Spec: https://html.spec.whatwg.org/multipage/input.html#input-type-change
In short, this resets the selection to the start of the field when the
type has changed from one which doesn't support the selection API to one
that does.
I couldn't see an existing WPT test covering this.
Per the spec, selectionStart and selectionEnd should return the same
values regardless of the selectionDirection. (That is, selectionStart is
always less than or equal to selectionEnd; the direction then implies
which of selectionStart or selectionEnd is the cursor position.)
There was no explicit WPT test for this, so I added one.
This bug was initially quite hard to wrap my head around, and I think
part of the problem is the code in TextInput. Therefore, in the process
of fixing it I have refactored the implementation of TextInput:
* Rename selection_begin to selection_origin. This value doesn't
necessarily correspond directly to the selectionStart DOM value - in
the case of a backward selection, it corresponds to selectionEnd.
I feel that "origin" doesn't imply a specific ordering as strongly as
"begin" (or "start" for that matter) does.
* In various other cases where "begin" is used as a synonym for "start",
just use "start" for consistency.
* Implement selection_start() and selection_end() methods (and their
_offset() variants) which directly correspond to their DOM
equivalents.
* Rename other related methods to make them less wordy and more
consistent / intention-revealing.
* Add assertions to assert_ok_selection() to ensure that our assumptions
about the ordering of selection_origin and edit_point are met. This
then revealed a bug in adjust_selection_for_horizontal_change() where
the value of selection_direction was not maintained correctly (causing
a unit test failure when the new assertion failed).
The selection API only applies to certain <input> types:
https://html.spec.whatwg.org/multipage/#do-not-apply
This commit ensures that we handle that correctly.
Some notes:
1. TextControl::set_dom_selection_direction now calls
set_selection_range(), which means that setting selectionDirection will
now fire a selection event, as it should per the spec.
2. There is a test for the firing of the select event in
tests/wpt/web-platform-tests/html/semantics/forms/textfieldselection/select-event.html,
however the test did not run due to this syntax error:
(pid:26017) "ERROR:script::dom::bindings::error: Error at http://web-platform.test:8000/html/semantics/forms/textfieldselection/select-event.html:50:11 missing = in const declaration"
This happens due to the us of the "for (const foo of ...)" construct.
Per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of
this should actually work, so it's somewhat unsatisfying to have to
change the test.
4. If an <input>'s type is unset, it defaults to a text, and the
selection API applies. Also, if an <input>'s type is set to an
invalid value, it defaults to a text too. I've expanded the tests
to account for this second case.
I had to change the test a little bit to avoid some failures due to
color and text both having a sanitizedValue which was making the test
use the first assertion instead of the second one in some cases.
The sanitize_value implementation is pretty simple, we iterate over the
content and checks that the content is 7 characters long, that the first
character is a `#` and then that all the following characters are
hexadecimal. If all those requirements are met, we lowercase the
content, otherwise we put `#000000` in it.
Move assertions about the initial value of selection{Start,End} to their
own tests. This ensures that when one of these assertions fails, it
doesn't prevent other tests from being defined. Thus we have a clearer
view of which tests are passing or failing, since all tests get defined
regardless of which assertions fail.
