DRW: Manager: Add ClearMulti command

Allows to record `GPU_framebuffer_multi_clear` inside `draw::Pass`.

source/blender/draw/intern/draw_command.cc

@@ -158,6 +158,12 @@ void Clear::execute() const
   GPU_framebuffer_clear(fb, (eGPUFrameBufferBits)clear_channels, color, depth, stencil);
 }
 
+void ClearMulti::execute() const
+{
+  GPUFrameBuffer *fb = GPU_framebuffer_active_get();
+  GPU_framebuffer_multi_clear(fb, (const float(*)[4])colors.data());
+}
+
 void StateSet::execute(RecordingState &recording_state) const
 {
   /**
@@ -471,6 +477,15 @@ std::string Clear::serialize() const
   return std::string(".clear(") + ss.str() + ")";
 }
 
+std::string ClearMulti::serialize() const
+{
+  std::stringstream ss;
+  for (float4 color : colors) {
+    ss << color << ", ";
+  }
+  return std::string(".clear_multi(colors={") + ss.str() + "})";
+}
+
 std::string StateSet::serialize() const
 {
   /* TODO(@fclem): Better serialization... */

source/blender/draw/intern/draw_command.hh

@@ -84,6 +84,7 @@ enum class Type : uint8_t {
   /** Commands stored as Undetermined in regular command buffer. */
   Barrier,
   Clear,
+  ClearMulti,
   Dispatch,
   DispatchIndirect,
   Draw,
@@ -323,6 +324,13 @@ struct Clear {
   std::string serialize() const;
 };
 
+struct ClearMulti {
+  Span<float4> colors;
+
+  void execute() const;
+  std::string serialize() const;
+};
+
 struct StateSet {
   DRWState new_state;
   int clip_plane_count;
@@ -352,6 +360,7 @@ union Undetermined {
   DispatchIndirect dispatch_indirect;
   Barrier barrier;
   Clear clear;
+  ClearMulti clear_multi;
   StateSet state_set;
   StencilSet stencil_set;
 };

source/blender/draw/intern/draw_pass.hh

@@ -172,6 +172,11 @@ class PassBase {
   void clear_stencil(uint8_t stencil);
   void clear_depth_stencil(float depth, uint8_t stencil);
   void clear_color_depth_stencil(float4 color, float depth, uint8_t stencil);
+  /**
+   * Clear each color attachment with different values. Span needs to be appropriately sized.
+   * IMPORTANT: The source is dereference on pass submission.
+   */
+  void clear_multi(Span<float4> colors);
 
   /**
    * Reminders:
@@ -469,6 +474,11 @@ inline void PassBase<T>::clear(eGPUFrameBufferBits planes,
   create_command(command::Type::Clear).clear = {uint8_t(planes), stencil, depth, color};
 }
 
+template<class T> inline void PassBase<T>::clear_multi(Span<float4> colors)
+{
+  create_command(command::Type::ClearMulti).clear_multi = {colors};
+}
+
 template<class T> inline GPUBatch *PassBase<T>::procedural_batch_get(GPUPrimType primitive)
 {
   switch (primitive) {
@@ -540,6 +550,9 @@ template<class T> void PassBase<T>::submit(command::RecordingState &state) const
       case command::Type::Clear:
         commands_[header.index].clear.execute();
         break;
+      case command::Type::ClearMulti:
+        commands_[header.index].clear_multi.execute();
+        break;
       case command::Type::StateSet:
         commands_[header.index].state_set.execute(state);
         break;
@@ -598,6 +611,9 @@ template<class T> std::string PassBase<T>::serialize(std::string line_prefix) co
       case Type::Clear:
         ss << line_prefix << commands_[header.index].clear.serialize() << std::endl;
         break;
+      case Type::ClearMulti:
+        ss << line_prefix << commands_[header.index].clear_multi.serialize() << std::endl;
+        break;
       case Type::StateSet:
         ss << line_prefix << commands_[header.index].state_set.serialize() << std::endl;
         break;