@@ Line 1: / Line 1: @@
-=Porting an existing activity to GTK3=
+Replaced with
-This is a guide to porting an existing activity from GTK2 to [http://developer.gnome.org/gtk3/stable/ GTK3]. It also shows the changes to use the new Sugar toolkit that also now uses [[Features/GTK3|GTK3]]. This guide uses the [https://github.com/sugarlabs/hello-world hello-world] activity as a simple example.
+https://github.com/sugarlabs/sugar-docs/blob/master/src/gtk3-porting-guide.md
-There is another guide that uses this one as reference. It was made while porting GetBooks Activity [[Features/GTK3/Porting/GetBooks]]
-If you would like to reference other examples of GTK3 port:
-* [https://github.com/sugarlabs/biorhythm/commit/c16de3b70cce2cc6f8af933e2b062c844a47c144/ Biorhythm]
-* [https://github.com/sugarlabs/peru-learns-english-activity/commit/caa2cde526b3823a5a1f7d200a76ad5bc3502b0e Peru Learns English, includes GStreamer and GST update]
-==Cleanup, adopt to API changes in sugar-toolkit-gtk3 ==
-* the keep button has been removed completely
-* the old-style toolbar has been removed
-* set_toolbar_box is used instead of set_toolbox (see in [http://git.sugarlabs.org/~walter/abacus/walter-cairo/commit/6871dd340a89ade3b5361457e1bd1d58276a8efc Abacus])
-* remove import of deprecated ActivityToolbox (see [http://git.sugarlabs.org/hello-world/mainline/commit/22060a3063b2d6fd38d6b1cd8d44946170255af3 hello-world])
-* support for 'service_name' and 'class' has been removed from the activity.info make sure you are using: 'bundle_id' instead of 'service_name' and 'exec' instead of 'class' (see in [http://git.sugarlabs.org/record/mainline/commit/6e8968c71e474e2d8d86886badf5cf7d70217dc5 Record])
-==Port the activity from GTK2 to GTK3==
-To start, change the importing instruction for GTK from
- import gtk
-to
- import gi
- gi.require_version('Gtk', '3.0')
- from gi.repository import Gtk
-Note that require_version needs to called only the first time when Gtk is being imported.
-Here are some more examples of imports that may be used:
-<pre>
-from gi.repository import Gdk, Pango, Gobject
-</pre>
-Then you have to change each call that involves Gtk, for example creating a button will look now like this:
- button = Gtk.Button()
-A simple hello world program in GTK3 looks like this:
-<pre>
-from gi.repository import Gtk
-def _destroy_cb(widget, data=None):
-    Gtk.main_quit()
-w = Gtk.Window()
-w.connect("destroy", _destroy_cb)
-label = Gtk.Label('Hello World!')
-w.add(label)
-w.show_all()
-Gtk.main()
-</pre>
-For porting your activity you do have to change your calls for accessing widgets and services in the new GTK3 sugar-toolkit as well. The new namespace is called [https://developer.sugarlabs.org/sugar3/ sugar3], trying to reflect that GTK3 is the underlying technology. For example the import of the base activity class has to be changed from
- from sugar.activity import activity
-to
- from sugar3.activity import activity
-Make sure you change the setup.py in your activity to point to the new toolkit as well:
-  from sugar3.activity import bundlebuilder
-The changes that were needed to port the hello-world activity can be seen in [http://git.sugarlabs.org/hello-world/mainline/commit/508e1c518b56cbde5508e560c8a2ff38a3518583 this commit].
-Ok, let's do these changes now for your activity. Make sure you are in your master branch using the 'git branch' command (the master branch should have a '*' before it). Make your changes, commit them ('git commit -a') and push them to the remote repository ('git push origin master').
-====Simple example on creating a toolbar====
-One of Sugar's activity most unique user interface includes the toolbar. In order to reference the relevant modules and graphics, the sugar3 library has to be imported. These are the relevant ones that would enable us to create a simple toolbar containing the activity button and the stop button.
-<pre>
-from sugar3.activity import activity
-from sugar3.graphics.toolbarbox import ToolbarBox
-from sugar3.activity.widgets import ActivityToolbarButton
-from sugar3.activity.widgets import StopButton
-from sugar3.graphics.toolbarbox import ToolbarButton
-from sugar3.graphics import style
-</pre>
-Since the ActivityToolbar() module has been deprecated, the toolbar can now be called using
- ToolbarBox()
-Then, from the ToolbarBox(), include the ActivityButton and StopButton. In order for the StopButton to be align to the right as per Sugar activity interface, a separator has to be included as well.
-<pre>
-toolbar_box = ToolbarBox()
-activity_button = ActivityToolbarButton(self)
-toolbar_box.toolbar.insert(activity_button, 0)
-activity_button.show()
-separator = Gtk.SeparatorToolItem()
-separator.props.draw = False
-separator.set_expand(True)
-toolbar_box.toolbar.insert(separator, -1)
-separator.show()
-stop_button = StopButton(self)
-toolbar_box.toolbar.insert(stop_button, -1)
-stop_button.show()
-self.set_toolbar_box(toolbar_box)
-toolbar_box.show()
-</pre>
-===Tools===
-There are tools to help you do the porting. There is a script in the pygobject repository for porting called [http://git.gnome.org/browse/pygobject/tree/pygi-convert.sh pygi-convert.sh], more info about the script can be found in [http://live.gnome.org/PyGObject/IntrospectionPorting the PyGObject Introspection Porting guide].
-Here is a script to automate the rename of the imports '''sugar''' to '''sugar3''': [http://dev.laptop.org/~manuq/sugar-convert.sh sugar-convert.sh].
-If you are having trouble finding how a particular GTK class/method/constant has been named in PyGI, run [http://dev.laptop.org/~dsd/20110806/pygi-enumerate.py pygi-enumerate.py] and grep the output. (this app lists all identified methods and constants).  Usage example:
-<pre>
-$ python pygi-enumerate.py | grep get_selection
-Gtk.AccelLabel.get_selection_bounds() (instance method)
-Gtk.Editable.get_selection_bounds() (instance method)
-Gtk.Entry.get_selection_bounds() (instance method)
-Gtk.IconView.get_selection_mode() (instance method)
-Gtk.Label.get_selection_bounds() (instance method)
-Gtk.SelectionData.get_selection() (instance method)
-Gtk.SpinButton.get_selection_bounds() (instance method)
-Gtk.TextBuffer.get_selection_bound() (instance method)
-Gtk.TextBuffer.get_selection_bounds() (instance method)
-Gtk.TreeView.get_selection() (instance method)
-</pre>
-=== Constructor considerations ===
-With PyGI it is possible to use Python-like constructors, or "new" functions e.g. the following are (usually) equivalent:
- label = Gtk.Button()
- label = Gtk.Button.new()
-However, the first form is preferred: it is more Python-like. Internally, the difference is that Gtk.Label.new() translates to a call to gtk_label_new(), whereas Gtk.Label() (the preferred form) will directly construct an instance of GtkLabel at the GObject level.
-If the constructor takes parameters, they '''must''' be named. The parameters correspond to GObject properties in the API documentation which are usually marked as "Construct". For example, the following code will not work:
- expander = Gtk.Expander("my expander")
-The (confusing) error is:
- TypeError: GObject.__init__() takes exactly 0 arguments (1 given)
-The solution is to go to the [http://developer.gnome.org/gtk3/3.2/GtkExpander.html#GtkExpander.properties GtkExpander API documentation] and find the appropriate property that we wish to set. In this case it is <b>label</b> (which is a Construct property, further increasing our confidence of success), so the code should be:
- expander = Gtk.Expander(label="my expander")
-Combining the two points above, if you wish to call a construct-like function such as gtk_button_new_with_label(), you do have the option of calling Gtk.Button.new_with_label(), however if we check the [http://developer.gnome.org/gtk3/3.2/GtkButton.html#GtkButton.properties GtkButton properties] we see one called "label" which is equivalent. Therefore gtk_button_new_with_label("foo") should be called as:
- button = Gtk.Button(label="foo")
-=== HBox, VBox, pack_start and pack_end ===
-GtkHBox and GtkVBox, commonly used containers in GTK2 code, have pack_start and pack_end methods. These take 4 parameters:
-# The widget to pack into the container
-# '''expand''': Whether the child should receive extra space when the container grows (default True)
-# '''fill''': True if space given to child by the expand option is actually allocated to child, rather than just padding it. This parameter has no effect if expand is set to False. A child is always allocated the full height of a gtk.HBox and the full width of a gtk.VBox. This option affects the other dimension. (default True)
-# '''padding''': extra space in pixels to put between child and its neighbor (default 0)
-In PyGTK, the expand, fill and padding parameters were optional: if unspecified, the default values above were used. In PyGI, these parameters are '''not''' optional: all 4 must be specified. Hence the rules for adding in the extra parameters are:
-# If '''expand''' was not set, use value True
-# If '''fill''' was not set, use value True. (however, if expand is False, this parameter gets ignored so False is an equally acceptable option when expand=False)
-# If '''padding''' was not set, use value 0.
-These parameters can be specified either as positional arguments or as named keyword arguments, however all 4 must always be specified. Some developers prefer keyword arguments, arguing that the following:
-<pre>box.pack_start(widget, expand=True, fill=False, padding=4)</pre>
-is much more readable than:
-<pre>box.pack_start(widget, True, False, 4)</pre>
-However, these functions are called extremely often; any mildly seasoned GTK developer will have memorized the order and meaning of the parameters. Some developers therefore prefer to avoid the extra work of dropping in hundreds of keyword arguments throughout the code and just use the positional ones. This is really up to you.
-If you are using pack_start with the default values (expand=True, fill=True and padding=0), you can avoid using pack_start (and the parameter pain that it brings with it) by just using .add for some added cleanliness, e.g.
-<pre>box.pack_start(widget, True, True, 0)</pre>
-can be replaced with:
-<pre>box.add(widget)</pre>
-This is as far as you need to go for now. However, in GTK3, GtkVBox and GtkHBox have been deprecated, which means they might be removed in GTK3. The replacement is to use GtkBox directly, and you may wish to make this change now. e.g.:
-<pre>vbox = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)</pre>
-<pre>hbox = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL, homogeneous=True, spacing=8)</pre>
-However, it must be noted that if GtkBox is used directly (instead of using GtkHBox/GtkVBox), the default value of '''expand''' is now '''False'''. The implications of this are:
-# You need to check your .add() calls, as previously they would behave as pack_start with expand=True, but now they will behave as expand=False (you need to change them to use pack_start with expand=True to retain the old behaviour)
-# Every single pack_start call that has expand=False and padding=0 (and any value of fill) can be converted to .add() for cleanliness
-=== GtkAlignment considerations ===
-In PyGTK, the gtk.Alignment constructor takes four optional parameters:
-# xalign: the fraction of horizontal free space to the left of the child widget. Ranges from 0.0 to 1.0. Default value 0.0.
-# yalign: the fraction of vertical free space above the child widget. Ranges from 0.0 to 1.0. Default value 0.0.
-# xscale: the fraction of horizontal free space that the child widget absorbs, from 0.0 to 1.0. Default value 0.0.
-# yscale: the fraction of vertical free space that the child widget absorbs, from 0.0 to 1.0. Default value 0.0
-In PyGI/GTK3, these parameters are still optional when used in the Gtk.Alignment constructor (as keyword arguments, as explained above). However, the default values have changed. They are now:
-# xalign: default value 0.5
-# yalign: default value 0.5
-# xscale: default value 1
-# yscale: default value 1
-If your code was relying on the default value of 0 for any of these parameters in PyGTK, you will now need to explicitly specify that in your constructor. Similarly, if you were previously using construction parameters to select the now-default values, those parameters can be dropped.
-Additionally, PyGTK accepted these construction parameters as positional arguments. As explained above, they must now be converted to keyword arguments.
-=== Gtk Menu Popup ===
-The Gtk.Menu.popup function now works slightly differently.
-The user supplied positioning function now takes different parameters. These are menu, x, y, push_in and user_data.
-=== Gdk ===
-Previously, gdk was an attribute of the gtk module, which means that it can be called through gtk. For example, if we want to use color_parse():
- gtk.gdk.color_parse(color)
-However, what we have to do now is:
- from gi.repository import Gdk
-Then we can modify the code to the following:
- Gdk.color_parse(color)
-=== Pango ===
-Following the release of Gtk3, we should not be importing pango like this:
- import pango
-In fact, we can now import pango as an attribute within the gtk3 library:
- from gi.repository import Pango as pango
-=== Gio.Settings from GConf ===
-Any use of GConf should be ported to Gio.Settings.
-=== Other considerations ===
-''self.allocation'' property is no longer available.  Please search your code for "self.allocation" and replace it for "self.get_allocation()".
-So to get the allocation size:
- self.allocation.width
- self.allocation.height
-should be replaced by:
- self.get_allocated_width()
- self.get_allocated_height()
-=== Constants ===
-Most of the constants have slightly different formats, e.g.,
-gtk.STATE_NORMAL became Gtk.StateFlags.NORMAL
-gtk.RESPONSE_ACCEPT became Gtk.ResponseType.ACCEPT
-gtk.JUSTIFY_CENTER became Gtk.Justification.CENTER
-gtk.RELIEF_NONE became Gtk.ReliefStyle.NONE
-=== Pixbufs ===
-The pixbuf libraies are in their own repository
- from gi.repository import GdkPixbuf
- GdkPixbuf.Pixbuf.new_from_file()
-==Releasing activities (for maintainers)==
-Once an activity is ported, a new release can be made. The major version should be greater than the existing one.
-Please follow [https://github.com/sugarlabs/sugar-docs/blob/master/src/contributing.md#checklist---maintainer this] guide for releasing a new version
-==Port to Python 3==
-We are migrating towards Python 3. Python 3 does not support GTK+ 2. Hence, once the activity is ported to GTK+ 3, please also continue porting the activity from Python 2 to Python 3.
-Ref: [https://github.com/sugarlabs/sugar-docs/blob/master/src/python-porting-guide.md Guide to port activities to Python 3]
-== Tips to Activity Developers ==
-===Changes to the Clipboard===
-Two things to note:
-. You need to specify a clipboard using get()
-    clipboard = Gtk.Clipboard.get(Gdk.SELECTION_CLIPBOARD)
-. You need to pass a length to set_text()
-    clipboard.set_text(string, len(string))
-See [http://python-gtk-3-tutorial.readthedocs.org/en/latest/clipboard.html] for more details.
-===Changes to Drag-and-Drop===
-Slightly different syntax:
-        self.drag_dest_set(Gtk.DestDefaults.ALL, [],
-                           Gdk.DragAction.COPY)
-        self.drag_dest_set_target_list(Gtk.TargetList.new([]))
-        self.drag_dest_add_text_targets()
-        self.connect('drag_data_received', self._drag_data_received)
-and:
-        data.get_text()
-or:
-        data.get_image()
-See [http://python-gtk-3-tutorial.readthedocs.org/en/latest/drag_and_drop.html] for more details.
-===Going from Drawable to Cairo===
-GTK-3 does not support gtk Drawable objects, so the first step is to get your activity running under Cairo.
-<pre>
-import cairo
-# From activity.Activity, you inherit a canvas.
-# Create a Cairo context from the window.
-cairo_context = self.canvas.get_window().cairo_create()
-# Create an XLib surface to be used for drawing
-xlib_surface = surface.create_similar(cairo.CONTENT_COLOR,
-                                      gtk.gdk.screen_width(),
-                                      gtk.gdk.screen_height())
-# You'll need a Cairo context from which you'll build a GTK Cairo context
-cairo_context = cairo.Context(xlib_surface)
-cairo_context = gtk.gdk.CairoContext(cairo_context)
-# Use this context as you would a Drawable, substituting Cairo commands
-# for gtk commands, e.g.,
-cairo_context.move_to(0, 0)
-cairo_context.line_to(100, 100)
-# Cairo uses floats from 0 to 1 for RGB values
-cairo_context.set_source_rgb(r, g, b)
-cairo_context.rectangle(x, y, w, h)
-cairo_context.fill()
-# To invalidate a region to force a refresh, use:
-self.canvas.queue_draw_area(x, y, w, h)
-# Handle the expose event
-# "expose" became "draw" for the cairo signal
-def do_expose_event(self, event):
-    # Create the cairo context
-    cairo_context = self.canvas.get_window().cairo_create()
-    cairo_context.rectangle(event.area.x, event.area.y,
-                            event.area.width, event.area.height)
-    cairo_context.clip()
-    cairo_context.set_source_surface(xlib_surface)
-    cairo_context.paint()
-</pre>
-Pango is a bit different when used with Cairo:
-<pre>
-import pango, pangocairo
-# Again, from the xlib_surface...
-cairo_context = cairo.Context(xlib_surface)
-# Create a PangoCairo context
-cairo_context = pangocairo.CairoContext(cairo_context)
-# The pango layout is created from the Cairo context
-pango_layout = cairo_context.create_layout()
-# You still use pango to set up font descriptions.
-fd = pango.FontDescription('Sans')
-fd.set_size(12 * pango.SCALE)
-# Tell your pango layout about your font description
-pango_layout.set_font_description(fd)
-# Write text to your pango layout
-pango_layout.set_text('Hello world', -1)
-# Position it within the Cairo context
-cairo_context.save()
-cairo_context.translate(x, y)
-cairo_context.rotate(pi / 3)  # You can rotate text and images in Cairo
-cairo_context.set_source_rgb(1, 0, 0)
-# Finally, draw the text
-cairo_context.update_layout(pango_layout)
-cairo_context.show_layout(pango_layout)
-cairo_context.restore()
-</pre>
-To draw a bitmap...
-<pre>
-# Again, from the xlib_surface...
-cairo_context = cairo.Context(xlib_surface)
-# Create a gtk context
-cairo_context = gtk.gdk.CairoContext(cairo_context)
-cairo_context.set_source_pixbuf(pixbuf, x, y)
-cairo_context.rectangle(x, y, w, h)
-cairo_context.fill()
-</pre>
-To read a pixel from the xlib surface...
-<pre>
-# create a new 1x1 cairo surface
-cairo_surface = cairo.ImageSurface(cairo.FORMAT_RGB24, 1, 1);
-cairo_context = cairo.Context(cairo_surface)
-# translate xlib_surface so that target pixel is at 0, 0
-cairo_context.set_source_surface(xlib_surface, -x, -y)
-cairo_context.rectangle(0,0,1,1)
-cairo_context.set_operator(cairo.OPERATOR_SOURCE)
-cairo_context.fill()
-cairo_surface.flush() # ensure all writing is done
-# Read the pixel
-return (ord(pixels[2]), ord(pixels[1]), ord(pixels[0]), 0)
-</pre>
-===Going from Cairo in GTK-2 to Cairo in GTK-3===
-(See http://developer.gnome.org/pangomm/2.28/annotated.html for more details)
-Not much changes, but...
-The Cairo/Pango interaction is a little different:
-<pre>
-from gi.repository import Pango, PangoCairo
-cairo_context = ...
-pango_layout = PangoCairo.create_layout(cairo_context)
-fd = Pango.FontDescription('Sans')
-fd.set_size(12 * Pango.SCALE)
-pango_layout.set_font_description(fd)
-pango_layout.set_text('Hello World', -1)
-cairo_context.set_source_rgb(1, 0, 0)
-PangoCairo.update_layout(cairo_context, pango_layout)
-PangoCairo.show_layout(cairo_context, pango_layout)
-</pre>
-The get_extents() method if different in PangoCairo. It calculates an extent as a Rectangle, but doesn't return anything. There is a method, get_logical_extents() that returns a Rectangle. Alas, it is not necessarily available after v1.16. Note that Rectangle is not a list but a class with methods for get_x(), get_y(), get_width(), and get_height(), so you cannot iter over it.
-Note that the <samp>cairo.Region</samp> will no longer work in Gtk+3
-==== Replacing pixmaps with Cairo ====
-You need to replace your pixmaps with Cairo in GTK3. See http://developer.gnome.org/gtk3/3.5/ch24s02.html#idp129615008 for example code.
-===Taking a screenshot and making a thumbnail===
-To make a screenshot of the window:
-<pre>
-width, height = window.get_width(), window.get_height()
-thumb_surface = Gdk.Window.create_similar_surface(window,
-                                                  cairo.CONTENT_COLOR,
-                                                  width, height)
-thumb_width, thumb_height = style.zoom(100), style.zoom(80)
-cairo_context = cairo.Context(thumb_surface)
-thumb_scale_w = thumb_width * 1.0 / width
-thumb_scale_h = thumb_height * 1.0 / height
-cairo_context.scale(thumb_scale_w, thumb_scale_h)
-Gdk.cairo_set_source_window(cairo_context, window, 0, 0)
-cairo_context.paint()
-thumb_surface.write_to_png(png_path_or_filelike_object)
-</pre>
-===Creating a video widget===
-Haven't gotten this working yet, but some necessary changes include:
-Instead of
- window.xid
-use
- get_property('window').get_xid()
-Instead of
- unset_flags(gtk.DOUBLE_BUFFERED)
- set_flags(gtk.APP_PAINTABLE)
-use
- set_double_buffered(False)
- set_app_paintable(True)
-A more basic question is whether or not we migrate to gstreamer-1.0. If we do, some helpful documentation is found here [https://wiki.ubuntu.com/Novacut/GStreamer1.0].
-== Resources ==
-PyGI Documentation: https://lazka.github.io/pgi-docs/
-gtk2: http://www.pygtk.org/docs/pygtk/
-* Reference Manual
-:: Gtk3: http://developer.gnome.org/gtk3/3.4/
-* Gdk documentation:
-:: Gdk3: http://developer.gnome.org/gdk/2.24/
-* Pango documentation:
-:: GTK3: http://developer.gnome.org/pangomm
-* Gst-1.0 documentation
-:: Gst-1: http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/index.html
-* Gst-1.0 porting hints
-:: https://wiki.ubuntu.com/Novacut/GStreamer1.0
-[[Category:Developer]]
-= More porting wiki pages =
-{{Special:PrefixIndex/Features/GTK3/Porting}}

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