feat(editor): add old cursor position before changed for selection ch…

…ange event

editor/src/main/java/io/github/rosemoe/sora/event/SelectionChangeEvent.java

@@ -24,6 +24,7 @@
 package io.github.rosemoe.sora.event;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 import io.github.rosemoe.sora.text.CharPosition;
 import io.github.rosemoe.sora.widget.CodeEditor;
@@ -74,12 +75,18 @@ public class SelectionChangeEvent extends Event {
      * From mouse
      */
     public final static int CAUSE_MOUSE_INPUT = 8;
+    @Nullable
+    private final CharPosition oldLeft;
+    @Nullable
+    private final CharPosition oldRight;
     private final CharPosition left;
     private final CharPosition right;
     private final int cause;
 
-    public SelectionChangeEvent(@NonNull CodeEditor editor, int cause) {
+    public SelectionChangeEvent(@NonNull CodeEditor editor, @Nullable CharPosition oldLeft, @Nullable CharPosition oldRight, int cause) {
         super(editor);
+        this.oldLeft = oldLeft;
+        this.oldRight = oldRight;
         var cursor = editor.getText().getCursor();
         left = cursor.left();
         right = cursor.right();
@@ -101,6 +108,22 @@ public int getCause() {
         return cause;
     }
 
+    /**
+     * Get the last left selection's position before changed
+     */
+    @Nullable
+    public CharPosition getOldLeft() {
+        return oldLeft;
+    }
+
+    /**
+     * Get the last right selection's position before changed
+     */
+    @Nullable
+    public CharPosition getOldRight() {
+        return oldRight;
+    }
+
     /**
      * Get the left selection's position
      */

editor/src/main/java/io/github/rosemoe/sora/widget/CodeEditor.java

@@ -347,6 +347,7 @@ public class CodeEditor extends View implements ContentListener, Formatter.Forma
     private boolean horizontalAbsorb;
     private LineSeparator lineSeparator;
     private TextRange lastInsertion;
+    private TextRange lastSelectedTextRange;
     private SnippetController snippetController;
 
     public CodeEditor(Context context) {
@@ -3209,6 +3210,7 @@ protected void ensureSelectionAnchorAvailable() {
 
     /**
      * Move or extend selection, according to {@code extend} param.
+     *
      * @param extend True if you want to extend selection.
      */
     public void moveOrExtendSelection(@NonNull SelectionMovement movement, boolean extend) {
@@ -4376,7 +4378,15 @@ protected EditorRenderer onCreateRenderer() {
      * Called when the text is edited or {@link CodeEditor#setSelection} is called
      */
     protected void onSelectionChanged(int cause) {
-        dispatchEvent(new SelectionChangeEvent(this, cause));
+        CharPosition oldLeft = null;
+        CharPosition oldRight = null;
+        final TextRange lastTextRange = this.lastSelectedTextRange;
+        if (lastTextRange != null) {
+            oldLeft = lastTextRange.getStart();
+            oldRight = lastTextRange.getEnd();
+        }
+        dispatchEvent(new SelectionChangeEvent(this, oldLeft, oldRight, cause));
+        this.lastSelectedTextRange = getCursorRange();
     }
 
     /**