Auto merge of #20676 - fabricedesre:ime-embedding, r=cbrewster

Notify the embedder when it should display or hide an IME

<!-- Please describe your changes on the following line: -->
This adds a couple of embedder messages triggered when an editable element is focused or blured. The embedder also gets the type of data to edit so it can display a different keyboard type or a custom input method eg. for color choosing.

This is a partial fix for issue #12127

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach build-geckolib` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because there are no tests for the embedding api :(

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/20676)
<!-- Reviewable:end -->

7 files changed, 87 insertions, 2 deletions

diff --git a/components/compositing/compositor_thread.rs b/components/compositing/compositor_thread.rs
index 3d9a320c897..0b042ec5350 100644
--- a/components/compositing/compositor_thread.rs
+++ b/components/compositing/compositor_thread.rs
@@ -8,7 +8,7 @@ use SendableFrameTree;
 use compositor::CompositingReason;
 use gfx_traits::Epoch;
 use ipc_channel::ipc::IpcSender;
-use msg::constellation_msg::{Key, KeyModifiers, KeyState, PipelineId, TopLevelBrowsingContextId};
+use msg::constellation_msg::{InputMethodType, Key, KeyModifiers, KeyState, PipelineId, TopLevelBrowsingContextId};
 use net_traits::image::base::Image;
 use profile_traits::mem;
 use profile_traits::time;
@@ -143,6 +143,10 @@ pub enum EmbedderMsg {
     Panic(TopLevelBrowsingContextId, String, Option<String>),
     /// Open dialog to select bluetooth device.
     GetSelectedBluetoothDevice(Vec<String>, IpcSender<Option<String>>),
+    /// Request to present an IME to the user when an editable element is focused.
+    ShowIME(TopLevelBrowsingContextId, InputMethodType),
+    /// Request to hide the IME when the editable element is blurred.
+    HideIME(TopLevelBrowsingContextId),
     /// Servo has shut down
     Shutdown,
 }
@@ -244,6 +248,8 @@ impl Debug for EmbedderMsg {
             EmbedderMsg::LoadComplete(..) => write!(f, "LoadComplete"),
             EmbedderMsg::Panic(..) => write!(f, "Panic"),
             EmbedderMsg::GetSelectedBluetoothDevice(..) => write!(f, "GetSelectedBluetoothDevice"),
+            EmbedderMsg::ShowIME(..) => write!(f, "ShowIME"),
+            EmbedderMsg::HideIME(..) => write!(f, "HideIME"),
             EmbedderMsg::Shutdown => write!(f, "Shutdown"),
         }
     }
diff --git a/components/constellation/constellation.rs b/components/constellation/constellation.rs
index 261ed6e265b..cea098f310c 100644
--- a/components/constellation/constellation.rs
+++ b/components/constellation/constellation.rs
@@ -1247,6 +1247,14 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             FromScriptMsg::SetFullscreenState(state) => {
                 self.embedder_proxy.send(EmbedderMsg::SetFullscreenState(source_top_ctx_id, state));
             }
+            FromScriptMsg::ShowIME(kind) => {
+                debug!("constellation got ShowIME message");
+                self.embedder_proxy.send(EmbedderMsg::ShowIME(source_top_ctx_id, kind));
+            }
+            FromScriptMsg::HideIME => {
+                debug!("constellation got HideIME message");
+                self.embedder_proxy.send(EmbedderMsg::HideIME(source_top_ctx_id));
+            }
         }
     }
 
diff --git a/components/msg/constellation_msg.rs b/components/msg/constellation_msg.rs
index f7dab637298..1197341d308 100644
--- a/components/msg/constellation_msg.rs
+++ b/components/msg/constellation_msg.rs
@@ -401,3 +401,23 @@ pub const TEST_BROWSING_CONTEXT_INDEX: BrowsingContextIndex =
 #[cfg(feature = "unstable")]
 pub const TEST_BROWSING_CONTEXT_ID: BrowsingContextId =
     BrowsingContextId { namespace_id: TEST_NAMESPACE, index: TEST_BROWSING_CONTEXT_INDEX };
+
+// Used to specify the kind of input method editor appropriate to edit a field.
+// This is a subset of htmlinputelement::InputType because some variants of InputType
+// don't make sense in this context.
+#[derive(Deserialize, Serialize)]
+pub enum InputMethodType {
+    Color,
+    Date,
+    DatetimeLocal,
+    Email,
+    Month,
+    Number,
+    Password,
+    Search,
+    Tel,
+    Text,
+    Time,
+    Url,
+    Week,
+}
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 71df0e70356..5c9cd57b128 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -812,6 +812,11 @@ impl Document {
             elem.set_focus_state(false);
             // FIXME: pass appropriate relatedTarget
             self.fire_focus_event(FocusEventType::Blur, node, None);
+
+            // Notify the embedder to hide the input method.
+            if elem.input_method_type().is_some() {
+                self.send_to_constellation(ScriptMsg::HideIME);
+            }
         }
 
         self.focused.set(self.possibly_focused.get().r());
@@ -826,6 +831,11 @@ impl Document {
             if focus_type == FocusType::Element {
                 self.send_to_constellation(ScriptMsg::Focus);
             }
+
+            // Notify the embedder to display an input method.
+            if let Some(kind) = elem.input_method_type() {
+                self.send_to_constellation(ScriptMsg::ShowIME(kind));
+            }
         }
     }
 
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index a53446fd4a3..11b9168eb41 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -83,6 +83,7 @@ use html5ever::serialize::TraversalScope;
 use html5ever::serialize::TraversalScope::{ChildrenOnly, IncludeNode};
 use js::jsapi::Heap;
 use js::jsval::JSVal;
+use msg::constellation_msg::InputMethodType;
 use net_traits::request::CorsSettings;
 use ref_filter_map::ref_filter_map;
 use script_layout_interface::message::ReflowGoal;
@@ -1087,6 +1088,22 @@ impl Element {
         None
     }
 
+    // Returns the kind of IME control needed for a focusable element, if any.
+    pub fn input_method_type(&self) -> Option<InputMethodType> {
+        if !self.is_focusable_area() {
+            return None;
+        }
+
+        if let Some(input) = self.downcast::<HTMLInputElement>() {
+            input.input_type().as_ime_type()
+        } else if self.is::<HTMLTextAreaElement>() {
+            Some(InputMethodType::Text)
+        } else {
+            // Other focusable elements that are not input fields.
+            None
+        }
+    }
+
     pub fn is_focusable_area(&self) -> bool {
         if self.is_actually_disabled() {
             return false;
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index 5618b366702..ab7d55d5b9a 100755
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -40,6 +40,7 @@ use dom::virtualmethods::VirtualMethods;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix};
 use mime_guess;
+use msg::constellation_msg::InputMethodType;
 use net_traits::{CoreResourceMsg, IpcSend};
 use net_traits::blob_url_store::get_blob_origin;
 use net_traits::filemanager_thread::{FileManagerThreadMsg, FilterPattern};
@@ -137,6 +138,25 @@ impl InputType {
             InputType::Week => "week",
         }
     }
+
+    pub fn as_ime_type(&self) -> Option<InputMethodType> {
+        match *self {
+            InputType::Color => Some(InputMethodType::Color),
+            InputType::Date => Some(InputMethodType::Date),
+            InputType::DatetimeLocal => Some(InputMethodType::DatetimeLocal),
+            InputType::Email => Some(InputMethodType::Email),
+            InputType::Month => Some(InputMethodType::Month),
+            InputType::Number => Some(InputMethodType::Number),
+            InputType::Password => Some(InputMethodType::Password),
+            InputType::Search => Some(InputMethodType::Search),
+            InputType::Tel => Some(InputMethodType::Tel),
+            InputType::Text => Some(InputMethodType::Text),
+            InputType::Time => Some(InputMethodType::Time),
+            InputType::Url => Some(InputMethodType::Url),
+            InputType::Week => Some(InputMethodType::Week),
+            _ => None,
+        }
+    }
 }
 
 impl<'a> From<&'a Atom> for InputType {
diff --git a/components/script_traits/script_msg.rs b/components/script_traits/script_msg.rs
index 43812ad097a..d263753c7de 100644
--- a/components/script_traits/script_msg.rs
+++ b/components/script_traits/script_msg.rs
@@ -17,7 +17,7 @@ use euclid::{Size2D, TypedSize2D};
 use gfx_traits::Epoch;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use msg::constellation_msg::{BrowsingContextId, HistoryStateId, PipelineId, TraversalDirection};
-use msg::constellation_msg::{Key, KeyModifiers, KeyState};
+use msg::constellation_msg::{InputMethodType, Key, KeyModifiers, KeyState};
 use net_traits::CoreResourceMsg;
 use net_traits::request::RequestInit;
 use net_traits::storage_thread::StorageType;
@@ -163,6 +163,10 @@ pub enum ScriptMsg {
     GetScreenSize(IpcSender<(DeviceUintSize)>),
     /// Get the available screen size (pixel)
     GetScreenAvailSize(IpcSender<(DeviceUintSize)>),
+    /// Request to present an IME to the user when an editable element is focused.
+    ShowIME(InputMethodType),
+    /// Request to hide the IME when the editable element is blurred.
+    HideIME,
     /// Requests that the compositor shut down.
     Exit,
 }