Bug 1593683 - Part 2. Handle arrow left/right key when having composition. r=geckoview-reviewers,esawin

Most IMEs handle arrow key, then set caret position by IME. But GBoard doesn't
handle it. GBoard will dispatch key event to application for arrow left/right
even if having IME composition.

Since Gecko doesn't dispatch key press during IME composition due to DOM UI
events spec, we have to emulate arrow key's behaviour.

And, `GeckoEditable` has a hack that composition text is committed when
dispatching key event. This hack is unnecessary after landing
bug 1613804 that `InputConnection.finishComposingText` is implemented.

Differential Revision: https://phabricator.services.mozilla.com/D76658

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/TextInputDelegateTest.kt

@@ -791,4 +791,24 @@ class TextInputDelegateTest : BaseSessionTest() {
 
         assertText("commit abc", ic, "abc")
     }
+
+    // Bug 1593683 - Cursor is jumping when using the arrow keys in input field on GBoard
+    @WithDisplay(width = 512, height = 512) // Child process updates require having a display.
+    @Test fun inputConnection_bug1593683() {
+        setupContent("")
+
+        val ic = mainSession.textInput.onCreateInputConnection(EditorInfo())!!
+
+        setComposingText(ic, "foo", 1)
+        assertTextAndSelectionAt("Can set the composing text", ic, "foo", 3)
+        // Arrow key should keep composition then move caret
+        pressKey(ic, KeyEvent.KEYCODE_DPAD_LEFT)
+        pressKey(ic, KeyEvent.KEYCODE_DPAD_LEFT)
+        pressKey(ic, KeyEvent.KEYCODE_DPAD_LEFT)
+        assertSelection("IME caret is moved to top", ic, 0, 0, /* checkGecko */ false)
+
+        setComposingText(ic, "bar", 1)
+        finishComposingText(ic)
+        assertText("commit abc", ic, "bar")
+    }
 }

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoEditable.java

@@ -1014,10 +1014,52 @@ import android.view.inputmethod.EditorInfo;
                 return;
             }
 
+            // Most IMEs handle arrow key, then set caret position. But GBoard
+            // doesn't handle it. GBoard will dispatch KeyEvent for arrow left/right
+            // even if having IME composition.
+            // Since Gecko doesn't dispatch keypress during IME composition due to
+            // DOM UI events spec, we have to emulate arrow key's behaviour.
+            boolean commitCompositionBeforeKeyEvent = action == KeyEvent.ACTION_DOWN;
+            if (isComposing(mText.getShadowText()) &&
+                action == KeyEvent.ACTION_DOWN && event.hasNoModifiers()) {
+                final int selStart = Selection.getSelectionStart(mText.getShadowText());
+                final int selEnd = Selection.getSelectionEnd(mText.getShadowText());
+                if (selStart == selEnd) {
+                    // If dispatching arrow left/right key into composition,
+                    // we update IME caret.
+                    switch (event.getKeyCode()) {
+                        case KeyEvent.KEYCODE_DPAD_LEFT:
+                            if (getComposingStart(mText.getShadowText()) < selStart) {
+                                Selection.setSelection(getEditable(), selStart - 1, selStart - 1);
+                                mNeedUpdateComposition = true;
+                                commitCompositionBeforeKeyEvent = false;
+                            } else if (selStart == 0) {
+                                // Keep current composition
+                                commitCompositionBeforeKeyEvent = false;
+                            }
+                            break;
+                        case KeyEvent.KEYCODE_DPAD_RIGHT:
+                            if (getComposingEnd(mText.getShadowText()) > selEnd) {
+                                Selection.setSelection(getEditable(), selStart + 1, selStart + 1);
+                                mNeedUpdateComposition = true;
+                                commitCompositionBeforeKeyEvent = false;
+                            } else if (selEnd == mText.getShadowText().length()) {
+                                // Keep current composition
+                                commitCompositionBeforeKeyEvent = false;
+                            }
+                            break;
+                    }
+                }
+            }
+
             // Focused; key event may go to chrome window or to content window.
             if (mNeedUpdateComposition) {
                 icMaybeSendComposition(mText.getShadowText(), SEND_COMPOSITION_NOTIFY_GECKO);
             }
+
+            if (commitCompositionBeforeKeyEvent) {
+                mFocusedChild.onImeRequestCommit();
+            }
             onKeyEvent(mFocusedChild, event, action, metaState,
                        /* isSynthesizedImeKey */ false);
             icOfferAction(new Action(Action.TYPE_EVENT));
@@ -2251,5 +2293,29 @@ import android.view.inputmethod.EditorInfo;
 
         return false;
     }
+
+    private static int getComposingStart(final Spanned text) {
+        int composingStart = Integer.MAX_VALUE;
+        final Object[] spans = text.getSpans(0, text.length(), Object.class);
+        for (final Object span : spans) {
+            if ((text.getSpanFlags(span) & Spanned.SPAN_COMPOSING) != 0) {
+                composingStart = Math.min(composingStart, text.getSpanStart(span));
+            }
+        }
+
+        return composingStart;
+    }
+
+    private static int getComposingEnd(final Spanned text) {
+        int composingEnd = -1;
+        final Object[] spans = text.getSpans(0, text.length(), Object.class);
+        for (final Object span : spans) {
+            if ((text.getSpanFlags(span) & Spanned.SPAN_COMPOSING) != 0) {
+                composingEnd = Math.max(composingEnd, text.getSpanEnd(span));
+            }
+        }
+
+        return composingEnd;
+    }
 }
 

widget/android/GeckoEditableSupport.cpp

@@ -502,7 +502,6 @@ void GeckoEditableSupport::OnKeyEvent(int32_t aAction, int32_t aKeyCode,
     // these keys are dispatched in sequence.
     mIMEKeyEvents.AppendElement(UniquePtr<WidgetEvent>(event.Duplicate()));
   } else {
-    RemoveComposition();
     NS_ENSURE_SUCCESS_VOID(BeginInputTransaction(dispatcher));
     dispatcher->DispatchKeyboardEvent(msg, event, status);
     if (widget->Destroyed() || status == nsEventStatus_eConsumeNoDefault) {