i3bar: explicitly set cursor using libxcursor if available

Even if the X11 root window cursor is not set up correctly for some
reason, with this fix, users should at least see the correct cursor when
the pointer is over i3bar.

see issue #2114

i3bar/i3bar.mk

@@ -4,8 +4,8 @@ CLEAN_TARGETS += clean-i3bar
 
 i3bar_SOURCES := $(wildcard i3bar/src/*.c)
 i3bar_HEADERS := $(wildcard i3bar/include/*.h)
-i3bar_CFLAGS   = $(XCB_CFLAGS) $(PANGO_CFLAGS) $(YAJL_CFLAGS) $(LIBEV_CFLAGS)
+i3bar_CFLAGS   = $(XCB_CFLAGS) $(XCB_CURSOR_CFLAGS) $(PANGO_CFLAGS) $(YAJL_CFLAGS) $(LIBEV_CFLAGS)
-i3bar_LIBS     = $(XCB_LIBS) $(PANGO_LIBS) $(YAJL_LIBS) $(LIBEV_LIBS) $(XCB_XKB_LIBS)
+i3bar_LIBS     = $(XCB_LIBS) $(XCB_CURSOR_LIBS) $(PANGO_LIBS) $(YAJL_LIBS) $(LIBEV_LIBS) $(XCB_XKB_LIBS)
 
 i3bar_OBJECTS := $(i3bar_SOURCES:.c=.o)
 

i3bar/src/xcb.c

@@ -11,6 +11,7 @@
 #include <xcb/xkb.h>
 #include <xcb/xproto.h>
 #include <xcb/xcb_aux.h>
+#include <xcb/xcb_cursor.h>
 
 #ifdef XCB_COMPAT
 #include "xcb_compat.h"
@@ -34,6 +35,10 @@
 #include "common.h"
 #include "libi3.h"
 
+/** This is the equivalent of XC_left_ptr. I’m not sure why xcb doesn’t have a
+ * constant for that. */
+#define XCB_CURSOR_LEFT_PTR 68
+
 /* We save the atoms in an easy to access array, indexed by an enum */
 enum {
 #define ATOM_DO(name) name,
@@ -49,6 +54,7 @@ xcb_connection_t *xcb_connection;
 int screen;
 xcb_screen_t *root_screen;
 xcb_window_t xcb_root;
+static xcb_cursor_t cursor;
 
 /* selection window for tray support */
 static xcb_window_t selwin = XCB_NONE;
@@ -1206,6 +1212,24 @@ char *init_xcb_early() {
     colormap = root_screen->default_colormap;
     visual_type = get_visualtype(root_screen);
 
+    xcb_cursor_context_t *cursor_ctx;
+    if (xcb_cursor_context_new(conn, root_screen, &cursor_ctx) == 0) {
+        cursor = xcb_cursor_load_cursor(cursor_ctx, "left_ptr");
+        xcb_cursor_context_free(cursor_ctx);
+    } else {
+        cursor = xcb_generate_id(xcb_connection);
+        i3Font cursor_font = load_font("cursor", false);
+        xcb_create_glyph_cursor(
+            xcb_connection,
+            cursor,
+            cursor_font.specific.xcb.id,
+            cursor_font.specific.xcb.id,
+            XCB_CURSOR_LEFT_PTR,
+            XCB_CURSOR_LEFT_PTR + 1,
+            0, 0, 0,
+            65535, 65535, 65535);
+    }
+
     /* The various watchers to communicate with xcb */
     xcb_io = smalloc(sizeof(ev_io));
     xcb_prep = smalloc(sizeof(ev_prepare));
@@ -1462,6 +1486,7 @@ void clean_xcb(void) {
     FREE_SLIST(outputs, i3_output);
     FREE(outputs);
 
+    xcb_free_cursor(xcb_connection, cursor);
     xcb_flush(xcb_connection);
     xcb_aux_sync(xcb_connection);
     xcb_disconnect(xcb_connection);
@@ -1605,7 +1630,7 @@ xcb_void_cookie_t config_strut_partial(i3_output *output) {
  */
 void reconfig_windows(bool redraw_bars) {
     uint32_t mask;
-    uint32_t values[5];
+    uint32_t values[6];
     static bool tray_configured = false;
 
     i3_output *walk;
@@ -1623,7 +1648,7 @@ void reconfig_windows(bool redraw_bars) {
             xcb_window_t bar_id = xcb_generate_id(xcb_connection);
             xcb_pixmap_t buffer_id = xcb_generate_id(xcb_connection);
             xcb_pixmap_t statusline_buffer_id = xcb_generate_id(xcb_connection);
-            mask = XCB_CW_BACK_PIXEL | XCB_CW_BORDER_PIXEL | XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK | XCB_CW_COLORMAP;
+            mask = XCB_CW_BACK_PIXEL | XCB_CW_BORDER_PIXEL | XCB_CW_OVERRIDE_REDIRECT | XCB_CW_EVENT_MASK | XCB_CW_COLORMAP | XCB_CW_CURSOR;
 
             values[0] = colors.bar_bg.colorpixel;
             values[1] = root_screen->black_pixel;
@@ -1645,6 +1670,7 @@ void reconfig_windows(bool redraw_bars) {
                 walk->visible = true;
             }
             values[4] = colormap;
+            values[5] = cursor;
 
             xcb_void_cookie_t win_cookie = xcb_create_window_checked(xcb_connection,
                                                                      depth,