How to trigger animation in Turbo-C with a mouse?

Question

I am currently working on a project in Computer Graphics in C language. Our professor wants us to make a project which consists of animation, but which gets triggered on clicking by mouse and not keyboard. I searched on the internet for solutions, but nothing has worked for me. The project is to be done in Turbo-C.

Answer 1

You will need a DOS mouse driver installed. If using DOSBox one is already available. You need to make Interrupt calls to the mouse services¹ routines via (Int 0x33). One of the best sources for DOS interrupt related information is Ralph Brown's Interrupt List. Turbo-C has support for calling BIOS services via the int86 function (include DOS.H).

Int 0x33 provides the mouse services, but for the purpose of getting you started the mouse functions that are immediately useful are:

• Show mouse cursor with Int 0x33/AX=1
• Hide mouse cursor with Int 0x33/AX=2
• Set initial mouse cursor position with Int 0x33/AX=4
• Get current mouse state including button information with Int 0x33/AX=3

Using the mouse interrupt information on RBIL to specify the input and output parameters you could create some basic mouse wrappers for your Turbo-C code. Basic wrappers would look like:

#include<stdio.h>
#include<conio.h>
#include<dos.h>

#define MOUSE_INT           0x33
#define MOUSE_FUNC_SHOW     1
#define MOUSE_FUNC_HIDE     2
#define MOUSE_FUNC_GETSTATE 3
#define MOUSE_FUNC_SETPOS   4
#define MOUSE_LEFT_BUTTON   0x01
#define MOUSE_RIGHT_BUTTON  0x02

typedef struct {
    unsigned int cur_x;
    unsigned int cur_y;
    unsigned int buttons;
} mouse_state_t;

void mouse_hide()
{
    union REGS regs_in, regs_out;
    regs_in.x.ax = MOUSE_FUNC_HIDE;
    int86(MOUSE_INT, &regs_in, &regs_out);
}

void mouse_show()
{
    union REGS regs_in, regs_out;
    regs_in.x.ax = MOUSE_FUNC_SHOW;
    int86(MOUSE_INT, &regs_in, &regs_out);
}

void mouse_get_state(mouse_state_t *mouse_state)
{
    union REGS regs_in, regs_out;

    regs_in.x.ax = MOUSE_FUNC_GETSTATE;
    int86(MOUSE_INT, &regs_in, &regs_out);

    mouse_state->cur_x   = regs_out.x.cx;
    mouse_state->cur_y   = regs_out.x.dx;
    mouse_state->buttons = regs_out.x.bx;
    /* buttons field is a bit mask. Bit 0 (lowest bit) is set when left
       mouse button is pressed. Bit 1 is set when right mouse button is pressed */
}

void mouse_set_pos(int pos_x, int pos_y)
{
    union REGS regs_in, regs_out;

    regs_in.x.ax = MOUSE_FUNC_SETPOS;
    regs_in.x.cx = pos_x;
    regs_in.x.dx = pos_y;
    int86(MOUSE_INT, &regs_in, &regs_out);
}

int main()
{
    mouse_state_t mouse_state;

    /* Show mouse and set initial position to middle of text screen */
    clrscr();
    mouse_show();
    mouse_set_pos(80*8/2, 25*8/2);

    /* Repeat until any key is pressed */
    do
    {
        /* Get current mouse state and display it */
        mouse_get_state(&mouse_state);

        gotoxy(1, 1);
        printf("Mouse X: %3d\n", mouse_state.cur_x);
        printf("Mouse Y: %3d\n", mouse_state.cur_y);
        printf("Buttons: %3d\n", mouse_state.buttons);
        /* Display the button state as LEFT/RIGHT when pressed */
        if (mouse_state.buttons & MOUSE_LEFT_BUTTON)
            printf("LEFT ");
        else
            printf("     ");

        if (mouse_state.buttons & MOUSE_RIGHT_BUTTON)
            printf("RIGHT");
        else
            printf("     ");

    } while (!kbhit());

    mouse_hide();
    return 0;
}

This code provides a mouse_show, mouse_hide, mouse_get_state, and mouse_set_pos functions to provide a basic mouse polling interface using Turbo-C's int86 function. The test code repeatedly updates the current mouse state in the upper left hand corner of the screen until a key is pressed. This is as it appears in DOSBox:

As you are doing a homework assignment I won't provide you code that checks the button state and draws images, but this is enough to allow you to determine the current mouse state and trigger the animation yourself.

The mouse interface should work in most of the standard graphics mode.

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Footnotes

- ¹Generally PC BIOSes do not support `Int 0x33` directly. A DOS mouse driver implements this interface to augment the standard BIOS services.