi32.inc
includelib masm32libuser32.lib
includelib masm32libkernel32.lib
includelib masm32libgdi32.lib
.data
BitmapName db "MySplashBMP",0
ClassName db "SplashWndClass",0
hBitMap dd 0
TimerID dd 0

.data
hInstance dd ?

.code

DllEntry proc hInst:DWORD, reason:DWORD, reserved1:DWORD
   .if reason==DLL_PROCESS_ATTACH  ; When the dll is loaded
      push hInst
      pop hInstance
      call ShowBitMap
   .endif
   mov eax,TRUE
   ret
DllEntry Endp
ShowBitMap proc
        LOCAL wc:WNDCLASSEX
        LOCAL msg:MSG
        LOCAL hwnd:HWND
        mov   wc.cbSize,SIZEOF WNDCLASSEX
        mov   wc.style, CS_HREDRAW or CS_VREDRAW
        mov   wc.lpfnWndProc, OFFSET WndProc
        mov   wc.cbClsExtra,NULL
        mov   wc.cbWndExtra,NULL
        push  hInstance
        pop   wc.hInstance
        mov   wc.hbrBackground,COLOR_WINDOW+1
        mov   wc.lpszMenuName,NULL
        mov   wc.lpszClassName,OFFSET ClassName
        invoke LoadIcon,NULL,IDI_APPLICATION
        mov   wc.hIcon,eax
        mov   wc.hIconSm,0
        invoke LoadCursor,NULL,IDC_ARROW
        mov   wc.hCursor,eax
        invoke RegisterClassEx, addr wc
        INVOKE CreateWindowEx,NULL,ADDR ClassName,NULL,
           WS_POPUP,CW_USEDEFAULT,
           CW_USEDEFAULT,250,250,NULL,NULL,
           hInstance,NULL
        mov   hwnd,eax
        INVOKE ShowWindow, hwnd,SW_SHOWNORMAL
        .WHILE TRUE
                INVOKE GetMessage, ADDR msg,NULL,0,0
                .BREAK .IF (!eax)
                INVOKE TranslateMessage, ADDR msg
                INVOKE DispatchMessage, ADDR msg
        .ENDW
        mov     eax,msg.wParam
        ret
ShowBitMap endp
WndProc proc hWnd:DWORD,uMsg:DWORD,wParam:DWORD,lParam:DWORD
        LOCAL ps:PAINTSTRUCT
        LOCAL hdc:HDC
        LOCAL hMemoryDC:HDC
        LOCAL hOldBmp:DWORD
        LOCAL bitmap:BITMAP
        LOCAL DlgHeight:DWORD
        LOCAL DlgWidth:DWORD
        LOCAL DlgRect:RECT
        LOCAL DesktopRect:RECT

        .if uMsg==WM_DESTROY
                .if hBitMap!=0
                        invoke DeleteObject,hBitMap
                .endif
                invoke PostQuitMessage,NULL
        .elseif uMsg==WM_CREATE
                invoke GetWindowRect,hWnd,addr DlgRect
                invoke GetDesktopWindow
                mov ecx,eax
                invoke GetWindowRect,ecx,addr DesktopRect
                push  0
                mov  eax,DlgRect.bottom
                sub  eax,DlgRect.top
                mov  DlgHeight,eax
                push eax
                mov  eax,DlgRect.right
                sub  eax,DlgRect.left
                mov  DlgWidth,eax
                push eax
                mov  eax,DesktopRect.bottom
                sub  eax,DlgHeight
                shr  eax,1
                push eax
                mov  eax,DesktopRect.right
                sub  eax,DlgWidth
                shr  eax,1
                push eax
                push hWnd
                call MoveWindow
                invoke LoadBitmap,hInstance,addr BitmapName
                mov hBitMap,eax
                invoke SetTimer,hWnd,1,2000,NULL
                mov TimerID,eax
        .elseif uMsg==WM_TIMER
                invoke SendMessage,hWnd,WM_LBUTTONDOWN,NULL,NULL
                invoke KillTimer,hWnd,TimerID
        .elseif uMsg==WM_PAINT
                invoke BeginPaint,hWnd,addr ps
                mov hdc,eax
                invoke CreateCompatibleDC,hdc
                mov hMemoryDC,eax
                invoke SelectObject,eax,hBitMap
                mov hOldBmp,eax
                invoke GetObject,hBitMap,sizeof BITMAP,addr bitmap
                invoke StretchBlt,hdc,0,0,250,250,
                       hMemoryDC,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY
                invoke SelectObject,hMemoryDC,hOldBmp
                invoke DeleteDC,hMemoryDC
                invoke EndPaint,hWnd,addr ps
        .elseif uMsg==WM_LBUTTONDOWN
                invoke DestroyWindow,hWnd
        .else
                invoke DefWindowProc,hWnd,uMsg,wParam,lParam
                ret
        .endif
        xor eax,eax
        ret
WndProc endp

End DllEntry

Analysis:

We will examine the code in the main program first.

 invoke LoadLibrary,addr Libname
 .if eax!=NULL
    invoke FreeLibrary,eax
 .endif

We call LoadLibrary to load the DLL named "splash.dll". And after that, unload it from memory with FreeLibrary. LoadLibrary will not return until the DLL is finished with its initialization.
That's all the main program does. The interesting part is in the DLL.

   .if reason==DLL_PROCESS_ATTACH  ; When the dll is loaded
      push hInst
      pop hInstance
      call ShowBitMap

When the DLL is loaded, Windows calls its entrypoint function with DLL_PROCESS_ATTACH flag. We take this opportunity to display the splash screen. First we store the instance handle of the DLL for future use. Then call a function named ShowBitMap to do the real job. ShowBitMap registers a window class, creates a window and enters the message loop as usual. The interesting part is in the CreateWindowEx call:

        INVOKE CreateWindowEx,NULL,ADDR ClassName,NULL,
           WS_POPUP,CW_USEDEFAULT,
           CW_USEDEFAULT,250,250,NULL,NULL,
           hInstance,NULL

Note that the window style is only WS_POPUP which will make the window borderless and without caption. We also limit the width and height of the window to 250x250 pixels.
Now when the window is created, in WM_CREATE message handler we move the window to the center of the screen with the following code.

                invoke GetWindowRect,hWnd,addr DlgRect
                invoke GetDesktopWindow
                mov ecx,eax
                invoke GetWindowRect,ecx,addr DesktopRect
                push  0
                mov  eax,DlgRect.bottom
                sub  eax,DlgRect.top
                mov  DlgHeight,eax
                push eax
                mov  eax,DlgRect.right
                sub  eax,DlgRect.left
                mov  DlgWidth,eax
                push eax
                mov  eax,DesktopRect.bottom
                sub  eax,DlgHeight
                shr  eax,1
                push eax
                mov  eax,DesktopRect.right
                sub  eax,DlgWidth
                shr  eax,1
                push eax
                push hWnd
                call MoveWindow

It retrieves the dimensions of the desktop and the window then calculates the appropriate coordinate of the left upper corner of the window to make it center.

                invoke LoadBitmap,hInstance,addr BitmapName
                mov hBitMap,eax
                invoke SetTimer,hWnd,1,2000,NULL
                mov TimerID,eax

Next it loads the bitmap from the resource with LoadBitmap and creates a timer with the timer ID of 1 and the time interval 2 seconds. The timer will send WM_TIMER messages to the window every 2 seconds.

        .elseif uMsg==WM_PAINT
                invoke BeginPaint,hWnd,addr ps
                mov hdc,eax
                invoke CreateCompatibleDC,hdc
                mov hMemoryDC,eax
                invoke SelectObject,eax,hBitMap
                mov hOldBmp,eax
                invoke GetObject,hBitMap,sizeof BITMAP,addr bitmap
                invoke StretchBlt,hdc,0,0,250,250,
                       hMemoryDC,0,0,bitmap.bmWidth,bitmap.bmHeight,SRCCOPY
                invoke SelectObject,hMemoryDC,hOldBmp
                invoke DeleteDC,hMemoryDC
                invoke EndPaint,hWnd,addr ps

When the window receives WM_PAINT message, it creates a memory DC, select the bitmap into the memory DC, obtain the size of the bitmap with GetObject and then put the bitmap on the window by calling StretchBlt which performs like BitBlt but it can stretch or compress the bitmap to the desired dimension. In this case, we want the bitmap to fit into the window so we use StretchBlt instead of BitBlt. We delete the memory DC after that.

        .elseif uMsg==WM_LBUTTONDOWN
                invoke DestroyWindow,hWnd

It would be frustrating to the user if he has to wait until the splash screen to disappear. We can provide the user with a choice. When he clicks on the splash screen, it will disappear. That's why we need to process WM_LBUTTONDOWN message in the DLL. Upon receiving this message, the window is destroyed by DestroyWindow call.

        .elseif uMsg==WM_TIMER
                invoke SendMessage,hWnd,WM_LBUTTONDOWN,NULL,NULL
                invoke KillTimer,hWnd,TimerID

If the user chooses to wait, the splash screen will disappear when the specified time has elapsed (in our example, it's 2 seconds). We can do this by processing WM_TIMER message. Upon receiving this message, we closes the window by sending WM_LBUTTONDOWN message to the window. This is to avoid code duplication. We don't have further use for the timer so we destroy it with KillTimer.
When the window is closed, the DLL will return control to the main program.