csstokenizer: Handle backslash at end of document

Testcases included.

gtk/css/gtkcsstokenizer.c

@@ -633,13 +633,6 @@ is_name (char c)
       || c == '-';
 }
 
-static gboolean
-is_valid_escape (char c1, char c2)
-{
-  return c1 == '\\'
-      && !is_newline (c2);
-}
-
 static gboolean
 is_non_printable (char c)
 {
@@ -650,6 +643,25 @@ is_non_printable (char c)
       || c == 0x7F;
 }
 
+static gboolean
+is_valid_escape (const char *data,
+                 const char *end)
+{
+  switch (end - data)
+    {
+      default:
+        if (is_newline (data[1]))
+          return FALSE;
+        G_GNUC_FALLTHROUGH;
+
+      case 1:
+        return data[0] == '\\';
+
+      case 0:
+        return FALSE;
+    }
+}
+
 static inline gsize
 gtk_css_tokenizer_remaining (GtkCssTokenizer *tokenizer)
 {
@@ -659,15 +671,7 @@ gtk_css_tokenizer_remaining (GtkCssTokenizer *tokenizer)
 static gboolean
 gtk_css_tokenizer_has_valid_escape (GtkCssTokenizer *tokenizer)
 {
-  switch (gtk_css_tokenizer_remaining (tokenizer))
-    {
-      case 0:
-        return FALSE;
-      case 1:
-        return *tokenizer->data == '\\';
-      default:
-        return is_valid_escape (tokenizer->data[0], tokenizer->data[1]);
-    }
+  return is_valid_escape (tokenizer->data, tokenizer->end);
 }
 
 static gboolean
@@ -814,7 +818,11 @@ gtk_css_tokenizer_read_escape (GtkCssTokenizer *tokenizer)
 
   if (i == 0)
     {
-      value = g_utf8_get_char_validated (tokenizer->data, gtk_css_tokenizer_remaining (tokenizer));
+      gsize remaining = gtk_css_tokenizer_remaining (tokenizer);
+      if (remaining == 0)
+        return 0xFFFD;
+
+      value = g_utf8_get_char_validated (tokenizer->data, remaining);
       if (value == (gunichar) -1 || value == (gunichar) -2)
         value = 0;
 

testsuite/css/parser/backslash-eof-is-identifier.css

@@ -0,0 +1,2 @@
+a {
+  animation-name: \

testsuite/css/parser/backslash-eof-is-identifier.errors

@@ -0,0 +1,2 @@
+backslash-eof-is-identifier.css:2:3-20: error: GTK_CSS_PARSER_WARNING_SYNTAX
+backslash-eof-is-identifier.css:1:3-2:20: error: GTK_CSS_PARSER_WARNING_SYNTAX

testsuite/css/parser/backslash-eof-is-identifier.ref.css

@@ -0,0 +1,3 @@
+a {
+  animation-name: <EFBFBD>;
+}

testsuite/css/parser/backslash.css

@@ -0,0 +1 @@
+\

testsuite/css/parser/backslash.errors

@@ -0,0 +1 @@
+backslash.css:1:2: error: GTK_CSS_PARSER_ERROR_SYNTAX

testsuite/css/parser/meson.build

@@ -160,6 +160,12 @@ test_data = [
   'background-shorthand-single.ref.css',
   'background-size.css',
   'background-size.ref.css',
+  'backslash.css',
+  'backslash.errors',
+  'backslash.ref.css',
+  'backslash-eof-is-identifier.css',
+  'backslash-eof-is-identifier.errors',
+  'backslash-eof-is-identifier.ref.css',
   'border-color.css',
   'border-color-currentcolor.css',
   'border-color-currentcolor.ref.css',