The following page is extracted from the
Turbo C++ Graphics Tutor Copyright ©
Digital International Ltd 1997.
Note : for any additional information concerning this page & the source code included,
download the :-
Turbo C++ mouse & images demo program files & source code.
Turbo Pascal mouse & images demo program files & source code.
The two primary input devices used with GUIs are the keyboard and the mouse. The mouse is
the input device of choice for many users because it offers greater flexibility and
movement than manual keyboard input.
The mouse is very easy to access and control. The mouse system consist of the mouse and the
mouse driver. The mouse is the device manipulated by the user to provide directional input
to the program. The mouse driver is the memory resident
program that provides communication between the mouse and the computer. The mouse driver
maintains the cursor position of the mouse and the status of the mouse buttons. You can
access the cursor position and the button status with in any application through software
interrupt 33h. The C++ function int86 can be used to generate the software interrupt 33h and
the Turbo Pascal procedure Intr can be used for the same purpose as well.
The mouse driver has several functions by specifying the function number in the AX register
when calling interrupt 33h. The BX,CX, and DX registers are used to pass parameters to the
mouse functions.
| Function | Meaning |
|---|---|
| 0 | Resets the mouse and retrieves the mouse status. |
| 1 | Displays the mouse cursor. |
| 2 | Hides the mouse cursor. |
| 3 | Retrieves the mouse cursor positioned the status of the mouse buttons. |
| 4 | Retrieves the number of times a button was pressed since the last call. |
| 5 | Retrieves the number of times a button was released since the last call. |
| 6 | Specifies the horizontal limits for the cursor. |
| 7 | Specifies the vertical limits for the cursor. |
| 8 | Specifies the cursor to use for graphics modes. |
| 9 | Specifies the cursor to use for text modes. |
There are two things you need to know before we started to use the mouse. First under DOS, you must load the mouse driver software that came with your mouse before trying to use it.
Service 0 - put AX = 0
Returns : AX = 0 means Failure.
C++ Example:
int mouse_init(void)
{
int result;
asm {
mov ax,00h;
int 33h;
mov result,ax;
}
return(result);
}
Turbo Pascal Example:
Function Mouse_Init : Boolean;
Var
Result : Word;
Begin
ASM
MOV AX,$00
INT $33
MOV Result,ax
End;
Mouse_Init := (Result <> 0);
End;
Using INT 33H service 0 is the necessary first step toward using the mouse. If this service
returns a nonzero value, the mouse is initialized. Otherwise, the mouse can not be used
(because it is not installed in the computer or the mouse driver is missing). In that case,
and if your program depends on the use of a mouse, you should print out an error message
and quit.
Once the mouse is initialized, you've all set until the computer is turned off- you don't
have to initialize it again (although doing so does no harm). Note that initializing the
mouse does not display the mouse cursor. A function that initialize the mouse and returns
the result is included in the *.ZIP files specified above "MOUSE.INC" & "MOUSE.PAS".
Service 1 - put AX = 1
C++ Example:
void mouse_show(void)
{
asm {
mov ax,01h;
int 33h;
}
}
Turbo Pascal Example:
procedure Mouse_Show;
Begin
ASM
MOV AX,$01
INT $33
End;
End;
Next we have to display the mouse cursor using INT 33H service 1. A small
procedure that displays the mouse cursor is included in the *.ZIP files specified above "MOUSE.INC" & "MOUSE.PAS".
At this point, the mouse system is active and the
cursor has appeared on the screen. We can also make it vanish using INT 33H service
2 to hides the mouse cursor. If the cursor is already off, it stays off. There are times when
the mouse cursor be a distraction on the screen, and this service can fix that.
The very important reason for hiding the mouse cursor, as the mouse cursor moves over the
screen, the mouse driver software reads the character at the preset position before it
displays the mouse cursor. Then, when the mouse cursor moves on, that character is restored,
attributes and all. However, this means that if you have changed the screen display behind
the mouse cursor (for example, opened a window there), it will still restore the original-and
wrong- character, leaving a one-character hole. To avoid this problem, you should always turn
the mouse cursor off when displaying a window or over-writing the mouse cursor in any way,
and turn it on again immediately afterwards.
C++ Example:
void mouse_hide(void)
{
asm {
mov ax,02h;
int 33h;
}
}
Turbo Pascal Example:
Procedure Mouse_Hide;
Begin
ASM
MOV AX,$02
INT $33
End;
End;
We can also read right and left button information from the mouse INT 33H service 3. Let's
look at that process next.
Service 3-set these things : AX = 3
This will return:
| BX | Means |
|---|---|
| 0 | No button down |
| 1 | Left button down |
| 2 | Right button down |
| 3 | Both button down |
unsigned int co,ro,bo;
/* This fuction is to return the
mouse information
bo = mouse button
ro = the y position of the mouse cursor
co = the x position of the mouse cursor */
void mouse_info(void)
{
asm {
mov ax,03h;
int 33h;
mov bo,bx;
mov ro,dx;
mov co,cx;
}
}
Turbo Pascal Example:
(* This Procedure is to return the
mouse information
Bu = mouse button
Ro = the y position of the mouse cursor
Co = the x position of the mouse cursor *)
Procedure Mouse_info;
Var
B, C, R : Word;
Begin
ASM
MOV AX,$03
INT $33
MOV B,BX
MOV C,CX
MOV R,DX
End;
Co := C; Ro := R; Bu := B;
End;
This serve, service 3, returns information in BX, DX, and CX. BX indicates which button(s)
is (are) down. This service also returns the current row and column of the mouse cursor in
DX and CX, respectively. These numbers are measured in pixels, in 640 x 200 mode, DX can
range from 0 to 199 and CX from 0 to 639.