load emoji keyboards only when used, and not on keyboard start

ca 30% faster keyboard loading (on first start, or when theme/color change)
ca 5-10% reduced memory use
may result in short loading times when an emoji tab is opened for the first time

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/Key.java

@@ -265,6 +265,34 @@ public class Key implements Comparable<Key> {
         mEnabled = key.mEnabled;
     }
 
+    /** constructor for creating emoji recent keys when there is no keyboard to take keys from */
+    public Key(@NonNull final Key key, @Nullable final MoreKeySpec[] moreKeys,
+             @Nullable final String labelHint, final int backgroundType, final int code, @Nullable final String outputText) {
+        // Final attributes.
+        mCode = outputText == null ? code : CODE_OUTPUT_TEXT;
+        mLabel = outputText == null ? StringUtils.newSingleCodePointString(code) : outputText;
+        mHintLabel = labelHint;
+        mLabelFlags = key.mLabelFlags;
+        mIconId = key.mIconId;
+        mWidth = key.mWidth;
+        mHeight = key.mHeight;
+        mHorizontalGap = key.mHorizontalGap;
+        mVerticalGap = key.mVerticalGap;
+        mX = key.mX;
+        mY = key.mY;
+        mHitBox.set(key.mHitBox);
+        mMoreKeys = moreKeys;
+        mMoreKeysColumnAndFlags = key.mMoreKeysColumnAndFlags;
+        mBackgroundType = backgroundType;
+        mActionFlags = key.mActionFlags;
+        mKeyVisualAttributes = key.mKeyVisualAttributes;
+        mOptionalAttributes = outputText == null ? null : Key.OptionalAttributes.newInstance(outputText, CODE_UNSPECIFIED, ICON_UNDEFINED, 0, 0);
+        mHashCode = key.mHashCode;
+        // Key state.
+        mPressed = key.mPressed;
+        mEnabled = key.mEnabled;
+    }
+
     /** constructor from KeyParams */
     private Key(KeyParams keyParams) {
         // stuff to copy

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/emoji/DynamicGridKeyboard.java

@@ -158,7 +158,7 @@ final class DynamicGridKeyboard extends Keyboard {
         Settings.writeEmojiRecentKeys(mPrefs, jsonStr);
     }
 
-    private static Key getKeyByCode(final Collection<DynamicGridKeyboard> keyboards,
+    private Key getKeyByCode(final Collection<DynamicGridKeyboard> keyboards,
             final int code) {
         for (final DynamicGridKeyboard keyboard : keyboards) {
             for (final Key key : keyboard.getSortedKeys()) {
@@ -167,10 +167,12 @@ final class DynamicGridKeyboard extends Keyboard {
                 }
             }
         }
-        return null;
+
+        // fall back to creating the key
+        return new Key(getTemplateKey(TEMPLATE_KEY_CODE_0), null, null, Key.BACKGROUND_TYPE_EMPTY, code, null);
     }
 
-    private static Key getKeyByOutputText(final Collection<DynamicGridKeyboard> keyboards,
+    private Key getKeyByOutputText(final Collection<DynamicGridKeyboard> keyboards,
             final String outputText) {
         for (final DynamicGridKeyboard keyboard : keyboards) {
             for (final Key key : keyboard.getSortedKeys()) {
@@ -179,7 +181,9 @@ final class DynamicGridKeyboard extends Keyboard {
                 }
             }
         }
-        return null;
+
+        // fall back to creating the key
+        return new Key(getTemplateKey(TEMPLATE_KEY_CODE_0), null, null, Key.BACKGROUND_TYPE_EMPTY, 0, outputText);
     }
 
     public void loadRecentKeys(final Collection<DynamicGridKeyboard> keyboards) {

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/emoji/EmojiCategory.java

@@ -48,10 +48,14 @@ final class EmojiCategory {
 
     public final class CategoryProperties {
         public final int mCategoryId;
-        public final int mPageCount;
+        private int mPageCount = -1;
-        public CategoryProperties(final int categoryId, final int pageCount) {
+        public CategoryProperties(final int categoryId) {
             mCategoryId = categoryId;
-            mPageCount = pageCount;
+        }
+        public int getPageCount() {
+            if (mPageCount < 0)
+                mPageCount = computeCategoryPageCount(mCategoryId);
+            return mPageCount;
         }
     }
 
@@ -147,8 +151,7 @@ final class EmojiCategory {
         }
         addShownCategoryId(EmojiCategory.ID_EMOTICONS);
 
-        DynamicGridKeyboard recentsKbd =
+        DynamicGridKeyboard recentsKbd = getKeyboard(EmojiCategory.ID_RECENTS, 0);
-                getKeyboard(EmojiCategory.ID_RECENTS, 0 /* categoryPageId */);
         recentsKbd.loadRecentKeys(mCategoryKeyboardMap.values());
 
         mCurrentCategoryId = Settings.readLastShownEmojiCategoryId(mPrefs, defaultCategoryId);
@@ -167,9 +170,7 @@ final class EmojiCategory {
 
     private void addShownCategoryId(final int categoryId) {
         // Load a keyboard of categoryId
-        getKeyboard(categoryId, 0 /* categoryPageId */);
+        final CategoryProperties properties = new CategoryProperties(categoryId);
-        final CategoryProperties properties =
-                new CategoryProperties(categoryId, computeCategoryPageCount(categoryId));
         mShownCategories.add(properties);
     }
 
@@ -214,7 +215,7 @@ final class EmojiCategory {
     public int getCategoryPageCount(final int categoryId) {
         for (final CategoryProperties prop : mShownCategories) {
             if (prop.mCategoryId == categoryId) {
-                return prop.mPageCount;
+                return prop.getPageCount();
             }
         }
         Log.w(TAG, "Invalid category id: " + categoryId);
@@ -258,7 +259,7 @@ final class EmojiCategory {
             if (props.mCategoryId == categoryId) {
                 return sum + categoryPageId;
             }
-            sum += props.mPageCount;
+            sum += props.getPageCount();
         }
         Log.w(TAG, "categoryId not found: " + categoryId);
         return 0;

app/src/main/java/org/dslul/openboard/inputmethod/keyboard/internal/keyboard_parser/EmojiParser.kt

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-3.0-only
 package org.dslul.openboard.inputmethod.keyboard.internal.keyboard_parser
 
 import android.content.Context