doc: add Mithil to the credits

[git-cola.git] / cola / qtutils.py

"""Miscellaneous Qt utility functions."""
from __future__ import absolute_import, division, print_function, unicode_literals
import os

from qtpy import compat
from qtpy import QtGui
from qtpy import QtCore
from qtpy import QtWidgets
from qtpy.QtCore import Qt
from qtpy.QtCore import Signal

from . import core
from . import hotkeys
from . import icons
from . import utils
from .i18n import N_
from .compat import int_types
from .compat import ustr
from .models import prefs
from .widgets import defs


STRETCH = object()
SKIPPED = object()


def active_window():
    """Return the active window for the current application"""
    return QtWidgets.QApplication.activeWindow()


def connect_action(action, fn):
    """Connect an action to a function"""
    action.triggered[bool].connect(lambda x: fn())


def connect_action_bool(action, fn):
    """Connect a triggered(bool) action to a function"""
    action.triggered[bool].connect(fn)


def connect_button(button, fn):
    """Connect a button to a function"""
    # Some versions of Qt send the `bool` argument to the clicked callback,
    # and some do not.  The lambda consumes all callback-provided arguments.
    button.clicked.connect(lambda *args, **kwargs: fn())


def connect_checkbox(widget, fn):
    """Connect a checkbox to a function taking bool"""
    widget.clicked.connect(lambda *args, **kwargs: fn(get(checkbox)))


def connect_released(button, fn):
    """Connect a button to a function"""
    button.released.connect(fn)


def button_action(button, action):
    """Make a button trigger an action"""
    connect_button(button, action.trigger)


def connect_toggle(toggle, fn):
    """Connect a toggle button to a function"""
    toggle.toggled.connect(fn)


def disconnect(signal):
    """Disconnect signal from all slots"""
    try:
        signal.disconnect()
    except TypeError:  # allow unconnected slots
        pass


def get(widget):
    """Query a widget for its python value"""
    if hasattr(widget, 'isChecked'):
        value = widget.isChecked()
    elif hasattr(widget, 'value'):
        value = widget.value()
    elif hasattr(widget, 'text'):
        value = widget.text()
    elif hasattr(widget, 'toPlainText'):
        value = widget.toPlainText()
    elif hasattr(widget, 'sizes'):
        value = widget.sizes()
    elif hasattr(widget, 'date'):
        value = widget.date().toString(Qt.ISODate)
    else:
        value = None
    return value


def hbox(margin, spacing, *items):
    """Create an HBoxLayout with the specified sizes and items"""
    return box(QtWidgets.QHBoxLayout, margin, spacing, *items)


def vbox(margin, spacing, *items):
    """Create a VBoxLayout with the specified sizes and items"""
    return box(QtWidgets.QVBoxLayout, margin, spacing, *items)


def buttongroup(*items):
    """Create a QButtonGroup for the specified items"""
    group = QtWidgets.QButtonGroup()
    for i in items:
        group.addButton(i)
    return group


def set_margin(layout, margin):
    """Set the content margins for a layout"""
    layout.setContentsMargins(margin, margin, margin, margin)


def box(cls, margin, spacing, *items):
    """Create a QBoxLayout with the specified sizes and items"""
    stretch = STRETCH
    skipped = SKIPPED
    layout = cls()
    layout.setSpacing(spacing)
    set_margin(layout, margin)

    for i in items:
        if isinstance(i, QtWidgets.QWidget):
            layout.addWidget(i)
        elif isinstance(
            i,
            (
                QtWidgets.QHBoxLayout,
                QtWidgets.QVBoxLayout,
                QtWidgets.QFormLayout,
                QtWidgets.QLayout,
            ),
        ):
            layout.addLayout(i)
        elif i is stretch:
            layout.addStretch()
        elif i is skipped:
            continue
        elif isinstance(i, int_types):
            layout.addSpacing(i)

    return layout


def form(margin, spacing, *widgets):
    """Create a QFormLayout with the specified sizes and items"""
    layout = QtWidgets.QFormLayout()
    layout.setSpacing(spacing)
    layout.setFieldGrowthPolicy(QtWidgets.QFormLayout.ExpandingFieldsGrow)
    set_margin(layout, margin)

    for idx, (name, widget) in enumerate(widgets):
        if isinstance(name, (str, ustr)):
            layout.addRow(name, widget)
        else:
            layout.setWidget(idx, QtWidgets.QFormLayout.LabelRole, name)
            layout.setWidget(idx, QtWidgets.QFormLayout.FieldRole, widget)

    return layout


def grid(margin, spacing, *widgets):
    """Create a QGridLayout with the specified sizes and items"""
    layout = QtWidgets.QGridLayout()
    layout.setSpacing(spacing)
    set_margin(layout, margin)

    for row in widgets:
        item = row[0]
        if isinstance(item, QtWidgets.QWidget):
            layout.addWidget(*row)
        elif isinstance(item, QtWidgets.QLayoutItem):
            layout.addItem(*row)

    return layout


def splitter(orientation, *widgets):
    """Create a spliter over the specified widgets

    :param orientation: Qt.Horizontal or Qt.Vertical

    """
    layout = QtWidgets.QSplitter()
    layout.setOrientation(orientation)
    layout.setHandleWidth(defs.handle_width)
    layout.setChildrenCollapsible(True)

    for idx, widget in enumerate(widgets):
        layout.addWidget(widget)
        layout.setStretchFactor(idx, 1)

    # Workaround for Qt not setting the WA_Hover property for QSplitter
    # Cf. https://bugreports.qt.io/browse/QTBUG-13768
    layout.handle(1).setAttribute(Qt.WA_Hover)

    return layout


def label(text=None, align=None, fmt=None, selectable=True):
    """Create a QLabel with the specified properties"""
    widget = QtWidgets.QLabel()
    if align is not None:
        widget.setAlignment(align)
    if fmt is not None:
        widget.setTextFormat(fmt)
    if selectable:
        widget.setTextInteractionFlags(Qt.TextBrowserInteraction)
        widget.setOpenExternalLinks(True)
    if text:
        widget.setText(text)
    return widget


class ComboBox(QtWidgets.QComboBox):
    """Custom read-only combobox with a convenient API"""

    def __init__(self, items=None, editable=False, parent=None, transform=None):
        super(ComboBox, self).__init__(parent)
        self.setEditable(editable)
        self.transform = transform
        self.item_data = []
        if items:
            self.addItems(items)
            self.item_data.extend(items)

    def set_index(self, idx):
        idx = utils.clamp(idx, 0, self.count() - 1)
        self.setCurrentIndex(idx)

    def add_item(self, text, data):
        self.addItem(text)
        self.item_data.append(data)

    def current_data(self):
        return self.item_data[self.currentIndex()]

    def set_value(self, value):
        if self.transform:
            value = self.transform(value)
        try:
            index = self.item_data.index(value)
        except ValueError:
            index = 0
        self.setCurrentIndex(index)


def combo(items, editable=False, parent=None):
    """Create a readonly (by default) combobox from a list of items"""
    return ComboBox(editable=editable, items=items, parent=parent)


def combo_mapped(data, editable=False, transform=None, parent=None):
    """Create a readonly (by default) combobox from a list of items"""
    widget = ComboBox(editable=editable, transform=transform, parent=parent)
    for (k, v) in data:
        widget.add_item(k, v)
    return widget


def textbrowser(text=None):
    """Create a QTextBrowser for the specified text"""
    widget = QtWidgets.QTextBrowser()
    widget.setOpenExternalLinks(True)
    if text:
        widget.setText(text)
    return widget


def add_completer(widget, items):
    """Add simple completion to a widget"""
    completer = QtWidgets.QCompleter(items, widget)
    completer.setCaseSensitivity(Qt.CaseInsensitive)
    completer.setCompletionMode(QtWidgets.QCompleter.InlineCompletion)
    widget.setCompleter(completer)


def prompt(msg, title=None, text='', parent=None):
    """Presents the user with an input widget and returns the input."""
    if title is None:
        title = msg
    if parent is None:
        parent = active_window()
    result = QtWidgets.QInputDialog.getText(
        parent, title, msg, QtWidgets.QLineEdit.Normal, text
    )
    return (result[0], result[1])


def prompt_n(msg, inputs):
    """Presents the user with N input widgets and returns the results"""
    dialog = QtWidgets.QDialog(active_window())
    dialog.setWindowModality(Qt.WindowModal)
    dialog.setWindowTitle(msg)

    long_value = msg
    for k, v in inputs:
        if len(k + v) > len(long_value):
            long_value = k + v

    metrics = QtGui.QFontMetrics(dialog.font())
    min_width = metrics.width(long_value) + 100
    if min_width > 720:
        min_width = 720
    dialog.setMinimumWidth(min_width)

    ok_b = ok_button(msg, enabled=False)
    close_b = close_button()

    form_widgets = []

    def get_values():
        return [pair[1].text().strip() for pair in form_widgets]

    for name, value in inputs:
        lineedit = QtWidgets.QLineEdit()
        # Enable the OK button only when all fields have been populated
        # pylint: disable=no-member
        lineedit.textChanged.connect(lambda x: ok_b.setEnabled(all(get_values())))
        if value:
            lineedit.setText(value)
        form_widgets.append((name, lineedit))

    # layouts
    form_layout = form(defs.no_margin, defs.button_spacing, *form_widgets)
    button_layout = hbox(defs.no_margin, defs.button_spacing, STRETCH, close_b, ok_b)
    main_layout = vbox(defs.margin, defs.button_spacing, form_layout, button_layout)
    dialog.setLayout(main_layout)

    # connections
    connect_button(ok_b, dialog.accept)
    connect_button(close_b, dialog.reject)

    accepted = dialog.exec_() == QtWidgets.QDialog.Accepted
    text = get_values()
    ok = accepted and all(text)
    return (ok, text)


class TreeWidgetItem(QtWidgets.QTreeWidgetItem):

    TYPE = QtGui.QStandardItem.UserType + 101

    def __init__(self, path, icon, deleted):
        QtWidgets.QTreeWidgetItem.__init__(self)
        self.path = path
        self.deleted = deleted
        self.setIcon(0, icons.from_name(icon))
        self.setText(0, path)

    def type(self):
        return self.TYPE


def paths_from_indexes(model, indexes, item_type=TreeWidgetItem.TYPE, item_filter=None):
    """Return paths from a list of QStandardItemModel indexes"""
    items = [model.itemFromIndex(i) for i in indexes]
    return paths_from_items(items, item_type=item_type, item_filter=item_filter)


def _true_filter(_x):
    return True


def paths_from_items(items, item_type=TreeWidgetItem.TYPE, item_filter=None):
    """Return a list of paths from a list of items"""
    if item_filter is None:
        item_filter = _true_filter
    return [i.path for i in items if i.type() == item_type and item_filter(i)]


def tree_selection(tree_item, items):
    """Returns an array of model items that correspond to the selected
    QTreeWidgetItem children"""
    selected = []
    count = min(tree_item.childCount(), len(items))
    for idx in range(count):
        if tree_item.child(idx).isSelected():
            selected.append(items[idx])

    return selected


def tree_selection_items(tree_item):
    """Returns selected widget items"""
    selected = []
    for idx in range(tree_item.childCount()):
        child = tree_item.child(idx)
        if child.isSelected():
            selected.append(child)

    return selected


def selected_item(list_widget, items):
    """Returns the model item that corresponds to the selected QListWidget
    row."""
    widget_items = list_widget.selectedItems()
    if not widget_items:
        return None
    widget_item = widget_items[0]
    row = list_widget.row(widget_item)
    if row < len(items):
        item = items[row]
    else:
        item = None
    return item


def selected_items(list_widget, items):
    """Returns an array of model items that correspond to the selected
    QListWidget rows."""
    item_count = len(items)
    selected = []
    for widget_item in list_widget.selectedItems():
        row = list_widget.row(widget_item)
        if row < item_count:
            selected.append(items[row])
    return selected


def open_file(title, directory=None):
    """Creates an Open File dialog and returns a filename."""
    result = compat.getopenfilename(
        parent=active_window(), caption=title, basedir=directory
    )
    return result[0]


def open_files(title, directory=None, filters=''):
    """Creates an Open File dialog and returns a list of filenames."""
    result = compat.getopenfilenames(
        parent=active_window(), caption=title, basedir=directory, filters=filters
    )
    return result[0]


def opendir_dialog(caption, path):
    """Prompts for a directory path"""

    options = (
        QtWidgets.QFileDialog.ShowDirsOnly | QtWidgets.QFileDialog.DontResolveSymlinks
    )
    return compat.getexistingdirectory(
        parent=active_window(), caption=caption, basedir=path, options=options
    )


def save_as(filename, title='Save As...'):
    """Creates a Save File dialog and returns a filename."""
    result = compat.getsavefilename(
        parent=active_window(), caption=title, basedir=filename
    )
    return result[0]


def copy_path(filename, absolute=True):
    """Copy a filename to the clipboard"""
    if filename is None:
        return
    if absolute:
        filename = core.abspath(filename)
    set_clipboard(filename)


def set_clipboard(text):
    """Sets the copy/paste buffer to text."""
    if not text:
        return
    clipboard = QtWidgets.QApplication.clipboard()
    clipboard.setText(text, QtGui.QClipboard.Clipboard)
    if not utils.is_darwin() and not utils.is_win32():
        clipboard.setText(text, QtGui.QClipboard.Selection)
    persist_clipboard()


# pylint: disable=line-too-long
def persist_clipboard():
    """Persist the clipboard

    X11 stores only a reference to the clipboard data.
    Send a clipboard event to force a copy of the clipboard to occur.
    This ensures that the clipboard is present after git-cola exits.
    Otherwise, the reference is destroyed on exit.

    C.f. https://stackoverflow.com/questions/2007103/how-can-i-disable-clear-of-clipboard-on-exit-of-pyqt4-application

    """  # noqa
    clipboard = QtWidgets.QApplication.clipboard()
    event = QtCore.QEvent(QtCore.QEvent.Clipboard)
    QtWidgets.QApplication.sendEvent(clipboard, event)


def add_action_bool(widget, text, fn, checked, *shortcuts):
    tip = text
    action = _add_action(widget, text, tip, fn, connect_action_bool, *shortcuts)
    action.setCheckable(True)
    action.setChecked(checked)
    return action


def add_action(widget, text, fn, *shortcuts):
    tip = text
    return _add_action(widget, text, tip, fn, connect_action, *shortcuts)


def add_action_with_status_tip(widget, text, tip, fn, *shortcuts):
    return _add_action(widget, text, tip, fn, connect_action, *shortcuts)


def _add_action(widget, text, tip, fn, connect, *shortcuts):
    action = QtWidgets.QAction(text, widget)
    if hasattr(action, 'setIconVisibleInMenu'):
        action.setIconVisibleInMenu(True)
    if tip:
        action.setStatusTip(tip)
    connect(action, fn)
    if shortcuts:
        action.setShortcuts(shortcuts)
        if hasattr(Qt, 'WidgetWithChildrenShortcut'):
            action.setShortcutContext(Qt.WidgetWithChildrenShortcut)
        widget.addAction(action)
    return action


def set_selected_item(widget, idx):
    """Sets a the currently selected item to the item at index idx."""
    if isinstance(widget, QtWidgets.QTreeWidget):
        item = widget.topLevelItem(idx)
        if item:
            item.setSelected(True)
            widget.setCurrentItem(item)


def add_items(widget, items):
    """Adds items to a widget."""
    for item in items:
        if item is None:
            continue
        widget.addItem(item)


def set_items(widget, items):
    """Clear the existing widget contents and set the new items."""
    widget.clear()
    add_items(widget, items)


def create_treeitem(filename, staged=False, deleted=False, untracked=False):
    """Given a filename, return a TreeWidgetItem for a status widget

    "staged", "deleted, and "untracked" control which icon is used.

    """
    icon_name = icons.status(filename, deleted, staged, untracked)
    icon = icons.name_from_basename(icon_name)
    return TreeWidgetItem(filename, icon, deleted=deleted)


def add_close_action(widget):
    """Adds close action and shortcuts to a widget."""
    return add_action(widget, N_('Close...'), widget.close, hotkeys.CLOSE, hotkeys.QUIT)


def app():
    """Return the current application"""
    return QtWidgets.QApplication.instance()


def desktop():
    """Return the desktop"""
    return app().desktop()


def desktop_size():
    desk = desktop()
    rect = desk.screenGeometry(QtGui.QCursor().pos())
    return (rect.width(), rect.height())


def center_on_screen(widget):
    """Move widget to the center of the default screen"""
    width, height = desktop_size()
    cx = width // 2
    cy = height // 2
    widget.move(cx - widget.width() // 2, cy - widget.height() // 2)


def default_size(parent, width, height, use_parent_height=True):
    """Return the parent's size, or the provided defaults"""
    if parent is not None:
        width = parent.width()
        if use_parent_height:
            height = parent.height()
    return (width, height)


def default_monospace_font():
    if utils.is_darwin():
        family = 'Monaco'
    else:
        family = 'Monospace'
    mfont = QtGui.QFont()
    mfont.setFamily(family)
    return mfont


def diff_font_str(context):
    cfg = context.cfg
    font_str = cfg.get(prefs.FONTDIFF)
    if not font_str:
        font_str = default_monospace_font().toString()
    return font_str


def diff_font(context):
    return font(diff_font_str(context))


def font(string):
    qfont = QtGui.QFont()
    qfont.fromString(string)
    return qfont


def create_button(
    text='', layout=None, tooltip=None, icon=None, enabled=True, default=False
):
    """Create a button, set its title, and add it to the parent."""
    button = QtWidgets.QPushButton()
    button.setCursor(Qt.PointingHandCursor)
    button.setFocusPolicy(Qt.NoFocus)
    if text:
        button.setText(' ' + text)
    if icon is not None:
        button.setIcon(icon)
        button.setIconSize(QtCore.QSize(defs.small_icon, defs.small_icon))
    if tooltip is not None:
        button.setToolTip(tooltip)
    if layout is not None:
        layout.addWidget(button)
    if not enabled:
        button.setEnabled(False)
    if default:
        button.setDefault(True)
    return button


def tool_button():
    """Create a flat border-less button"""
    button = QtWidgets.QToolButton()
    button.setPopupMode(QtWidgets.QToolButton.InstantPopup)
    button.setCursor(Qt.PointingHandCursor)
    button.setFocusPolicy(Qt.NoFocus)
    # Highlight colors
    palette = QtGui.QPalette()
    highlight = palette.color(QtGui.QPalette.Highlight)
    highlight_rgb = rgb_css(highlight)

    button.setStyleSheet(
        """
        /* No borders */
        QToolButton {
            border: none;
            background-color: none;
        }
        /* Hide the menu indicator */
        QToolButton::menu-indicator {
            image: none;
        }
        QToolButton:hover {
            border: %(border)spx solid %(highlight_rgb)s;
        }
    """
        % dict(border=defs.border, highlight_rgb=highlight_rgb)
    )
    return button


def create_action_button(tooltip=None, icon=None):
    """Create a small toolbutton for use in dock title widgets"""
    button = tool_button()
    if tooltip is not None:
        button.setToolTip(tooltip)
    if icon is not None:
        button.setIcon(icon)
        button.setIconSize(QtCore.QSize(defs.small_icon, defs.small_icon))
    return button


def ok_button(text, default=True, enabled=True, icon=None):
    if icon is None:
        icon = icons.ok()
    return create_button(text=text, icon=icon, default=default, enabled=enabled)


def close_button(text=None, icon=None):
    text = text or N_('Close')
    icon = icons.mkicon(icon, icons.close)
    return create_button(text=text, icon=icon)


def edit_button(enabled=True, default=False):
    return create_button(
        text=N_('Edit'), icon=icons.edit(), enabled=enabled, default=default
    )


def refresh_button(enabled=True, default=False):
    return create_button(
        text=N_('Refresh'), icon=icons.sync(), enabled=enabled, default=default
    )


def checkbox(text='', tooltip='', checked=None):
    """Create a checkbox"""
    return _checkbox(QtWidgets.QCheckBox, text, tooltip, checked)


def radio(text='', tooltip='', checked=None):
    """Create a radio button"""
    return _checkbox(QtWidgets.QRadioButton, text, tooltip, checked)


def _checkbox(cls, text, tooltip, checked):
    """Create a widget and apply properties"""
    widget = cls()
    if text:
        widget.setText(text)
    if tooltip:
        widget.setToolTip(tooltip)
    if checked is not None:
        widget.setChecked(checked)
    return widget


class DockTitleBarWidget(QtWidgets.QFrame):
    def __init__(self, parent, title, stretch=True):
        QtWidgets.QFrame.__init__(self, parent)
        self.setAutoFillBackground(True)
        self.label = qlabel = QtWidgets.QLabel(title, self)
        qfont = qlabel.font()
        qfont.setBold(True)
        qlabel.setFont(qfont)
        qlabel.setCursor(Qt.OpenHandCursor)

        self.close_button = create_action_button(
            tooltip=N_('Close'), icon=icons.close()
        )

        self.toggle_button = create_action_button(
            tooltip=N_('Detach'), icon=icons.external()
        )

        self.corner_layout = hbox(defs.no_margin, defs.spacing)

        if stretch:
            separator = STRETCH
        else:
            separator = SKIPPED

        self.main_layout = hbox(
            defs.small_margin,
            defs.titlebar_spacing,
            qlabel,
            separator,
            self.corner_layout,
            self.toggle_button,
            self.close_button,
        )
        self.setLayout(self.main_layout)

        connect_button(self.toggle_button, self.toggle_floating)
        connect_button(self.close_button, self.toggle_visibility)

    def toggle_floating(self):
        self.parent().setFloating(not self.parent().isFloating())
        self.update_tooltips()

    def toggle_visibility(self):
        self.parent().toggleViewAction().trigger()

    def set_title(self, title):
        self.label.setText(title)

    def add_corner_widget(self, widget):
        self.corner_layout.addWidget(widget)

    def update_tooltips(self):
        if self.parent().isFloating():
            tooltip = N_('Attach')
        else:
            tooltip = N_('Detach')
        self.toggle_button.setToolTip(tooltip)


def create_dock(title, parent, stretch=True, widget=None, fn=None):
    """Create a dock widget and set it up accordingly."""
    dock = QtWidgets.QDockWidget(parent)
    dock.setWindowTitle(title)
    dock.setObjectName(title)
    titlebar = DockTitleBarWidget(dock, title, stretch=stretch)
    dock.setTitleBarWidget(titlebar)
    dock.setAutoFillBackground(True)
    if hasattr(parent, 'dockwidgets'):
        parent.dockwidgets.append(dock)
    if fn:
        widget = fn(dock)
        assert isinstance(widget, QtWidgets.QFrame), "Docked widget has to be a QFrame"
    if widget:
        dock.setWidget(widget)
    return dock


def hide_dock(widget):
    widget.toggleViewAction().setChecked(False)
    widget.hide()


def create_menu(title, parent):
    """Create a menu and set its title."""
    qmenu = DebouncingMenu(title, parent)
    return qmenu


class DebouncingMenu(QtWidgets.QMenu):
    """Menu that debounces mouse release action ie. stops it if occurred
    right after menu creation.

    Disables annoying behaviour when RMB is pressed to show menu, cursor is
    moved accidentally 1px onto newly created menu and released causing to
    execute menu action
    """

    threshold_ms = 400

    def __init__(self, title, parent):
        QtWidgets.QMenu.__init__(self, title, parent)
        self.created_at = utils.epoch_millis()
        if hasattr(self, 'setToolTipsVisible'):
            self.setToolTipsVisible(True)

    def mouseReleaseEvent(self, event):
        threshold = DebouncingMenu.threshold_ms
        if (utils.epoch_millis() - self.created_at) > threshold:
            QtWidgets.QMenu.mouseReleaseEvent(self, event)


def add_menu(title, parent):
    """Create a menu and set its title."""
    menu = create_menu(title, parent)
    if hasattr(parent, 'addMenu'):
        parent.addMenu(menu)
    else:
        parent.addAction(menu.menuAction())
    return menu


def create_toolbutton(text=None, layout=None, tooltip=None, icon=None):
    button = tool_button()
    if icon is not None:
        button.setIcon(icon)
        button.setIconSize(QtCore.QSize(defs.default_icon, defs.default_icon))
    if text is not None:
        button.setText(' ' + text)
        button.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
    if tooltip is not None:
        button.setToolTip(tooltip)
    if layout is not None:
        layout.addWidget(button)
    return button


# pylint: disable=line-too-long
def mimedata_from_paths(context, paths):
    """Return mimedata with a list of absolute path URLs

    The text/x-moz-list format is always included by Qt, and doing
    mimedata.removeFormat('text/x-moz-url') has no effect.
    C.f. http://www.qtcentre.org/threads/44643-Dragging-text-uri-list-Qt-inserts-garbage

    gnome-terminal expects utf-16 encoded text, but other terminals,
    e.g. terminator, prefer utf-8, so allow cola.dragencoding
    to override the default.

    """  # noqa
    cfg = context.cfg
    abspaths = [core.abspath(path) for path in paths]
    urls = [QtCore.QUrl.fromLocalFile(path) for path in abspaths]

    mimedata = QtCore.QMimeData()
    mimedata.setUrls(urls)

    paths_text = core.list2cmdline(abspaths)
    encoding = cfg.get('cola.dragencoding', 'utf-16')
    moz_text = core.encode(paths_text, encoding=encoding)
    mimedata.setData('text/x-moz-url', moz_text)

    return mimedata


def path_mimetypes():
    return ['text/uri-list', 'text/x-moz-url']


class BlockSignals(object):
    """Context manager for blocking a signals on a widget"""

    def __init__(self, *widgets):
        self.widgets = widgets
        self.values = []

    def __enter__(self):
        """Block Qt signals for all of the captured widgets"""
        self.values = [widget.blockSignals(True) for widget in self.widgets]
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """Restore Qt signals when we exit the scope"""
        for (widget, value) in zip(self.widgets, self.values):
            widget.blockSignals(value)


class Channel(QtCore.QObject):
    finished = Signal(object)
    result = Signal(object)


class Task(QtCore.QRunnable):
    """Disable auto-deletion to avoid gc issues

    Python's garbage collector will try to double-free the task
    once it's finished, so disable Qt's auto-deletion as a workaround.

    """

    def __init__(self, parent):
        QtCore.QRunnable.__init__(self)

        self.channel = Channel(parent)
        self.result = None
        self.setAutoDelete(False)

    def run(self):
        self.result = self.task()
        self.channel.result.emit(self.result)
        self.channel.finished.emit(self)

    # pylint: disable=no-self-use
    def task(self):
        return None

    def connect(self, handler):
        self.channel.result.connect(handler, type=Qt.QueuedConnection)


class SimpleTask(Task):
    """Run a simple callable as a task"""

    def __init__(self, parent, fn, *args, **kwargs):
        Task.__init__(self, parent)

        self.fn = fn
        self.args = args
        self.kwargs = kwargs

    def task(self):
        return self.fn(*self.args, **self.kwargs)


class RunTask(QtCore.QObject):
    """Runs QRunnable instances and transfers control when they finish"""

    def __init__(self, parent=None):
        QtCore.QObject.__init__(self, parent)
        self.tasks = []
        self.task_details = {}
        self.threadpool = QtCore.QThreadPool.globalInstance()
        self.result_fn = None

    def start(self, task, progress=None, finish=None, result=None):
        """Start the task and register a callback"""
        self.result_fn = result
        if progress is not None:
            progress.show()
        # prevents garbage collection bugs in certain PyQt4 versions
        self.tasks.append(task)
        task_id = id(task)
        self.task_details[task_id] = (progress, finish, result)
        task.channel.finished.connect(self.finish, type=Qt.QueuedConnection)
        self.threadpool.start(task)

    def finish(self, task):
        task_id = id(task)
        try:
            self.tasks.remove(task)
        except ValueError:
            pass
        try:
            progress, finish, result = self.task_details[task_id]
            del self.task_details[task_id]
        except KeyError:
            finish = progress = result = None

        if progress is not None:
            progress.hide()

        if result is not None:
            result(task.result)

        if finish is not None:
            finish(task)


# Syntax highlighting


def rgb(r, g, b):
    color = QtGui.QColor()
    color.setRgb(r, g, b)
    return color


def rgba(r, g, b, a=255):
    color = rgb(r, g, b)
    color.setAlpha(a)
    return color


def RGB(args):
    return rgb(*args)


def rgb_css(color):
    """Convert a QColor into an rgb(int, int, int) CSS string"""
    return 'rgb(%d, %d, %d)' % (color.red(), color.green(), color.blue())


def rgb_hex(color):
    """Convert a QColor into a hex aabbcc string"""
    return '%02x%02x%02x' % (color.red(), color.green(), color.blue())


def hsl(h, s, light):
    return QtGui.QColor.fromHslF(
        utils.clamp(h, 0.0, 1.0), utils.clamp(s, 0.0, 1.0), utils.clamp(light, 0.0, 1.0)
    )


def hsl_css(h, s, light):
    return rgb_css(hsl(h, s, light))


def make_format(fg=None, bg=None, bold=False):
    fmt = QtGui.QTextCharFormat()
    if fg:
        fmt.setForeground(fg)
    if bg:
        fmt.setBackground(bg)
    if bold:
        fmt.setFontWeight(QtGui.QFont.Bold)
    return fmt


class ImageFormats(object):
    def __init__(self):
        # returns a list of QByteArray objects
        formats_qba = QtGui.QImageReader.supportedImageFormats()
        # portability: python3 data() returns bytes, python2 returns str
        decode = core.decode
        formats = [decode(x.data()) for x in formats_qba]
        self.extensions = set(['.' + fmt for fmt in formats])

    def ok(self, filename):
        _, ext = os.path.splitext(filename)
        return ext.lower() in self.extensions


def set_scrollbar_values(widget, hscroll_value, vscroll_value):
    """Set scrollbars to the specified values"""
    hscroll = widget.horizontalScrollBar()
    if hscroll and hscroll_value is not None:
        hscroll.setValue(hscroll_value)

    vscroll = widget.verticalScrollBar()
    if vscroll and vscroll_value is not None:
        vscroll.setValue(vscroll_value)


def get_scrollbar_values(widget):
    """Return the current (hscroll, vscroll) scrollbar values for a widget"""
    hscroll = widget.horizontalScrollBar()
    if hscroll:
        hscroll_value = get(hscroll)
    else:
        hscroll_value = None
    vscroll = widget.verticalScrollBar()
    if vscroll:
        vscroll_value = get(vscroll)
    else:
        vscroll_value = None
    return (hscroll_value, vscroll_value)


def scroll_to_item(widget, item):
    """Scroll to an item while retaining the horizontal scroll position"""
    hscroll = None
    hscrollbar = widget.horizontalScrollBar()
    if hscrollbar:
        hscroll = get(hscrollbar)
    widget.scrollToItem(item)
    if hscroll is not None:
        hscrollbar.setValue(hscroll)


def select_item(widget, item):
    """Scroll to and make a QTreeWidget item selected and current"""
    scroll_to_item(widget, item)
    widget.setCurrentItem(item)
    item.setSelected(True)


def get_selected_values(widget, top_level_idx, values):
    """Map the selected items under the top-level item to the values list"""
    # Get the top-level item
    item = widget.topLevelItem(top_level_idx)
    return tree_selection(item, values)


def get_selected_items(widget, idx):
    """Return the selected items under the top-level item"""
    item = widget.topLevelItem(idx)
    return tree_selection_items(item)