[PATCH wayland] cursor: add wl_cursor_frame_and_duration

[Derek Foreman]

It's useful to know how long the current cursor frame should be displayed
so we can wait that long to change it.

Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
---
differences from v1:
 Add comment about 0 durations
 document return of 0 duration as unchanging image
 make sure duration calculation doesn't wrap around or return 0
 fix obvious pointer brain damage


 cursor/wayland-cursor.c | 45 ++++++++++++++++++++++++++++++++++++++++++---
 cursor/wayland-cursor.h |  4 ++++
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/cursor/wayland-cursor.c b/cursor/wayland-cursor.c
index dba3b51..1a5393a 100644
--- a/cursor/wayland-cursor.c
+++ b/cursor/wayland-cursor.c
@@ -458,28 +458,67 @@ wl_cursor_theme_get_cursor(struct wl_cursor_theme *theme,
 }
 
 /** Find the frame for a given elapsed time in a cursor animation
+ *  as well as the time left until next cursor change.
  *
  * \param cursor The cursor
- * \param time Elapsed time since the beginning of the animation
+ * \param time Elapsed time in ms since the beginning of the animation
+ * \param duration pointer to uint32_t to store time left for this image or
+ *                 zero if the cursor won't change.
  *
  * \return The index of the image that should be displayed for the
  * given time in the cursor animation.
  */
 WL_EXPORT int
-wl_cursor_frame(struct wl_cursor *_cursor, uint32_t time)
+wl_cursor_frame_and_duration(struct wl_cursor *_cursor, uint32_t time,
+			     uint32_t *duration)
 {
 	struct cursor *cursor = (struct cursor *) _cursor;
 	uint32_t t;
 	int i;
 
-	if (cursor->cursor.image_count == 1)
+	if (cursor->cursor.image_count == 1) {
+		if (duration)
+			*duration = 0;
 		return 0;
+	}
 
 	i = 0;
 	t = time % cursor->total_delay;
 
+	/* If there is a 0 delay in the image set then this
+	 * loop breaks on it and we display that cursor until
+	 * time % cursor->total_delay wraps again.
+	 * Since a 0 delay is silly, and we've never actually
+	 * seen one in a cursor file, we haven't bothered to
+	 * "fix" this.
+	 */
 	while (t - cursor->cursor.images[i]->delay < t)
 		t -= cursor->cursor.images[i++]->delay;
 
+	if (!duration)
+		return i;
+
+	/* Make sure we don't accidentally tell the caller this is
+	 * a static cursor image.
+	 */
+	if (t >= cursor->cursor.images[i]->delay)
+		*duration = 1;
+	else
+		*duration = cursor->cursor.images[i]->delay - t;
+
 	return i;
 }
+
+/** Find the frame for a given elapsed time in a cursor animation
+ *
+ * \param cursor The cursor
+ * \param time Elapsed time in ms since the beginning of the animation
+ *
+ * \return The index of the image that should be displayed for the
+ * given time in the cursor animation.
+ */
+WL_EXPORT int
+wl_cursor_frame(struct wl_cursor *_cursor, uint32_t time)
+{
+	return wl_cursor_frame_and_duration(_cursor, time, NULL);
+}
diff --git a/cursor/wayland-cursor.h b/cursor/wayland-cursor.h
index c7548ae..c3884a0 100644
--- a/cursor/wayland-cursor.h
+++ b/cursor/wayland-cursor.h
@@ -63,6 +63,10 @@ wl_cursor_image_get_buffer(struct wl_cursor_image *image);
 int
 wl_cursor_frame(struct wl_cursor *cursor, uint32_t time);
 
+int
+wl_cursor_frame_and_duration(struct wl_cursor *cursor, uint32_t time,
+			     uint32_t *duration);
+
 #ifdef  __cplusplus
 }
 #endif
-- 
2.1.4