From 4d3251a93b4ba309d573aca6ff397df44c4ff760 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sat, 2 Nov 2019 00:48:07 +0100
Subject: [PATCH] render: last_buf may point to a free:d buffer

So, store last buf's width/height separately
---
 render.c   | 26 ++++++++++++++++++--------
 terminal.h |  6 +++++-
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/render.c b/render.c
index 0b0c6d5b..d1917eef 100644
--- a/render.c
+++ b/render.c
@@ -451,25 +451,33 @@ grid_render(struct terminal *term)
     bool all_clean = tll_length(term->grid->scroll_damage) == 0;
 
     /* If we resized the window, or is flashing, or just stopped flashing */
-    if (term->render.last_buf != buf ||
+    if (term->render.last_shm.buf != buf ||
         term->flash.active || term->render.was_flashing ||
         term->is_searching != term->render.was_searching)
     {
-        if (term->render.last_buf != NULL &&
-            term->render.last_buf->width == buf->width &&
-            term->render.last_buf->height == buf->height &&
+        /*
+         * TODO: shm buffers may be purged, meaning our last_buf (when
+         * != buf) may point to a free:d buffer.
+         *
+         * It *shouldn't*, as long as the sizes match... but would
+         * still be good to find a better solution for this.
+         */
+        if (term->render.last_shm.buf != NULL &&
+            term->render.last_shm.width == buf->width &&
+            term->render.last_shm.height == buf->height &&
             !term->flash.active &&
             !term->render.was_flashing &&
             term->is_searching == term->render.was_searching)
         {
             static bool has_warned = false;
             if (!has_warned) {
-                LOG_WARN("it appears your Wayland compositor does not support buffer re-use for SHM clients; expect lower performance.");
+                LOG_WARN(
+                    "it appears your Wayland compositor does not support "
+                    "buffer re-use for SHM clients; expect lower performance.");
                 has_warned = true;
             }
 
-            assert(term->render.last_buf->size == buf->size);
-            memcpy(buf->mmapped, term->render.last_buf->mmapped, buf->size);
+            memcpy(buf->mmapped, term->render.last_shm.buf->mmapped, buf->size);
         }
 
         else {
@@ -505,7 +513,9 @@ grid_render(struct terminal *term)
             term_damage_view(term);
         }
 
-        term->render.last_buf = buf;
+        term->render.last_shm.buf = buf;
+        term->render.last_shm.width = buf->width;
+        term->render.last_shm.height = buf->height;
         term->render.was_flashing = term->flash.active;
         term->render.was_searching = term->is_searching;
     }
diff --git a/terminal.h b/terminal.h
index 11571519..4962aae4 100644
--- a/terminal.h
+++ b/terminal.h
@@ -276,7 +276,11 @@ struct terminal {
             struct cell *cell; /* For easy access to content */
         } last_cursor;
 
-        struct buffer *last_buf;     /* Buffer we rendered to last time */
+        struct {
+            struct buffer *buf;     /* Buffer we rendered to last time */
+            int width;
+            int height;
+        } last_shm;
         bool was_flashing;           /* Flash was active last time we rendered */
         bool was_searching;
     } render;