[AD] A possibly useful variation on d_keyboard_proc

["Philippe Lorin" <palpalpalpal@xxxxxxxxxx>]

I needed to use a function key as a shortcut in my GUI, but apparently 
shortcuts are only handled as ASCII codes.

d_keyboard_proc accepts scancodes, but I didn't want to write a wrapper 
function for every new shortcut. So I wrote this function, which is similar 
to d_keyboard_proc except that instead of calling a function (pointed to by 
dp), it sends a MSG_KEY to a DIALOG (pointed to by dp). Put differently, 
it's an invisible object that forwards keypresses corresponding to its 
shortcut or to a scancode (in d1 or d2) to the DIALOG pointed to by dp.

Additionally, this function allows using multiple shortcuts for the same 
DIALOG easily. Not that I would recommend that kind of design though.

The code for an example is at the end of this message. Adding the function 
to Allegro would just be a matter of copying d_keyboard_forward_proc into 
allegro/guiproc.c, and the prototype to gui.h.

Maybe there's already some way to do the same thing but I didn't found one 
although I read the docs thoroughly. Why aren't scancodes supported as 
shortcuts? As DIALOG.key is an int, we could store a scancode in addition to 
the ASCII code using the readkey() format. This would be better than nothing 
and shouldn't break compatibility, except where reading shortcuts from 
DIALOGs is involved, which shouldn't happen often. What do you think?

There is a problem with my function though. Not all keys will work. Function 
keys, cursor keys, "extra cursor keys", numpad keys, esc, tab, enter and 
print screen work, but shifts, controls, alts, windows, caps lock, pause and 
scroll lock don't. I have no idea why, but I don't know if it's worth 
examining the issue.

PS I'm not subscribed to this list but I will watch this space for any 
follow-ups of course.



#include <allegro.h>

// This is the interesting function.
// The code is very similar to d_keyboard_proc in allegro/guiproc.c.
// I retained the same coding style for this function.
int d_keyboard_forward_proc(int msg, DIALOG *d, int c)
{
  int ret = D_O_K;
  switch (msg) {

     case MSG_START:
	 d->w = d->h = 0;
	 break;

     case MSG_XCHAR:
	 if (((c>>8) != d->d1) && ((c>>8) != d->d2))
	    break;

	 ret |= D_USED_CHAR;
	 /* fall through */

     case MSG_KEY:
	 ret |= object_message((DIALOG*) (d->dp), MSG_KEY, 0);
	 break;
  }

  return ret;
}

void menu_play() {
	DIALOG widgets[8];

	widgets[0] = (DIALOG) {d_clear_proc,		0, 0, SCREEN_W, SCREEN_H,	0, 255, 0, 
0,		0, 0,			NULL, NULL, NULL};
	widgets[1] = (DIALOG) {d_check_proc,		0, 0, SCREEN_W, 32,		0, 255, 'C', 
0,		1, 0,			"&Checkbox (F1)", NULL, NULL};
	widgets[2] = (DIALOG) {d_button_proc,		0, 32, SCREEN_W, 32,		0, 255, 'B', 
0,		0, 0,			"&Button (F2 or home)", NULL, NULL};
	widgets[3] = (DIALOG) {d_button_proc,		0, 64, SCREEN_W, 32,		0, 255, 'X', 
D_EXIT,	0, 0,			"E&XIT", NULL, NULL};
	widgets[4] = (DIALOG) {d_keyboard_forward_proc,	0, 0, 0, 0,			0, 255, 0, 
0,		KEY_F1, 0,		&widgets[1], NULL, NULL};
	widgets[5] = (DIALOG) {d_keyboard_forward_proc,	0, 0, 0, 0,			0, 255, 0, 
0,		KEY_F2, KEY_HOME,	&widgets[2], NULL, NULL};
	widgets[6] = (DIALOG) {d_yield_proc};
	widgets[7] = (DIALOG) {NULL};

	popup_dialog(widgets, -1);
}

int main() {
	allegro_init();
	install_keyboard();
	install_mouse();
	if (set_gfx_mode(GFX_SAFE, 640, 480, 0, 0)) {
		allegro_message("Error; set_gfx_mode");
		return 1;
	}

	menu_play();

	return 0;
}
END_OF_MAIN();

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