If we get consecutive preedit string updates that announce a NULL
string, we still do end up issuing ::preedit-changed with those.
Ignore changes from NULL to NULL, it is the other combinations which
must issue this signal.
For reasons that only apply to the old serial handling, asking for
the surrounding after IM changes resulted in lazy handling of
commit() afterwards.
With the recent interpretation of serials, this problem became more
apparent, since it is in fact very likely that the last interaction
step after an IM change is notifying of the changed surrounding
text after the IM change was applied.
Make handling of surrounding text similar to caret position changes,
always commit() after the state change, but skip through non-changes.
This makes the compositor state fully up-to-date after an IM change.
(cherry-picked from commit eb7c78aa48)
Similarly, uses casts in `gtk_image_definition_unref()`. Compilation
succeeds without them, unlike in `gtk_image_definition_ref()`, because
`gtk_image_definition_unref()` is not called internally, unlike
`gtk_image_definition_ref()`. But the build would fail if some function
defined in the module were changed in the future to call
`gtk_image_definition_unref()`, and we can future-proof it now. This
also removes an inconsistency in how we access the members of the union.
`jhbuild build gtk+-3` with GCC 12 fails with:
```
In function ‘gtk_image_definition_ref’,
inlined from ‘gtk_image_definition_new_empty’
at ../../../../jhbuild/checkout/gtk+-3/gtk/gtkimagedefinition.c:107:10:
../../../../jhbuild/checkout/gtk+-3/gtk/gtkimagedefinition.c:241:13: error:
array subscript ‘GtkImageDefinition {aka union _GtkImageDefinition}[0]’
is partly outside array bounds of ‘GtkImageDefinitionEmpty[1]’
{aka ‘struct _GtkImageDefinitionEmpty[1]’} [-Werror=array-bounds]
241 | def->empty.ref_count++;
| ~~~~~~~~~~^~~~~~~~~~
../../../../jhbuild/checkout/gtk+-3/gtk/gtkimagedefinition.c:
In function ‘gtk_image_definition_new_empty’:
../../../../jhbuild/checkout/gtk+-3/gtk/gtkimagedefinition.c:105:34: note:
object ‘empty’ of size 8
105 | static GtkImageDefinitionEmpty empty = { GTK_IMAGE_EMPTY, 1 };
| ^~~~~
```
and many similar errors.
Fix it by casting `GtkImageDefinition` to `GtkImageDefinitionEmpty` or
similar, as appropriate.
Essentially backports 4dcd02e853 from main to gtk-3-24.
Instead of performing keyboard layout substitution whenever we find a matching
entry in the registry, first try to load the original layout and only attempt
substitution when that fails.
See #4724
