Implement :placeholder-shown (fixes #10561)

[nox]

This change is

[highfive]

Heads up! This PR modifies the following files:

• @bholley: components/style/element_state.rs, components/style/selector_impl.rs
• @KiChjang: components/script/dom/element.rs, components/script/dom/htmlinputelement.rs, components/script/textinput.rs

[highfive]

Warning

• These commits modify style, layout, and script code, but no tests are modified. Please consider adding a test!

[nox]

r? @SimonSapin

[nox]

Err, forgot textarea...

[highfive]

New code was committed to pull request.

[highfive]

New code was committed to pull request.

[nox]

Just realised that textarea doesn't support placeholder in Servo yet anyway, so this is ready to be reviewed.

[nox]

@bors-servo try

[bors-servo]

⌛ Trying commit 4227283 with merge ae30947...

[bors-servo]

💔 Test failed - linux-dev

[highfive]

New code was committed to pull request.

[nox]

Fixed the geckolib failure.

[SimonSapin]

Reviewed 2 of 6 files at r1, 4 of 4 files at r3, 1 of 1 files at r4.
Review status: all files reviewed at latest revision, 2 unresolved discussions.

---

components/script/dom/htmlinputelement.rs, line 721 [r4] (raw file):

        let has_value = !self.textinput.borrow().is_empty();
        let el = self.upcast::<Element>();
        el.set_placeholder_shown_state(has_placeholder && !has_value);

Shouldn’t this logic involve "the element has focus" too? Can it be de-duplicated with whatever code decides to show the placholder or not?

---

ports/geckolib/wrapper.rs, line 355 [r4] (raw file):

    fn get_state(&self) -> ElementState {
        unsafe {
            ElementState::from_bits_truncate(Gecko_ElementState(self.element) as u16)

@bholley @heycam @emilio, This changes ElementState’s representation from u8 to u16. Do you need to change something on the Gecko side for this?

---

Comments from Reviewable

[emilio]

It seems to me that there shouldn't be a problem with the gecko side of this PR.

Gecko uses a 64 bit integer to represent state, and in the servo case we crop it to an u8. So probably at some point we might need to expand it more, but it should keep working as it was with this patch.

[SimonSapin]

Alright, thanks Emilio.

(Discussed my other comment with @nox on IRC.)

@bors-servo r+

[bors-servo]

📌 Commit ff899dc has been approved by SimonSapin

[bors-servo]

⌛ Testing commit ff899dc with merge 3c50368...

[bors-servo]

💔 Test failed - linux-rel

[highfive]

  ▶ FAIL [expected PASS] /css-transforms-1_dev/html/transform-abspos-002.htm
  └   → /css-transforms-1_dev/html/transform-abspos-002.htm 71f0313eedfbfcce0b0fcc5ae55f34b1daa3b8d8
/css-transforms-1_dev/html/reference/transform-abspos-ref.htm 78d197606924062e8dd2a773c977afcecf8940f8
Testing 71f0313eedfbfcce0b0fcc5ae55f34b1daa3b8d8 == 78d197606924062e8dd2a773c977afcecf8940f8

[cbrewster]

@bors-servo retry

• #11561

[bors-servo]

⚡ Previous build results for android, arm32, arm64, linux-dev, mac-dev-unit, mac-rel-css, mac-rel-wpt, windows are reusable. Rebuilding only linux-rel...

[bors-servo]

💔 Test failed - linux-rel

[highfive]

  ▶ FAIL [expected PASS] /css-transforms-1_dev/html/transform-table-007.htm
  └   → /css-transforms-1_dev/html/transform-table-007.htm a5c014b20ef1363bea6f24eda28c7efb7c45698a
/css-transforms-1_dev/html/reference/transform-blank-ref.htm fa6407b1acbbfea27e27061e7d1bdeca98e4a728
Testing a5c014b20ef1363bea6f24eda28c7efb7c45698a == fa6407b1acbbfea27e27061e7d1bdeca98e4a728

[cbrewster]

@bors-servo retry

• #11574

[bors-servo]

⌛ Testing commit ff899dc with merge 0f1f99a...

[bors-servo]

☀️ Test successful - android, arm32, arm64, linux-dev, linux-rel, mac-dev-unit, mac-rel-css, mac-rel-wpt, windows