From 60fd4a262c5a3ce1c3951e305bcade3a88019f8a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Fri, 15 Mar 2024 15:19:43 +0100
Subject: [PATCH] sixel: initialize the color table to colors used by the VT340

---
 CHANGELOG.md |  4 ++++
 sixel.c      | 39 ++++++++++++++++++++++++++++++++++++---
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a67ff8fa..04571604 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -143,6 +143,10 @@
 * Crash when failing to load an xcursor image ([#1624][1624]).
 * Crash when resizing a dynamically sized sixel (no raster
   attributes), with a non-1:1 aspect ratio.
+* The default sixel color table is now initialized to the colors used
+  by the VT340, instead of not being initialized at all (thus
+  requiring the sixel escape sequence to explicitly set all colors it
+  used).
 
 [1531]: https://codeberg.org/dnkl/foot/issues/1531
 [1573]: https://codeberg.org/dnkl/foot/issues/1573
diff --git a/sixel.c b/sixel.c
index 7684e657..f485e4c1 100644
--- a/sixel.c
+++ b/sixel.c
@@ -4,7 +4,7 @@
 #include <limits.h>
 
 #define LOG_MODULE "sixel"
-#define LOG_ENABLE_DBG 0
+#define LOG_ENABLE_DBG 1
 #include "log.h"
 #include "debug.h"
 #include "grid.h"
@@ -19,6 +19,29 @@ static size_t count;
 static void sixel_put_generic(struct terminal *term, uint8_t c);
 static void sixel_put_ar_11(struct terminal *term, uint8_t c);
 
+/* VT330/VT340 Programmer Reference Manual  - Table 2-3 VT340 Default Color Map */
+static const uint32_t vt340_default_colors[16] = {
+    0xff000000,
+    0xff3333cc,
+    0xffcc2121,
+    0xff33cc33,
+    0xffcc33cc,
+    0xff33cccc,
+    0xffcccc33,
+    0xff878787,
+    0xff424242,
+    0xff545499,
+    0xff994242,
+    0xff549954,
+    0xff995499,
+    0xff549999,
+    0xff999954,
+    0xffcccccc,
+};
+
+_Static_assert(sizeof(vt340_default_colors) / sizeof(vt340_default_colors[0]) == 16,
+               "wrong number of elements");
+
 void
 sixel_fini(struct terminal *term)
 {
@@ -68,17 +91,27 @@ sixel_init(struct terminal *term, int p1, int p2, int p3)
     term->sixel.image.width = 0;
     term->sixel.image.height = 0;
 
-    /* TODO: default palette */
-
     if (term->sixel.use_private_palette) {
         xassert(term->sixel.private_palette == NULL);
         term->sixel.private_palette = xcalloc(
             term->sixel.palette_size, sizeof(term->sixel.private_palette[0]));
+
+        memcpy(
+            term->sixel.private_palette, vt340_default_colors,
+            min(sizeof(vt340_default_colors),
+                term->sixel.palette_size * sizeof(term->sixel.private_palette[0])));
+
         term->sixel.palette = term->sixel.private_palette;
+
     } else {
         if (term->sixel.shared_palette == NULL) {
             term->sixel.shared_palette = xcalloc(
                 term->sixel.palette_size, sizeof(term->sixel.shared_palette[0]));
+
+            memcpy(
+                term->sixel.shared_palette, vt340_default_colors,
+                min(sizeof(vt340_default_colors),
+                    term->sixel.palette_size * sizeof(term->sixel.shared_palette[0])));
         } else {
             /* Shared palette - do *not* reset palette for new sixels */
         }