1 files changed, 95 insertions, 0 deletions
diff --git a/src/unicode-extra.c b/src/unicode-extra.c
new file mode 100644
index 0000000..3a59378
--- /dev/null
+++ b/src/unicode-extra.c
@@ -0,0 +1,95 @@
+#include <glib.h>
+
+#include "vt100.h"
+
+/*
+ * so, here's the story. unicode doesn't actually define monospace width for
+ * characters in a way that's useful. there's an "east asian width" property
+ * that mostly works, but leaves a bunch of things ambiguous (if you're
+ * displaying this as part of a bunch of east asian text, then it's wide, but
+ * if you're not, then it's narrow). we in general treat ambiguous characters
+ * as narrow for now (although this should perhaps be an option in the future).
+ * one place where this does not work out, though, is emoji. emoji do not have
+ * a useful width property (see
+ * http://www.unicode.org/L2/L2016/16027-emoji-terminals-eaw.pdf), and even the
+ * proposal in that link to make every character with Emoji_Presentation=true a
+ * wide character isn't really how things work in practice - for instance,
+ * U+231A (WATCH) is rendered by most monospace fonts (that I've seen, anyway)
+ * as a narrow character. as far as i can tell, it appears (although i'm not
+ * certain of this) that all BMP characters with Emoji_Presentation=true are
+ * narrow and all astral plane characters with Emoji_Presentation=true are
+ * wide, so that's what i'm going to go with here. character ranges and data in
+ * this file are taken from
+ * http://www.unicode.org/Public/emoji/2.0//emoji-data.txt.
+ */
+struct vt100_char_range {
+    gunichar start;
+    gunichar end;
+};
+
+static struct vt100_char_range vt100_wide_emoji[] = {
+    { 0x1F004, 0x1F004 },
+    { 0x1F0CF, 0x1F0CF },
+    { 0x1F18E, 0x1F18E },
+    { 0x1F191, 0x1F19A },
+    { 0x1F1E6, 0x1F1FF },
+    { 0x1F201, 0x1F201 },
+    { 0x1F21A, 0x1F21A },
+    { 0x1F22F, 0x1F22F },
+    { 0x1F232, 0x1F236 },
+    { 0x1F238, 0x1F23A },
+    { 0x1F250, 0x1F251 },
+    { 0x1F300, 0x1F320 },
+    { 0x1F32D, 0x1F335 },
+    { 0x1F337, 0x1F37C },
+    { 0x1F37E, 0x1F393 },
+    { 0x1F3A0, 0x1F3CA },
+    { 0x1F3CF, 0x1F3D3 },
+    { 0x1F3E0, 0x1F3F0 },
+    { 0x1F3F4, 0x1F3F4 },
+    { 0x1F3F8, 0x1F43E },
+    { 0x1F440, 0x1F440 },
+    { 0x1F442, 0x1F4FC },
+    { 0x1F4FF, 0x1F53D },
+    { 0x1F54B, 0x1F54E },
+    { 0x1F550, 0x1F567 },
+    { 0x1F595, 0x1F596 },
+    { 0x1F5FB, 0x1F64F },
+    { 0x1F680, 0x1F6C5 },
+    { 0x1F6CC, 0x1F6CC },
+    { 0x1F6D0, 0x1F6D0 },
+    { 0x1F6EB, 0x1F6EC },
+    { 0x1F910, 0x1F918 },
+    { 0x1F980, 0x1F984 },
+    { 0x1F9C0, 0x1F9C0 },
+};
+
+static int vt100_is_wide_emoji(gunichar codepoint);
+
+int vt100_is_wide_char(gunichar codepoint)
+{
+    return g_unichar_iswide(codepoint) || vt100_is_wide_emoji(codepoint);
+}
+
+static int vt100_is_wide_emoji(gunichar codepoint)
+{
+    static size_t ranges = sizeof(vt100_wide_emoji) / sizeof(struct vt100_char_range);
+    ssize_t low = 0, high = ranges - 1;
+
+    do {
+        ssize_t cur = (high + low) / 2;
+        struct vt100_char_range range = vt100_wide_emoji[cur];
+
+        if (codepoint < range.start) {
+            high = cur - 1;
+        }
+        else if (codepoint > range.end) {
+            low = cur + 1;
+        }
+        else {
+            return 1;
+        }
+    } while (low <= high);
+
+    return 0;
+}