Add a timeout: delay_exit_on_zero_displays

Outputs may disappear momentarily and come back later.
To prevent i3 from exit when no output is available momentarily, add a timeout delay_exit_on_zero_displays.

docs/userguide

@@ -1003,6 +1003,31 @@ force_display_urgency_hint <timeout> ms
 force_display_urgency_hint 500 ms
 ---------------------------------
 
+=== Delaying exiting on zero displays
+
+Outputs may disappear momentarily and come back later. For example,
+using a docking station that does not announce the undock (e.g. ACPI Undock 
+event triggered through manually pushing a button before actually ejecting 
+the notebook). During the removal of the notebook from the docking station,
+all outputs disappear momentarily.
+
+To prevent i3 from exiting when no output is available momentarily, you can 
+tell i3 to delay a certain time first and check available outputs again using 
+the +delay_exit_on_zero_displays+ directive. Setting the value to 0 disables 
+this feature.
+
+The default is 500ms.
+
+*Syntax*:
+----------------------------------------
+delay_exit_on_zero_displays <timeout> ms
+----------------------------------------
+
+*Example*:
+----------------------------------
+delay_exit_on_zero_displays 500 ms
+----------------------------------
+
 === Focus on window activation
 
 [[focus_on_window_activation]]

include/config.h

@@ -167,6 +167,10 @@ struct Config {
      * flag can be delayed using an urgency timer. */
     float workspace_urgency_timer;
 
+    /** Use a timer to delay exiting when no output is available.
+      * This can prevent i3 from exiting when all outputs disappear momentarily. */
+    float zero_disp_exit_timer_ms;
+
     /** Behavior when a window sends a NET_ACTIVE_WINDOW message. */
     enum {
         /* Focus if the target workspace is visible, set urgency hint otherwise. */

include/config_directives.h

@@ -51,6 +51,7 @@ CFGFUN(force_focus_wrapping, const char *value);
 CFGFUN(force_xinerama, const char *value);
 CFGFUN(fake_outputs, const char *outputs);
 CFGFUN(force_display_urgency_hint, const long duration_ms);
+CFGFUN(delay_exit_on_zero_displays, const long duration_ms);
 CFGFUN(focus_on_window_activation, const char *mode);
 CFGFUN(show_marks, const char *value);
 CFGFUN(hide_edge_borders, const char *borders);

parser-specs/config.spec

@@ -39,6 +39,7 @@ state INITIAL:
   'workspace_auto_back_and_forth'          -> WORKSPACE_BACK_AND_FORTH
   'fake_outputs', 'fake-outputs'           -> FAKE_OUTPUTS
   'force_display_urgency_hint'             -> FORCE_DISPLAY_URGENCY_HINT
+  'delay_exit_on_zero_displays'            -> DELAY_EXIT_ON_ZERO_DISPLAYS
   'focus_on_window_activation'             -> FOCUS_ON_WINDOW_ACTIVATION
   'show_marks'                             -> SHOW_MARKS
   'workspace'                              -> WORKSPACE
@@ -227,6 +228,17 @@ state FORCE_DISPLAY_URGENCY_HINT_MS:
   end
       -> call cfg_force_display_urgency_hint(&duration_ms)
 
+# delay_exit_on_zero_displays <delay> ms
+state DELAY_EXIT_ON_ZERO_DISPLAYS:
+  duration_ms = number
+      -> DELAY_EXIT_ON_ZERO_DISPLAYS_MS
+
+state DELAY_EXIT_ON_ZERO_DISPLAYS_MS:
+  'ms'
+      ->
+  end
+      -> call cfg_delay_exit_on_zero_displays(&duration_ms)
+
 # focus_on_window_activation <smart|urgent|focus|none>
 state FOCUS_ON_WINDOW_ACTIVATION:
   mode = word

src/config.c

@@ -203,6 +203,10 @@ void load_configuration(xcb_connection_t *conn, const char *override_configpath,
     if (config.workspace_urgency_timer == 0)
         config.workspace_urgency_timer = 0.5;
 
+    /* Set default zero displays exit delay to 500ms */
+    if (config.zero_disp_exit_timer_ms == 0)
+        config.zero_disp_exit_timer_ms = 500;
+
     parse_configuration(override_configpath, true);
 
     if (reload) {

src/config_directives.c

@@ -329,6 +329,10 @@ CFGFUN(force_display_urgency_hint, const long duration_ms) {
     config.workspace_urgency_timer = duration_ms / 1000.0;
 }
 
+CFGFUN(delay_exit_on_zero_displays, const long duration_ms) {
+    config.zero_disp_exit_timer_ms = duration_ms;
+}
+
 CFGFUN(focus_on_window_activation, const char *mode) {
     if (strcmp(mode, "smart") == 0)
         config.focus_on_window_activation = FOWA_SMART;

src/main.c

@@ -621,6 +621,8 @@ int main(int argc, char *argv[]) {
             ELOG("ERROR: No screen at (%d, %d), starting on the first screen\n",
                  pointerreply->root_x, pointerreply->root_y);
             output = get_first_output();
+            if (!output)
+                die("No usable outputs available.\n");
         }
 
         con_focus(con_descend_focused(output_get_content(output->con)));

src/randr.c

@@ -69,7 +69,7 @@ Output *get_first_output(void) {
     if (output->active)
         return output;
 
-    die("No usable outputs available.\n");
+    return NULL;
 }
 
 /*
@@ -564,6 +564,8 @@ static void handle_output(xcb_connection_t *conn, xcb_randr_output_t id,
     if (!new->active) {
         DLOG("width/height 0/0, disabling output\n");
         return;
+    } else {
+        new->to_be_disabled = false;
     }
 
     DLOG("mode: %dx%d+%d+%d\n", new->rect.width, new->rect.height,
@@ -585,11 +587,7 @@ static void handle_output(xcb_connection_t *conn, xcb_randr_output_t id,
     new->changed = true;
 }
 
-/*
+static bool __randr_query_outputs(void) {
- * (Re-)queries the outputs via RandR and stores them in the list of outputs.
- *
- */
-void randr_query_outputs(void) {
     Output *output, *other, *first;
     xcb_randr_get_output_primary_cookie_t pcookie;
     xcb_randr_get_screen_resources_current_cookie_t rcookie;
@@ -603,7 +601,7 @@ void randr_query_outputs(void) {
     xcb_randr_output_t *randr_outputs;
 
     if (randr_disabled)
-        return;
+        return true;
 
     /* Get screen resources (primary output, crtcs, outputs, modes) */
     rcookie = xcb_randr_get_screen_resources_current(conn, root);
@@ -615,7 +613,7 @@ void randr_query_outputs(void) {
         DLOG("primary output is %08x\n", primary->output);
     if ((res = xcb_randr_get_screen_resources_current_reply(conn, rcookie, NULL)) == NULL) {
         disable_randr(conn);
-        return;
+        return true;
     }
     cts = res->config_timestamp;
 
@@ -697,6 +695,11 @@ void randr_query_outputs(void) {
             DLOG("Output %s disabled, re-assigning workspaces/docks\n", output->name);
 
             first = get_first_output();
+            if (!first) {
+                FREE(res);
+                FREE(primary);
+                return false;
+            }
 
             /* TODO: refactor the following code into a nice function. maybe
              * use an on_destroy callback which is implement differently for
@@ -812,6 +815,32 @@ void randr_query_outputs(void) {
 
     FREE(res);
     FREE(primary);
+
+    return true;
+}
+
+/*
+ * (Re-)queries the outputs via RandR and stores them in the list of outputs.
+ *
+ */
+void randr_query_outputs(void) {
+    static bool first_query = true;
+
+    if (first_query) {
+        /* find monitors at least once via RandR */
+        if (!__randr_query_outputs())
+            die("No usable outputs available.\n");
+        first_query = false;
+    } else {
+        /* requery */
+        if (!__randr_query_outputs()) {
+            DLOG("sleep %f ms due to zero displays\n", config.zero_disp_exit_timer_ms);
+            usleep(config.zero_disp_exit_timer_ms * 1000);
+
+            if (!__randr_query_outputs())
+                die("No usable outputs available.\n");
+        }
+    }
 }
 
 /*

testcases/t/201-config-parser.t

@@ -365,6 +365,40 @@ is(parser_calls($config),
    $expected,
    'force_display_urgency_hint ok');
 
+################################################################################
+# delay_exit_on_zero_displays
+################################################################################
+
+is(parser_calls('delay_exit_on_zero_displays 300'),
+   "cfg_delay_exit_on_zero_displays(300)\n",
+   'delay_exit_on_zero_displays ok');
+
+is(parser_calls('delay_exit_on_zero_displays 500 ms'),
+   "cfg_delay_exit_on_zero_displays(500)\n",
+   'delay_exit_on_zero_displays ok');
+
+is(parser_calls('delay_exit_on_zero_displays 700ms'),
+   "cfg_delay_exit_on_zero_displays(700)\n",
+   'delay_exit_on_zero_displays ok');
+
+$config = <<'EOT';
+delay_exit_on_zero_displays 300
+delay_exit_on_zero_displays 500 ms
+delay_exit_on_zero_displays 700ms
+delay_exit_on_zero_displays 700
+EOT
+
+$expected = <<'EOT';
+cfg_delay_exit_on_zero_displays(300)
+cfg_delay_exit_on_zero_displays(500)
+cfg_delay_exit_on_zero_displays(700)
+cfg_delay_exit_on_zero_displays(700)
+EOT
+
+is(parser_calls($config),
+   $expected,
+   'delay_exit_on_zero_displays ok');
+
 ################################################################################
 # workspace
 ################################################################################
@@ -437,7 +471,7 @@ client.focused          #4c7899 #285577 #ffffff #2e9ef4
 EOT
 
 my $expected_all_tokens = <<'EOT';
-ERROR: CONFIG: Expected one of these tokens: <end>, '#', 'set', 'bindsym', 'bindcode', 'bind', 'bar', 'font', 'mode', 'floating_minimum_size', 'floating_maximum_size', 'floating_modifier', 'default_orientation', 'workspace_layout', 'new_window', 'new_float', 'hide_edge_borders', 'for_window', 'assign', 'no_focus', 'focus_follows_mouse', 'mouse_warping', 'force_focus_wrapping', 'force_xinerama', 'force-xinerama', 'workspace_auto_back_and_forth', 'fake_outputs', 'fake-outputs', 'force_display_urgency_hint', 'focus_on_window_activation', 'show_marks', 'workspace', 'ipc_socket', 'ipc-socket', 'restart_state', 'popup_during_fullscreen', 'exec_always', 'exec', 'client.background', 'client.focused_inactive', 'client.focused', 'client.unfocused', 'client.urgent', 'client.placeholder'
+ERROR: CONFIG: Expected one of these tokens: <end>, '#', 'set', 'bindsym', 'bindcode', 'bind', 'bar', 'font', 'mode', 'floating_minimum_size', 'floating_maximum_size', 'floating_modifier', 'default_orientation', 'workspace_layout', 'new_window', 'new_float', 'hide_edge_borders', 'for_window', 'assign', 'no_focus', 'focus_follows_mouse', 'mouse_warping', 'force_focus_wrapping', 'force_xinerama', 'force-xinerama', 'workspace_auto_back_and_forth', 'fake_outputs', 'fake-outputs', 'force_display_urgency_hint', 'delay_exit_on_zero_displays', 'focus_on_window_activation', 'show_marks', 'workspace', 'ipc_socket', 'ipc-socket', 'restart_state', 'popup_during_fullscreen', 'exec_always', 'exec', 'client.background', 'client.focused_inactive', 'client.focused', 'client.unfocused', 'client.urgent', 'client.placeholder'
 EOT
 
 my $expected_end = <<'EOT';