draw_gpu_context.cc

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/* SPDX-FileCopyrightText: 2016 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

 
#include "BKE_global.hh"
 
#include "GPU_capabilities.hh"
#include "GPU_context.hh"
#include "GPU_state.hh"
 
#include "RE_engine.h"
#include "RE_pipeline.h"
 
#include "DRW_engine.hh"
#include "DRW_render.hh"
 
#include "WM_api.hh"
#include "wm_window.hh"
 
/* -------------------------------------------------------------------- */
 
static TicketMutex *draw_mutex = nullptr;
static TicketMutex *submission_mutex = nullptr;
 
void DRW_mutexes_init()
{
  draw_mutex = BLI_ticket_mutex_alloc();
  submission_mutex = BLI_ticket_mutex_alloc();
}
 
void DRW_mutexes_exit()
{
  BLI_ticket_mutex_free(draw_mutex);
  BLI_ticket_mutex_free(submission_mutex);
}
 
void DRW_lock_start()
{
  bool locked = BLI_ticket_mutex_lock_check_recursive(draw_mutex);
  BLI_assert(locked);
  UNUSED_VARS_NDEBUG(locked);
}
 
void DRW_lock_end()
{
  BLI_ticket_mutex_unlock(draw_mutex);
}
 
void DRW_submission_start()
{
  bool locked = BLI_ticket_mutex_lock_check_recursive(submission_mutex);
  BLI_assert(locked);
  UNUSED_VARS_NDEBUG(locked);
  GPU_render_begin();
}
 
void DRW_submission_end()
{
  GPU_render_end();
  BLI_ticket_mutex_unlock(submission_mutex);
}

 
/* -------------------------------------------------------------------- */
 
/* Context that can be shared across threads. Usage is guarded by a ticket mutex.
 * Should eventually be moved to GPU module after we get rid of the WM calls. */
class ContextShared {
  /* Should be private but needs to be public for XR workaround.*/
 public:
  TicketMutex *mutex_ = nullptr;
  void *system_gpu_context_ = nullptr;
  GPUContext *blender_gpu_context_ = nullptr;
 
  /* NOTE: This changes the active context. */
  ContextShared()
  {
    mutex_ = BLI_ticket_mutex_alloc();
 
    system_gpu_context_ = WM_system_gpu_context_create();
    WM_system_gpu_context_activate(system_gpu_context_);
    blender_gpu_context_ = GPU_context_create(nullptr, system_gpu_context_);
  }
 
  ~ContextShared()
  {
    WM_system_gpu_context_activate(system_gpu_context_);
    GPU_context_active_set(blender_gpu_context_);
 
    GPU_context_discard(blender_gpu_context_);
    WM_system_gpu_context_dispose(system_gpu_context_);
 
    BLI_ticket_mutex_free(mutex_);
  }
 
  void enable()
  {
    DRW_lock_start();
    /* IMPORTANT: We don't support immediate mode in render mode!
     * This shall remain in effect until immediate mode supports
     * multiple threads. */
    BLI_ticket_mutex_lock(mutex_);
 
    GPU_render_begin();
 
    WM_system_gpu_context_activate(system_gpu_context_);
    GPU_context_active_set(blender_gpu_context_);
    GPU_context_begin_frame(blender_gpu_context_);
  }
 
  /* Restore window drawable after disabling if restore is true. */
  void disable(bool restore = false)
  {
    GPU_context_end_frame(blender_gpu_context_);
 
    if (BLI_thread_is_main() && restore) {
      wm_window_reset_drawable();
    }
    else {
      WM_system_gpu_context_release(system_gpu_context_);
      GPU_context_active_set(nullptr);
    }
    /* Render boundaries are opened and closed here as this may be
     * called outside of an existing render loop. */
    GPU_render_end();
 
    BLI_ticket_mutex_unlock(mutex_);
    DRW_lock_end();
  }
};

 
/* -------------------------------------------------------------------- */

static ContextShared *viewport_context = nullptr;
static ContextShared *preview_context = nullptr;
 
void DRW_gpu_context_create()
{
  BLI_assert(viewport_context == nullptr); /* Ensure it's called once */
 
  DRW_mutexes_init();
 
  viewport_context = MEM_new<ContextShared>(__func__);
  preview_context = MEM_new<ContextShared>(__func__);
 
  /* Some part of the code assumes no context is left bound. */
  GPU_context_active_set(nullptr);
  WM_system_gpu_context_release(preview_context->system_gpu_context_);
 
  /* Activate the window's context if any. */
  wm_window_reset_drawable();
}
 
void DRW_gpu_context_destroy()
{
  BLI_assert(BLI_thread_is_main());
  if (viewport_context == nullptr) {
    return;
  }
  DRW_mutexes_exit();
 
  MEM_SAFE_DELETE(viewport_context);
  MEM_SAFE_DELETE(preview_context);
}

 
/* -------------------------------------------------------------------- */
 
void DRW_gpu_context_enable_ex(bool /*restore*/)
{
  if (viewport_context == nullptr) {
    return;
  }
  viewport_context->enable();
}
 
void DRW_gpu_context_disable_ex(bool restore)
{
  if (viewport_context == nullptr) {
    return;
  }
  viewport_context->disable(restore);
}
 
static void drw_gpu_preview_context_enable()
{
  if (preview_context == nullptr) {
    return;
  }
  preview_context->enable();
}
 
static void drw_gpu_preview_context_disable()
{
  if (preview_context == nullptr) {
    return;
  }
  preview_context->disable();
}
 
void DRW_gpu_context_enable()
{
  /* TODO: should be replace by a more elegant alternative. */
 
  if (G.background && viewport_context == nullptr) {
    WM_init_gpu();
  }
  DRW_gpu_context_enable_ex(true);
}
 
bool DRW_gpu_context_try_enable()
{
  if (viewport_context == nullptr) {
    return false;
  }
  DRW_gpu_context_enable_ex(true);
  return true;
}
 
void DRW_gpu_context_disable()
{
  DRW_gpu_context_disable_ex(true);
}
 
void DRW_system_gpu_render_context_enable(void *re_system_gpu_context)
{
  /* If thread is main you should use DRW_gpu_context_enable(). */
  BLI_assert(!BLI_thread_is_main());
 
  DRW_lock_start();
  WM_system_gpu_context_activate(re_system_gpu_context);
}
 
void DRW_system_gpu_render_context_disable(void *re_system_gpu_context)
{
  WM_system_gpu_context_release(re_system_gpu_context);
  DRW_lock_end();
}
 
void DRW_blender_gpu_render_context_enable(void *re_gpu_context)
{
  /* If thread is main you should use DRW_gpu_context_enable(). */
  BLI_assert(!BLI_thread_is_main());
 
  GPU_context_active_set(static_cast<GPUContext *>(re_gpu_context));
}
 
void DRW_blender_gpu_render_context_disable(void * /*re_gpu_context*/)
{
  GPU_flush();
  GPU_context_active_set(nullptr);
}
 
void DRW_render_context_enable(Render *render)
{
  if (G.background && viewport_context == nullptr) {
    WM_init_gpu();
  }
 
  GPU_render_begin();
 
  if (GPU_use_main_context_workaround()) {
    GPU_context_main_lock();
    DRW_gpu_context_enable();
    return;
  }
 
  void *re_viewport_system_gpu_context = RE_system_gpu_context_get(render);
 
  /* Changing Context */
  if (re_viewport_system_gpu_context != nullptr) {
    DRW_system_gpu_render_context_enable(re_viewport_system_gpu_context);
    /* We need to query gpu context after a gl context has been bound. */
    void *re_viewport_context = RE_blender_gpu_context_ensure(render);
    DRW_blender_gpu_render_context_enable(re_viewport_context);
  }
  else {
    drw_gpu_preview_context_enable();
  }
}
 
void DRW_render_context_disable(Render *render)
{
  if (GPU_use_main_context_workaround()) {
    DRW_gpu_context_disable();
    GPU_render_end();
    GPU_context_main_unlock();
    return;
  }
 
  void *re_viewport_system_gpu_context = RE_system_gpu_context_get(render);
 
  if (re_viewport_system_gpu_context != nullptr) {
    void *re_viewport_context = RE_blender_gpu_context_ensure(render);
    /* GPU rendering may occur during context disable. */
    DRW_blender_gpu_render_context_disable(re_viewport_context);
    GPU_render_end();
    DRW_system_gpu_render_context_disable(re_viewport_system_gpu_context);
  }
  else {
    /* Usually the case for a preview job. The `Render` is created inside the render thread which
     * is too late to create a GPU context. */
    drw_gpu_preview_context_disable();
    GPU_render_end();
  }
}

 
/* -------------------------------------------------------------------- */
 
#ifdef WITH_XR_OPENXR
 
void *DRW_system_gpu_context_get()
{
  /* XXX: There should really be no such getter, but for VR we currently can't easily avoid it.
   * OpenXR needs some low level info for the GPU context that will be used for submitting the
   * final frame-buffer. VR could in theory create its own context, but that would mean we have to
   * switch to it just to submit the final frame, which has notable performance impact.
   *
   * We could "inject" a context through DRW_system_gpu_render_context_enable(), but that would
   * have to work from the main thread, which is tricky to get working too. The preferable solution
   * would be using a separate thread for VR drawing where a single context can stay active. */
 
  return viewport_context->system_gpu_context_;
}
 
void *DRW_xr_blender_gpu_context_get()
{
  /* XXX: See comment on #DRW_system_gpu_context_get(). */
 
  return viewport_context->blender_gpu_context_;
}
 
void DRW_xr_drawing_begin()
{
  /* XXX: See comment on #DRW_system_gpu_context_get(). */
 
  DRW_lock_start();
  BLI_ticket_mutex_lock(viewport_context->mutex_);
}
 
void DRW_xr_drawing_end()
{
  /* XXX: See comment on #DRW_system_gpu_context_get(). */
 
  BLI_ticket_mutex_unlock(viewport_context->mutex_);
  DRW_lock_end();
}
 
#endif

 
/* -------------------------------------------------------------------- */
 
bool DRW_gpu_context_release()
{
  if (!BLI_thread_is_main()) {
    return false;
  }
 
  if (GPU_context_active_get() != viewport_context->blender_gpu_context_) {
    /* Context release is requested from the outside of the draw manager main draw loop, indicate
     * this to the `DRW_gpu_context_activate()` so that it restores drawable of the window.
     */
    return false;
  }
 
  GPU_context_active_set(nullptr);
  WM_system_gpu_context_release(viewport_context->system_gpu_context_);
 
  return true;
}
 
void DRW_gpu_context_activate(bool drw_state)
{
  if (!BLI_thread_is_main()) {
    return;
  }
 
  if (drw_state) {
    WM_system_gpu_context_activate(viewport_context->system_gpu_context_);
    GPU_context_active_set(viewport_context->blender_gpu_context_);
  }
  else {
    wm_window_reset_drawable();
  }
}