GPUFrameBuffer: GL backend isolation

This is related to the Vulkan port T68990.

This is a full cleanup of the Framebuffer module and a separation
of OpenGL related functions.

There is some changes with how the default framebuffers are handled.
Now the default framebuffers are individually wrapped inside special
GLFrameBuffers. This make it easier to keep track of the currently bound
framebuffer state and have some specificity for operations on these
framebuffers.

Another change is dropping the optimisation of only configuring the
changed attachements during framebuffers update. This does not give
any benefits and add some complexity to the code. This might be brought
back if it has a performance impact on some systems.

This also adds support for naming framebuffers but it is currently not
used.

1 files changed, 86 insertions, 30 deletions

diff --git a/source/blender/gpu/intern/gpu_framebuffer_private.hh b/source/blender/gpu/intern/gpu_framebuffer_private.hh
index cc5ae048c7c..93551b0ef8b 100644
--- a/source/blender/gpu/intern/gpu_framebuffer_private.hh
+++ b/source/blender/gpu/intern/gpu_framebuffer_private.hh
@@ -19,19 +19,26 @@
 
 /** \file
  * \ingroup gpu
+ *
+ * GPU Framebuffer
+ * - this is a wrapper for an OpenGL framebuffer object (FBO). in practice
+ *   multiple FBO's may be created.
+ * - actual FBO creation & config is deferred until GPU_framebuffer_bind or
+ *   GPU_framebuffer_check_valid to allow creation & config while another
+ *   opengl context is bound (since FBOs are not shared between ogl contexts).
  */
 
 #pragma once
 
+#include "BLI_span.hh"
+
 #include "MEM_guardedalloc.h"
 
 #include "GPU_framebuffer.h"
 
-#include "glew-mx.h" /* For GLuint. To remove. */
-
 struct GPUTexture;
 
-typedef enum {
+typedef enum GPUAttachmentType : int {
   GPU_FB_DEPTH_ATTACHMENT = 0,
   GPU_FB_DEPTH_STENCIL_ATTACHMENT,
   GPU_FB_COLOR_ATTACHMENT0,
@@ -45,50 +52,99 @@ typedef enum {
   /* Keep in mind that GL max is GL_MAX_DRAW_BUFFERS and is at least 8, corresponding to
    * the maximum number of COLOR attachments specified by glDrawBuffers. */
   GPU_FB_MAX_ATTACHEMENT,
+
+  GPU_FB_MAX_COLOR_ATTACHMENT = (GPU_FB_MAX_ATTACHEMENT - GPU_FB_COLOR_ATTACHMENT0),
 } GPUAttachmentType;
 
-namespace blender {
-namespace gpu {
+inline constexpr GPUAttachmentType operator-(GPUAttachmentType a, int b)
+{
+  return static_cast<GPUAttachmentType>(static_cast<int>(a) - b);
+}
 
-#define FOREACH_ATTACHMENT_RANGE(att, _start, _end) \
-  for (GPUAttachmentType att = static_cast<GPUAttachmentType>(_start); att < _end; \
-       att = static_cast<GPUAttachmentType>(att + 1))
+inline constexpr GPUAttachmentType operator+(GPUAttachmentType a, int b)
+{
+  return static_cast<GPUAttachmentType>(static_cast<int>(a) + b);
+}
 
-#define GPU_FB_MAX_COLOR_ATTACHMENT (GPU_FB_MAX_ATTACHEMENT - GPU_FB_COLOR_ATTACHMENT0)
+inline GPUAttachmentType &operator++(GPUAttachmentType &a)
+{
+  a = a + 1;
+  return a;
+}
 
-#define GPU_FB_DIRTY_DRAWBUFFER (1 << 15)
+inline GPUAttachmentType &operator--(GPUAttachmentType &a)
+{
+  a = a - 1;
+  return a;
+}
 
-#define GPU_FB_ATTACHEMENT_IS_DIRTY(flag, type) ((flag & (1 << type)) != 0)
-#define GPU_FB_ATTACHEMENT_SET_DIRTY(flag, type) (flag |= (1 << type))
+namespace blender {
+namespace gpu {
+
+#ifdef DEBUG
+#  define DEBUG_NAME_LEN 64
+#else
+#  define DEBUG_NAME_LEN 16
+#endif
 
 class FrameBuffer {
- public:
-  GPUContext *ctx;
-  GLuint object;
-  GPUAttachment attachments[GPU_FB_MAX_ATTACHEMENT];
-  uint16_t dirty_flag;
-  int width, height;
-  bool multisample;
-  /* TODO Check that we always use the right context when binding
-   * (FBOs are not shared across ogl contexts). */
-  // void *ctx;
+ protected:
+  /** Set of texture attachements to render to. DEPTH and DEPTH_STENCIL are mutualy exclusive. */
+  GPUAttachment attachments_[GPU_FB_MAX_ATTACHEMENT];
+  /** Is true if internal representation need to be updated. */
+  bool dirty_attachments_;
+  /** Size of attachement textures. */
+  int width_, height_;
+  /** Debug name. */
+  char name_[DEBUG_NAME_LEN];
 
  public:
-  GPUTexture *depth_tex(void) const
+  FrameBuffer(const char *name);
+  virtual ~FrameBuffer();
+
+  virtual void bind(bool enabled_srgb) = 0;
+  virtual bool check(char err_out[256]) = 0;
+  virtual void clear(eGPUFrameBufferBits buffers,
+                     const float clear_col[4],
+                     float clear_depth,
+                     uint clear_stencil) = 0;
+  virtual void clear_multi(const float (*clear_col)[4]) = 0;
+
+  virtual void read(eGPUFrameBufferBits planes,
+                    eGPUDataFormat format,
+                    const int area[4],
+                    int channel_len,
+                    int slot,
+                    void *r_data) = 0;
+
+  virtual void blit_to(eGPUFrameBufferBits planes,
+                       int src_slot,
+                       FrameBuffer *dst,
+                       int dst_slot,
+                       int dst_offset_x,
+                       int dst_offset_y) = 0;
+
+  void attachment_set(GPUAttachmentType type, const GPUAttachment &new_attachment);
+
+  void recursive_downsample(int max_lvl,
+                            void (*callback)(void *userData, int level),
+                            void *userData);
+
+  inline GPUTexture *depth_tex(void) const
   {
-    if (attachments[GPU_FB_DEPTH_ATTACHMENT].tex) {
-      return attachments[GPU_FB_DEPTH_ATTACHMENT].tex;
+    if (attachments_[GPU_FB_DEPTH_ATTACHMENT].tex) {
+      return attachments_[GPU_FB_DEPTH_ATTACHMENT].tex;
     }
-    return attachments[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex;
+    return attachments_[GPU_FB_DEPTH_STENCIL_ATTACHMENT].tex;
   };
 
-  GPUTexture *color_tex(int slot) const
+  inline GPUTexture *color_tex(int slot) const
   {
-    return attachments[GPU_FB_COLOR_ATTACHMENT0 + slot].tex;
+    return attachments_[GPU_FB_COLOR_ATTACHMENT0 + slot].tex;
   };
-
-  MEM_CXX_CLASS_ALLOC_FUNCS("FrameBuffer")
 };
 
+#undef DEBUG_NAME_LEN
+
 }  // namespace gpu
 }  // namespace blender