Be a little more paranoid about XI 2.0 implementations

* src/xterm.c (xi_populate_device_from_info):
(xi_disable_devices): Do not restore valuator values if the
valuator info has a mode of Relative and a value of 0.0.

1 files changed, 39 insertions, 18 deletions

diff --git a/src/xterm.c b/src/xterm.c
index fd04061436a..a175a4a6bbb 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -5339,7 +5339,7 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
   struct xi_known_valuator *values, *tem;
   int actual_valuator_count, c;
   XIScrollClassInfo *info;
-  XIValuatorClassInfo *val_info;
+  XIValuatorClassInfo *valuator_info;
 #endif
 #ifdef HAVE_XINPUT2_2
   XITouchClassInfo *touch_info;
@@ -5450,12 +5450,23 @@ xi_populate_device_from_info (struct x_display_info *dpyinfo,
 
         case XIValuatorClass:
           {
-            val_info = (XIValuatorClassInfo *) device->classes[c];
+            valuator_info = (XIValuatorClassInfo *) device->classes[c];
             tem = SAFE_ALLOCA (sizeof *tem);
 
+            /* Avoid restoring bogus values if some driver
+               accidentally specifies relative values in scroll
+               valuator classes how the input extension spec says they
+               should be, but allow restoring values when a value is
+               set, which is how the input extension actually
+               behaves.  */
+
+            if (valuator_info->value == 0.0
+                && valuator_info->mode != XIModeAbsolute)
+              continue;
+
             tem->next = values;
-            tem->number = val_info->number;
-            tem->current_value = val_info->value;
+            tem->number = valuator_info->number;
+            tem->current_value = valuator_info->value;
 
             values = tem;
             break;
@@ -13182,22 +13193,32 @@ xi_handle_new_classes (struct x_display_info *dpyinfo, struct xi_device_t *devic
 
   for (i = 0; i < num_classes; ++i)
     {
-      switch (classes[i]->type)
-        {
-        case XIValuatorClass:
-          valuator_info = (XIValuatorClassInfo *) classes[i];
+      if (classes[i]->type != XIValuatorClass)
+        continue;
 
-          valuator = xi_get_scroll_valuator (device,
-                                             valuator_info->number);
-          if (valuator)
-            {
-              valuator->invalid_p = false;
-              valuator->current_value = valuator_info->value;
-              valuator->emacs_value = 0;
-            }
+      valuator_info = (XIValuatorClassInfo *) classes[i];
 
-          break;
-        }
+      /* Avoid restoring bogus values if some driver accidentally
+         specifies relative values in scroll valuator classes how the
+         input extension spec says they should be, but allow restoring
+         values when a value is set, which is how the input extension
+         actually behaves.  */
+
+      if (valuator_info->value == 0.0
+          && valuator_info->mode != XIModeAbsolute)
+        continue;
+
+      valuator = xi_get_scroll_valuator (device,
+                                         valuator_info->number);
+
+      if (!valuator)
+        continue;
+
+      valuator->invalid_p = false;
+      valuator->current_value = valuator_info->value;
+      valuator->emacs_value = 0;
+
+      break;
     }
 }