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, 81 insertions, 0 deletions

diff --git a/source/blender/gpu/opengl/gl_texture.hh b/source/blender/gpu/opengl/gl_texture.hh
new file mode 100644
index 00000000000..c1194941038
--- /dev/null
+++ b/source/blender/gpu/opengl/gl_texture.hh
@@ -0,0 +1,81 @@
+
+/*
+ * 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.
+ *
+ * The Original Code is Copyright (C) 2020 Blender Foundation.
+ * All rights reserved.
+ */
+
+/** \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_assert.h"
+
+#include "glew-mx.h"
+
+namespace blender {
+namespace gpu {
+
+static GLenum to_gl(eGPUDataFormat format)
+{
+  switch (format) {
+    case GPU_DATA_FLOAT:
+      return GL_FLOAT;
+    case GPU_DATA_INT:
+      return GL_INT;
+    case GPU_DATA_UNSIGNED_INT:
+      return GL_UNSIGNED_INT;
+    case GPU_DATA_UNSIGNED_BYTE:
+      return GL_UNSIGNED_BYTE;
+    case GPU_DATA_UNSIGNED_INT_24_8:
+      return GL_UNSIGNED_INT_24_8;
+    case GPU_DATA_10_11_11_REV:
+      return GL_UNSIGNED_INT_10F_11F_11F_REV;
+    default:
+      BLI_assert(!"Unhandled data format");
+      return GL_FLOAT;
+  }
+}
+
+/* Assume Unorm / Float target. Used with glReadPixels. */
+static GLenum channel_len_to_gl(int channel_len)
+{
+  switch (channel_len) {
+    case 1:
+      return GL_RED;
+    case 2:
+      return GL_RG;
+    case 3:
+      return GL_RGB;
+    case 4:
+      return GL_RGBA;
+    default:
+      BLI_assert(!"Wrong number of texture channels");
+      return GL_RED;
+  }
+}
+
+}  // namespace gpu
+}  // namespace blender