[beginner] How to control program using keyboard?

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mkng

Joined: 13 May 2012
Posts: 5

mkng 13 May 2012, 10:06

Hi. I'm begginer trying to learn assembler. I'm trying to modify the transparent window example to make it able to control everything by keyboard. I was trying to use something like this:

Code:

in    al,60h
cmp   al,0x50      ; scan code for down arrow
je   przyciskMniej

Code:

xor   ax,ax                         ; Get a key
int   16h                           ; Call interrupt service
cmp   al,13                         ; Enter?
je   przyciskMniej

but my program just crashes and I have no idea what's going on. These codes were taken from this forum. Can anobody help me please? Smile

Last edited by mkng on 13 May 2012, 13:45; edited 1 time in total

13 May 2012, 10:06

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19872
Location: In your JS exploiting you and your system

revolution 13 May 2012, 10:56

In Windows you can't use direct I/O because it is a protected OS.

You have to call some of the API functions like ReadFile.

13 May 2012, 10:56

mkng

Joined: 13 May 2012
Posts: 5

mkng 13 May 2012, 10:58

revolution wrote:

In Windows you can't use direct I/O because it is a protected OS.

You have to call some of the API functions like ReadFile.

Can you be more precise? How ReadFile could help me with keyboard?

13 May 2012, 10:58

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 19872
Location: In your JS exploiting you and your system

revolution 13 May 2012, 11:00

Get the STDIN handle and then use ReadFile to get the characters.

There are already example of code for this on this forum.

13 May 2012, 11:00

mkng

Joined: 13 May 2012
Posts: 5

mkng 13 May 2012, 11:34

Don't think I'm lazy or stupid, but... I can't find any example that could be helpful. Everything I've found is about console applications or dialog boxes. Any clue?

13 May 2012, 11:34

AsmGuru62

Joined: 28 Jan 2004
Posts: 1561
Location: Toronto, Canada

AsmGuru62 13 May 2012, 11:45

Before you start with a keyboard -- what kind of application you will
be controlling? There are two type of applications for Windows:

- Console (you just see a black box, like DOS, but it is NOT DOS!)
- GUI (you have one or more windows)

So, what kind of application it will be?

P.S. The keyboard input is programmed DIFFERENTLY for these two app types.

13 May 2012, 11:45

Picnic

Joined: 05 May 2007
Posts: 1378
Location: Piraeus, Greece

Picnic 13 May 2012, 11:50

Hi,

for the specific GUI example simply add a WM_KEYDOWN event

Code:

        cmp [wmsg], WM_KEYDOWN
        je wmkeydown

Code:

wmkeydown:
        ; get WM_KEYDOWN message
        push [wparam]
        pop eax
        ; examine virtual-key code
        .if (al = VK_LEFT)
            jmp lineleft
        .elseif (al = VK_RIGHT)
            jmp lineright
        .endif
        jmp     defwndproc  

      ; see also http://msdn.microsoft.com/en-us/library/windows/desktop/hh298359(28v=vs.85).aspx

Use arrow keys to scroll, if that is what you want.

13 May 2012, 11:50

mkng

Joined: 13 May 2012
Posts: 5

mkng 13 May 2012, 12:37

@AsmGuru62: GUI.

@Picnic: great, thank you! But...
I understand that You gave me a pseudocode, right? Now how should I write the "if" section in assembler? I've tried this:

Code:

cmp     AL, WM_KEYDOWN
je      lineleft

but I get "value out of range" error.

Last edited by mkng on 13 May 2012, 13:45; edited 1 time in total

13 May 2012, 12:37

Picnic

Joined: 05 May 2007
Posts: 1378
Location: Piraeus, Greece

Picnic 13 May 2012, 12:45

WM_KEYDOWN is a 16-bit value while al an 8-bit register.

It's full working code.
Replace the line (sorry my bad),

Code:

include 'win32w.inc'

with

Code:

include 'win32wx.inc'

may be better to start with fasm documentation, learn about windows programming headers here, then read more about windows messages in msdn, before you start writing code.

13 May 2012, 12:45

mkng

Joined: 13 May 2012
Posts: 5

mkng 13 May 2012, 12:59

Wow, that's pretty cool! Thank you! Smile

Looking at the code I wonder why there's jump to defwndproc (just after .endif)? It seems that this jump will never be executed, so there's no need for it to be there.

By the way - just to know - this ".if" clauses are equal to what asm code? I mean - if I wanted to write equal if-clause in pure assembler, how should it look?

13 May 2012, 12:59

Picnic

Joined: 05 May 2007
Posts: 1378
Location: Piraeus, Greece

Picnic 13 May 2012, 14:18

Actually the jump will executed every time there is a WM_KEYDOWN event which is not a VK_LEFT or VK_RIGHT.

Code:

wmkeydown:
        ; get WM_KEYDOWN message 
        push [wparam]
        pop eax

        ; examine virtual-key code 
        cmp al, VK_LEFT
        je lineleft
        cmp al, VK_RIGHT
        je lineright
        ;
        ;       
        jmp     defwndproc

13 May 2012, 14:18

AsmGuru62

Joined: 28 Jan 2004
Posts: 1561
Location: Toronto, Canada

AsmGuru62 13 May 2012, 14:28

@Picnic: why not 'mov eax, [wparam]'?

13 May 2012, 14:28

shutdownall

Joined: 02 Apr 2010
Posts: 517
Location: Munich

shutdownall 13 May 2012, 17:38

AsmGuru62 wrote:

@Picnic: why not 'mov eax, [wparam]'?

Maybe a personal style of coding. Cool

13 May 2012, 17:38

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