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Port get_preview method to cairo

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Previously we were using a GdkPixmap [1] created with the get_snapshot [2]
method of the Gtk.Widget. GTK 3 encourages to use cairo surfaces
now instead.

The ported mothod does create a cairo surface similar to that of the canvas'
window and draws on that. Then we create a cairo image surface with
the desired preview size and scale the canvas surface on that.

Several people have been involved in this work: Gonzalo Odiard,
Manuel Quiñones and Benjamin Berg.

[1] http://developer.gnome.org/gdk/stable/gdk-Bitmaps-and-Pixmaps.html#GdkPixmap
[2] http://developer.gnome.org/gtk/stable/GtkWidget.html#gtk-widget-get-snapshot
This commit is contained in:
Simon Schampijer 2012-03-14 17:37:23 +01:00
parent ca751fe004
commit afcb2fcea9
1 changed files with 44 additions and 15 deletions
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59
src/sugar3/activity/activity.py
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@ -54,11 +54,12 @@ import os
import time import time
from hashlib import sha1 from hashlib import sha1
from functools import partial from functools import partial
import StringIO
import cairo
from gi.repository import GConf from gi.repository import GConf
from gi.repository import Gtk from gi.repository import Gtk
from gi.repository import Gdk from gi.repository import Gdk
from gi.repository import GdkPixbuf
from gi.repository import GObject from gi.repository import GObject
import dbus import dbus
import dbus.service import dbus.service
@ -641,27 +642,55 @@ class Activity(Window, Gtk.Container):
Activities can override this method, which should return a str with the Activities can override this method, which should return a str with the
binary content of a png image with a width of 300 and a height of 225 binary content of a png image with a width of 300 and a height of 225
pixels. pixels.
The method does create a cairo surface similar to that of the canvas'
window and draws on that. Then we create a cairo image surface with
the desired preview size and scale the canvas surface on that.
""" """
if self.canvas is None or not hasattr(self.canvas, 'get_snapshot'): if self.canvas is None or not hasattr(self.canvas, 'get_window'):
return None return None
pixmap = self.canvas.get_snapshot((-1, -1, 0, 0))
width, height = pixmap.get_size() window = self.canvas.get_window()
pixbuf = GdkPixbuf.Pixbuf(GdkPixbuf.Colorspace.RGB, 0, 8, width, height) alloc = self.canvas.get_allocation()
pixbuf = pixbuf.get_from_drawable(pixmap, pixmap.get_colormap(),
0, 0, 0, 0, width, height)
pixbuf = pixbuf.scale_simple(style.zoom(300), style.zoom(225),
GdkPixbuf.InterpType.BILINEAR)
preview_data = [] dummy_cr = Gdk.cairo_create(window)
target = dummy_cr.get_target()
canvas_width, canvas_height = alloc.width, alloc.height
screenshot_surface = target.create_similar(cairo.CONTENT_COLOR,
canvas_width, canvas_height)
del dummy_cr, target
def save_func(buf, data): cr = cairo.Context(screenshot_surface)
data.append(buf) r, g, b, a_ = style.COLOR_PANEL_GREY.get_rgba()
cr.set_source_rgb(r, g, b)
cr.paint()
self.canvas.draw(cr)
del cr
pixbuf.save_to_callback(save_func, 'png', user_data=preview_data) preview_width, preview_height = style.zoom(300), style.zoom(225)
preview_data = ''.join(preview_data) preview_surface = cairo.ImageSurface(cairo.FORMAT_ARGB32,
preview_width, preview_height)
cr = cairo.Context(preview_surface)
return preview_data scale_w = preview_width * 1.0 / canvas_width
scale_h = preview_height * 1.0 / canvas_height
scale = min(scale_w, scale_h)
translate_x = int((preview_width - (canvas_width * scale)) / 2)
translate_y = int((preview_height - (canvas_height * scale)) / 2)
cr.translate(translate_x, translate_y)
cr.scale(scale, scale)
cr.set_source_rgba(1, 1, 1, 0)
cr.set_operator(cairo.OPERATOR_SOURCE)
cr.paint()
cr.set_source_surface(screenshot_surface)
cr.paint()
preview_str = StringIO.StringIO()
preview_surface.write_to_png(preview_str)
return preview_str.getvalue()
def _get_buddies(self): def _get_buddies(self):
if self.shared_activity is not None: if self.shared_activity is not None: