From 9150507209fd60a4eeb6374f7aabd3f1226f150f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 3 Feb 2022 19:20:41 +0100
Subject: [PATCH] sixel: resize: truncate instead of failing, when new size
 exceeds max size
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If the size we’re trying to set exceeds the configured max size,
truncate instead of failing.
---
 CHANGELOG.md |  2 ++
 sixel.c      | 32 +++++++++++++++++++-------------
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b3b95c7..1a75036b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -120,6 +120,8 @@
   (https://codeberg.org/dnkl/foot/issues/883).
 * Bash completion giving an error when completing a list of short
   options
+* Sixel: large image resizes (triggered by e.g. large repeat counts in
+  `DECGRI`) are now truncated instead of ignored.
 
 
 ### Security
diff --git a/sixel.c b/sixel.c
index b659a3c0..335700c5 100644
--- a/sixel.c
+++ b/sixel.c
@@ -1104,7 +1104,7 @@ sixel_unhook(struct terminal *term)
     render_refresh(term);
 }
 
-static bool
+static void
 resize_horizontally(struct terminal *term, int new_width)
 {
     LOG_DBG("resizing image horizontally: %dx(%d) -> %dx(%d)",
@@ -1112,10 +1112,13 @@ resize_horizontally(struct terminal *term, int new_width)
             new_width, term->sixel.image.height);
 
     if (unlikely(new_width > term->sixel.max_width)) {
-        LOG_WARN("maximum image dimensions reached");
-        return false;
+        LOG_WARN("maximum image dimensions exceeded, truncating");
+        new_width = term->sixel.max_width;
     }
 
+    if (unlikely(term->sixel.image.width == new_width))
+        return;
+
     uint32_t *old_data = term->sixel.image.data;
     const int old_width = term->sixel.image.width;
     const int height = term->sixel.image.height;
@@ -1145,7 +1148,6 @@ resize_horizontally(struct terminal *term, int new_width)
     term->sixel.image.data = new_data;
     term->sixel.image.width = new_width;
     term->sixel.row_byte_ofs = term->sixel.pos.row * new_width;
-    return true;
 }
 
 static bool
@@ -1197,11 +1199,14 @@ resize(struct terminal *term, int new_width, int new_height)
             term->sixel.image.width, term->sixel.image.height,
             new_width, new_height);
 
-    if (new_width > term->sixel.max_width ||
-        new_height > term->sixel.max_height)
-    {
-        LOG_WARN("maximum image dimensions reached");
-        return false;
+    if (unlikely(new_width > term->sixel.max_width)) {
+        LOG_WARN("maximum image width exceeded, truncating");
+        new_width = term->sixel.max_width;
+    }
+
+    if (unlikely(new_height > term->sixel.max_height)) {
+        LOG_WARN("maximum image height exceeded, truncating");
+        new_height = term->sixel.max_height;
     }
 
     uint32_t *old_data = term->sixel.image.data;
@@ -1291,9 +1296,9 @@ sixel_add_many(struct terminal *term, uint8_t c, unsigned count)
     int width = term->sixel.image.width;
 
     if (unlikely(col + count - 1 >= width)) {
-        width = col + count;
-        if (unlikely(!resize_horizontally(term, width)))
-            return;
+        resize_horizontally(term, col + count);
+        width = term->sixel.image.width;
+        count = min(count, width - col);
     }
 
     uint32_t color = term->sixel.color;
@@ -1412,7 +1417,8 @@ decgra(struct terminal *term, uint8_t c)
 
             /* This ensures the sixel’s final image size is *at least*
              * this large */
-            term->sixel.max_non_empty_row_no = pv - 1;
+            term->sixel.max_non_empty_row_no =
+                min(pv, term->sixel.image.height) - 1;
         }
 
         term->sixel.state = SIXEL_DECSIXEL;