ImageViewer: zoom gesture center

[godiard]

when using a gesture to zoom in / out, the image center is displaced

[humitos]

From Carlos Garnacho's email:

there is a get_center() method at the SugarTouchController class level,
both the rotate and zoom controllers inherit from that class.

[humitos]

This patch just zooms the image always from its centre

[humitos]

This commit removes the image vibration of my initial patch: ​http://git.sugarlabs.org/imageviewer/mainline/commit/163e6b5e8110e5106fa57dc9d1f4a825c1851e3a

[humitos]

Patch for sugar-toolkit-gtk3

[humitos]

Taking a look at the eog (Eye Of GNOME - the application to see images on GNOME) I found that it uses: g_signal_handlers_block_matched before setting the adjustment value. I understand that this is to avoid the vibration that my patch added.

​http://git.gnome.org/browse/eog/tree/src/eog-scroll-view.c#n311

I tried to use that function but I'm not being able to pass None as the fifth argument and trying with another thing I'm getting a segmentation fault.

Here are a code example:

from gi.repository import Gtk
from gi.repository import GObject


def my_func(*args, **kargs):
    print 'my_func was called.'


adj = Gtk.Adjustment()
sw = Gtk.ScrolledWindow()
GObject.signal_handlers_block_matched(
    adj, GObject.SignalMatchType.DATA, 0, 0, None, my_func, sw)

[humitos]

Could be related with ​http://bugs.sugarlabs.org/ticket/4060

[humitos]

An intersting approach to the "zoom to fixed point" feature

[humitos]

The patch attached implements the "Zoom to fixed point" feature, but it does not work when the image is rotated.

This patch works better in conjunction with this patch on XO-4:

• ​http://bugs.sugarlabs.org/attachment/ticket/4075/simulate-scale-1.0-xo-4.diff

[dsd]

There are alternatives to GObject.signal_handlers_block_matched which might work better, e.g. signal_handlers_block_by_func. Or you can store the signal ID when you connect it in some "global" variable and block it using that (g_signal_handler_block).

[humitos]

Replying to dsd:

Or you can store the signal ID when you connect it in some "global" variable and block it using that (g_signal_handler_block).

Yes, but the thing here is that I wanted to disconnect some default behaviour: I didn't connect the adjustment to anything and it was moved by default when the widget changes it size. So, when I change the widget's size and the adjustment value, the adjustment was moved to 0,0 in the middle of my actions and a flickering was noticed.

I have to check this again after applying this patch: ​http://bugs.sugarlabs.org/attachment/ticket/4060/0001-scrolledwindow-Stop-scrolling-when-a-second-touch-po.patch

[humitos]

This is already pushed here:

​http://git.sugarlabs.org/imageviewer/mainline/commit/290189d892861a30fb97cefe9197cd2194e89594

Comment: this patch does not work when the image is rotated at 90º or 270º. In that case the patch does not do anything. It works as it was working before: zooming from the left-top corner

[dnarvaez]

Milestone 0.98 deleted