1 files changed, 88 insertions, 23 deletions

diff --git a/source/blender/draw/intern/DRW_gpu_wrapper.hh b/source/blender/draw/intern/DRW_gpu_wrapper.hh
index d7e752a43f4..257f01a5562 100644
--- a/source/blender/draw/intern/DRW_gpu_wrapper.hh
+++ b/source/blender/draw/intern/DRW_gpu_wrapper.hh
@@ -102,7 +102,7 @@ class DataBuffer {
   {
     BLI_STATIC_ASSERT(!device_only, "");
     BLI_assert(index >= 0);
-    BLI_assert(index < len);
+    BLI_assert(index < len_);
     return data_[index];
   }
 
@@ -110,7 +110,7 @@ class DataBuffer {
   {
     BLI_STATIC_ASSERT(!device_only, "");
     BLI_assert(index >= 0);
-    BLI_assert(index < len);
+    BLI_assert(index < len_);
     return data_[index];
   }
 
@@ -139,7 +139,7 @@ class DataBuffer {
   const T *end() const
   {
     BLI_STATIC_ASSERT(!device_only, "");
-    return data_ + len;
+    return data_ + len_;
   }
 
   T *begin()
@@ -150,13 +150,13 @@ class DataBuffer {
   T *end()
   {
     BLI_STATIC_ASSERT(!device_only, "");
-    return data_ + len;
+    return data_ + len_;
   }
 
   operator Span<T>() const
   {
     BLI_STATIC_ASSERT(!device_only, "");
-    return Span<T>(data_, len);
+    return Span<T>(data_, len_);
   }
 };
 
@@ -217,7 +217,9 @@ class StorageCommon : public DataBuffer<T, len, false>, NonMovable, NonCopyable
     if (name) {
       name_ = name;
     }
-    init(len);
+    this->len_ = len;
+    constexpr GPUUsageType usage = device_only ? GPU_USAGE_DEVICE_ONLY : GPU_USAGE_DYNAMIC;
+    ssbo_ = GPU_storagebuf_create_ex(sizeof(T) * this->len_, nullptr, usage, this->name_);
   }
 
   ~StorageCommon()
@@ -225,15 +227,6 @@ class StorageCommon : public DataBuffer<T, len, false>, NonMovable, NonCopyable
     GPU_storagebuf_free(ssbo_);
   }
 
-  void resize(int64_t new_size)
-  {
-    BLI_assert(new_size > 0);
-    if (new_size != this->len_) {
-      GPU_storagebuf_free(ssbo_);
-      this->init(new_size);
-    }
-  }
-
   void push_update(void)
   {
     BLI_assert(device_only == false);
@@ -249,14 +242,6 @@ class StorageCommon : public DataBuffer<T, len, false>, NonMovable, NonCopyable
   {
     return &ssbo_;
   }
-
- private:
-  void init(int64_t new_size)
-  {
-    this->len_ = new_size;
-    GPUUsageType usage = device_only ? GPU_USAGE_DEVICE_ONLY : GPU_USAGE_DYNAMIC;
-    ssbo_ = GPU_storagebuf_create_ex(sizeof(T) * this->len_, nullptr, usage, this->name_);
-  }
 };
 
 }  // namespace detail
@@ -333,6 +318,34 @@ class StorageArrayBuffer : public detail::StorageCommon<T, len, device_only> {
   {
     MEM_freeN(this->data_);
   }
+
+  void resize(int64_t new_size)
+  {
+    BLI_assert(new_size > 0);
+    if (new_size != this->len_) {
+      /* Manual realloc since MEM_reallocN_aligned does not exists. */
+      T *new_data_ = (T *)MEM_mallocN_aligned(new_size * sizeof(T), 16, this->name_);
+      memcpy(new_data_, this->data_, min_uu(this->len_, new_size) * sizeof(T));
+      MEM_freeN(this->data_);
+      this->data_ = new_data_;
+      GPU_storagebuf_free(this->ssbo_);
+
+      this->len_ = new_size;
+      constexpr GPUUsageType usage = device_only ? GPU_USAGE_DEVICE_ONLY : GPU_USAGE_DYNAMIC;
+      this->ssbo_ = GPU_storagebuf_create_ex(sizeof(T) * this->len_, nullptr, usage, this->name_);
+    }
+  }
+
+  /* Resize on access. */
+  T &get_or_resize(int64_t index)
+  {
+    BLI_assert(index >= 0);
+    if (index >= this->len_) {
+      size_t size = power_of_2_max_u(index + 1);
+      this->resize(size);
+    }
+    return this->data_[index];
+  }
 };
 
 template<
@@ -880,4 +893,56 @@ class Framebuffer : NonCopyable {
 
 /** \} */
 
+/* -------------------------------------------------------------------- */
+/** \name Double & Triple buffering util
+ *
+ * This is not strictly related to a GPU type and could be moved elsewhere.
+ * \{ */
+
+template<typename T, int64_t len> class SwapChain {
+ private:
+  std::array<T, len> chain_;
+  int64_t index_ = 0;
+
+ public:
+  void swap()
+  {
+    index_ = (index_ + 1) % len;
+  }
+
+  T &current()
+  {
+    return chain_[index_];
+  }
+
+  T &previous()
+  {
+    /* Avoid modulo operation with negative numbers. */
+    return chain_[(index_ + len - 1) % len];
+  }
+
+  T &next()
+  {
+    return chain_[(index_ + 1) % len];
+  }
+
+  const T &current() const
+  {
+    return chain_[index_];
+  }
+
+  const T &previous() const
+  {
+    /* Avoid modulo operation with negative numbers. */
+    return chain_[(index_ + len - 1) % len];
+  }
+
+  const T &next() const
+  {
+    return chain_[(index_ + 1) % len];
+  }
+};
+
+/** \} */
+
 }  // namespace blender::draw