From 9c48e7f59b3aad484aac6aa52b30173b25c1dc7f Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Thu, 2 Feb 2023 16:15:43 +0100
Subject: [PATCH] Fix assertion failures when reactivating plugins

`.set_slices()` makes sure all slices' lengths are equal to the first
argument, so in these functions we'll need to manually overwrite any
existing element with empty slices.
---
 src/wrapper/clap/wrapper.rs | 12 +++++++++---
 src/wrapper/vst3/wrapper.rs | 12 +++++++++---
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/wrapper/clap/wrapper.rs b/src/wrapper/clap/wrapper.rs
index ec0a9cb7..abfa59f8 100644
--- a/src/wrapper/clap/wrapper.rs
+++ b/src/wrapper/clap/wrapper.rs
@@ -1869,7 +1869,11 @@ impl<P: ClapPlugin> Wrapper<P> {
                 .output_buffer
                 .borrow_mut()
                 .set_slices(0, |output_slices| {
-                    output_slices.resize_with(bus_config.num_output_channels as usize, || &mut [])
+                    output_slices.resize_with(bus_config.num_output_channels as usize, || &mut []);
+                    // All slices must have the same length, so if the number of output channels has
+                    // changed since the last call then we should make sure to clear any old
+                    // (dangling) slices to be consistent
+                    output_slices.fill_with(|| &mut []);
                 });
 
             // Also allocate both the buffers and the slices pointing to those buffers for sidechain
@@ -1896,7 +1900,8 @@ impl<P: ClapPlugin> Wrapper<P> {
                     channel_slices
                         .resize_with(bus_config.aux_input_busses.num_channels as usize, || {
                             &mut []
-                        })
+                        });
+                    channel_slices.fill_with(|| &mut []);
                 });
             }
 
@@ -1911,7 +1916,8 @@ impl<P: ClapPlugin> Wrapper<P> {
                     channel_slices
                         .resize_with(bus_config.aux_output_busses.num_channels as usize, || {
                             &mut []
-                        })
+                        });
+                    channel_slices.fill_with(|| &mut []);
                 });
             }
 
diff --git a/src/wrapper/vst3/wrapper.rs b/src/wrapper/vst3/wrapper.rs
index 4f2c6211..31087d69 100644
--- a/src/wrapper/vst3/wrapper.rs
+++ b/src/wrapper/vst3/wrapper.rs
@@ -405,7 +405,11 @@ impl<P: Vst3Plugin> IComponent for Wrapper<P> {
                         .borrow_mut()
                         .set_slices(0, |output_slices| {
                             output_slices
-                                .resize_with(bus_config.num_output_channels as usize, || &mut [])
+                                .resize_with(bus_config.num_output_channels as usize, || &mut []);
+                            // All slices must have the same length, so if the number of output
+                            // channels has changed since the last call then we should make sure to
+                            // clear any old (dangling) slices to be consistent
+                            output_slices.fill_with(|| &mut []);
                         });
 
                     // Also allocate both the buffers and the slices pointing to those buffers for
@@ -434,7 +438,8 @@ impl<P: Vst3Plugin> IComponent for Wrapper<P> {
                             channel_slices.resize_with(
                                 bus_config.aux_input_busses.num_channels as usize,
                                 || &mut [],
-                            )
+                            );
+                            channel_slices.fill_with(|| &mut []);
                         });
                     }
 
@@ -449,7 +454,8 @@ impl<P: Vst3Plugin> IComponent for Wrapper<P> {
                             channel_slices.resize_with(
                                 bus_config.aux_output_busses.num_channels as usize,
                                 || &mut [],
-                            )
+                            );
+                            channel_slices.fill_with(|| &mut []);
                         });
                     }