GLTexture: Add Feedback loop check

The check is better than before as we take into
consideration the attached mip level.

source/blender/gpu/intern/gpu_texture_private.hh

@@ -91,11 +91,12 @@ class Texture {
   /** Number of mipmaps this texture has (Max miplvl). */
   /* TODO(fclem) Should become immutable and the need for mipmaps should be specified upfront. */
   int mipmaps_ = -1;
+  /** For error checking */
+  int mip_min_ = 0, mip_max_ = 0;
 
   /** For debugging */
   char name_[DEBUG_NAME_LEN];
 
- private:
   /** Framebuffer references to update on deletion. */
   GPUAttachmentType fb_attachment_[GPU_TEX_MAX_FBO_ATTACHED];
   FrameBuffer *fb_[GPU_TEX_MAX_FBO_ATTACHED];

source/blender/gpu/opengl/gl_framebuffer.hh

@@ -39,6 +39,9 @@ class GLStateManager;
  * Implementation of FrameBuffer object using OpenGL.
  **/
 class GLFrameBuffer : public FrameBuffer {
+  /* For debugging purpose. */
+  friend class GLTexture;
+
  private:
   /** OpenGL handle. */
   GLuint fbo_id_ = 0;

source/blender/gpu/opengl/gl_state.cc

@@ -434,6 +434,9 @@ void GLStateManager::texture_bind(Texture *tex_, eGPUSamplerState sampler_type,
 {
   BLI_assert(unit < GPU_max_textures());
   GLTexture *tex = static_cast<GLTexture *>(tex_);
+  if (G.debug & G_DEBUG_GPU) {
+    tex->check_feedback_loop();
+  }
   /* Eliminate redundant binds. */
   if ((textures_[unit] == tex->tex_id_) &&
       (samplers_[unit] == GLTexture::samplers_[sampler_type])) {

source/blender/gpu/opengl/gl_texture.cc

@@ -446,6 +446,8 @@ void GLTexture::swizzle_set(const char swizzle[4])
 void GLTexture::mip_range_set(int min, int max)
 {
   BLI_assert(min <= max && min >= 0 && max <= mipmaps_);
+  mip_min_ = min;
+  mip_max_ = max;
   if (GLEW_ARB_direct_state_access) {
     glTextureParameteri(tex_id_, GL_TEXTURE_BASE_LEVEL, min);
     glTextureParameteri(tex_id_, GL_TEXTURE_MAX_LEVEL, max);
@@ -649,6 +651,35 @@ bool GLTexture::proxy_check(int mip)
 
 /** \} */
 
+void GLTexture::check_feedback_loop(void)
+{
+  /* Recursive downsample workaround break this check.
+   * See recursive_downsample() for more infos. */
+  if (GPU_mip_render_workaround()) {
+    return;
+  }
+  GLFrameBuffer *fb = static_cast<GLFrameBuffer *>(GPU_context_active_get()->active_fb);
+  for (int i = 0; i < ARRAY_SIZE(fb_); i++) {
+    if (fb_[i] == fb) {
+      GPUAttachmentType type = fb_attachment_[i];
+      GPUAttachment attachment = fb->attachments_[type];
+      if (attachment.mip <= mip_max_ && attachment.mip >= mip_min_) {
+        char msg[256];
+        SNPRINTF(msg,
+                 "Feedback loop: Trying to bind a texture (%s) with mip range %d-%d but mip %d is "
+                 "attached to the active framebuffer (%s)",
+                 name_,
+                 mip_min_,
+                 mip_max_,
+                 attachment.mip,
+                 fb->name_);
+        debug::raise_gl_error(msg);
+      }
+      return;
+    }
+  }
+}
+
 /* TODO(fclem) Legacy. Should be removed at some point. */
 uint GLTexture::gl_bindcode_get(void) const
 {

source/blender/gpu/opengl/gl_texture.hh

@@ -75,6 +75,8 @@ class GLTexture : public Texture {
   void mip_range_set(int min, int max) override;
   void *read(int mip, eGPUDataFormat format) override;
 
+  void check_feedback_loop(void);
+
   /* TODO(fclem) Legacy. Should be removed at some point. */
   uint gl_bindcode_get(void) const override;