# image.py
#
# Copyright 2018-2023 Romain F. T.
#
# 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 3 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, see <http://www.gnu.org/licenses/>.

import cairo, random, math
from gi.repository import Gtk, Gdk, Gio, GdkPixbuf, Pango, GLib
from .history_manager import DrHistoryManager
from .selection_manager import DrSelectionManager
from .properties import DrPropertiesDialog
from .utilities_files import InvalidFileFormatException
from .utilities_overlay import utilities_generic_canvas_outline

class DrMotionBehavior():
	_LIMIT = 10

	HOVER = 0
	DRAW = 1
	SLIP = 2

class NoPixbufNoChangeException(Exception):
	def __init__(self, pb_name):
		# Context: an error message
		message = _("New pixbuf empty, no change applied to %s")
		super().__init__(message % pb_name)

################################################################################

@Gtk.Template(resource_path='/com/github/maoschanz/drawing/ui/image.ui')
class DrImage(Gtk.Box):
	__gtype_name__ = 'DrImage'

	_drawing_area = Gtk.Template.Child()
	_h_scrollbar = Gtk.Template.Child()
	_v_scrollbar = Gtk.Template.Child()
	reload_info_bar = Gtk.Template.Child()
	reload_label = Gtk.Template.Child()

	# HiDPI scale factor
	SCALE_FACTOR = 1.0 # XXX doesn't work well enough to be anything else

	# Threshold between normal rendering and crisp rendering
	ZOOM_THRESHOLD = 4.0

	# Maximal level of zoom (crisp rendering only)
	ZOOM_MAX = 2000

	def __init__(self, window, **kwargs):
		super().__init__(**kwargs)
		self.window = window

		self.gfile = None
		self.filename = None
		self._waiting_for_monitor = False
		self._gfile_monitor = None
		self._can_reload()

		# Closing the info bar
		self.reload_info_bar.connect('close', self.hide_reload_message)
		self.reload_info_bar.connect('response', self.hide_reload_message)

		# Framerate limit
		self._rendering_is_locked = False
		self._framerate_hint = 0

		self._ctrl_pressed = False

		if self.window.devel_mode:
			# Framerate tracking (debug only)
			self._skipped_frames = 0
			self._fps_counter = 0
			if self.window.should_track_framerate:
				self.reset_fps_counter()

		self._init_drawing_area()

		self._update_background_color()
		self.window.gsettings.connect('changed::ui-background-rgba', \
		                                          self._update_background_color)

		self._update_zoom_behavior()
		self.window.gsettings.connect('changed::ctrl-zoom', \
		                                             self._update_zoom_behavior)

	def _init_drawing_area(self):
		self._drawing_area.add_events( \
			Gdk.EventMask.BUTTON_PRESS_MASK | \
			Gdk.EventMask.BUTTON_RELEASE_MASK | \
			Gdk.EventMask.POINTER_MOTION_MASK | \
			Gdk.EventMask.SMOOTH_SCROLL_MASK | \
			Gdk.EventMask.ENTER_NOTIFY_MASK | \
			Gdk.EventMask.LEAVE_NOTIFY_MASK)
		# Using BUTTON_MOTION_MASK instead of POINTER_MOTION_MASK would be less
		# algorithmically complex but not "powerful" enough.

		# For displaying things on the widget
		self._drawing_area.connect('draw', self.on_draw)

		# For drawing with tools
		self._drawing_area.connect('motion-notify-event', self.on_motion_on_area)
		self._drawing_area.connect('button-press-event', self.on_press_on_area)
		self._drawing_area.connect('button-release-event', self.on_release_on_area)

		# For scrolling
		self._drawing_area.connect('scroll-event', self.on_scroll_on_area)
		self._h_scrollbar.connect('value-changed', self.on_scrollbar_value_change)
		self._v_scrollbar.connect('value-changed', self.on_scrollbar_value_change)

		# For the cursor
		self._drawing_area.connect('enter-notify-event', self.on_enter_image)
		self._drawing_area.connect('leave-notify-event', self.on_leave_image)

	def _update_background_color(self, *args):
		rgba = self.window.gsettings.get_strv('ui-background-rgba')
		self._bg_rgba = (float(rgba[0]), float(rgba[1]), \
		                                         float(rgba[2]), float(rgba[3]))
		# We remember this data here for performance: it will eb used by the
		# `on_draw` method which is called a lot, and reading a gsettings costs
		# a lot.

	def _update_zoom_behavior(self, *args):
		self._ctrl_to_zoom = self.window.gsettings.get_boolean('ctrl-zoom')

	############################################################################
	# Image initialization #####################################################

	def _init_image_common(self):
		"""Part of the initialization common to both a new blank image and an
		opened image."""
		self._is_pressed = False

		# Zoom and scroll initialization
		self.scroll_x = 0
		self.scroll_y = 0
		self.zoom_level = 1.0
		self.motion_behavior = DrMotionBehavior.HOVER
		self._slip_press_x = 0.0
		self._slip_press_y = 0.0
		self._slip_init_x = 0.0
		self._slip_init_y = 0.0

		# Selection initialization
		self.selection = DrSelectionManager(self)

		# History initialization
		self._history = DrHistoryManager(self)
		self.set_action_sensitivity('undo', False)
		self.set_action_sensitivity('redo', False)

	def init_background(self, width, height, background_rgba):
		self._init_image_common()
		self._history.set_initial_operation(background_rgba, None, width, height)
		self.restore_last_state()

	def try_load_pixbuf(self, pixbuf):
		self._init_image_common()
		self._load_pixbuf_common(pixbuf)
		self.restore_last_state()
		self.update_title()

	def _new_blank_pixbuf(self, w, h):
		return GdkPixbuf.Pixbuf.new(GdkPixbuf.Colorspace.RGB, True, 8, w, h)

	def restore_last_state(self):
		"""Set the last saved pixbuf from the history as the main_pixbuf. This
		is used to rebuild the picture from its history."""
		last_saved_pixbuf_op = self._history.get_last_saved_state()
		self._apply_state(last_saved_pixbuf_op)

	def reset_to_initial_pixbuf(self):
		self._apply_state(self._history.initial_operation)
		self._history.rewind_history()

	def _apply_state(self, state_op):
		# restore the state found in the history
		pixbuf = state_op['pixbuf']
		width = state_op['width']
		height = state_op['height']
		self.set_temp_pixbuf(self._new_blank_pixbuf(1, 1))
		self.selection.init_pixbuf()
		self.surface = cairo.ImageSurface(cairo.Format.ARGB32, width, height)
		if pixbuf is None:
			# no pixbuf in the operation: the restored state is a blank one
			rgba = state_op['rgba']
			r = rgba.red
			g = rgba.green
			b = rgba.blue
			a = rgba.alpha
			self.set_main_pixbuf(self._new_blank_pixbuf(width, height))
			cairo_context = cairo.Context(self.surface)
			cairo_context.set_source_rgba(r, g, b, a)
			cairo_context.paint()
			self.update()
			self.set_surface_as_stable_pixbuf()
		else:
			self.set_main_pixbuf(state_op['pixbuf'].copy())
			self.use_stable_pixbuf()

	############################################################################
	# (re)loading the pixbuf of a given file ###################################

	def _load_pixbuf_common(self, pixbuf):
		if not pixbuf.get_has_alpha():
			pixbuf = pixbuf.add_alpha(False, 255, 255, 255)
		background_rgba = self.window.gsettings.get_strv('default-rgba')
		self._history.set_initial_operation(background_rgba, pixbuf, \
		                                pixbuf.get_width(), pixbuf.get_height())
		self.set_main_pixbuf(pixbuf)

	def reload_from_disk(self):
		"""Safely reloads the image from the disk."""
		if self.gfile is None:
			# the action shouldn't be active in the first place
			return
		disk_pixbuf = GdkPixbuf.Pixbuf.new_from_file(self.get_file_path())
		self._load_pixbuf_common(disk_pixbuf)
		self.window.update_picture_title()
		self.use_stable_pixbuf()
		self.update()
		self.remember_current_state()

	def try_load_file(self, gfile):
		try:
			self.gfile = gfile
			pixbuf = GdkPixbuf.Pixbuf.new_from_file(self.get_file_path())
			self.connect_gfile_monitoring()
		except Exception as ex:
			if not ex.message:
				ex.message = "[exception without a valid message]"
			ex = InvalidFileFormatException(ex.message, gfile.get_path())
			self.window.reveal_action_report(ex.message)
			self.gfile = None
			pixbuf = self._new_blank_pixbuf(100, 100)
			# XXX dans l'idéal on devrait ne rien ouvrir non ? ou si besoin (si
			# ya pas de fenêtre) ouvrir un truc respectant les settings, plutôt
			# qu'un petit pixbuf corrompu
		self.try_load_pixbuf(pixbuf)
		self._can_reload()

	def connect_gfile_monitoring(self):
		flags = Gio.FileMonitorFlags.WATCH_MOUNTS
		self._gfile_monitor = self.gfile.monitor(flags)
		self._gfile_monitor.connect('changed', self.reveal_reload_message)

	def set_monitoring(self, value):
		self._waiting_for_monitor = value

	def reveal_reload_message(self, *args):
		if self._waiting_for_monitor:
			# I'm not sure this lock is 100% correct because i'm monitoring the
			# portal proxy file when testing with flatpak. Better than nothing.
			if args[3] != Gio.FileMonitorEvent.CHANGED:
				self._waiting_for_monitor = False
			return
		self._can_reload()
		self.reload_label.set_visible(self.window.get_allocated_width() > 500)
		self.reload_info_bar.set_visible(True)

	def hide_reload_message(self, *args):
		self.reload_info_bar.set_visible(False)

	def _can_reload(self):
		self.set_action_sensitivity('reload_file', self.gfile is not None)

	############################################################################
	# Image title and tab management ###########################################

	def build_tab_widget(self):
		"""Build the GTK widget displayed as the tab title."""
		# The tab can be closed with a button.
		btn = Gtk.Button.new_from_icon_name('window-close-symbolic', Gtk.IconSize.BUTTON)
		btn.set_relief(Gtk.ReliefStyle.NONE)
		btn.connect('clicked', self.try_close_tab)
		# The title is a label. Middle-clicking on it closes the tab too.
		self.tab_label = Gtk.Label(label=self.get_filename_for_display())
		self.tab_label.set_ellipsize(Pango.EllipsizeMode.END)
		event_box = Gtk.EventBox()
		event_box.add(self.tab_label)
		event_box.connect('button-press-event', self.on_tab_title_clicked)
		# These widgets are packed in a regular box, which is returned.
		tab_title = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL, expand=True)
		if self.window.deco_layout == 'he':
			tab_title.pack_start(btn, expand=False, fill=False, padding=0)
			tab_title.pack_end(event_box, expand=True, fill=True, padding=0)
		else:
			tab_title.pack_start(event_box, expand=True, fill=True, padding=0)
			tab_title.pack_end(btn, expand=False, fill=False, padding=0)
		tab_title.show_all()
		return tab_title
	
	def on_tab_title_clicked(self, widget, event_button):
		if event_button.type == Gdk.EventType.BUTTON_PRESS \
		and event_button.button == Gdk.BUTTON_MIDDLE:
			self.try_close_tab()
			return True
		return False # This callback HAS TO return a boolean

	def update_title(self):
		main_title = self.get_filename_for_display()
		if not self.is_saved():
			main_title = "*" + main_title
		self.set_tab_label(main_title)
		return main_title

	def get_filename_for_display(self):
		if self.get_file_path() is None:
			unsaved_file_name = _("Unsaved file")
		else:
			unsaved_file_name = self.get_file_path().split('/')[-1]
		return unsaved_file_name

	def try_close_tab(self, *args):
		"""Ask the window to close the image/tab. Then unallocate widgets and
		pixbufs."""
		if self.window.close_tab(self):
			self.destroy()
			self.selection.reset(False)
			self.main_pixbuf = None
			self.temp_pixbuf = None
			self._history.empty_history()
			return True
		else:
			return False

	def set_tab_label(self, title_text):
		self.tab_label.set_label(title_text)

	def get_file_path(self):
		if self.gfile is None:
			return None
		else:
			return self.gfile.get_path()

	def show_properties(self):
		DrPropertiesDialog(self.window, self)

	def update_image_wide_actions(self):
		self.update_history_sensitivity()
		self._can_reload()

	############################################################################
	# History management #######################################################

	def try_undo(self):
		self._history.try_undo()

	def try_redo(self):
		self._history.try_redo()

	def is_saved(self):
		return self._history.get_saved()

	def remember_current_state(self):
		self._history.add_state(self.main_pixbuf.copy())

	def update_history_sensitivity(self):
		self.set_action_sensitivity('undo', self._history.can_undo())
		self.set_action_sensitivity('redo', self._history.can_redo())
		# self.update_history_actions_labels()

	def add_to_history(self, operation):
		self._history.add_operation(operation)

	def should_replace(self):
		if self._history.can_undo():
			return False
		return not self._history.has_initial_pixbuf()

	def get_initial_rgba(self):
		return self._history.initial_operation['rgba']

	############################################################################
	# Misc ? ###################################################################

	def set_action_sensitivity(self, action_name, state):
		self.window.lookup_action(action_name).set_enabled(state)

	def update_actions_state(self):
		# XXX shouldn't it be done by the selection_manager?
		state = self.selection.is_active
		self.set_action_sensitivity('unselect', state)
		self.set_action_sensitivity('select_all', not state)
		self.set_action_sensitivity('selection_cut', state)
		self.set_action_sensitivity('selection_copy', state)
		self.set_action_sensitivity('selection_delete', state)
		self.set_action_sensitivity('selection_export', state)
		self.set_action_sensitivity('new_tab_selection', state)
		self.set_action_sensitivity('selection-replace-canvas', state)
		self.set_action_sensitivity('selection-expand-canvas', state)
		self.active_tool().update_actions_state()

	def active_tool(self):
		return self.window.active_tool()

	def get_mouse_is_pressed(self):
		return self._is_pressed

	############################################################################
	# Drawing area, main pixbuf, and surface management ########################

	def on_draw(self, area, cairo_context):
		"""Signal callback. Executed when self._drawing_area is redrawn."""
		if self.window.devel_mode:
			self._fps_counter += 1

		# Background color
		cairo_context.set_source_rgba(*self._bg_rgba)
		cairo_context.paint()

		# Zoom level
		cairo_context.scale(self.zoom_level, self.zoom_level)

		# Image (with scroll position)
		cairo_context.set_source_surface(self.get_surface(), \
		                                 -1 * self.scroll_x, -1 * self.scroll_y)
		if self.is_zoomed_surface_sharp():
			cairo_context.get_source().set_filter(cairo.FILTER_NEAREST)
		cairo_context.paint()

		# What the tool shows on the canvas, upon what it paints, for example an
		# overlay to imply how to interact with a previewed operation.
		self.active_tool().on_draw_above(area, cairo_context)

		# Limit of the canvas (for readability)
		utilities_generic_canvas_outline(cairo_context, self.zoom_level, \
		                              self.get_pixbuf_width() - self.scroll_x, \
		                             self.get_pixbuf_height() - self.scroll_y)

	def on_press_on_area(self, area, event):
		"""Signal callback. Executed when a mouse button is pressed on
		self._drawing_area, if the button is the mouse wheel the colors are
		exchanged, otherwise the signal is transmitted to the selected tool."""
		if self._is_pressed:
			# reject attempts to draw with a given button if an other one is
			# already doing something
			return
		event_x, event_y = self.get_event_coords(event)
		if event.button == 2:
			self.motion_behavior = DrMotionBehavior.SLIP
			self._slip_press_x = event.x
			self._slip_press_y = event.y
			self._slip_init_x = self.scroll_x
			self._slip_init_y = self.scroll_y
			return
		self.motion_behavior = DrMotionBehavior.DRAW
		self._is_pressed = True
		self.window.set_window_subtitles()
		# subtitles must be generated *before* calling the tool, otherwise any
		# property changed by a modifier would be reset by `get_editing_tips`
		self.active_tool().on_press_on_area(event, self.surface, event_x, event_y)

	def on_motion_on_area(self, area, event):
		"""Signal callback. Executed when the mouse pointer moves upon
		self._drawing_area, the signal is transmitted to the selected tool.
		If a button (not the mouse wheel) is pressed, the tool's method should
		have an effect on the image, otherwise it shouldn't change anything
		except the mouse cursor icon for example."""
		event_x, event_y = self.get_event_coords(event)

		if self.motion_behavior == DrMotionBehavior.HOVER:
			# Some tools need the coords in the image, others need the coords on
			# the widget, so the entire event is given.
			self.active_tool().on_unclicked_motion_on_area(event, self.surface)

		elif self.motion_behavior == DrMotionBehavior.DRAW:
			# implicitly impossible if not self._is_pressed
			self.active_tool().on_motion_on_area(event, self.surface, event_x, \
			                                 event_y, self._rendering_is_locked)
			if self._rendering_is_locked:
				if self.window.devel_mode:
					self._skipped_frames += 1
				return
			self._rendering_is_locked = True
			self.update()
			GLib.timeout_add(self._framerate_hint, self._async_unlock, {})

		else: # self.motion_behavior == DrMotionBehavior.SLIP:
			self.scroll_x = self._slip_init_x
			self.scroll_y = self._slip_init_y
			delta_x = self._slip_press_x - event.x
			delta_y = self._slip_press_y - event.y
			self.add_deltas(delta_x, delta_y, 1 / self.zoom_level)

		# If <Ctrl> is pressed, a tooltip displaying contextual information is
		# shown: by default, it contains at least the pointer coordinates.
		if (event.state & Gdk.ModifierType.CONTROL_MASK) == Gdk.ModifierType.CONTROL_MASK:
			self._ctrl_pressed = True
		if self._ctrl_pressed:
			full_tooltip_text = str(event_x) + ", " + str(event_y)
			tool_tooltip = self._get_tool_tooltip(event_x, event_y)
			if tool_tooltip is not None:
				full_tooltip_text += "\n" + tool_tooltip
			self._drawing_area.set_tooltip_text(full_tooltip_text)
		else:
			self._drawing_area.set_tooltip_text(None)

	def on_release_on_area(self, area, event):
		"""Signal callback. Executed when a mouse button is released on
		self._drawing_area, if the button is not the signal is transmitted to
		the selected tool."""
		self._ctrl_pressed = False
		if self.motion_behavior == DrMotionBehavior.SLIP:
			if not self._is_slip_moving():
				self.window.on_middle_click()
			self.motion_behavior = DrMotionBehavior.HOVER
			return
		self.motion_behavior = DrMotionBehavior.HOVER
		event_x, event_y = self.get_event_coords(event)
		self.active_tool().on_release_on_area(event, self.surface, event_x, event_y)
		self._is_pressed = False
		self.window.update_picture_title() # just to add the star
		self.window.set_window_subtitles() # the tool's state changed

	def _is_slip_moving(self):
		"""Tells if the pointer moved while the middle button of the mouse is
		pressed, depending on a constant hardcoded limit."""
		mx = abs(self._slip_init_x - self.scroll_x) > DrMotionBehavior._LIMIT
		my = abs(self._slip_init_y - self.scroll_y) > DrMotionBehavior._LIMIT
		return mx or my

	def _get_tool_tooltip(self, ev_x, ev_y):
		return self.active_tool().get_tooltip(ev_x, ev_y ,self.motion_behavior)

	def update(self):
		# print('image.py: _drawing_area.queue_draw')
		self._drawing_area.queue_draw()

	def _async_unlock(self, content_params={}):
		"""This is used as a GSourceFunc so it should return False."""
		self._rendering_is_locked = False
		return False

	def get_surface(self):
		return self.surface

	def on_enter_image(self, *args):
		self.window.set_cursor(True)

	def on_leave_image(self, *args):
		self.window.set_cursor(False)

	def post_save(self):
		self.use_stable_pixbuf()
		self.update()

	def set_surface_as_stable_pixbuf(self):
		w = self.surface.get_width()
		h = self.surface.get_height()
		self.main_pixbuf = Gdk.pixbuf_get_from_surface(self.surface, 0, 0, w, h)
		self._framerate_hint = math.sqrt(w * h) - 1000
		self._framerate_hint = int(self._framerate_hint * 0.2)
		# between 500 and 33ms (= between 2 and 30 fps)
		self._framerate_hint = max(33, min(500, self._framerate_hint))
		# print("image.py: hint =", self._framerate_hint)

	def use_stable_pixbuf(self):
		"""This is called by tools' `restore_pixbuf`, so at the beginning of
		each operation (even unapplied)."""
		# maybe the "scale" parameter should be 1 instead of 0
		self.surface = Gdk.cairo_surface_create_from_pixbuf(self.main_pixbuf, 0, None)
		# print('image.py: use_stable_pixbuf')
		self.surface.set_device_scale(self.SCALE_FACTOR, self.SCALE_FACTOR)

	def get_pixbuf_width(self):
		return self.main_pixbuf.get_width()

	def get_pixbuf_height(self):
		return self.main_pixbuf.get_height()

	def set_main_pixbuf(self, new_pixbuf):
		"""Safely set a pixbuf as the main one (not used everywhere internally
		in image.py, but it's normal)."""
		if new_pixbuf is None:
			raise NoPixbufNoChangeException('main_pixbuf')
		else:
			self.main_pixbuf = new_pixbuf

	############################################################################
	# Temporary pixbuf management ##############################################

	def set_temp_pixbuf(self, new_pixbuf):
		if new_pixbuf is None:
			raise NoPixbufNoChangeException('temp_pixbuf')
		else:
			self.temp_pixbuf = new_pixbuf

	def reset_temp(self):
		self.set_temp_pixbuf(self._new_blank_pixbuf(1, 1))
		self.use_stable_pixbuf()
		self.update()

	############################################################################
	# Framerate tracking (debug only) ##########################################

	def reset_fps_counter(self, async_cb_data={}):
		"""Development only: live-display the evolution of the framerate of the
		drawing area. The max should be around 60, but many tools don't require
		so many redraws.
		This is used as a GSourceFunc so it should return False."""
		if self.window.should_track_framerate:
			# Context: this is a debug information that users will never see
			msg = _("%s frames per second") % self._fps_counter
			msg += " (" + str(self._skipped_frames) + " motion inputs skipped)"
			self.window.reveal_message(msg)
			self._fps_counter = 0
			self._skipped_frames = 0
			GLib.timeout_add(1000, self.reset_fps_counter, {})
		elif self.window.info_bar.get_visible():
			self.window.reveal_message("Tracking stopped.", True)
		return False

	############################################################################
	# Interaction with the minimap #############################################

	def get_widget_width(self):
		return self._drawing_area.get_allocated_width()

	def get_widget_height(self):
		return self._drawing_area.get_allocated_height()

	def generate_mini_pixbuf(self, preview_size):
		mpb_width = self.get_pixbuf_width()
		mpb_height = self.get_pixbuf_height()
		if mpb_height > mpb_width:
			mw = preview_size * (mpb_width/mpb_height)
			mh = preview_size
		else:
			mw = preview_size
			mh = preview_size * (mpb_height/mpb_width)
		return self.main_pixbuf.scale_simple(mw, mh, GdkPixbuf.InterpType.TILES)

	def get_minimap_need_overlay(self):
		mpb_width = self.get_pixbuf_width()
		mpb_height = self.get_pixbuf_height()
		show_x = self.get_widget_width() < mpb_width * self.zoom_level
		show_y = self.get_widget_height() < mpb_height * self.zoom_level
		show_overlay = show_x or show_y
		return show_overlay

	def get_minimap_ratio(self, mini_width):
		return mini_width/self.get_pixbuf_width()

	def get_visible_size(self):
		visible_width = int(self.get_widget_width() / self.zoom_level)
		visible_height = int(self.get_widget_height() / self.zoom_level)
		return visible_width, visible_height

	############################################################################
	# Scroll and zoom levels ###################################################

	def get_previewed_width(self):
		# Indirect way to know if it's a transform tool
		if self.active_tool().menu_id == 1:
			if not self.active_tool().apply_to_selection:
				return self.temp_pixbuf.get_width() + 12
		return self.get_pixbuf_width()

	def get_previewed_height(self):
		# Indirect way to know if it's a transform tool
		if self.active_tool().menu_id == 1:
			if not self.active_tool().apply_to_selection:
				return self.temp_pixbuf.get_height() + 12
		return self.get_pixbuf_height()

	def fake_scrollbar_update(self):
		self.add_deltas(0, 0, 0)

	def get_event_coords(self, event, as_integers=True):
		event_x = self.scroll_x + (event.x / self.zoom_level)
		event_y = self.scroll_y + (event.y / self.zoom_level)
		if as_integers:
			# `int()` will truncate to the lower integer so we need this to get
			# an accurate behavior when doing pixel-art for example
			event_x += 0.5
			event_y += 0.5
			return int(event_x), int(event_y)
		else:
			return event_x, event_y

	def get_corrected_coords(self, x1, x2, y1, y2, with_selection, with_zoom):
		"""Do whatever coordinates conversions are needed by tools like `crop`
		and `scale` to display things (selection pixbuf, mouse cursors on hover,
		etc.) correctly enough."""
		w = x2 - x1
		h = y2 - y1
		x1 = x1 - self.scroll_x
		y1 = y1 - self.scroll_y
		if with_selection:
			x1 += self.selection.selection_x
			y1 += self.selection.selection_y
		x2 = x1 + w
		y2 = y1 + h
		if with_zoom:
			x1 *= self.zoom_level
			x2 *= self.zoom_level
			y1 *= self.zoom_level
			y2 *= self.zoom_level
		return x1, x2, y1, y2

	def get_nineths_sizes(self, apply_to_selection, x1, y1):
		"""Returns the sizes of the 'nineths' of the image used for example by
		'scale' or 'crop' to decide the cursor they'll show."""
		height = self.temp_pixbuf.get_height()
		width = self.temp_pixbuf.get_width()
		if not apply_to_selection:
			x1 = 0
			y1 = 0
		# width_left, width_right, height_top, height_bottom
		wl, wr, ht, hb = self.get_corrected_coords(int(x1), width, int(y1), \
		                                       height, apply_to_selection, True)
		# XXX using local deltas this way "works" but isn't mathematically
		# correct: scaled selections have a "null" and excentred central ninth
		# ^ c'est toujours vrai ça ??
		wl += 0.4 * width * self.zoom_level
		wr -= 0.4 * width * self.zoom_level
		ht += 0.4 * height * self.zoom_level
		hb -= 0.4 * height * self.zoom_level
		return {'wl': wl, 'wr': wr, 'ht': ht, 'hb': hb}

	def on_scroll_on_area(self, area, event):
		# TODO https://lazka.github.io/pgi-docs/index.html#Gdk-3.0/classes/EventScroll.html#Gdk.EventScroll
		ctrl_is_used = (event.state & Gdk.ModifierType.CONTROL_MASK) == Gdk.ModifierType.CONTROL_MASK
		if ctrl_is_used == self._ctrl_to_zoom:
			self._zoom_to_point(event)
		else:
			acceleration = 20 / self._zoom_profile()
			self.add_deltas(event.delta_x, event.delta_y, acceleration)

	def on_scrollbar_value_change(self, scrollbar):
		self.correct_coords(self._h_scrollbar.get_value(), self._v_scrollbar.get_value())
		self.update() # allowing imperfect framerate would likely be useless

	def reset_deltas(self, delta_x, delta_y):
		if delta_x > 0:
			wanted_x = self.get_previewed_width()
		elif delta_x < 0:
			wanted_x = 0
		else:
			wanted_x = self.scroll_x

		if delta_y > 0:
			wanted_y = self.get_previewed_height()
		elif delta_y < 0:
			wanted_y = 0
		else:
			wanted_y = self.scroll_y

		self.correct_coords(wanted_x, wanted_y)
		self.window.minimap.update_overlay()

	def add_deltas(self, delta_x, delta_y, factor):
		wanted_x = self.scroll_x + int(delta_x * factor)
		wanted_y = self.scroll_y + int(delta_y * factor)
		self.correct_coords(wanted_x, wanted_y)
		self.window.minimap.update_overlay()

	def correct_coords(self, wanted_x, wanted_y):
		available_w = self.get_widget_width()
		available_h = self.get_widget_height()
		if available_w < 2:
			return # could be better handled

		# Update the horizontal scrollbar
		mpb_width = self.get_previewed_width()
		wanted_x = min(wanted_x, self.get_max_coord(mpb_width, available_w))
		wanted_x = max(wanted_x, 0)
		self.update_scrollbar(False, available_w, int(mpb_width), int(wanted_x))

		# Update the vertical scrollbar
		mpb_height = self.get_previewed_height()
		wanted_y = min(wanted_y, self.get_max_coord(mpb_height, available_h))
		wanted_y = max(wanted_y, 0)
		self.update_scrollbar(True, available_h, int(mpb_height), int(wanted_y))

	def get_max_coord(self, mpb_size, available_size):
		max_coord = mpb_size - (available_size / self.zoom_level)
		return max_coord

	def update_scrollbar(self, is_vertical, allocated_size, pixbuf_size, coord):
		if is_vertical:
			scrollbar = self._v_scrollbar
		else:
			scrollbar = self._h_scrollbar
		scrollbar.set_visible(allocated_size / self.zoom_level < pixbuf_size)
		scrollbar.set_range(0, pixbuf_size)
		scrollbar.get_adjustment().set_page_size(allocated_size / self.zoom_level)
		scrollbar.set_value(coord)
		if is_vertical:
			self.scroll_y = int(scrollbar.get_value())
		else:
			self.scroll_x = int(scrollbar.get_value())

	def _zoom_to_point(self, event):
		"""Zoom in or out the image in a way such that the point under the
		pointer stays as much as possible under the pointer."""
		event_x, event_y = self.get_event_coords(event)

		# Updating the zoom level
		zoom_delta = (event.delta_x + event.delta_y) * -1 * self._zoom_profile()
		self.inc_zoom_level(zoom_delta)

		new_event_x, new_event_y = self.get_event_coords(event)
		delta_correction_x = event_x - new_event_x
		delta_correction_y = event_y - new_event_y

		# Updating the scroll position based on the values previously found
		self.add_deltas(delta_correction_x, delta_correction_y, 1)

	def inc_zoom_level(self, delta):
		self.set_zoom_level((self.zoom_level * 100) + delta)

	def set_zoom_level(self, level):
		normalized_zoom_level = max(min(level, self.ZOOM_MAX), 20)
		self.zoom_level = (int(normalized_zoom_level)/100)
		self.window.minimap.update_zoom_scale(self.zoom_level)
		if self.is_zoomed_surface_sharp():
			self.window.minimap.set_zoom_label(self.zoom_level * 100)
		self.fake_scrollbar_update()
		self.update()

	def set_opti_zoom_level(self, *args):
		allocated_width = self.get_widget_width()
		allocated_height = self.get_widget_height()
		h_ratio = allocated_width / self.get_previewed_width()
		v_ratio = allocated_height / self.get_previewed_height()
		opti = min(h_ratio, v_ratio) * 99 # Not 100 because some margin is cool
		self.set_zoom_level(opti)
		self.scroll_x = 0
		self.scroll_y = 0

	def is_zoomed_surface_sharp(self):
		return self.zoom_level > self.ZOOM_THRESHOLD

	def _zoom_profile(self):
		"""This is the 'speed' of the zoom scrolling: when between 20% and 100%
		it's quite precise, but between 1000% and 2000% we prefer being as fast
		as possible."""
		if self.zoom_level < 2.0:
			return 3.0
		elif self.zoom_level < 4.0:
			return 6.0
		elif self.zoom_level < 10.0:
			return 10.0
		else:
			return 20.0

	############################################################################
################################################################################