path: root/src/sugar/tutorius/overlayer.py

"""
This guy manages drawing of overlayed widgets. The class responsible for drawing
management (Overlayer) and overlayable widgets are defined here.
"""
# Copyright (C) 2009, Tutorius.org
#
# 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 2 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, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

import gobject
import gtk
import cairo
import pangocairo

# This is the CanvasDrawable protocol. Any widget wishing to be drawn on the
# overlay must implement it. See TextBubble for a sample implementation.
#class CanvasDrawable(object):
#    """Defines the CanvasDrawable protocol"""
#    no_expose = None
#    def draw_with_context(self, context):
#        """
#            Draws the cairo widget with the passed cairo context.
#            This will be called if the widget is child of an overlayer.
#        """
#        pass

class Overlayer(gtk.Layout):
    """
    This guy manages drawing of overlayed widgets. Those can be standard GTK
    widgets or special "cairoDrawable" widgets which support the defined
    interface (see the put method).

    @param overlayed widget to be overlayed. Will be resized to full size.
    """
    def __init__(self, overlayed=None):
        gtk.Layout.__init__(self)

        self._overlayed = overlayed
        if overlayed:
            self.put(overlayed, 0, 0)

        self.__realizer = self.connect("expose-event", self.__init_realized)
        self.connect("size-allocate", self.__size_allocate)
        self.show()

        self.__render_handle = None

    def put(self, child, x, y):
        """
        Adds a child widget to be overlayed. This can be, overlay widgets or
        normal GTK widgets (though normal widgets will alwas appear under
        cairo widgets due to the rendering chain).

        @param child the child to add
        @param x the horizontal coordinate for positionning
        @param y the vertical coordinate for positionning
        """
        if hasattr(child, "draw_with_context"):
            # if the widget has the CanvasDrawable protocol, use it.
            child.no_expose = True
        gtk.Layout.put(self, child, x, y)


    def __init_realized(self, widget, event):
        """
        Initializer to set once widget is realized.
        Since an expose event is signaled only to realized widgets, we set this
        callback for the first expose run. It should also be called after
        beign reparented to ensure the window used for drawing is set up.
        """
        assert hasattr(self.window, "set_composited"), \
            "compositing not supported or widget not realized."
        self.disconnect(self.__realizer)
        del self.__realizer

        self.parent.set_app_paintable(True)

        # the parent is composited, so we can access gtk's rendered buffer
        # and overlay over. If we don't composite, we won't be able to read
        # pixels and background will be black.
        self.window.set_composited(True)
        self.__render_handle = self.parent.connect_after("expose-event", \
            self.__expose_overlay)

    def __expose_overlay(self, widget, event):
        """expose event handler to draw the thing."""
        #get our child (in this case, the event box)
        child = widget.get_child()

        #create a cairo context to draw to the window
        ctx = widget.window.cairo_create()

        #the source data is the (composited) event box
        ctx.set_source_pixmap(child.window,
                              child.allocation.x,
                              child.allocation.y)

        #draw no more than our expose event intersects our child
        region = gtk.gdk.region_rectangle(child.allocation)
        rect = gtk.gdk.region_rectangle(event.area)
        region.intersect(rect)
        ctx.region (region)
        ctx.clip()

        ctx.set_operator(cairo.OPERATOR_OVER)
        # has to be blended and a 1.0 alpha would not make it blend
        ctx.paint_with_alpha(0.99)

        #draw overlay
        for drawn_child in self.get_children():
            if hasattr(drawn_child, "draw_with_context"):
                drawn_child.draw_with_context(ctx)


    def __size_allocate(self, widget, allocation):
        """
            Set size allocation (actual gtk widget size) and propagate it to
            overlayed child
        """
        self.allocation = allocation
        # One may wonder why using size_request instead of size_allocate;
        # Since widget is laid out in a Layout box, the Layout will honor the
        # requested size. Using size_allocate could make a nasty nested loop in
        # some cases.
        self._overlayed.set_size_request(allocation.width, allocation.height)


class TextBubble(gtk.Widget):
    """
        A CanvasDrawableWidget drawing a round textbox and a tail pointing
        to a specified widget.
    """
    def __init__(self, text, speaker=None, tailpos=None):
        """
        Creates a new cairo rendered text bubble.

        @param text the text to render in the bubble
        @param speaker the widget to compute the tail position from
        @param tailpos (optional) position relative to the bubble to use as 
            the tail position, if no speaker
        """
        gtk.Widget.__init__(self)

        # FIXME: ensure previous call does not interfere with widget stacking,
        # as using a gtk.Layout and stacking widgets may reveal a screwed up
        # order with the cairo widget on top.
        self.__label = None
        self.__text_dimentions = None

        self.label = text
        self.speaker = speaker
        self.tailpos = tailpos
        self.line_width = 5

        self.__exposer = self.connect("expose-event", self.__on_expose)

    def draw_with_context(self, context):
        """
        Draw using the passed cairo context instead of creating a new cairo
        context. This eases blending between multiple cairo-rendered
        widgets.
        """
        context.translate(self.allocation.x, self.allocation.y)
        width = self.allocation.width
        height = self.allocation.height
        xradius = width/2
        yradius = height/2
        width -= self.line_width
        height -= self.line_width

        # bubble border
        context.move_to(self.line_width, yradius)
        context.curve_to(self.line_width, self.line_width,
            self.line_width, self.line_width, xradius, self.line_width)
        context.curve_to(width, self.line_width,
            width, self.line_width, width, yradius)
        context.curve_to(width, height, width, height, xradius, height)
        context.curve_to(self.line_width, height,
            self.line_width, height, self.line_width, yradius)
        context.set_line_width(self.line_width)
        context.set_source_rgb(0.0, 0.0, 0.0)
        context.stroke()

        # TODO fetch speaker coordinates

        # draw bubble tail
        if self.tailpos:
            context.move_to(xradius-40, yradius)
            context.line_to(self.tailpos[0], self.tailpos[1])
            context.line_to(xradius+40, yradius)
            context.set_line_width(self.line_width)
            context.set_source_rgb(0.0, 0.0, 0.0)
            context.stroke_preserve()
            context.set_source_rgb(1.0, 1.0, 0.0)
            context.fill()

        # bubble painting. Redrawing the inside after the tail will combine
        # both shapes.
        # TODO: we could probably generate the shape at initialization to
        # lighten computations.
        context.move_to(self.line_width, yradius)
        context.curve_to(self.line_width, self.line_width,
            self.line_width, self.line_width, xradius, self.line_width)
        context.curve_to(width, self.line_width,
            width, self.line_width, width, yradius)
        context.curve_to(width, height, width, height, xradius, height)
        context.curve_to(self.line_width, height,
            self.line_width, height, self.line_width, yradius)
        context.set_source_rgb(1.0, 1.0, 0.0)
        context.fill()

        # text
        # FIXME create text layout when setting text or in realize method
        context.set_source_rgb(0.0, 0.0, 0.0)
        pangoctx = pangocairo.CairoContext(context)
        text_layout = pangoctx.create_layout()
        text_layout.set_text(self.__label)
        pangoctx.move_to(
            int((self.allocation.width-self.__text_dimentions[0])/2),
            int((self.allocation.height-self.__text_dimentions[1])/2))
        pangoctx.show_layout(text_layout)

        # work done. Be kind to next cairo widgets and reset matrix.
        context.identity_matrix()

    def do_realize(self):
        """ Setup gdk window creation. """
        self.set_flags(gtk.REALIZED | gtk.NO_WINDOW)
        # TODO: cleanup window creation code as lot here probably isn't
        # necessary.
        # See http://www.learningpython.com/2006/07/25/writing-a-custom-widget-using-pygtk/
        # as the following was taken there.
        self.window = self.get_parent_window()
        if not isinstance(self.parent, Overlayer):
            self.unset_flags(gtk.NO_WINDOW)
            self.window = gtk.gdk.Window(
                    self.get_parent_window(),
                    width=self.allocation.width,
                    height=self.allocation.height,
                    window_type=gtk.gdk.WINDOW_CHILD,
                    wclass=gtk.gdk.INPUT_OUTPUT,
                    event_mask=self.get_events()|gtk.gdk.EXPOSURE_MASK)

            # Associate the gdk.Window with ourselves, Gtk+ needs a reference
            # between the widget and the gdk window
            self.window.set_user_data(self)

            # Attach the style to the gdk.Window, a style contains colors and
            # GC contextes used for drawing
            self.style.attach(self.window)

            # The default color of the background should be what
            # the style (theme engine) tells us.
            self.style.set_background(self.window, gtk.STATE_NORMAL)
            self.window.move_resize(*self.allocation)

    def __on_expose(self, widget, event):
        """Redraw event callback."""
        ctx = self.window.cairo_create()

        self.draw_with_context(ctx)

        return True

    def _set_label(self, value):
        """Sets the label and flags the widget to be redrawn."""
        self.__label = value
        # FIXME hack to calculate size. necessary because may not have been
        # realized. We create a fake surface to use builtin math. This should
        # probably be done at realization and/or on text setter.
        surf = cairo.SVGSurface("/dev/null", 0, 0)
        ctx = cairo.Context(surf)
        pangoctx = pangocairo.CairoContext(ctx)
        text_layout = pangoctx.create_layout()
        text_layout.set_text(value)
        self.__text_dimentions = text_layout.get_pixel_size()
        del text_layout, pangoctx, ctx, surf

    def do_size_request(self, requisition):
        """Fill requisition with size occupied by the widget."""
        width, height = self.__text_dimentions

        # FIXME bogus values follows. will need to replace them with 
        # padding relative to font size and line border size
        requisition.width = int(width+30)
        requisition.height = int(height+40)

    def do_size_allocate(self, allocation):
        """Save zone allocated to the widget."""
        self.allocation = allocation

    def _get_label(self):
        """Getter method for the label property"""
        return self.__label

    def _set_no_expose(self, value):
        """setter for no_expose property"""
        if self.__exposer and value:
            self.disconnect(self.__exposer)
            self.__exposer = None
        elif (not self.__exposer) and (not value):
            self.__exposer = self.connect("expose-event", self.__on_expose)

    def _get_no_expose(self):
        """getter for no_expose property"""
        return not self.__exposer

    no_expose = property(fset=_set_no_expose, fget=_get_no_expose,
        doc="Whether the widget should handle exposition events or not.")

    label = property(fget=_get_label, fset=_set_label,
        doc="Text label which is to be painted on the top of the widget")

gobject.type_register(TextBubble)


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