Features/GTK3/Porting/InfoSlicer

This page is being performed while I'm porting InfoSlicer Activity to Gtk3.

There is a ticket with some useful information that I'm using on the porting and to keep tracking this port. Besides, this wiki page will be useful to write some code snippets about what are the difficulties that I'm having on the port and maybe can be useful for someone else.

I will take this guide as reference on the Gtk3 porting.

Remove hippo

First of all, I had to remove the hippo related things and the sugar-port (ticket) wrapper.

Code Snippets

Signals

Change TYPE_PYOBJECT type from a signal

We should replace the TYPE_PYOBJECT

'article-selected' : (SIGNAL_RUN_FIRST, None, [TYPE_PYOBJECT]),

by the Python's object type

'article-selected' : (GObject.SignalFlags.RUN_FIRST, None, [object]),

Drag And Drop: drag-motion

• http://www.pygtk.org/pygtk2tutorial/sec-DNDMethods.html#sec-SettingUpDestinationWidget
• http://developer.gnome.org/gdk/2.24/gdk-Drag-and-Drop.html#GdkDragContext

The signal drag-motion works in the same way as it was working on gtk2, but the callback used by InfoSlicer should be a bit modified to use the new method:

context.drag_status(Gdk.DragAction.COPY, timestamp)

changed by:

Gdk.drag_status(context, Gdk.DragAction.COPY, timestamp)

Drag And Drop: drag-data-received

• http://developer.gnome.org/gtk3/3.5/gtk3-Selections.html#GtkSelectionData-struct

data_received_type = str(selection_data.type)    
data = cPickle.loads(str(selection_data.data))

replaced by:

data_received_type = str(selection_data.get_data_type())    
data = cPickle.loads(str(selection_data.get_data()))

Working with threads

InfoSlicer uses threads to retrieve the information from internet (Wikipedia articles). The pygi script will replace it by Gdk.threads_init() by I found this is not the correct way to do this. In fact, I was dealing with some strange behaviour of the Activity because of this. So, I used:

from gi.repository import GObject
GObject.threads_init()

gtk.gdk._2BUTTON_PRESS

We should replace:

gtk.gdk._2BUTTON_PRESS
gtk.gdk._3BUTTON_PRESS

by:

Gdk.EventType._2BUTTON_PRESS
Gdk.EventType._3BUTTON_PRESS

Gtk.TextBuffer.get_slice() needs a new argument

We need a new argument to indicate if we want to include the hidden_chars as well. It wasn't required in gtk2 and by default it was True

buf = gtk.TextBuffer()
buf.get_slice(start, end)

replaced by:

buf = Gtk.TextBuffer()
buf.get_slice(start, end, include_hidden_chars)

Alerts

We have to change the way that alerts were shown because self.notify_alert is no longer available after applying this patch

Example about how to use the different types of alerts:

• http://git.sugarlabs.org/sugar-toolkit-gtk3/sugar-toolkit-gtk3/blobs/master/src/sugar3/graphics/alert.py#line11

• A simple alert:

 from sugar3.graphics.alert import Alert

 # Create a new simple alert
 alert = Alert()

 # Populate the title and text body of the alert.
 alert.props.title = _('Title of Alert Goes Here')
 alert.props.msg = _('Text message of alert goes here')

 # Call the add_alert() method (inherited via the sugar3.graphics.Window
 # superclass of Activity) to add this alert to the activity window.
 self.add_alert(alert)
 alert.show()

• NotifyAlert

from sugar3.graphics.alert import NotifyAlert

def __alert_notify_response_cb(alert, response_id, activity):
    activity.remove_alert(alert)

alert = NotifyAlert(5)
alert.props.title = _('Nothing to publish')
alert.props.msg = _('Mark arcticles from "Custom" '
                    'panel and try again.')
alert.connect('response', __alert_notify_response_cb, activity)
activity.add_alert(alert)
alert.show()

Gtk.Widget.drag_source_set()

• Python docs: http://python-gtk-3-tutorial.readthedocs.org/en/latest/drag_and_drop.html
• C docs: http://developer.gnome.org/gtk3/3.5/gtk3-Drag-and-Drop.html
• Good example about how drang-n-drop on Gtk3 works http://bugs.sugarlabs.org/raw-attachment/ticket/3742/drag-n-drop-example.tar.gz
  • The drag_data_received_event method is called ONLY if in drag_data_get_event method we modify the argument data

In Gtk3 the way to call this function is a bit different. Instead of passing a tuple we should pass a list of Gtk.TargetEntry's. So, we should replace this:

self.imagebox = Gtk.EventBox()
self.imagebox.drag_source_set(Gdk.ModifierType.BUTTON1_MASK, ("text/plain", Gtk.TargetFlags.SAME_APP, 80), Gdk.DragAction.COPY)

by this:

self.imagebox = Gtk.EventBox()
self.imagebox.drag_source_set(
       Gdk.ModifierType.BUTTON1_MASK,
       [Gtk.TargetEntry.new('text/plain', Gtk.TargetFlags.SAME_APP, 80)],
       Gdk.DragAction.COPY)

Gtk.TextView.scroll_to_iter

• gtk2: http://www.pygtk.org/docs/pygtk/class-gtktextview.html#method-gtktextview--scroll-to-iter
• Gtk3: http://developer.gnome.org/gtk3/3.5/GtkTextView.html#gtk-text-view-scroll-to-iter

This method in gtk2 takes only 2 required arguments but in Gtk3 all of them (5) are required. So, I had to change the call to this method:

self.scroll_to_iter(mouseiter, 0)

by:

self.scroll_to_iter(mouseiter, 0, False, 0.5, 0.5)

Gdk.atom_intern

• http://developer.gnome.org/gdk/2.24/gdk-Properties-and-Atoms.html#gdk-atom-intern
• http://www.pygtk.org/docs/pygtk/class-gdkatom.html#constructor-gdkatom-intern

I'm not sure about the meaning of this function. I've just took a look at the documentation and added the required attribute that was missing:

atom = Gdk.atom_intern("sentence")

replaced by:

atom = Gdk.atom_intern("sentence", only_if_exists=False)

Missing / Problematic things (not ported yet)

• [DONE] Select text from the Edit View (TextView) and the Home View. This error happens in many places of the code.
  • http://developer.gnome.org/gdk3/stable/gdk3-Event-Structures.html#GdkEventMotion
  • https://bugzilla.gnome.org/show_bug.cgi?id=679795

Traceback (most recent call last):
  File "/home/humitos/Activities/InfoSlicer.activity/infoslicer/widgets/Readonly_Textbox.py", line 116, in motion_notify
    self.emit("motion-notify-event", event)
TypeError: could not convert type EventMotion to GdkEvent required for parameter 0

• [ALTERNATIVE] Issue related with "adding columns to the TreeView": https://bugzilla.gnome.org/show_bug.cgi?id=679415
  • There is a workaround on the code to solve this issue
• [IMPORTANT] Drag and Drop Images from the Edit View is not working. Line #52 (infoslicer/widgets/Gallery_View.py)
  • Example about how to use the drag-n-drop http://git.gnome.org/browse/pygobject/tree/demos/gtk-demo/demos/clipboard.py#n96
  • Walter Bender helped me to solve this issue. Thanks!
  • [ALTERNATIVE] Drag and drop is working but the image is being added twice. This is because the SIGNAL is being emitted twice. The same happens with the text, but there is an error related with the index of the selection on the second time that the signal is called, so it fails and add just once the text.
• After drag-n-drop an arrow is added inside the article (right side) that is being edited. This is not working due: https://bugzilla.gnome.org/show_bug.cgi?id=651962
  • Line #641 (infoslicer/processing/Article.py)
• On "Home View" under the Custom TreeView if I add some articles there I cannot move them up or down
  • The same happens on the Wiki TreeView
  • TODO: This is not working because of the port to Gtk3. TreePath object does not support indexing
• Check boxes on "Home View" Custom TreeView don't show the tick after clicking (Is this related with the theme?)
  • After clicking on all the articles under this TreeView I see the Custom check box is checked automatically
• Wiki and Custom TreeView under "Home View" has a different background color (lighter)

Notes

• I had to write a workaround over this bug (adding columns with properties) on bookview.py Line #129

        # FIXME: insert_column_with_attributes does not exist on pygobject
        # column = self.tree.insert_column_with_attributes(0, '', cell, active=0)

        # TODO: this is a workaround due
        # https://bugzilla.gnome.org/show_bug.cgi?id=679415

        column = Gtk.TreeViewColumn('Wiki', cell)
        column.props.sizing = Gtk.TreeViewColumnSizing.FIXED
        column.props.fixed_width = 50
        column.props.visible = custom

        self.tree.insert_column(column, 0)

        cell = Gtk.CellRendererText()
        cell.connect('edited', self._cell_edited_cb)
        cell.props.editable = True

        # FIXME: insert_column_with_attributes does not exist on pygobject
        # self.tree.insert_column_with_attributes(1, '', cell, text=1)

        # TODO: this is a workaround due
        # https://bugzilla.gnome.org/show_bug.cgi?id=679415
        column = Gtk.TreeViewColumn('Custom', cell, text=1)
        self.tree.insert_column(column, 1)

Useful links

• Ticket that removes hippo and sugar-port: http://bugs.sugarlabs.org/ticket/3743