Menus Using Mouse

Menus Using Mouse

Quite often we navigate within menus of bestselling softwares using mouse without thinking for a moment how these menus are developed. The following program shows how such programs can be written. Care has been taken to ensure that the menu would work for all memory models and for different types of adapters like CGA, VGA, EGA, etc.

#include "dos.h"

#include "graphics.h"

#include "alloc.h"

char *menu[ ] = { "Samosa", "Sambarwada", "Dahiwada", "Exit" } ;

union REGS i, o ;

main( )

{

int gd = DETECT, gm, choice = 1, bill = 0, width = 0, i, count ;

char **buffer ;

initgraph ( &gd, &gm, "c:\\tc\\bgi" ) ;

if ( initmouse( ) == 0 )

{

printf ( "\nUnable to initialise Mouse..." ) ;

exit( ) ;

}

count = sizeof ( menu ) / sizeof ( char * ) ;

settextstyle ( TRIPLEX_FONT, 0, 3 ) ;

displaymenu ( menu, count, 100, 100 ) ;

for ( i = 0 ; i <count ; i++ )

{

if ( textwidth ( menu[i] ) > width )

width = textwidth ( menu[i] ) ;

}

buffer = malloc ( sizeof ( menu ) ) ;

savemenu ( menu, buffer, width, count, 100, 100 ) ;

while ( choice != 4 )

{

choice = getresponse ( menu, buffer, width, count, 100, 100 ) ;

gotoxy ( 50, 15 ) ;

printf ( "You selected %s ", menu[choice - 1] ) ;

}

}

displaymenu ( char **menu, int count, int x1, int y1 )

{

int i, h ;

h = textheight ( menu[0] ) ;

for ( i = 0 ; i <count ; i++ )

outtextxy ( x1, y1 + i * ( h + 5 ), menu[i] ) ;

}

savemenu ( char **menu, char** buffer, int width, int count, int x1, int y1 )

{

int i, x2, yy1, yy2, area, h ;

h = textheight ( menu[0] ) ;

for ( i = 0 ; i <count ; i++ )

{

x2 = x1 + width ;

yy1 = y1 + i * ( h + 5 ) ;

yy2 = y1 + ( i + 1 ) * ( h + 5 ) ;

area = imagesize ( x1, yy1, x2, yy2 ) ;

buffer[i] = malloc ( area ) ;

getimage ( x1, yy1, x2, yy2, buffer[i] ) ;

}

}

getresponse ( char ** menu, char** buffer, int width, int count, int x1, int y1 )

{

int choice = 1, prevchoice = 0, x, y, x2, y2, button ;

int in, i, h ;

h = textheight ( menu[0] ) ;

y2 = y1 + count * ( h + 5 ) ;

x2 = x1 + width ;

rectangle ( x1 - 5, y1 - 5, x2 + 5, y2 + 5 ) ;

while ( 1 )

{

getmousepos ( &button, &x, &y ) ;

if ( x >= x1 && x <= x2 && y >= y1 && y <= y2 )

{

in = 1 ;

for ( i = 1 ; i <= count ; i++ )

{

if ( y <= y1 + i * ( h + 5 ) )

{

choice = i ;

break ;

}

}

if ( prevchoice != choice )

{

hidemouseptr( ) ;

highlight ( buffer, choice, h, x1, y1 ) ;

if ( prevchoice )

dehighlight ( buffer, prevchoice, h, x1, y1 ) ;

prevchoice = choice ;

showmouseptr( ) ;

}

if ( ( button & 1 ) == 1 )

{

while ( ( button & 1 ) == 1 )

getmousepos ( &button, &x, &y ) ;

if ( x >= x1 && x <= x2 && y >= y1 && y <= y2 )

return ( choice ) ;

}

}

else

{

if ( in == 1 )

{

in = 0 ;

prevchoice = 0 ;

hidemouseptr( ) ;

dehighlight ( buffer, choice, h, x1, y1 ) ;

showmouseptr( ) ;

}

}

}

}

highlight ( char **buffer, int ch, int h, int x1, int y1 )

{

putimage( x1, y1 + ( ch - 1 ) * ( h + 5 ), buffer[ch - 1], NOT_PUT ) ;

}

dehighlight ( char **buffer, int ch, int h, int x1, int y1 )

{

putimage( x1, y1 + ( ch - 1 ) * ( h + 5 ), buffer[ch - 1], COPY_PUT ) ;

}

initmouse( )

{

i.x.ax = 0 ;

int86 ( 0x33, &i, &o ) ;

return ( o.x.ax ) ;

}

showmouseptr( )

{

i.x.ax = 1 ;

int86 ( 0x33, &i, &o ) ;

}

hidemouseptr( )

{

i.x.ax = 2 ;

int86 ( 0x33, &i, &o ) ;

}

getmousepos ( int *button, int *x, int *y )

{

i.x.ax = 3 ;

int86 ( 0x33, &i, &o ) ;

*button = o.x.bx ;

*x = o.x.cx ;

*y = o.x.dx ;

}

Note that the menu items are stored in an array of pointers to strings menu[ ]. Once the graphics system and the mouse has been initialised, the number of items in the menu are determined, text style is set and the menu is displayed on the screen using the function displaymenu( ). To highlight or de-highlight the menu items, rather than building the items from scratch their existing images are stored in a buffer. The space for this buffer is allocated using malloc( ) and the actual saving of images is done through the function savemenu( ). The base addresses of these images are stored in an array of pointers, pointed to by the variable buffer. Using these addresses let us now see how do we go about moving the highlighted bar using mouse and then make a selection from the menu by clicking on the left mouse button. All this is achieved by the function getresponse( ). To begin with, the getresponse( ) function checks the position of the mouse pointer. If the mouse pointer is inside the area occupied by menu then it checks on which menu item is it placed and highlights that item. If the user attempts to move the mouse pointer outside this menu item then it is de-highlighted. If an item is highlighted and the left mouse button is clicked then it is assumed that the menu item has been selected and an appropriate value is returned. Observe that, to highlight an item, the putimage( ) function has been used in such a manner that the existing image of the item is just reversed.