From 5812242405bf5e9efb3f6148596872fd99d5dd71 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Sat, 2 Nov 2019 00:35:02 +0100
Subject: [PATCH] shm: purge unused buffers

When we need to create a new buffer (because the cache doesn't have
any buffers of correct size, or because they're all busy), purge
buffers with a size mismatch.
---
 shm.c | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/shm.c b/shm.c
index 7c649ac3..6785cbfb 100644
--- a/shm.c
+++ b/shm.c
@@ -17,6 +17,15 @@
 
 static tll(struct buffer) buffers;
 
+static void
+buffer_destroy(struct buffer *buf)
+{
+    if (buf->pix != NULL)
+        pixman_image_unref(buf->pix);
+    wl_buffer_destroy(buf->wl_buf);
+    munmap(buf->mmapped, buf->size);
+}
+
 static void
 buffer_release(void *data, struct wl_buffer *wl_buffer)
 {
@@ -48,6 +57,24 @@ shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie)
         }
     }
 
+    /* Purge old buffers associated with this cookie */
+    tll_foreach(buffers, it) {
+        if (it->item.cookie != cookie)
+            continue;
+
+        if (it->item.busy)
+            continue;
+
+        if (it->item.width == width && it->item.height == height)
+            continue;
+
+        LOG_DBG("cookie=%lx: purging buffer (width=%d, height=%d)",
+                cookie, it->item.width, it->item.height);
+
+        buffer_destroy(&it->item);
+        tll_remove(buffers, it);
+    }
+
     /*
      * No existing buffer available. Create a new one by:
      *
@@ -151,13 +178,7 @@ void
 shm_fini(void)
 {
     tll_foreach(buffers, it) {
-        struct buffer *buf = &it->item;
-
-        if (buf->pix != NULL)
-            pixman_image_unref(buf->pix);
-        wl_buffer_destroy(buf->wl_buf);
-        munmap(buf->mmapped, buf->size);
-
+        buffer_destroy(&it->item);
         tll_remove(buffers, it);
     }
 }