evas text: fix _ellipsis_get to return -1.0 on failure.

Summary:
When getting ellipsis value from evas text object fails,
the most reasonable return value is -1.0.
Currently, evas_object_text_ellipsis_get API with NULL returns 0.0.
It means ellipsis is not off. It must return -1.0 when API fails.
@fix

Comments by Tom: until now, this was inconsistent. With this change, it
now returns -1.0 consistently. Also, fixed commit summary.

Reviewers: woohyun, Hermet, seoz, tasn

Reviewed By: tasn

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D1944

src/lib/evas/canvas/evas_text.eo

@@ -58,12 +58,12 @@ class Evas.Text (Evas.Object, Efl.Text, Efl.Text_Properties)
             /*@
             @brief Gets the ellipsis currently set on the text object.
 
-            @return The ellipsis set on the text object.
+            @return The ellipsis set on the text object. The ellipsis is -1.0.
             @see evas_object_text_ellipsis_set.
             @since 1.8 */
          }
          values {
-            double ellipsis; /*@ the ellipsis. */
+            double ellipsis(-1); /*@ the ellipsis. */
          }
       }
       bidi_delimiters {

src/tests/evas/evas_test_text.c

@@ -224,6 +224,10 @@ START_TEST(evas_text_ellipsis)
    /* Ligatures */
    buf = "Fffffffffffffffffffffffffffffffffff";
    _test_ellipsis(to, buf, font, size, 0.0);
+
+   /* Check ellipsis value with NULL */
+   fail_if(evas_object_text_ellipsis_get(NULL) != -1.0);
+
    END_TEXT_TEST();
 }
 END_TEST