/* gskglcommandqueueprivate.h
 *
 * Copyright 2020 Christian Hergert <chergert@redhat.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#ifndef __GSK_GL_COMMAND_QUEUE_PRIVATE_H__
#define __GSK_GL_COMMAND_QUEUE_PRIVATE_H__

#include <gsk/gskprofilerprivate.h>

#include "gskgltypesprivate.h"
#include "gskglbufferprivate.h"
#include "gskglattachmentstateprivate.h"
#include "gskgluniformstateprivate.h"

#include "inlinearray.h"

#include "gskglprofilerprivate.h"

G_BEGIN_DECLS

#define GSK_TYPE_GL_COMMAND_QUEUE (gsk_gl_command_queue_get_type())

G_DECLARE_FINAL_TYPE (GskGLCommandQueue, gsk_gl_command_queue, GSK, GL_COMMAND_QUEUE, GObject)

typedef enum _GskGLCommandKind
{
  /* The batch will perform a glClear() */
  GSK_GL_COMMAND_KIND_CLEAR,

  /* The batch will perform a glDrawArrays() */
  GSK_GL_COMMAND_KIND_DRAW,
} GskGLCommandKind;

typedef struct _GskGLCommandBind
{
  /* @texture is the value passed to glActiveTexture(), the "slot" the
   * texture will be placed into. We always use GL_TEXTURE_2D so we don't
   * waste any bits here to indicate that.
   */
  guint texture : 5;

  /* The identifier for the texture created with glGenTextures(). */
  guint id : 27;
} GskGLCommandBind;

G_STATIC_ASSERT (sizeof (GskGLCommandBind) == 4);

typedef struct _GskGLCommandBatchAny
{
  /* A GskGLCommandKind indicating what the batch will do */
  guint kind : 8;

  /* The program's identifier to use for determining if we can merge two
   * batches together into a single set of draw operations. We put this
   * here instead of the GskGLCommandDraw so that we can use the extra
   * bits here without making the structure larger.
   */
  guint program : 24;

  /* The index of the next batch following this one. This is used
   * as a sort of integer-based linked list to simplify out-of-order
   * batching without moving memory around. -1 indicates last batch.
   */
  gint16 next_batch_index;

  /* Same but for reverse direction as we sort in reverse to get the
   * batches ordered by framebuffer.
   */
  gint16 prev_batch_index;

  /* The viewport size of the batch. We check this as we process
   * batches to determine if we need to resize the viewport.
   */
  struct {
    guint16 width;
    guint16 height;
  } viewport;
} GskGLCommandBatchAny;

G_STATIC_ASSERT (sizeof (GskGLCommandBatchAny) == 12);

typedef struct _GskGLCommandDraw
{
  GskGLCommandBatchAny head;

  /* There doesn't seem to be a limit on the framebuffer identifier that
   * can be returned, so we have to use a whole unsigned for the framebuffer
   * we are drawing to. When processing batches, we check to see if this
   * changes and adjust the render target accordingly. Some sorting is
   * performed to reduce the amount we change framebuffers.
   */
  guint framebuffer;

  /* The number of uniforms to change. This must be less than or equal to
   * GL_MAX_UNIFORM_LOCATIONS but only guaranteed up to 1024 by any OpenGL
   * implementation to be conformant.
   */
  guint uniform_count : 11;

  /* The number of textures to bind, which is only guaranteed up to 16
   * by the OpenGL specification to be conformant.
   */
  guint bind_count : 5;

  /* GL_MAX_ELEMENTS_VERTICES specifies 33000 for this which requires 16-bit
   * to address all possible counts <= GL_MAX_ELEMENTS_VERTICES.
   */
  guint vbo_count : 16;

  /* The offset within the VBO containing @vbo_count vertices to send with
   * glDrawArrays().
   */
  guint vbo_offset;

  /* The offset within the array of uniform changes to be made containing
   * @uniform_count `GskGLCommandUniform` elements to apply.
   */
  guint uniform_offset;

  /* The offset within the array of bind changes to be made containing
   * @bind_count `GskGLCommandBind` elements to apply.
   */
  guint bind_offset;
} GskGLCommandDraw;

G_STATIC_ASSERT (sizeof (GskGLCommandDraw) == 32);

typedef struct _GskGLCommandClear
{
  GskGLCommandBatchAny  any;
  guint                 bits;
  guint                 framebuffer;
} GskGLCommandClear;

G_STATIC_ASSERT (sizeof (GskGLCommandClear) == 20);

typedef struct _GskGLCommandUniform
{
  GskGLUniformInfo info;
  guint             location;
} GskGLCommandUniform;

G_STATIC_ASSERT (sizeof (GskGLCommandUniform) == 8);

typedef union _GskGLCommandBatch
{
  GskGLCommandBatchAny any;
  GskGLCommandDraw     draw;
  GskGLCommandClear    clear;
} GskGLCommandBatch;

G_STATIC_ASSERT (sizeof (GskGLCommandBatch) == 32);

DEFINE_INLINE_ARRAY (GskGLCommandBatches, gsk_gl_command_batches, GskGLCommandBatch)
DEFINE_INLINE_ARRAY (GskGLCommandBinds, gsk_gl_command_binds, GskGLCommandBind)
DEFINE_INLINE_ARRAY (GskGLCommandUniforms, gsk_gl_command_uniforms, GskGLCommandUniform)

struct _GskGLCommandQueue
{
  GObject parent_instance;

  /* The GdkGLContext we make current before executing GL commands. */
  GdkGLContext *context;

  /* Array of GskGLCommandBatch which is a fixed size structure that will
   * point into offsets of other arrays so that all similar data is stored
   * together. The idea here is that we reduce the need for pointers so that
   * using g_realloc()'d arrays is fine.
   */
  GskGLCommandBatches batches;

  /* Contains array of vertices and some wrapper code to help upload them
   * to the GL driver. We can also tweak this to use double buffered arrays
   * if we find that to be faster on some hardware and/or drivers.
   */
  GskGLBuffer vertices;

  /* The GskGLAttachmentState contains information about our FBO and texture
   * attachments as we process incoming operations. We snapshot them into
   * various batches so that we can compare differences between merge
   * candidates.
   */
  GskGLAttachmentState *attachments;

  /* The uniform state across all programs. We snapshot this into batches so
   * that we can compare uniform state between batches to give us more
   * chances at merging draw commands.
   */
  GskGLUniformState *uniforms;

  /* Current program if we are in a draw so that we can send commands
   * to the uniform state as needed.
   */
  GskGLUniformProgram *program_info;

  /* The profiler instance to deliver timing/etc data */
  GskProfiler *profiler;
  GskGLProfiler *gl_profiler;

  /* Array of GskGLCommandBind which denote what textures need to be attached
   * to which slot. GskGLCommandDraw.bind_offset and bind_count reference this
   * array to determine what to attach.
   */
  GskGLCommandBinds batch_binds;

  /* Array of GskGLCommandUniform denoting which uniforms must be updated
   * before the glDrawArrays() may be called. These are referenced from the
   * GskGLCommandDraw.uniform_offset and uniform_count fields.
   */
  GskGLCommandUniforms batch_uniforms;

  /* Discovered max texture size when loading the command queue so that we
   * can either scale down or slice textures to fit within this size. Assumed
   * to be both height and width.
   */
  int max_texture_size;

  /* The index of the last batch in @batches, which may not be the element
   * at the end of the array, as batches can be reordered. This is used to
   * update the "next" index when adding a new batch.
   */
  gint16 tail_batch_index;
  gint16 head_batch_index;

  /* Max framebuffer we used, so we can sort items faster */
  guint fbo_max;

  /* Various GSK and GDK metric counter ids */
  struct {
    GQuark n_frames;
    GQuark cpu_time;
    GQuark gpu_time;
    guint n_binds;
    guint n_fbos;
    guint n_uniforms;
    guint n_uploads;
    guint n_programs;
    guint queue_depth;
  } metrics;

  /* Counter for uploads on the frame */
  guint n_uploads;

  /* If we're inside a begin/end_frame pair */
  guint in_frame : 1;

  /* If we're inside of a begin_draw()/end_draw() pair. */
  guint in_draw : 1;

  /* If we've warned about truncating batches */
  guint have_truncated : 1;
};

GskGLCommandQueue *gsk_gl_command_queue_new                   (GdkGLContext         *context,
                                                               GskGLUniformState    *uniforms);
void                gsk_gl_command_queue_set_profiler         (GskGLCommandQueue    *self,
                                                               GskProfiler          *profiler);
GdkGLContext       *gsk_gl_command_queue_get_context          (GskGLCommandQueue    *self);
void                gsk_gl_command_queue_make_current         (GskGLCommandQueue    *self);
void                gsk_gl_command_queue_begin_frame          (GskGLCommandQueue    *self);
void                gsk_gl_command_queue_end_frame            (GskGLCommandQueue    *self);
void                gsk_gl_command_queue_execute              (GskGLCommandQueue    *self,
                                                               guint                 surface_height,
                                                               guint                 scale_factor,
                                                               const cairo_region_t *scissor,
                                                               guint                 default_framebuffer);
int                 gsk_gl_command_queue_upload_texture       (GskGLCommandQueue    *self,
                                                               GdkTexture           *texture,
                                                               int                   min_filter,
                                                               int                   mag_filter);
int                 gsk_gl_command_queue_create_texture       (GskGLCommandQueue    *self,
                                                               int                   width,
                                                               int                   height,
                                                               int                   format,
                                                               int                   min_filter,
                                                               int                   mag_filter);
guint               gsk_gl_command_queue_create_framebuffer   (GskGLCommandQueue    *self);
gboolean            gsk_gl_command_queue_create_render_target (GskGLCommandQueue    *self,
                                                               int                   width,
                                                               int                   height,
                                                               int                   format,
                                                               int                   min_filter,
                                                               int                   mag_filter,
                                                               guint                *out_fbo_id,
                                                               guint                *out_texture_id);
void                gsk_gl_command_queue_delete_program       (GskGLCommandQueue    *self,
                                                               guint                 program_id);
void                gsk_gl_command_queue_clear                (GskGLCommandQueue    *self,
                                                               guint                 clear_bits,
                                                               const graphene_rect_t *viewport);
void                gsk_gl_command_queue_begin_draw           (GskGLCommandQueue    *self,
                                                               GskGLUniformProgram  *program_info,
                                                               guint                 width,
                                                               guint                 height);
void                gsk_gl_command_queue_end_draw             (GskGLCommandQueue    *self);
void                gsk_gl_command_queue_split_draw           (GskGLCommandQueue    *self);

static inline GskGLCommandBatch *
gsk_gl_command_queue_get_batch (GskGLCommandQueue *self)
{
  return gsk_gl_command_batches_tail (&self->batches);
}

static inline GskGLDrawVertex *
gsk_gl_command_queue_add_vertices (GskGLCommandQueue *self)
{
  gsk_gl_command_queue_get_batch (self)->draw.vbo_count += GSK_GL_N_VERTICES;
  return gsk_gl_buffer_advance (&self->vertices, GSK_GL_N_VERTICES);
}

static inline GskGLDrawVertex *
gsk_gl_command_queue_add_n_vertices (GskGLCommandQueue *self,
                                     guint              count)
{
  /* This is a batch form of gsk_gl_command_queue_add_vertices(). Note that
   * it does *not* add the count to .draw.vbo_count as the caller is responsible
   * for that.
   */
  return gsk_gl_buffer_advance (&self->vertices, GSK_GL_N_VERTICES * count);
}

static inline void
gsk_gl_command_queue_retract_n_vertices (GskGLCommandQueue *self,
                                         guint              count)
{
  /* Like gsk_gl_command_queue_add_n_vertices(), this does not tweak
   * the draw vbo_count.
   */
  gsk_gl_buffer_retract (&self->vertices, GSK_GL_N_VERTICES * count);
}

static inline guint
gsk_gl_command_queue_bind_framebuffer (GskGLCommandQueue *self,
                                       guint              framebuffer)
{
  guint ret = self->attachments->fbo.id;
  gsk_gl_attachment_state_bind_framebuffer (self->attachments, framebuffer);
  return ret;
}

G_END_DECLS

#endif /* __GSK_GL_COMMAND_QUEUE_PRIVATE_H__ */