[util] Add --text-before and --text-after to hb-shape / hb-view

Use with Arabic, for example, to see the effect on joining.

util/hb-ot-shape-closure.cc

@@ -61,7 +61,9 @@ struct shape_closure_consumer_t : option_group_t
   }
   void consume_line (hb_buffer_t  *buffer,
 		     const char   *text,
-		     unsigned int  text_len)
+		     unsigned int  text_len,
+		     const char   *text_before,
+		     const char   *text_after)
   {
     hb_set_clear (glyphs);
     shaper.shape_closure (text, text_len, font, buffer, glyphs);

util/main-font-text.hh

@@ -61,7 +61,7 @@ struct main_font_text_t
     unsigned int text_len;
     const char *text;
     while ((text = input.get_line (&text_len)))
-      consumer.consume_line (buffer, text, text_len);
+      consumer.consume_line (buffer, text, text_len, input.text_before, input.text_after);
     hb_buffer_destroy (buffer);
 
     consumer.finish (&font_opts);

util/options.cc

@@ -350,6 +350,8 @@ text_options_t::add_options (option_parser_t *parser)
   {
     {"text",		0, 0, G_OPTION_ARG_STRING,	&this->text,			"Set input text",			"string"},
     {"text-file",	0, 0, G_OPTION_ARG_STRING,	&this->text_file,		"Set input text file-name\n\n    If no text is provided, standard input is used for input.",		"filename"},
+    {"text-before",	0, 0, G_OPTION_ARG_STRING,	&this->text_before,		"Set text context before each line",	"string"},
+    {"text-after",	0, 0, G_OPTION_ARG_STRING,	&this->text_after,		"Set text context after each line",	"string"},
     {NULL}
   };
   parser->add_group (entries,

util/options.hh

@@ -167,10 +167,18 @@ struct shape_options_t : option_group_t
     hb_buffer_set_language (buffer, hb_language_from_string (language, -1));
   }
 
-  void populate_buffer (hb_buffer_t *buffer, const char *text, int text_len)
+  void populate_buffer (hb_buffer_t *buffer, const char *text, int text_len,
+			const char *text_before, const char *text_after)
   {
-    hb_buffer_reset (buffer);
+    hb_buffer_clear (buffer);
+    if (text_before) {
+      unsigned int len = strlen (text_before);
+      hb_buffer_add_utf8 (buffer, text_before, len, len, 0);
+    }
     hb_buffer_add_utf8 (buffer, text, text_len, 0, text_len);
+    if (text_after) {
+      hb_buffer_add_utf8 (buffer, text_after, -1, 0, 0);
+    }
 
     if (!utf8_clusters) {
       /* Reset cluster values to refer to Unicode character index
@@ -245,6 +253,9 @@ struct font_options_t : option_group_t
 struct text_options_t : option_group_t
 {
   text_options_t (option_parser_t *parser) {
+    text_before = NULL;
+    text_after = NULL;
+
     text = NULL;
     text_file = NULL;
 
@@ -273,6 +284,9 @@ struct text_options_t : option_group_t
 
   const char *get_line (unsigned int *len);
 
+  const char *text_before;
+  const char *text_after;
+
   const char *text;
   const char *text_file;
 

util/shape-consumer.hh

@@ -45,11 +45,13 @@ struct shape_consumer_t
   }
   void consume_line (hb_buffer_t  *buffer,
 		     const char   *text,
-		     unsigned int  text_len)
+		     unsigned int  text_len,
+		     const char   *text_before,
+		     const char   *text_after)
   {
     output.new_line ();
 
-    shaper.populate_buffer (buffer, text, text_len);
+    shaper.populate_buffer (buffer, text, text_len, text_before, text_after);
     output.consume_text (buffer, text, text_len, shaper.utf8_clusters);
 
     if (!shaper.shape (font, buffer)) {