Fix race condition crashes when unmapping views

This fixes two issues which were both introduced in #2396.

First issue:
The PR changes the location of the buffer save to transaction_apply, but
puts it inside the should_configure block. For unmapping (destroying)
views, should_configure returns false so it wasn't saving the buffer. If
a frame was rendered between the unmap and the transaction applying then
it would result in a crash.

Second issue:
If a destroying view is involved in two transactions, we must not
release the buffer between the transactions because there is no live
buffer to grab any more.

1 files changed, 15 insertions, 8 deletions

diff --git a/sway/desktop/transaction.c b/sway/desktop/transaction.c
index 94070363..4e6af86a 100644
--- a/sway/desktop/transaction.c
+++ b/sway/desktop/transaction.c
@@ -195,11 +195,18 @@ static void transaction_apply(struct sway_transaction *transaction) {
                                 sizeof(struct sway_container_state));
 
                 if (container->type == C_VIEW) {
-                        if (container->sway_view->saved_buffer) {
-                                view_remove_saved_buffer(container->sway_view);
-                        }
-                        if (container->instructions->length > 1) {
-                                view_save_buffer(container->sway_view);
+                        if (container->destroying) {
+                                if (container->instructions->length == 1 &&
+                                                container->sway_view->saved_buffer) {
+                                        view_remove_saved_buffer(container->sway_view);
+                                }
+                        } else {
+                                if (container->sway_view->saved_buffer) {
+                                        view_remove_saved_buffer(container->sway_view);
+                                }
+                                if (container->instructions->length > 1) {
+                                        view_save_buffer(container->sway_view);
+                                }
                         }
                 }
         }
@@ -276,9 +283,9 @@ static void transaction_commit(struct sway_transaction *transaction) {
                         // mapping and its default geometry doesn't intersect an output.
                         struct timespec when;
                         wlr_surface_send_frame_done(con->sway_view->surface, &when);
-                        if (!con->sway_view->saved_buffer) {
-                                view_save_buffer(con->sway_view);
-                        }
+                }
+                if (con->type == C_VIEW && !con->sway_view->saved_buffer) {
+                        view_save_buffer(con->sway_view);
                 }
                 list_add(con->instructions, instruction);
         }