Merge branch 'master' into temp-gpencil-automasktemp-gpencil-automask

8 files changed, 177 insertions, 23 deletions

diff --git a/source/blender/blenlib/BLI_cache_mutex.hh b/source/blender/blenlib/BLI_cache_mutex.hh
new file mode 100644
index 00000000000..8e2a0d1b1a5
--- /dev/null
+++ b/source/blender/blenlib/BLI_cache_mutex.hh
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/**
+ * A #CacheMutex is used to protect a lazily computed cache from being computed more than once.
+ * Using #CacheMutex instead of a "raw mutex" to protect a cache has some benefits:
+ * - Avoid common pitfalls like forgetting to use task isolation or a double checked lock.
+ * - Cleaner and less redundant code because the same locking patterns don't have to be repeated
+ *   everywhere.
+ * - One can benefit from potential future improvements to #CacheMutex of which there are a few
+ *   mentioned below.
+ *
+ * The data protected by #CacheMutex is not part of #CacheMutex. Instead, the #CacheMutex and its
+ * protected data should generally be placed next to each other.
+ *
+ * Each #CacheMutex protects exactly one cache, so multiple cache mutexes have to be used when a
+ * class has multiple caches. That is contrary to a "custom" solution using `std::mutex` where one
+ * mutex could protect multiple caches at the cost of higher lock contention.
+ *
+ * To make sure the cache is up to date, call `CacheMutex::ensure` and pass in the function that
+ * computes the cache.
+ *
+ * To tell the #CacheMutex that the cache is invalidated and to be re-evaluated upon next access
+ * use `CacheMutex::tag_dirty`.
+ *
+ * This example shows how one could implement a lazily computed average vertex position in an
+ * imaginary `Mesh` data structure:
+ *
+ * \code{.cpp}
+ * class Mesh {
+ *  private:
+ *   mutable CacheMutex average_position_cache_mutex_;
+ *   mutable float3 average_position_cache_;
+ *
+ *  public:
+ *   const float3 &average_position() const
+ *   {
+ *     average_position_cache_mutex_.ensure([&]() {
+ *       average_position_cache_ = actually_compute_average_position();
+ *     });
+ *     return average_position_cache_;
+ *   }
+ *
+ *   void tag_positions_changed()
+ *   {
+ *     average_position_cache_mutex_.tag_dirty();
+ *   }
+ * };
+ * \endcode
+ *
+ * Possible future improvements:
+ * - Avoid task isolation when we know that the cache computation does not use threading.
+ * - Try to use a smaller mutex. The mutex does not have to be fair for this use case.
+ * - Try to join the cache computation instead of blocking if another thread is computing the cache
+ *   already.
+ */
+
+#include <atomic>
+#include <mutex>
+
+#include "BLI_function_ref.hh"
+
+namespace blender {
+
+class CacheMutex {
+ private:
+  std::mutex mutex_;
+  std::atomic<bool> cache_valid_ = false;
+
+ public:
+  /**
+   * Make sure the cache exists and is up to date. This calls `compute_cache` once to update the
+   * cache (which is stored outside of this class) if it is dirty, otherwise it does nothing.
+   *
+   * This function is thread-safe under the assumption that the same parameters are passed from
+   * every thread.
+   */
+  void ensure(FunctionRef<void()> compute_cache);
+
+  /**
+   * Reset the cache. The next time #ensure is called, it will recompute that code.
+   */
+  void tag_dirty()
+  {
+    cache_valid_.store(false);
+  }
+
+  /**
+   * Return true if the cache currently does not exist or has been invalidated.
+   */
+  bool is_dirty() const
+  {
+    return !this->is_cached();
+  }
+
+  /**
+   * Return true if the cache exists and is valid.
+   */
+  bool is_cached() const
+  {
+    return cache_valid_.load(std::memory_order_relaxed);
+  }
+};
+
+}  // namespace blender
diff --git a/source/blender/blenlib/BLI_string.h b/source/blender/blenlib/BLI_string.h
index 17abcf52ecc..fb02ea5fb17 100644
--- a/source/blender/blenlib/BLI_string.h
+++ b/source/blender/blenlib/BLI_string.h
@@ -206,6 +206,13 @@ char *BLI_sprintfN(const char *__restrict format, ...) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL(1) ATTR_MALLOC ATTR_PRINTF_FORMAT(1, 2);
 
 /**
+ * A wrapper around ::sprintf() which does not generate security warnings.
+ *
+ * \note Use BLI_snprintf for cases when the string size is known.
+ */
+int BLI_sprintf(char *__restrict str, const char *__restrict format, ...);
+
+/**
  * This roughly matches C and Python's string escaping with double quotes - `"`.
  *
  * Since every character may need escaping,
diff --git a/source/blender/blenlib/CMakeLists.txt b/source/blender/blenlib/CMakeLists.txt
index 2ac77f000e9..693a4d98675 100644
--- a/source/blender/blenlib/CMakeLists.txt
+++ b/source/blender/blenlib/CMakeLists.txt
@@ -54,6 +54,7 @@ set(SRC
   intern/bitmap_draw_2d.c
   intern/boxpack_2d.c
   intern/buffer.c
+  intern/cache_mutex.cc
   intern/compute_context.cc
   intern/convexhull_2d.c
   intern/cpp_type.cc
@@ -178,6 +179,7 @@ set(SRC
   BLI_bounds.hh
   BLI_boxpack_2d.h
   BLI_buffer.h
+  BLI_cache_mutex.hh
   BLI_color.hh
   BLI_color_mix.hh
   BLI_compiler_attrs.h
diff --git a/source/blender/blenlib/intern/cache_mutex.cc b/source/blender/blenlib/intern/cache_mutex.cc
new file mode 100644
index 00000000000..db474b1ef87
--- /dev/null
+++ b/source/blender/blenlib/intern/cache_mutex.cc
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "BLI_cache_mutex.hh"
+#include "BLI_task.hh"
+
+namespace blender {
+
+void CacheMutex::ensure(const FunctionRef<void()> compute_cache)
+{
+  if (cache_valid_.load(std::memory_order_acquire)) {
+    return;
+  }
+  std::scoped_lock lock{mutex_};
+  /* Double checked lock. */
+  if (cache_valid_.load(std::memory_order_relaxed)) {
+    return;
+  }
+  /* Use task isolation because a mutex is locked and the cache computation might use
+   * multi-threading. */
+  threading::isolate_task(compute_cache);
+
+  cache_valid_.store(true, std::memory_order_release);
+}
+
+}  // namespace blender
diff --git a/source/blender/blenlib/intern/path_util.c b/source/blender/blenlib/intern/path_util.c
index d13f3fe5ced..2376bd82b69 100644
--- a/source/blender/blenlib/intern/path_util.c
+++ b/source/blender/blenlib/intern/path_util.c
@@ -123,7 +123,7 @@ int BLI_path_sequence_decode(const char *string, char *head, char *tail, ushort
 void BLI_path_sequence_encode(
     char *string, const char *head, const char *tail, ushort numlen, int pic)
 {
-  sprintf(string, "%s%.*d%s", head, numlen, MAX2(0, pic), tail);
+  BLI_sprintf(string, "%s%.*d%s", head, numlen, MAX2(0, pic), tail);
 }
 
 static int BLI_path_unc_prefix_len(const char *path); /* defined below in same file */
@@ -620,7 +620,7 @@ bool BLI_path_suffix(char *string, size_t maxlen, const char *suffix, const char
   }
 
   BLI_strncpy(extension, string + a, sizeof(extension));
-  sprintf(string + a, "%s%s%s", sep, suffix, extension);
+  BLI_sprintf(string + a, "%s%s%s", sep, suffix, extension);
   return true;
 }
 
diff --git a/source/blender/blenlib/intern/string.c b/source/blender/blenlib/intern/string.c
index 755d2dbd55d..3c3dcaf90f4 100644
--- a/source/blender/blenlib/intern/string.c
+++ b/source/blender/blenlib/intern/string.c
@@ -241,6 +241,17 @@ char *BLI_sprintfN(const char *__restrict format, ...)
   return n;
 }
 
+int BLI_sprintf(char *__restrict str, const char *__restrict format, ...)
+{
+  va_list arg;
+
+  va_start(arg, format);
+  const int result = vsprintf(str, format, arg);
+  va_end(arg);
+
+  return result;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -1114,7 +1125,7 @@ static size_t BLI_str_format_int_grouped_ex(char src[16], char dst[16], int num_
 size_t BLI_str_format_int_grouped(char dst[16], int num)
 {
   char src[16];
-  int num_len = sprintf(src, "%d", num);
+  const int num_len = BLI_snprintf(src, sizeof(src), "%d", num);
 
   return BLI_str_format_int_grouped_ex(src, dst, num_len);
 }
@@ -1124,7 +1135,7 @@ size_t BLI_str_format_uint64_grouped(char dst[16], uint64_t num)
   /* NOTE: Buffer to hold maximum `uint64`, which is 1.8e+19. but
    * we also need space for commas and null-terminator. */
   char src[27];
-  int num_len = sprintf(src, "%" PRIu64 "", num);
+  const int num_len = BLI_snprintf(src, sizeof(src), "%" PRIu64 "", num);
 
   return BLI_str_format_int_grouped_ex(src, dst, num_len);
 }
diff --git a/source/blender/blenlib/intern/uuid.cc b/source/blender/blenlib/intern/uuid.cc
index 023dd1ec409..b845208f0da 100644
--- a/source/blender/blenlib/intern/uuid.cc
+++ b/source/blender/blenlib/intern/uuid.cc
@@ -5,6 +5,7 @@
  */
 
 #include "BLI_assert.h"
+#include "BLI_string.h"
 #include "BLI_uuid.h"
 
 #include <cstdio>
@@ -85,19 +86,19 @@ bool BLI_uuid_equal(const bUUID uuid1, const bUUID uuid2)
 
 void BLI_uuid_format(char *buffer, const bUUID uuid)
 {
-  std::sprintf(buffer,
-               "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
-               uuid.time_low,
-               uuid.time_mid,
-               uuid.time_hi_and_version,
-               uuid.clock_seq_hi_and_reserved,
-               uuid.clock_seq_low,
-               uuid.node[0],
-               uuid.node[1],
-               uuid.node[2],
-               uuid.node[3],
-               uuid.node[4],
-               uuid.node[5]);
+  BLI_sprintf(buffer,
+              "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+              uuid.time_low,
+              uuid.time_mid,
+              uuid.time_hi_and_version,
+              uuid.clock_seq_hi_and_reserved,
+              uuid.clock_seq_low,
+              uuid.node[0],
+              uuid.node[1],
+              uuid.node[2],
+              uuid.node[3],
+              uuid.node[4],
+              uuid.node[5]);
 }
 
 bool BLI_uuid_parse_string(bUUID *uuid, const char *buffer)
diff --git a/source/blender/blenlib/intern/winstuff.c b/source/blender/blenlib/intern/winstuff.c
index 7e2c5e8f1dd..3a574b60ae2 100644
--- a/source/blender/blenlib/intern/winstuff.c
+++ b/source/blender/blenlib/intern/winstuff.c
@@ -110,7 +110,7 @@ bool BLI_windows_register_blend_extension(const bool background)
                            &hkey,
                            &dwd);
   if (lresult == ERROR_SUCCESS) {
-    sprintf(buffer, "\"%s\" \"%%1\"", BlPath);
+    BLI_snprintf(buffer, sizeof(buffer), "\"%s\" \"%%1\"", BlPath);
     lresult = RegSetValueEx(hkey, NULL, 0, REG_SZ, (BYTE *)buffer, strlen(buffer) + 1);
     RegCloseKey(hkey);
   }
@@ -129,7 +129,7 @@ bool BLI_windows_register_blend_extension(const bool background)
                            &hkey,
                            &dwd);
   if (lresult == ERROR_SUCCESS) {
-    sprintf(buffer, "\"%s\", 1", BlPath);
+    BLI_snprintf(buffer, sizeof(buffer), "\"%s\", 1", BlPath);
     lresult = RegSetValueEx(hkey, NULL, 0, REG_SZ, (BYTE *)buffer, strlen(buffer) + 1);
     RegCloseKey(hkey);
   }
@@ -167,10 +167,12 @@ bool BLI_windows_register_blend_extension(const bool background)
   RegCloseKey(root);
   printf("success (%s)\n", usr_mode ? "user" : "system");
   if (!background) {
-    sprintf(MBox,
-            "File extension registered for %s.",
-            usr_mode ? "the current user. To register for all users, run as an administrator" :
-                       "all users");
+    BLI_snprintf(MBox,
+                 sizeof(MBox),
+                 "File extension registered for %s.",
+                 usr_mode ?
+                     "the current user. To register for all users, run as an administrator" :
+                     "all users");
     MessageBox(0, MBox, "Blender", MB_OK | MB_ICONINFORMATION);
   }
   return true;