| DUMMY_HANDLER | Function (tigcc.a)

intr.h

INT_HANDLER DUMMY_HANDLER;

A dummy interrupt handler doing nothing.

DUMMY_HANDLER is an interrupt handler of type INT_HANDLER which consists only of `'rte'`. The purpose of this handler is to redirect an interrupt vector to "nothing", in cases when disabling interrupts is not possible. For example, you can not disable auto-int 1 in grayscale programs, because grayscale support is based on it. Grayscale support installs its own auto-int 1 handler, which executes the previously installed handler at the end. Suppose that you don't want it to call the default auto-int 1 handler, which trashes the status line by displaying keyboard status indicators. You can redirect auto-int 1 to the dummy handler before enabling grayscale, so after the grayscale interrupt, the dummy handler (i.e. nothing) will be called instead of the default auto-int 1 handler:

    INT_HANDLER save_int_1;
    ...
    save_int_1 = GetIntVec (AUTO_INT_1);
    SetIntVec (AUTO_INT_1, DUMMY_HANDLER);   // redirect auto-int 1 to "nothing"
    // enable grayscale
    // do whatever you want in grayscale
    // disable grayscale
    SetIntVec (AUTO_INT_1, save_int_1);