Add callbacks that get invoked before the next call to select(), which will allow for a nice fix to https://github.com/fish-shell/fish-shell/issues/608. Eliminate the poll handler, and replace it with this mechanism.

input_common.cpp

@@ -39,6 +39,12 @@ Implementation file for the low level input library
 /** Characters that have been read and returned by the sequence matching code */
 static std::stack<wint_t, std::list<wint_t> > lookahead_list;
 
+/* Queue of pairs of (function pointer, argument) to be invoked */
+typedef std::pair<void (*)(void *), void *> callback_info_t;
+typedef std::queue<callback_info_t, std::list<callback_info_t> > callback_queue_t;
+static callback_queue_t callback_queue;
+static void input_flush_callbacks(void);
+
 static bool has_lookahead(void)
 {
     return ! lookahead_list.empty();
@@ -64,20 +70,11 @@ static wint_t lookahead_top(void)
 /** Callback function for handling interrupts on reading */
 static int (*interrupt_handler)();
 
-/** Callback function to be invoked before reading each byte */
-static void (*poll_handler)();
-
-
 void input_common_init(int (*ih)())
 {
     interrupt_handler = ih;
 }
 
-void input_common_set_poll_callback(void (*handler)(void))
-{
-    poll_handler = handler;
-}
-
 void input_common_destroy()
 {
 
@@ -95,9 +92,8 @@ static wint_t readb()
 
     do
     {
-        /* Invoke any poll handler */
-        if (poll_handler)
-            poll_handler();
+        /* Flush callbacks */
+        input_flush_callbacks();
 
         fd_set fdset;
         int fd_max=0;
@@ -280,3 +276,25 @@ void input_common_unreadch(wint_t ch)
     lookahead_push(ch);
 }
 
+void input_common_add_callback(void (*callback)(void *), void *arg)
+{
+    ASSERT_IS_MAIN_THREAD();
+    callback_queue.push(callback_info_t(callback, arg));
+}
+
+static void input_flush_callbacks(void)
+{
+    /* Nothing to do if nothing to do */
+    if (callback_queue.empty())
+        return;
+    
+    /* We move the queue into a local variable, so that events queued up during a callback don't get fired until next round. */
+    callback_queue_t local_queue;
+    std::swap(local_queue, callback_queue);
+    while (! local_queue.empty())
+    {
+        const callback_info_t &callback = local_queue.front();
+        callback.first(callback.second); //cute
+        local_queue.pop();
+    }
+}

input_common.h

@@ -30,9 +30,6 @@ enum
 */
 void input_common_init(int (*ih)());
 
-/* Sets a callback to be invoked every time a byte is read */
-void input_common_set_poll_callback(void (*handler)(void));
-
 /**
    Free memory used by the library
 */
@@ -56,4 +53,9 @@ wchar_t input_common_readch(int timed);
 */
 void input_common_unreadch(wint_t ch);
 
+/** Adds a callback to be invoked at the next turn of the "event loop." The callback function will be invoked and passed arg. */
+void input_common_add_callback(void (*callback)(void *), void *arg);
+
+
+
 #endif

reader.cpp

@@ -815,9 +815,6 @@ void reader_init()
 #ifdef VDSUSP
     shell_modes.c_cc[VDSUSP] = _POSIX_VDISABLE;
 #endif
-
-    /* Repaint if necessary before each byte is read. This lets us react immediately to universal variable color changes. */
-    input_common_set_poll_callback(reader_repaint_if_needed);
 }
 
 
@@ -868,12 +865,21 @@ void reader_repaint_if_needed()
     }
 }
 
+static void reader_repaint_if_needed_one_arg(void * unused)
+{
+    reader_repaint_if_needed();
+}
+
 void reader_react_to_color_change()
 {
-    if (data)
+    if (! data)
+        return;
+    
+    if (! data->repaint_needed || ! data->screen_reset_needed)
     {
         data->repaint_needed = true;
         data->screen_reset_needed = true;
+        input_common_add_callback(reader_repaint_if_needed_one_arg, NULL);
     }
 }