DRW: GPU Wrapper: add possibility to swap Texture and TextureFromPool

Ownership is transfered from the pool to the `Texture` and vice versa.
This allows to have history buffers with only 1 persistent texture.

3 files changed, 42 insertions, 3 deletions

diff --git a/source/blender/draw/intern/DRW_gpu_wrapper.hh b/source/blender/draw/intern/DRW_gpu_wrapper.hh
index 639a1ed4aa1..5405afd2a90 100644
--- a/source/blender/draw/intern/DRW_gpu_wrapper.hh
+++ b/source/blender/draw/intern/DRW_gpu_wrapper.hh
@@ -807,12 +807,22 @@ class TextureFromPool : public Texture, NonMovable {
   }
 
   /**
-   * Swap the GPUTexture pointers of the two texture.
+   * Swap the content of the two textures.
+   * Also change ownership accordingly if needed.
    */
+  static void swap(TextureFromPool &a, Texture &b)
+  {
+    Texture::swap(a, b);
+    DRW_texture_pool_give_texture_ownership(DST.vmempool->texture_pool, a);
+    DRW_texture_pool_take_texture_ownership(DST.vmempool->texture_pool, b);
+  }
+  static void swap(Texture &a, TextureFromPool &b)
+  {
+    swap(b, a);
+  }
   static void swap(TextureFromPool &a, TextureFromPool &b)
   {
-    SWAP(GPUTexture *, a.tx_, b.tx_);
-    SWAP(const char *, a.name_, b.name_);
+    Texture::swap(a, b);
   }
 
   /** Remove methods that are forbidden with this type of textures. */
diff --git a/source/blender/draw/intern/draw_texture_pool.cc b/source/blender/draw/intern/draw_texture_pool.cc
index b36cb5c809e..017ecec7be2 100644
--- a/source/blender/draw/intern/draw_texture_pool.cc
+++ b/source/blender/draw/intern/draw_texture_pool.cc
@@ -160,6 +160,19 @@ void DRW_texture_pool_texture_release(DRWTexturePool *pool, GPUTexture *tmp_tex)
   pool->tmp_tex_released.append(tmp_tex);
 }
 
+void DRW_texture_pool_take_texture_ownership(DRWTexturePool *pool, GPUTexture *tex)
+{
+  pool->tmp_tex_acquired.remove_first_occurrence_and_reorder(tex);
+}
+
+void DRW_texture_pool_give_texture_ownership(DRWTexturePool *pool, GPUTexture *tex)
+{
+  BLI_assert(pool->tmp_tex_acquired.first_index_of_try(tex) == -1 &&
+             pool->tmp_tex_released.first_index_of_try(tex) == -1 &&
+             pool->tmp_tex_pruned.first_index_of_try(tex) == -1);
+  pool->tmp_tex_acquired.append(tex);
+}
+
 void DRW_texture_pool_reset(DRWTexturePool *pool)
 {
   pool->last_user_id = -1;
diff --git a/source/blender/draw/intern/draw_texture_pool.h b/source/blender/draw/intern/draw_texture_pool.h
index 7396b55d53a..9fbbf630833 100644
--- a/source/blender/draw/intern/draw_texture_pool.h
+++ b/source/blender/draw/intern/draw_texture_pool.h
@@ -41,6 +41,22 @@ GPUTexture *DRW_texture_pool_texture_acquire(DRWTexturePool *pool,
  * Releases a previously acquired texture.
  */
 void DRW_texture_pool_texture_release(DRWTexturePool *pool, GPUTexture *tmp_tex);
+
+/**
+ * This effectively remove a texture from the texture pool, giving full ownership to the caller.
+ * The given texture needs to be been acquired through DRW_texture_pool_texture_acquire().
+ * IMPORTANT: This removes the need for a DRW_texture_pool_texture_release() call on this texture.
+ */
+void DRW_texture_pool_take_texture_ownership(DRWTexturePool *pool, GPUTexture *tex);
+/**
+ * This Inserts a texture into the texture pool, giving full ownership to the texture pool.
+ * The texture needs not to be in the pool already.
+ * The texture may be reused in a latter call to DRW_texture_pool_texture_acquire();
+ * IMPORTANT: DRW_texture_pool_texture_release() still needs to be called on this texture
+ * after usage.
+ */
+void DRW_texture_pool_give_texture_ownership(DRWTexturePool *pool, GPUTexture *tex);
+
 /**
  * Resets the user bits for each texture in the pool and delete unused ones.
  */