GUAC-717: Add GUAC_CHAR_CONTINUATION sentinel. Add width property to characters.

src/terminal/common.c

@@ -21,6 +21,7 @@
  */
 
 #include "config.h"
+#include "types.h"
 
 #include <stdbool.h>
 #include <unistd.h>
@@ -83,7 +84,8 @@ int guac_terminal_encode_utf8(int codepoint, char* utf8) {
 bool guac_terminal_has_glyph(int codepoint) {
     return
            codepoint != 0
-        && codepoint != ' ';
+        && codepoint != ' '
+        && codepoint != GUAC_CHAR_CONTINUATION;
 }
 
 int guac_terminal_write_all(int fd, const char* buffer, int size) {

src/terminal/display.c

@@ -585,7 +585,8 @@ void guac_terminal_display_resize(guac_terminal_display* display, int width, int
         .attributes = {
             .foreground = 0,
             .background = 0
-        }
+        },
+        .width = 1
     };
 
     /* Free old operations buffer */

src/terminal/terminal.c

@@ -96,7 +96,8 @@ guac_terminal* guac_terminal_create(guac_client* client,
             .bold       = false,
             .reverse    = false,
             .underscore = false
-        }};
+        },
+        .width = 1};
 
     guac_terminal* term = malloc(sizeof(guac_terminal));
     term->client = client;

src/terminal/types.h

@@ -28,6 +28,15 @@
 
 #include <stdbool.h>
 
+/**
+ * A character which is not truly a character, but rather part of an
+ * existing character which spans multiple columns. The original
+ * character will be somewhere earlier in the row, separated from
+ * this character by a contiguous string of zero of more
+ * GUAC_CHAR_CONTINUATION characters.
+ */
+#define GUAC_CHAR_CONTINUATION -1
+
 /**
  * An RGB color, where each component ranges from 0 to 255.
  */
@@ -95,7 +104,9 @@ typedef struct guac_terminal_attributes {
 typedef struct guac_terminal_char {
 
     /**
-     * The Unicode codepoint of the character to display.
+     * The Unicode codepoint of the character to display, or
+     * GUAC_CHAR_CONTINUATION if this character is part of
+     * another character which spans multiple columns.
      */
     int value;
 
@@ -104,6 +115,12 @@ typedef struct guac_terminal_char {
      */
     guac_terminal_attributes attributes;
 
+    /**
+     * The number of columns this character occupies. If the character is
+     * GUAC_CHAR_CONTINUATION, this value is undefined and not applicable.
+     */
+    int width;
+
 } guac_terminal_char;
 
 #endif