Use RandR for learning about attached monitors

The code now tries the following options, in order:

• obtain monitors via RandR 1.5
• obtain outputs via RandR ≤ 1.4
• obtain screens via Xinerama

fixes #159
related to #101
related to #148
related to #149

Makefile

@@ -15,8 +15,8 @@ CFLAGS += -std=c99
 CFLAGS += -pipe
 CFLAGS += -Wall
 CPPFLAGS += -D_GNU_SOURCE
-CFLAGS += $(shell $(PKG_CONFIG) --cflags cairo xcb-xinerama xcb-atom xcb-image xcb-xkb xkbcommon xkbcommon-x11)
+CFLAGS += $(shell $(PKG_CONFIG) --cflags cairo xcb-xinerama xcb-randr xcb-atom xcb-image xcb-xkb xkbcommon xkbcommon-x11)
-LIBS += $(shell $(PKG_CONFIG) --libs cairo xcb-xinerama xcb-atom xcb-image xcb-xkb xkbcommon xkbcommon-x11)
+LIBS += $(shell $(PKG_CONFIG) --libs cairo xcb-xinerama xcb-randr xcb-atom xcb-image xcb-xkb xkbcommon xkbcommon-x11)
 LIBS += -lev
 LIBS += -lm
 

README.md

@@ -26,6 +26,7 @@ Requirements
 - libpam-dev
 - libcairo-dev
 - libxcb-xinerama
+- libxcb-randr
 - libev
 - libx11-dev
 - libx11-xcb-dev

i3lock.c

@@ -36,6 +36,7 @@
 #include <strings.h> /* explicit_bzero(3) */
 #endif
 #include <xcb/xcb_aux.h>
+#include <xcb/randr.h>
 
 #include "i3lock.h"
 #include "xcb.h"
@@ -85,6 +86,7 @@ static struct xkb_compose_table *xkb_compose_table;
 static struct xkb_compose_state *xkb_compose_state;
 static uint8_t xkb_base_event;
 static uint8_t xkb_base_error;
+static int randr_base = -1;
 
 cairo_surface_t *img = NULL;
 bool tile = false;
@@ -620,7 +622,7 @@ void handle_screen_resize(void) {
     xcb_configure_window(conn, win, mask, last_resolution);
     xcb_flush(conn);
 
-    xinerama_query_screens();
+    randr_query(screen->root);
     redraw_screen();
 }
 
@@ -743,8 +745,14 @@ static void xcb_check_cb(EV_P_ ev_check *w, int revents) {
                 break;
 
             default:
-                if (type == xkb_base_event)
+                if (type == xkb_base_event) {
                     process_xkb_event(event);
+                }
+                if (randr_base > -1 &&
+                    type == randr_base + XCB_RANDR_SCREEN_CHANGE_NOTIFY) {
+                    randr_query(screen->root);
+                    handle_screen_resize();
+                }
         }
 
         free(event);
@@ -987,11 +995,11 @@ int main(int argc, char *argv[]) {
 
     load_compose_table(locale);
 
-    xinerama_init();
-    xinerama_query_screens();
-
     screen = xcb_setup_roots_iterator(xcb_get_setup(conn)).data;
 
+    randr_init(&randr_base, screen->root);
+    randr_query(screen->root);
+
     last_resolution[0] = screen->width_in_pixels;
     last_resolution[1] = screen->height_in_pixels;
 

xinerama.c

@@ -12,6 +12,7 @@
 #include <math.h>
 #include <xcb/xcb.h>
 #include <xcb/xinerama.h>
+#include <xcb/randr.h>
 
 #include "i3lock.h"
 #include "xcb.h"
@@ -21,12 +22,55 @@
 int xr_screens = 0;
 
 /* The resolutions of the currently present Xinerama screens. */
-Rect *xr_resolutions;
+Rect *xr_resolutions = NULL;
 
 static bool xinerama_active;
+static bool has_randr = false;
+static bool has_randr_1_5 = false;
 extern bool debug_mode;
 
-void xinerama_init(void) {
+void _xinerama_init(void);
+
+void randr_init(int *event_base, xcb_window_t root) {
+    const xcb_query_extension_reply_t *extreply;
+
+    extreply = xcb_get_extension_data(conn, &xcb_randr_id);
+    if (!extreply->present) {
+        DEBUG("RandR is not present, falling back to Xinerama.\n");
+        _xinerama_init();
+        return;
+    }
+
+    xcb_generic_error_t *err;
+    xcb_randr_query_version_reply_t *randr_version =
+        xcb_randr_query_version_reply(
+            conn, xcb_randr_query_version(conn, XCB_RANDR_MAJOR_VERSION, XCB_RANDR_MINOR_VERSION), &err);
+    if (err != NULL) {
+        DEBUG("Could not query RandR version: X11 error code %d\n", err->error_code);
+        _xinerama_init();
+        return;
+    }
+
+    has_randr = true;
+
+    has_randr_1_5 = (randr_version->major_version >= 1) &&
+                    (randr_version->minor_version >= 5);
+
+    free(randr_version);
+
+    if (event_base != NULL)
+        *event_base = extreply->first_event;
+
+    xcb_randr_select_input(conn, root,
+                           XCB_RANDR_NOTIFY_MASK_SCREEN_CHANGE |
+                               XCB_RANDR_NOTIFY_MASK_OUTPUT_CHANGE |
+                               XCB_RANDR_NOTIFY_MASK_CRTC_CHANGE |
+                               XCB_RANDR_NOTIFY_MASK_OUTPUT_PROPERTY);
+
+    xcb_flush(conn);
+}
+
+void _xinerama_init(void) {
     if (!xcb_get_extension_data(conn, &xcb_xinerama_id)->present) {
         DEBUG("Xinerama extension not found, disabling.\n");
         return;
@@ -49,19 +93,168 @@ void xinerama_init(void) {
     free(reply);
 }
 
-void xinerama_query_screens(void) {
+/*
-    if (!xinerama_active)
+ * randr_query_outputs_15 uses RandR ≥ 1.5 to update outputs.
+ *
+ */
+static bool _randr_query_monitors_15(xcb_window_t root) {
+#if XCB_RANDR_MINOR_VERSION < 5
+    return false;
+#else
+    /* RandR 1.5 available at compile-time, i.e. libxcb is new enough */
+    if (!has_randr_1_5) {
+        return false;
+    }
+    /* RandR 1.5 available at run-time (supported by the server) */
+    DEBUG("Querying monitors using RandR 1.5\n");
+    xcb_generic_error_t *err;
+    xcb_randr_get_monitors_reply_t *monitors =
+        xcb_randr_get_monitors_reply(
+            conn, xcb_randr_get_monitors(conn, root, true), &err);
+    if (err != NULL) {
+        DEBUG("Could not get RandR monitors: X11 error code %d\n", err->error_code);
+        free(err);
+        /* Fall back to RandR ≤ 1.4 */
+        return false;
+    }
+
+    int screens = xcb_randr_get_monitors_monitors_length(monitors);
+    DEBUG("%d RandR monitors found (timestamp %d)\n",
+          screens, monitors->timestamp);
+
+    Rect *resolutions = malloc(screens * sizeof(Rect));
+    /* No memory? Just keep on using the old information. */
+    if (!resolutions) {
+        free(monitors);
+        return true;
+    }
+
+    xcb_randr_monitor_info_iterator_t iter;
+    int screen;
+    for (iter = xcb_randr_get_monitors_monitors_iterator(monitors), screen = 0;
+         iter.rem;
+         xcb_randr_monitor_info_next(&iter), screen++) {
+        const xcb_randr_monitor_info_t *monitor_info = iter.data;
+
+        resolutions[screen].x = monitor_info->x;
+        resolutions[screen].y = monitor_info->y;
+        resolutions[screen].width = monitor_info->width;
+        resolutions[screen].height = monitor_info->height;
+        DEBUG("found RandR monitor: %d x %d at %d x %d\n",
+              monitor_info->width, monitor_info->height,
+              monitor_info->x, monitor_info->y);
+    }
+    free(xr_resolutions);
+    xr_resolutions = resolutions;
+    xr_screens = screens;
+
+    free(monitors);
+    return true;
+#endif
+}
+
+/*
+ * randr_query_outputs_14 uses RandR ≤ 1.4 to update outputs.
+ *
+ */
+static bool _randr_query_outputs_14(xcb_window_t root) {
+    if (!has_randr) {
+        return false;
+    }
+    DEBUG("Querying outputs using RandR ≤ 1.4\n");
+
+    /* Get screen resources (primary output, crtcs, outputs, modes) */
+    xcb_randr_get_screen_resources_current_cookie_t rcookie;
+    rcookie = xcb_randr_get_screen_resources_current(conn, root);
+
+    xcb_randr_get_screen_resources_current_reply_t *res =
+        xcb_randr_get_screen_resources_current_reply(conn, rcookie, NULL);
+    if (res == NULL) {
+        DEBUG("Could not query screen resources.\n");
+        return false;
+    }
+
+    /* timestamp of the configuration so that we get consistent replies to all
+     * requests (if the configuration changes between our different calls) */
+    const xcb_timestamp_t cts = res->config_timestamp;
+
+    const int len = xcb_randr_get_screen_resources_current_outputs_length(res);
+
+    /* an output is VGA-1, LVDS-1, etc. (usually physical video outputs) */
+    xcb_randr_output_t *randr_outputs = xcb_randr_get_screen_resources_current_outputs(res);
+
+    /* Request information for each output */
+    xcb_randr_get_output_info_cookie_t ocookie[len];
+    for (int i = 0; i < len; i++) {
+        ocookie[i] = xcb_randr_get_output_info(conn, randr_outputs[i], cts);
+    }
+    Rect *resolutions = malloc(len * sizeof(Rect));
+    /* No memory? Just keep on using the old information. */
+    if (!resolutions) {
+        free(res);
+        return true;
+    }
+
+    /* Loop through all outputs available for this X11 screen */
+    int screen = 0;
+
+    for (int i = 0; i < len; i++) {
+        xcb_randr_get_output_info_reply_t *output;
+
+        if ((output = xcb_randr_get_output_info_reply(conn, ocookie[i], NULL)) == NULL) {
+            continue;
+        }
+
+        if (output->crtc == XCB_NONE) {
+            free(output);
+            continue;
+        }
+
+        xcb_randr_get_crtc_info_cookie_t icookie;
+        xcb_randr_get_crtc_info_reply_t *crtc;
+        icookie = xcb_randr_get_crtc_info(conn, output->crtc, cts);
+        if ((crtc = xcb_randr_get_crtc_info_reply(conn, icookie, NULL)) == NULL) {
+            DEBUG("Skipping output: could not get CRTC (0x%08x)\n", output->crtc);
+            free(output);
+            continue;
+        }
+
+        resolutions[screen].x = crtc->x;
+        resolutions[screen].y = crtc->y;
+        resolutions[screen].width = crtc->width;
+        resolutions[screen].height = crtc->height;
+
+        DEBUG("found RandR output: %d x %d at %d x %d\n",
+              crtc->width, crtc->height,
+              crtc->x, crtc->y);
+
+        screen++;
+
+        free(crtc);
+
+        free(output);
+    }
+    free(xr_resolutions);
+    xr_resolutions = resolutions;
+    xr_screens = screen;
+    free(res);
+    return true;
+}
+
+void _xinerama_query_screens(void) {
+    if (!xinerama_active) {
         return;
+    }
 
     xcb_xinerama_query_screens_cookie_t cookie;
     xcb_xinerama_query_screens_reply_t *reply;
     xcb_xinerama_screen_info_t *screen_info;
-
+    xcb_generic_error_t *err;
     cookie = xcb_xinerama_query_screens_unchecked(conn);
-    reply = xcb_xinerama_query_screens_reply(conn, cookie, NULL);
+    reply = xcb_xinerama_query_screens_reply(conn, cookie, &err);
     if (!reply) {
-        if (debug_mode)
+        DEBUG("Couldn't get Xinerama screens: X11 error code %d\n", err->error_code);
-            fprintf(stderr, "Couldn't get Xinerama screens\n");
+        free(err);
         return;
     }
     screen_info = xcb_xinerama_query_screens_screen_info(reply);
@@ -73,18 +266,32 @@ void xinerama_query_screens(void) {
         free(reply);
         return;
     }
-    xr_resolutions = resolutions;
-    xr_screens = screens;
 
     for (int screen = 0; screen < xr_screens; screen++) {
-        xr_resolutions[screen].x = screen_info[screen].x_org;
+        resolutions[screen].x = screen_info[screen].x_org;
-        xr_resolutions[screen].y = screen_info[screen].y_org;
+        resolutions[screen].y = screen_info[screen].y_org;
-        xr_resolutions[screen].width = screen_info[screen].width;
+        resolutions[screen].width = screen_info[screen].width;
-        xr_resolutions[screen].height = screen_info[screen].height;
+        resolutions[screen].height = screen_info[screen].height;
         DEBUG("found Xinerama screen: %d x %d at %d x %d\n",
               screen_info[screen].width, screen_info[screen].height,
               screen_info[screen].x_org, screen_info[screen].y_org);
     }
 
+    free(xr_resolutions);
+    xr_resolutions = resolutions;
+    xr_screens = screens;
+
     free(reply);
 }
+
+void randr_query(xcb_window_t root) {
+    if (_randr_query_monitors_15(root)) {
+        return;
+    }
+
+    if (_randr_query_outputs_14(root)) {
+        return;
+    }
+
+    _xinerama_query_screens();
+}

xinerama.h

@@ -11,7 +11,7 @@ typedef struct Rect {
 extern int xr_screens;
 extern Rect *xr_resolutions;
 
-void xinerama_init(void);
+void randr_init(int *event_base, xcb_window_t root);
-void xinerama_query_screens(void);
+void randr_query(xcb_window_t root);
 
 #endif