[Bugs] #4104 sugar HIGH: Screenshot is all black in XO-4

[Sugar Labs Bugs]

#4104: Screenshot is all black in XO-4
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    Reporter:  godiard  |          Owner:  erikos        
        Type:  defect   |         Status:  new           
    Priority:  High     |      Milestone:  0.98          
   Component:  sugar    |        Version:  Unspecified   
    Severity:  Major    |       Keywords:  regression, r+
Distribution:  OLPC     |   Status_field:  Assigned      
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Comment(by manuq):

 I've found that the issue is the creation of the screenshot surface.
 Using [http://developer.gnome.org/gdk3/stable/gdk3-Cairo-Interaction.html
 #gdk-window-create-similar-surface gdk_window_create_similar_surface]
 works because according to the documentation it creates a more compatible
 surface.  And is the same we are using in the toolkit.

 Current approach:

 1. create a cairo context for the root window (gdk_cairo_create) to get
 its target surface 'window_surface' (cairo_get_target),

 2. create a new surface with the same size as the window
 'screenshot_surface' and format cairo.FORMAT_ARGB32 (cairo.ImageSurface)

 3. create a new cairo context with that new surface as target
 (cairo.Context)

 4. set 'window_surface' as the source of the new cairo context

 5. paint it (cairo_paint) and save it to a PNG file
 (cairo.Surface.write_to_png)

 Browse approach:

 a. To create the new surface 'screenshot_surface' for step 2. above, use
 gdk_window_create_similar_surface instead.  In toolkit
 (Activity.get_preview) we do the same.  I think is better because
 according to the documentation it creates a more compatible surface.

 b. To set the window surface as the source surface on the new context,
 step 4. above, use gdk_cairo_set_source_window instead.  In toolkit
 (Activity.get_preview) we use widget.draw(cr) directly which Ithink is a
 better approach when you have a widget, but we have a Gdk window instead.

-- 
Ticket URL: <http://bugs.sugarlabs.org/ticket/4104#comment:15>
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