Screenshot is all black in XO-4

[godiard]

(And is not a rugby player)

TestCase:
Press Alt-1, go to the Journal and look at the screenshot created, you will see a black rectangle.

Tested in xo-4 and xo-1.75, the error only happens in xo-4.
Nothing in the log.

Other instances generate images like the preview associated to a activity, or the bookmarks in Browse or Read.

Is not solved installing pygobject3-3.3.91 (see #4102)

[humitos]

It does work on XO-1.5 too 13.1.0 os8

[tonyforster]

see also Laptop12277

[humitos]

I've just tested this on XO-4 build 13.1.0 os11 and it worked (no more black image)

After a while I took another screenshot and it was the same. I took another and another and they were the same than the first one.

[manuq]

I can confirm humitos comment, also with xo-4 build os11.

- take a screenshot, then go to the Journal, open it: all normal.
- navigate to another place in the Sugar UI, take another screenshot: is the same as the first one

All successive screenshots are the same.as the first one taken.

[manuq]

Seems specific to XO-4, so reporting in olpc trac:  http://dev.laptop.org/ticket/12314

[erikos]

 http://dev.laptop.org/ticket/12314 has been closed as a dup of  http://dev.laptop.org/ticket/12277

[humitos]

I attached a patch that works property on XO-4, XO-1.75 and XO-1.5.

I'm not sure what is the exactly difference with the old code. Please, take a look at the commit message and if you know what it is, provide the explanation here. Thanks!

[godiard]

I think the name of the varibles you are using is not clear.

window_surface = Gdk.Window.create_similar_surface(

window, cairo.CONTENT_COLOR, width, height)

should be:

screenshot_surface = Gdk.Window.create_similar_surface(

window, cairo.CONTENT_COLOR, width, height)

because that surface is not the real window surface, but the destination of the paint operation.

Other than that, I think is ok.

[humitos]

v2 - variable name changed as gonzalo suggested me

[humitos]

The "issue" that I see with the old code is that we are passing a GdkWindow ( link) to Gdk.cairo_create ( link) instead of a Cairo Context.

[godiard]

Reviewed and Tested

[erikos]

Replying to humitos:

The "issue" that I see with the old code is that we are passing a GdkWindow ( link) to Gdk.cairo_create ( link) instead of a Cairo Context.

Please update the patch message accordingly.

[godiard]

New patch with a better msg

[godiard]

erikos, new patch with a better header attached

[manuq]

Replying to humitos:

The "issue" that I see with the old code is that we are passing a GdkWindow ( link) to Gdk.cairo_create ( link) instead of a Cairo Context.

No, in the current code we use gdk.cairo_create which receives a GdkWindow.

 http://developer.gnome.org/gdk3/stable/gdk3-Cairo-Interaction.html#gdk-cairo-create

[manuq]

Updated commit message.

[manuq]

I've found that the issue is the creation of the screenshot surface. Using  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.

[manuq]

Pushed 34fb1f8d .

[greenfeld]

Screenshots work on all four current XO platforms in Sugar 0.98.2/OLPC 13.1.0 os20.