GPUBatch: GL backend isolation

This changes the drawing paradigm a bit. The VAO configuration is done
JIT-style and depends on context active shader.

This is to allow more flexibility for implementations to do optimization
at lower level.

The vao cache is now its own class to isolate the concept. It is this
class that is reference by the GLContext for ownership of the containing
VAO ids.

source/blender/gpu/opengl/gl_vertex_array.cc

@@ -0,0 +1,158 @@
+/*
+ * 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) 2016 by Mike Erwin.
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup gpu
+ */
+
+#include "GPU_glew.h"
+
+#include "GPU_shader_interface.h"
+#include "GPU_vertex_buffer.h"
+
+#include "gpu_vertex_format_private.h"
+
+#include "gl_batch.hh"
+#include "gl_context.hh"
+
+#include "gl_vertex_array.hh"
+
+using namespace blender::gpu;
+
+/* -------------------------------------------------------------------- */
+/** \name Vertex Array Bindings
+ * \{ */
+
+/* Returns enabled vertex pointers as a bitflag (one bit per attrib). */
+static uint16_t vbo_bind(const GPUShaderInterface *interface,
+                         const GPUVertFormat *format,
+                         uint v_first,
+                         uint v_len,
+                         const bool use_instancing)
+{
+  uint16_t enabled_attrib = 0;
+  const uint attr_len = format->attr_len;
+  uint stride = format->stride;
+  uint offset = 0;
+  GLuint divisor = (use_instancing) ? 1 : 0;
+
+  for (uint a_idx = 0; a_idx < attr_len; a_idx++) {
+    const GPUVertAttr *a = &format->attrs[a_idx];
+
+    if (format->deinterleaved) {
+      offset += ((a_idx == 0) ? 0 : format->attrs[a_idx - 1].sz) * v_len;
+      stride = a->sz;
+    }
+    else {
+      offset = a->offset;
+    }
+
+    const GLvoid *pointer = (const GLubyte *)0 + offset + v_first * stride;
+    const GLenum type = convert_comp_type_to_gl(static_cast<GPUVertCompType>(a->comp_type));
+
+    for (uint n_idx = 0; n_idx < a->name_len; n_idx++) {
+      const char *name = GPU_vertformat_attr_name_get(format, a, n_idx);
+      const GPUShaderInput *input = GPU_shaderinterface_attr(interface, name);
+
+      if (input == NULL) {
+        continue;
+      }
+
+      enabled_attrib |= (1 << input->location);
+
+      if (a->comp_len == 16 || a->comp_len == 12 || a->comp_len == 8) {
+        BLI_assert(a->fetch_mode == GPU_FETCH_FLOAT);
+        BLI_assert(a->comp_type == GPU_COMP_F32);
+        for (int i = 0; i < a->comp_len / 4; i++) {
+          glEnableVertexAttribArray(input->location + i);
+          glVertexAttribDivisor(input->location + i, divisor);
+          glVertexAttribPointer(
+              input->location + i, 4, type, GL_FALSE, stride, (const GLubyte *)pointer + i * 16);
+        }
+      }
+      else {
+        glEnableVertexAttribArray(input->location);
+        glVertexAttribDivisor(input->location, divisor);
+
+        switch (a->fetch_mode) {
+          case GPU_FETCH_FLOAT:
+          case GPU_FETCH_INT_TO_FLOAT:
+            glVertexAttribPointer(input->location, a->comp_len, type, GL_FALSE, stride, pointer);
+            break;
+          case GPU_FETCH_INT_TO_FLOAT_UNIT:
+            glVertexAttribPointer(input->location, a->comp_len, type, GL_TRUE, stride, pointer);
+            break;
+          case GPU_FETCH_INT:
+            glVertexAttribIPointer(input->location, a->comp_len, type, stride, pointer);
+            break;
+        }
+      }
+    }
+  }
+  return enabled_attrib;
+}
+
+/* Update the Attrib Binding of the currently bound VAO. */
+void GLVertArray::update_bindings(const GLuint vao,
+                                  const GPUBatch *batch,
+                                  const GPUShaderInterface *interface,
+                                  const int base_instance)
+{
+  uint16_t attr_mask = interface->enabled_attr_mask;
+
+  glBindVertexArray(vao);
+
+  /* Reverse order so first VBO'S have more prevalence (in term of attribute override). */
+  for (int v = GPU_BATCH_VBO_MAX_LEN - 1; v > -1; v--) {
+    GPUVertBuf *vbo = batch->verts[v];
+    if (vbo) {
+      GPU_vertbuf_use(vbo);
+      attr_mask &= ~vbo_bind(interface, &vbo->format, 0, vbo->vertex_len, false);
+    }
+  }
+
+  for (int v = GPU_BATCH_INST_VBO_MAX_LEN - 1; v > -1; v--) {
+    GPUVertBuf *vbo = batch->inst[v];
+    if (vbo) {
+      GPU_vertbuf_use(vbo);
+      attr_mask &= ~vbo_bind(interface, &vbo->format, base_instance, vbo->vertex_len, true);
+    }
+  }
+
+  if (attr_mask != 0 && GLEW_ARB_vertex_attrib_binding) {
+    for (uint16_t mask = 1, a = 0; a < 16; a++, mask <<= 1) {
+      if (attr_mask & mask) {
+        GLContext *ctx = static_cast<GLContext *>(GPU_context_active_get());
+        /* This replaces glVertexAttrib4f(a, 0.0f, 0.0f, 0.0f, 1.0f); with a more modern style.
+         * Fix issues for some drivers (see T75069). */
+        glBindVertexBuffer(a, ctx->default_attr_vbo_, (intptr_t)0, (intptr_t)0);
+        glEnableVertexAttribArray(a);
+        glVertexAttribFormat(a, 4, GL_FLOAT, GL_FALSE, 0);
+        glVertexAttribBinding(a, a);
+      }
+    }
+  }
+
+  if (batch->elem) {
+    /* Binds the index buffer. This state is also saved in the VAO. */
+    GPU_indexbuf_use(batch->elem);
+  }
+}
+
+/** \} */