DRW: Manager: Add possibility to record a framebuffer change inside a pass

This is a convenience when one needs to often change the current framebuffer
and avoid the overhead of creating many Main/Simple passes.

source/blender/draw/intern/draw_command.cc

@@ -30,6 +30,11 @@ void ShaderBind::execute(RecordingState &state) const
   }
 }
 
+void FramebufferBind::execute() const
+{
+  GPU_framebuffer_bind(framebuffer);
+}
+
 void ResourceBind::execute() const
 {
   if (slot == -1) {
@@ -229,6 +234,11 @@ std::string ShaderBind::serialize() const
   return std::string(".shader_bind(") + GPU_shader_get_name(shader) + ")";
 }
 
+std::string FramebufferBind::serialize() const
+{
+  return std::string(".framebuffer_bind(") + GPU_framebuffer_get_name(framebuffer) + ")";
+}
+
 std::string ResourceBind::serialize() const
 {
   switch (type) {

source/blender/draw/intern/draw_command.hh

@@ -88,6 +88,7 @@ enum class Type : uint8_t {
   DispatchIndirect,
   Draw,
   DrawIndirect,
+  FramebufferBind,
   PushConstant,
   ResourceBind,
   ShaderBind,
@@ -118,6 +119,13 @@ struct ShaderBind {
   std::string serialize() const;
 };
 
+struct FramebufferBind {
+  GPUFrameBuffer *framebuffer;
+
+  void execute() const;
+  std::string serialize() const;
+};
+
 struct ResourceBind {
   eGPUSamplerState sampler;
   int slot;

source/blender/draw/intern/draw_pass.hh

@@ -14,8 +14,7 @@
  * #Pass. Use many #PassSub along with a main #Pass to reduce the overhead and allow groupings of
  * commands. \note The draw call order inside a batch of multiple draw with the exact same state is
  * not guaranteed and is not even deterministic. Use a #PassSimple or #PassSortable if ordering is
- * needed. \note As of now, it is also quite limited in the type of draw command it can record
- * (no custom vertex count, no custom first vertex).
+ * needed. Custom vertex count and custom first vertex will effectively disable batching.
  *
  * `PassSimple`:
  * Does not have the overhead of #PassMain but does not have the culling and batching optimization.
@@ -191,6 +190,12 @@ class PassBase {
    */
   void shader_set(GPUShader *shader);
 
+  /**
+   * Bind a framebuffer. This is equivalent to a deferred GPU_framebuffer_bind() call.
+   * \note Changes the global GPU state (outside of DRW).
+   */
+  void framebuffer_set(GPUFrameBuffer *framebuffer);
+
   /**
    * Bind a material shader along with its associated resources. Any following bind() or
    * push_constant() call will use its interface.
@@ -743,6 +748,11 @@ template<class T> inline void PassBase<T>::shader_set(GPUShader *shader)
   create_command(Type::ShaderBind).shader_bind = {shader};
 }
 
+template<class T> inline void PassBase<T>::framebuffer_set(GPUFrameBuffer *framebuffer)
+{
+  create_command(Type::FramebufferBind).framebuffer_bind = {framebuffer};
+}
+
 template<class T> inline void PassBase<T>::material_set(Manager &manager, GPUMaterial *material)
 {
   GPUPass *gpupass = GPU_material_get_pass(material);

source/blender/gpu/GPU_framebuffer.h

@@ -47,6 +47,9 @@ typedef struct GPUOffScreen GPUOffScreen;
 GPUFrameBuffer *GPU_framebuffer_create(const char *name);
 void GPU_framebuffer_free(GPUFrameBuffer *fb);
 void GPU_framebuffer_bind(GPUFrameBuffer *fb);
+
+const char *GPU_framebuffer_get_name(GPUFrameBuffer *fb);
+
 /**
  * Workaround for binding a SRGB frame-buffer without doing the SRGB transform.
  */

source/blender/gpu/intern/gpu_framebuffer.cc

@@ -238,6 +238,11 @@ void GPU_framebuffer_free(GPUFrameBuffer *gpu_fb)
   delete unwrap(gpu_fb);
 }
 
+const char *GPU_framebuffer_get_name(GPUFrameBuffer *gpu_fb)
+{
+  return unwrap(gpu_fb)->name_get();
+}
+
 /* ---------- Binding ----------- */
 
 void GPU_framebuffer_bind(GPUFrameBuffer *gpu_fb)

source/blender/gpu/intern/gpu_framebuffer_private.hh

@@ -204,6 +204,11 @@ class FrameBuffer {
   {
     return attachments_[GPU_FB_COLOR_ATTACHMENT0 + slot].tex;
   };
+
+  inline const char *const name_get() const
+  {
+    return name_;
+  };
 };
 
 /* Syntactic sugar. */