/* GDK - The GIMP Drawing Kit
 *
 * gdkglcontext.c: GL context abstraction
 * 
 * Copyright © 2014  Emmanuele Bassi
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * SECTION:gdkglcontext
 * @Title: GdkGLContext
 * @Short_description: OpenGL context
 *
 * #GdkGLContext is an object representing the platform-specific
 * OpenGL drawing context.
 *
 * #GdkGLContexts are created for a #GdkWindow using
 * gdk_window_create_gl_context(), and the context will match
 * the #GdkVisual of the window.
 *
 * A #GdkGLContext is not tied to any particular normal framebuffer.
 * For instance, it cannot draw to the #GdkWindow back buffer. The GDK
 * repaint system is in full control of the painting to that. Instead,
 * you can create render buffers or textures and use gdk_cairo_draw_from_gl()
 * in the draw function of your widget to draw them. Then GDK will handle
 * the integration of your rendering with that of other widgets.
 *
 * Support for #GdkGLContext is platform-specific, context creation
 * can fail, returning %NULL context.
 *
 * A #GdkGLContext has to be made "current" in order to start using
 * it, otherwise any OpenGL call will be ignored.
 *
 * ## Creating a new OpenGL context ##
 *
 * In order to create a new #GdkGLContext instance you need a
 * #GdkWindow, which you typically get during the realize call
 * of a widget.
 *
 * ## Using a GdkGLContext ##
 *
 * You will need to make the #GdkGLContext the current context
 * before issuing OpenGL calls; the system sends OpenGL commands to
 * whichever context is current. It is possible to have multiple
 * contexts, so you always need to ensure that the one which you
 * want to draw with is the current one before issuing commands:
 *
 * |[<!-- language="C" -->
 *   gdk_gl_context_make_current (context);
 * ]|
 *
 * You can now perform your drawing using OpenGL commands.
 *
 * You can check which #GdkGLContext is the current one by using
 * gdk_gl_context_get_current(); you can also unset any #GdkGLContext
 * that is currently set by calling gdk_gl_context_clear_current().
 */

#include "config.h"

#include "gdkglcontextprivate.h"
#include "gdkdisplayprivate.h"
#include "gdkvisual.h"
#include "gdkinternals.h"

#include "gdkintl.h"

#include <epoxy/gl.h>

typedef struct {
  GdkWindow *window;
  GdkVisual *visual;

  guint realized : 1;
  guint use_texture_rectangle : 1;

} GdkGLContextPrivate;

enum {
  PROP_0,

  PROP_WINDOW,
  PROP_VISUAL,

  LAST_PROP
};

static GParamSpec *obj_pspecs[LAST_PROP] = { NULL, };

G_DEFINE_QUARK (gdk-gl-error-quark, gdk_gl_error)

G_DEFINE_ABSTRACT_TYPE_WITH_PRIVATE (GdkGLContext, gdk_gl_context, G_TYPE_OBJECT)

static GPrivate thread_current_context = G_PRIVATE_INIT (g_object_unref);

static void
gdk_gl_context_dispose (GObject *gobject)
{
  GdkGLContext *context = GDK_GL_CONTEXT (gobject);
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);
  GdkGLContext *current;

  current = g_private_get (&thread_current_context);
  if (current == context)
    g_private_replace (&thread_current_context, NULL);

  g_clear_object (&priv->window);
  g_clear_object (&priv->visual);

  G_OBJECT_CLASS (gdk_gl_context_parent_class)->dispose (gobject);
}

static void
gdk_gl_context_set_property (GObject      *gobject,
                             guint         prop_id,
                             const GValue *value,
                             GParamSpec   *pspec)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private ((GdkGLContext *) gobject);

  switch (prop_id)
    {
    case PROP_WINDOW:
      {
        GdkWindow *window = g_value_get_object (value);

        if (window)
          g_object_ref (window);

        if (priv->window)
          g_object_unref (priv->window);

        priv->window = window;
      }
      break;

    case PROP_VISUAL:
      {
        GdkVisual *visual = g_value_get_object (value);

        if (visual != NULL)
          priv->visual = g_object_ref (visual);
      }
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
    }
}

static void
gdk_gl_context_get_property (GObject    *gobject,
                             guint       prop_id,
                             GValue     *value,
                             GParamSpec *pspec)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private ((GdkGLContext *) gobject);

  switch (prop_id)
    {
    case PROP_WINDOW:
      g_value_set_object (value, priv->window);
      break;

    case PROP_VISUAL:
      g_value_set_object (value, priv->visual);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
    }
}

static void
gdk_gl_context_class_init (GdkGLContextClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);

  /**
   * GdkGLContext:window:
   *
   * The #GdkWindow the gl context is bound to.
   *
   * Since: 3.16
   */
  obj_pspecs[PROP_WINDOW] =
    g_param_spec_object ("window",
                         P_("Window"),
                         P_("The GDK window bound to the GL context"),
                         GDK_TYPE_WINDOW,
                         G_PARAM_READWRITE |
                         G_PARAM_CONSTRUCT_ONLY |
                         G_PARAM_STATIC_STRINGS);

  /**
   * GdkGLContext:visual:
   *
   * The #GdkVisual matching the pixel format used by the context.
   *
   * Since: 3.16
   */
  obj_pspecs[PROP_VISUAL] =
    g_param_spec_object ("visual",
                         P_("Visual"),
                         P_("The GDK visual used by the GL context"),
                         GDK_TYPE_VISUAL,
                         G_PARAM_READWRITE |
                         G_PARAM_CONSTRUCT_ONLY |
                         G_PARAM_STATIC_STRINGS);

  gobject_class->set_property = gdk_gl_context_set_property;
  gobject_class->get_property = gdk_gl_context_get_property;
  gobject_class->dispose = gdk_gl_context_dispose;

  g_object_class_install_properties (gobject_class, LAST_PROP, obj_pspecs);
}

static void
gdk_gl_context_init (GdkGLContext *self)
{
}

/**
 * gdk_gl_context_get_visual:
 * @context: a #GdkGLContext
 *
 * Retrieves the #GdkVisual associated with the @context.
 *
 * Returns: (transfer none): the #GdkVisual
 *
 * Since: 3.16
 */
GdkVisual *
gdk_gl_context_get_visual (GdkGLContext *context)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);

  g_return_val_if_fail (GDK_IS_GL_CONTEXT (context), NULL);

  return priv->visual;
}

/*< private >
 * gdk_gl_context_end_frame:
 * @context: a #GdkGLContext
 * @painted: The area that has been redrawn this frame
 * @damage: The area that we know is actually different from the last frame
 *
 * Copies the back buffer to the front buffer.
 *
 * This function may call `glFlush()` implicitly before returning; it
 * is not recommended to call `glFlush()` explicitly before calling
 * this function.
 *
 * Since: 3.16
 */
void
gdk_gl_context_end_frame (GdkGLContext   *context,
                          cairo_region_t *painted,
                          cairo_region_t *damage)
{
  g_return_if_fail (GDK_IS_GL_CONTEXT (context));

  GDK_GL_CONTEXT_GET_CLASS (context)->end_frame (context, painted, damage);
}

gboolean
gdk_gl_context_use_texture_rectangle (GdkGLContext *context)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);

  return priv->use_texture_rectangle;
}

static void
gdk_gl_context_realize (GdkGLContext *context)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);
  gboolean has_npot, has_texture_rectangle;

  has_npot = epoxy_has_gl_extension ("GL_ARB_texture_non_power_of_two");
  has_texture_rectangle = epoxy_has_gl_extension ("GL_ARB_texture_rectangle");

  if (has_npot)
    priv->use_texture_rectangle = FALSE;
  else if (has_texture_rectangle)
    priv->use_texture_rectangle = TRUE;
  else
    g_warning ("Gl implementation doesn't support any form of non-power-of-two textures");

  priv->realized = TRUE;
}

/**
 * gdk_gl_context_make_current:
 * @context: a #GdkGLContext
 *
 * Makes the @context the current one.
 *
 * Since: 3.16
 */
void
gdk_gl_context_make_current (GdkGLContext *context)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);
  GdkGLContext *current;

  g_return_if_fail (GDK_IS_GL_CONTEXT (context));

  current = g_private_get (&thread_current_context);
  if (current == context)
    return;

  if (gdk_display_make_gl_context_current (gdk_window_get_display (priv->window), context))
    {
      g_private_replace (&thread_current_context, g_object_ref (context));
      if (!priv->realized)
        gdk_gl_context_realize (context);
    }
}

/**
 * gdk_gl_context_get_window:
 * @context: a #GdkGLContext
 *
 * Retrieves the #GdkWindow used by the @context.
 *
 * Returns: (transfer none): a #GdkWindow or %NULL
 *
 * Since: 3.16
 */
GdkWindow *
gdk_gl_context_get_window (GdkGLContext *context)
{
  GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (context);

  g_return_val_if_fail (GDK_IS_GL_CONTEXT (context), NULL);

  return priv->window;
}

/**
 * gdk_gl_context_clear_current:
 *
 * Clears the current #GdkGLContext.
 *
 * Any OpenGL call after this function returns will be ignored
 * until gdk_gl_context_make_current() is called.
 *
 * Since: 3.16
 */
void
gdk_gl_context_clear_current (void)
{
  GdkGLContext *current;

  current = g_private_get (&thread_current_context);
  if (current != NULL)
    {
      GdkGLContextPrivate *priv = gdk_gl_context_get_instance_private (current);

      if (gdk_display_make_gl_context_current (gdk_window_get_display (priv->window), NULL))
        g_private_replace (&thread_current_context, NULL);
    }
}

/**
 * gdk_gl_context_get_current:
 *
 * Retrieves the current #GdkGLContext.
 *
 * Returns: (transfer none): the current #GdkGLContext, or %NULL
 *
 * Since: 3.16
 */
GdkGLContext *
gdk_gl_context_get_current (void)
{
  GdkGLContext *current;

  current = g_private_get (&thread_current_context);

  return current;
}