// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "flutter/shell/platform/linux/fl_gl_area.h"

#include <epoxy/gl.h>

struct _FlGLArea {
  GtkWidget parent_instance;

  GdkGLContext* context;

  FlBackingStoreProvider* texture;
};

G_DEFINE_TYPE(FlGLArea, fl_gl_area, GTK_TYPE_WIDGET)

static void fl_gl_area_dispose(GObject* gobject) {
  FlGLArea* self = FL_GL_AREA(gobject);

  g_clear_object(&self->context);
  g_clear_object(&self->texture);

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

// Implements GtkWidget::realize.
static void fl_gl_area_realize(GtkWidget* widget) {
  GtkAllocation allocation;
  gtk_widget_get_allocation(widget, &allocation);

  gtk_widget_set_realized(widget, TRUE);

  GdkWindowAttr attributes;
  attributes.window_type = GDK_WINDOW_CHILD;
  attributes.x = allocation.x;
  attributes.y = allocation.y;
  attributes.width = allocation.width;
  attributes.height = allocation.height;
  attributes.wclass = GDK_INPUT_OUTPUT;
  attributes.visual = gtk_widget_get_visual(widget);
  attributes.event_mask = gtk_widget_get_events(widget);
  gint attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL;
  GdkWindow* window = gdk_window_new(gtk_widget_get_parent_window(widget),
                                     &attributes, attributes_mask);
  gtk_widget_set_window(widget, window);
  gtk_widget_register_window(widget, window);
}

// Implements GtkWidget::unrealize.
static void fl_gl_area_unrealize(GtkWidget* widget) {
  FlGLArea* self = FL_GL_AREA(widget);
  gdk_gl_context_make_current(self->context);
  g_clear_object(&self->texture);

  /* Make sure to unset the context if current */
  if (self->context == gdk_gl_context_get_current()) {
    gdk_gl_context_clear_current();
  }

  GTK_WIDGET_CLASS(fl_gl_area_parent_class)->unrealize(widget);
}

// Implements GtkWidget::size_allocate.
static void fl_gl_area_size_allocate(GtkWidget* widget,
                                     GtkAllocation* allocation) {
  gtk_widget_set_allocation(widget, allocation);

  if (gtk_widget_get_has_window(widget)) {
    if (gtk_widget_get_realized(widget)) {
      gdk_window_move_resize(gtk_widget_get_window(widget), allocation->x,
                             allocation->y, allocation->width,
                             allocation->height);
    }
  }
}

// Implements GtkWidget::draw.
static gboolean fl_gl_area_draw(GtkWidget* widget, cairo_t* cr) {
  FlGLArea* self = FL_GL_AREA(widget);

  gdk_gl_context_make_current(self->context);

  gint scale = gtk_widget_get_scale_factor(widget);

  if (self->texture) {
    uint32_t texture =
        fl_backing_store_provider_get_gl_texture_id(self->texture);
    GdkRectangle geometry =
        fl_backing_store_provider_get_geometry(self->texture);
    gdk_cairo_draw_from_gl(cr, gtk_widget_get_window(widget), texture,
                           GL_TEXTURE, scale, geometry.x, geometry.y,
                           geometry.width, geometry.height);
    gdk_gl_context_make_current(self->context);
  }

  return TRUE;
}

static void fl_gl_area_class_init(FlGLAreaClass* klass) {
  GObjectClass* gobject_class = G_OBJECT_CLASS(klass);
  gobject_class->dispose = fl_gl_area_dispose;

  GtkWidgetClass* widget_class = GTK_WIDGET_CLASS(klass);
  widget_class->realize = fl_gl_area_realize;
  widget_class->unrealize = fl_gl_area_unrealize;
  widget_class->size_allocate = fl_gl_area_size_allocate;
  widget_class->draw = fl_gl_area_draw;

  gtk_widget_class_set_accessible_role(widget_class, ATK_ROLE_DRAWING_AREA);
}

static void fl_gl_area_init(FlGLArea* self) {
  gtk_widget_set_can_focus(GTK_WIDGET(self), TRUE);
  gtk_widget_set_app_paintable(GTK_WIDGET(self), TRUE);
}

GtkWidget* fl_gl_area_new(GdkGLContext* context) {
  g_return_val_if_fail(GDK_IS_GL_CONTEXT(context), nullptr);
  FlGLArea* area =
      reinterpret_cast<FlGLArea*>(g_object_new(fl_gl_area_get_type(), nullptr));
  area->context = GDK_GL_CONTEXT(g_object_ref(context));
  return GTK_WIDGET(area);
}

void fl_gl_area_queue_render(FlGLArea* self, FlBackingStoreProvider* texture) {
  g_return_if_fail(FL_IS_GL_AREA(self));

  g_clear_object(&self->texture);
  g_set_object(&self->texture, texture);

  gtk_widget_queue_draw(GTK_WIDGET(self));
}