xruler

commit f1f8d511bbf84a85e5214a4246c5938a45ff7354
parent 811ca13d0ba503678f63fcf2108fedb836f6d2ee
Author: Matthias Balk <mbalk@mbalk.de>
Date:   Sun,  3 Nov 2019 10:02:26 +0100

set mouse cursor to crosshair

inspired by
https://www.x.org/releases/X11R7.5/doc/libxcb/tutorial/index.html#mousecursorexample

Diffstat:
M
xruler.c
 | 
57
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 57 insertions(+), 0 deletions(-)
diff --git a/xruler.c b/xruler.c
@@ -6,6 +6,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include <xcb/xcb.h>
 
@@ -13,6 +14,61 @@
 static uint32_t width = 1500;
 static uint32_t height = 50;
 
+
+static void set_crosshair_cursor(
+    xcb_connection_t *c,
+    xcb_screen_t     *screen,
+    xcb_window_t      window)
+{
+  int cursor_id = 33; /* Crosshair */
+
+  xcb_font_t font = xcb_generate_id(c);
+  xcb_void_cookie_t cookie_font =
+      xcb_open_font_checked(c, font, strlen("cursor"), "cursor");
+
+  xcb_generic_error_t *error;
+  error = xcb_request_check(c, cookie_font);
+  if (error) {
+    fprintf(stderr, "ERROR: can't open font : %d\n", error->error_code);
+    xcb_disconnect(c);
+    exit(-1);
+  }
+
+  xcb_cursor_t cursor = xcb_generate_id(c);
+  xcb_create_glyph_cursor(c, cursor, font, font,
+                          cursor_id, cursor_id + 1,
+                          0, 0, 0,
+                          0, 0, 0);
+
+  xcb_gcontext_t gc = xcb_generate_id(c);
+  uint32_t mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
+  uint32_t values_list[] = {screen->black_pixel, screen->white_pixel, font};
+  xcb_void_cookie_t cookie_gc =
+      xcb_create_gc_checked(c, gc, window, mask, values_list);
+
+  error = xcb_request_check(c, cookie_gc);
+  if (error) {
+    fprintf(stderr, "ERROR: can't create gc : %d\n", error->error_code);
+    xcb_disconnect(c);
+    exit(-1);
+  }
+
+  mask = XCB_CW_CURSOR;
+  uint32_t value_list = cursor;
+  xcb_change_window_attributes(c, window, mask, &value_list);
+
+  xcb_free_cursor(c, cursor);
+
+  cookie_font = xcb_close_font_checked(c, font);
+  error = xcb_request_check(c, cookie_font);
+  if (error) {
+    fprintf(stderr, "ERROR: can't close font : %d\n", error->error_code);
+    xcb_disconnect(c);
+    exit(-1);
+  }
+}
+
+
 int main (int argc, char** argv)
 {
   /* Open the connection to the X server */
@@ -58,6 +114,7 @@ int main (int argc, char** argv)
   xcb_map_window (connection, window);
   xcb_flush (connection);
 
+  set_crosshair_cursor(connection, screen, window);
 
   /* draw primitives */
   xcb_generic_event_t* event;