Allow a programmable backspace key for the login screen

The login screen uses hardcoded scancode values to identify particular keys. This is changed for the backspace key for Colemak support, as the caps lock key has been re-purposed as a backspace key. We now identify a backspace request by looking at the keysym for the key.
neutrinolabs · Nov 18, 2024 · 17ad375 · 17ad375
1 parent cbf5f7a
commit 17ad375
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Showing 3 changed files with 15 additions and 55 deletions.
diff --git a/xrdp/lang.c b/xrdp/lang.c
@@ -118,46 +118,6 @@ get_key_info_from_kbd_event(int keyboard_flags, int key_code, int *keys,
     return rv;
 }
 
-/*****************************************************************************/
-int
-get_keysym_from_kbd_event(int keyboard_flags, int key_code, int *keys,
-                          int caps_lock, int num_lock, int scroll_lock,
-                          struct xrdp_keymap *keymap)
-{
-    struct xrdp_key_info *ki;
-
-    ki = get_key_info_from_kbd_event(keyboard_flags, key_code, keys,
-                                     caps_lock, num_lock, scroll_lock,
-                                     keymap);
-
-    if (ki == 0)
-    {
-        return 0;
-    }
-
-    return ki->sym;
-}
-
-/*****************************************************************************/
-char32_t
-get_char_from_kbd_event(int keyboard_flags, int key_code, int *keys,
-                        int caps_lock, int num_lock, int scroll_lock,
-                        struct xrdp_keymap *keymap)
-{
-    struct xrdp_key_info *ki;
-
-    ki = get_key_info_from_kbd_event(keyboard_flags, key_code, keys,
-                                     caps_lock, num_lock, scroll_lock,
-                                     keymap);
-
-    if (ki == 0)
-    {
-        return 0;
-    }
-
-    return ki->chr;
-}
-
 /*****************************************************************************/
 /**
  * Converts a table key to a scancode index value

diff --git a/xrdp/xrdp.h b/xrdp/xrdp.h
@@ -442,14 +442,6 @@ get_key_info_from_kbd_event(int keyboard_flags, int key_code, int *keys,
                             int caps_lock, int num_lock, int scroll_lock,
                             struct xrdp_keymap *keymap);
 int
-get_keysym_from_kbd_event(int keyboard_flags, int key_code, int *keys,
-                          int caps_lock, int num_lock, int scroll_lock,
-                          struct xrdp_keymap *keymap);
-char32_t
-get_char_from_kbd_event(int keyboard_flags, int key_code, int *keys,
-                        int caps_lock, int num_lock, int scroll_lock,
-                        struct xrdp_keymap *keymap);
-int
 get_keymaps(int keylayout, struct xrdp_keymap *keymap);
 
 int

diff --git a/xrdp/xrdp_bitmap.c b/xrdp/xrdp_bitmap.c
@@ -29,7 +29,10 @@
 #include "log.h"
 #include "string_calls.h"
 
-
+// For a very few key functions, using the keysym is preferable to the
+// raw scancode. Here are defines to avoid pulling an X11 dependency
+// into the xrdp:-
+#define XK_BackSpace 0xff08
 
 
 static const unsigned int g_crc_table[256] =
@@ -1150,6 +1153,13 @@ xrdp_bitmap_def_proc(struct xrdp_bitmap *self, int msg,
         {
             int scan_code = SCANCODE_FROM_KBD_EVENT(param1, param2);
             int num_lock = self->wm->num_lock;
+            /* We may need a keysym or a printable character for the key */
+            struct xrdp_key_info *ki = get_key_info_from_kbd_event
+                                       (param2, param1, self->wm->keys,
+                                        self->wm->caps_lock,
+                                        self->wm->num_lock, self->wm->scroll_lock,
+                                        &(self->wm->keymap));
+
             /* left or up arrow */
             if ((scan_code == SCANCODE_LEFT_ARROW_KEY) ||
                     (scan_code == SCANCODE_UP_ARROW_KEY) ||
@@ -1174,8 +1184,9 @@ xrdp_bitmap_def_proc(struct xrdp_bitmap *self, int msg,
                     xrdp_bitmap_invalidate(self, 0);
                 }
             }
-            /* backspace */
-            else if (scan_code == SCANCODE_BACKSPACE_KEY)
+            /* backspace. Test keysym rather than scan code, so keys
+             * other than SCANCODE_BACKSPACE_KEY can generate backspace */
+            else if (ki != NULL && ki->sym == XK_BackSpace)
             {
                 n = utf8_char_count(self->caption1);
 
@@ -1229,10 +1240,7 @@ xrdp_bitmap_def_proc(struct xrdp_bitmap *self, int msg,
             }
             else
             {
-                char32_t c = get_char_from_kbd_event
-                             (param2, param1, self->wm->keys, self->wm->caps_lock,
-                              self->wm->num_lock, self->wm->scroll_lock,
-                              &(self->wm->keymap));
+                char32_t c = (ki == NULL) ? 0 : ki->chr;
                 // Add a printing character to the string. If successful,
                 // bump the edit position and re-display the string
                 if (c >= ' ' &&