From ef817f15f0eaec9704ec25d9468c2c8497a5bc13 Mon Sep 17 00:00:00 2001
From: Daniel Hirt <daniel.hirt@samsung.com>
Date: Wed, 13 Jul 2016 11:40:36 +0000
Subject: [PATCH] Evas font: fix width query for OT

Fixes T4068.
Simply querying the last glyph to determine the width of the glyph sequence
won't always work, as OT can have negative offsets (adjusts the placement of a
specific glyph better).

The solution is to calculate the "max width" of some sequence that will
guarantee us proper width results. The worst solution would be to iterate on all
the glyphs and sum up the max width. This is a bit impractical. Instead, we will
inspect just the "cluster" of the last glyph, if one exists.

This should have no performance impact on trivial cases, and very little impact
on the others.

@fix
---
 src/lib/evas/common/evas_font_query.c | 93 ++++++++++++++++++++++-----
 1 file changed, 76 insertions(+), 17 deletions(-)

diff --git a/src/lib/evas/common/evas_font_query.c b/src/lib/evas/common/evas_font_query.c
index f435b9b0c3..cf977e955a 100644
--- a/src/lib/evas/common/evas_font_query.c
+++ b/src/lib/evas/common/evas_font_query.c
@@ -314,6 +314,81 @@ evas_common_font_ascent_descent_get(RGBA_Font *fn, const Evas_Text_Props *text_p
    if (descent) *descent = (desc < max_desc) ? desc : max_desc;
 }
 
+#ifdef OT_SUPPORT
+static inline Evas_Coord
+_evas_common_font_query_width_ot(const Evas_Text_Props *text_props)
+{
+   Evas_Coord ret_w = 0;
+
+   if (text_props->len > 0)
+     {
+        size_t off = text_props->start + text_props->len - 1;
+        const Evas_Font_Glyph_Info *glyph = text_props->info->glyph + off;
+        Evas_Font_OT_Info *ot = text_props->info->ot + off;
+        size_t cluster = ot->source_cluster;
+
+        do
+          {
+             Evas_Coord pen_x = (off > 0) ? glyph[-1].pen_after : 0;
+             Evas_Coord w = pen_x + glyph->x_bear + glyph->width +
+                EVAS_FONT_ROUND_26_6_TO_INT(EVAS_FONT_OT_X_OFF_GET(*ot));
+             if (w > ret_w)
+               {
+                  ret_w = w;
+               }
+
+             glyph--;
+             ot--;
+          } while((off-- > text_props->start) && (ot->source_cluster == cluster));
+
+        if (text_props->start > 0)
+          {
+             ret_w -= text_props->info->glyph[text_props->start - 1].pen_after;
+          }
+     }
+
+   return ret_w;
+}
+#else
+static inline Evas_Coord
+_evas_common_font_query_width_regular(const Evas_Text_Props *text_props)
+{
+   Evas_Coord ret_w = 0;
+
+   if (text_props->len > 0)
+     {
+        const Evas_Font_Glyph_Info *last_glyph = text_props->info->glyph +
+           text_props->start + text_props->len - 1;
+
+        if (text_props->len > 1)
+          {
+             const Evas_Font_Glyph_Info *glyph = text_props->info->glyph +
+                text_props->start;
+
+             ret_w = last_glyph[-1].pen_after;
+             if (text_props->start > 0)
+                ret_w -= glyph[-1].pen_after;
+          }
+
+        ret_w += last_glyph->width + last_glyph->x_bear;
+     }
+
+   return ret_w;
+}
+#endif
+
+static inline Evas_Coord
+_evas_common_font_query_width(const Evas_Text_Props *text_props)
+{
+   Evas_Coord ret_w;
+#ifdef OT_SUPPORT
+   ret_w = _evas_common_font_query_width_ot(text_props);
+#else
+   ret_w = _evas_common_font_query_width_regular(text_props);
+#endif
+   return ret_w;
+}
+
 /**
  * @internal
  * Calculate the size of the string (width and height).
@@ -333,24 +408,8 @@ evas_common_font_query_size(RGBA_Font *fn, const Evas_Text_Props *text_props, in
 
    if (text_props->len > 0)
      {
-        const Evas_Font_Glyph_Info *glyph = text_props->info->glyph +
-           text_props->start;
-        const Evas_Font_Glyph_Info *last_glyph = glyph;
-
-        if (text_props->len > 1)
-          {
-             last_glyph += text_props->len - 1;
-             ret_w = last_glyph[-1].pen_after;
-             if (text_props->start > 0)
-                ret_w -= glyph[-1].pen_after;
-          }
-#ifdef OT_SUPPORT
-        ret_w += EVAS_FONT_ROUND_26_6_TO_INT(EVAS_FONT_OT_X_OFF_GET(
-              text_props->info->ot[text_props->start + text_props->len - 1]));
-#endif
-        ret_w += last_glyph->width + last_glyph->x_bear;
+        ret_w = _evas_common_font_query_width(text_props);
      }
-
    if (w) *w = ret_w;
    if (h) *h = evas_common_font_max_ascent_get(fn) + evas_common_font_max_descent_get(fn);
 }