GPUQuery: GL Backend isolation

This is part of the Vulkan task T68990.

This introduce a new GLQueryPool for managing queries in an
implementation agnostic manner.

This modify the GPU selection query to use this new object.
This also make use of blender::Vector for better code quality.

No real functionnal change.

4 files changed, 161 insertions, 8 deletions

diff --git a/source/blender/gpu/opengl/gl_backend.hh b/source/blender/gpu/opengl/gl_backend.hh
index 0c759d2cd62..94ac1692108 100644
--- a/source/blender/gpu/opengl/gl_backend.hh
+++ b/source/blender/gpu/opengl/gl_backend.hh
@@ -32,6 +32,7 @@
 #include "gl_drawlist.hh"
 #include "gl_framebuffer.hh"
 #include "gl_index_buffer.hh"
+#include "gl_query.hh"
 #include "gl_shader.hh"
 #include "gl_texture.hh"
 #include "gl_uniform_buffer.hh"
@@ -95,6 +96,11 @@ class GLBackend : public GPUBackend {
     return new GLIndexBuf();
   };
 
+  QueryPool *querypool_alloc(void) override
+  {
+    return new GLQueryPool();
+  };
+
   Shader *shader_alloc(const char *name) override
   {
     return new GLShader(name);
diff --git a/source/blender/gpu/opengl/gl_context.hh b/source/blender/gpu/opengl/gl_context.hh
index f05029c7075..8bce0d2e345 100644
--- a/source/blender/gpu/opengl/gl_context.hh
+++ b/source/blender/gpu/opengl/gl_context.hh
@@ -68,13 +68,13 @@ class GLContext : public GPUContext {
   static bool unused_fb_slot_workaround;
   static float derivative_signs[2];
 
+  /** VBO for missing vertex attrib binding. Avoid undefined behavior on some implementation. */
+  GLuint default_attr_vbo_;
+
   /** Used for debugging purpose. Bitflags of all bound slots. */
   uint16_t bound_ubo_slots;
 
-  /* TODO(fclem) these needs to become private. */
- public:
-  /** VBO for missing vertex attrib binding. Avoid undefined behavior on some implementation. */
-  GLuint default_attr_vbo_;
+ private:
   /**
    * GPUBatch & GPUFramebuffer have references to the context they are from, in the case the
    * context is destroyed, we need to remove any reference to it.
@@ -112,12 +112,12 @@ class GLContext : public GPUContext {
   static void buf_free(GLuint buf_id);
   static void tex_free(GLuint tex_id);
 
-  /* TODO(fclem) these needs to become private. */
- public:
-  static void orphans_add(Vector<GLuint> &orphan_list, std::mutex &list_mutex, GLuint id);
-  void orphans_clear(void);
   void vao_cache_register(GLVaoCache *cache);
   void vao_cache_unregister(GLVaoCache *cache);
+
+ private:
+  static void orphans_add(Vector<GLuint> &orphan_list, std::mutex &list_mutex, GLuint id);
+  void orphans_clear(void);
 };
 
 }  // namespace gpu
diff --git a/source/blender/gpu/opengl/gl_query.cc b/source/blender/gpu/opengl/gl_query.cc
new file mode 100644
index 00000000000..6da5cacfcb2
--- /dev/null
+++ b/source/blender/gpu/opengl/gl_query.cc
@@ -0,0 +1,78 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright 2020, Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup gpu
+ */
+
+#include "gl_query.hh"
+
+namespace blender::gpu {
+
+#define QUERY_CHUNCK_LEN 256
+
+GLQueryPool::~GLQueryPool()
+{
+  glDeleteQueries(query_ids_.size(), query_ids_.data());
+}
+
+void GLQueryPool::init(GPUQueryType type)
+{
+  BLI_assert(initialized_ == false);
+  initialized_ = true;
+  type_ = type;
+  gl_type_ = to_gl(type);
+  query_issued_ = 0;
+}
+
+#if 0 /* TODO to avoid realloc of permanent query pool. */
+void GLQueryPool::reset(GPUQueryType type)
+{
+  initialized_ = false;
+}
+#endif
+
+void GLQueryPool::begin_query(void)
+{
+  /* TODO add assert about expected usage. */
+  while (query_issued_ >= query_ids_.size()) {
+    int64_t prev_size = query_ids_.size();
+    query_ids_.resize(prev_size + QUERY_CHUNCK_LEN);
+    glGenQueries(QUERY_CHUNCK_LEN, &query_ids_[prev_size]);
+  }
+  glBeginQuery(gl_type_, query_ids_[query_issued_++]);
+}
+
+void GLQueryPool::end_query(void)
+{
+  /* TODO add assert about expected usage. */
+  glEndQuery(gl_type_);
+}
+
+void GLQueryPool::get_occlusion_result(MutableSpan<uint32_t> r_values)
+{
+  BLI_assert(r_values.size() == query_issued_);
+
+  for (int i = 0; i < query_issued_; i++) {
+    /* Note: This is a sync point. */
+    glGetQueryObjectuiv(query_ids_[i], GL_QUERY_RESULT, &r_values[i]);
+  }
+}
+
+}  // namespace blender::gpu
diff --git a/source/blender/gpu/opengl/gl_query.hh b/source/blender/gpu/opengl/gl_query.hh
new file mode 100644
index 00000000000..fc54c0ee1dd
--- /dev/null
+++ b/source/blender/gpu/opengl/gl_query.hh
@@ -0,0 +1,69 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Copyright 2020, Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup gpu
+ */
+
+#pragma once
+
+#include "BLI_vector.hh"
+
+#include "gpu_query.hh"
+
+#include "glew-mx.h"
+
+namespace blender::gpu {
+
+class GLQueryPool : public QueryPool {
+ private:
+  /** Contains queries object handles. */
+  Vector<GLuint> query_ids_;
+  /** Type of this query pool. */
+  GPUQueryType type_;
+  /** Associated GL type. */
+  GLenum gl_type_;
+  /** Number of queries that have been issued since last initialization.
+   * Should be equal to query_ids_.size(). */
+  uint32_t query_issued_;
+  /** Can only be initialized once. */
+  bool initialized_ = false;
+
+ public:
+  ~GLQueryPool();
+
+  void init(GPUQueryType type) override;
+
+  void begin_query(void) override;
+  void end_query(void) override;
+
+  void get_occlusion_result(MutableSpan<uint32_t> r_values) override;
+};
+
+static inline GLenum to_gl(GPUQueryType type)
+{
+  if (type == GPU_QUERY_OCCLUSION) {
+    /* TODO(fclem) try with GL_ANY_SAMPLES_PASSED​. */
+    return GL_SAMPLES_PASSED;
+  }
+  BLI_assert(0);
+  return GL_SAMPLES_PASSED;
+}
+
+}  // namespace blender::gpu
\ No newline at end of file