IDEA-177568 Weird mouse selection

platform/platform-impl/src/com/intellij/ide/ui/laf/darcula/ui/DarculaTextAreaUI.java

@@ -17,14 +17,12 @@ package com.intellij.ide.ui.laf.darcula.ui;
 
 import com.intellij.ide.ui.laf.darcula.DarculaUIUtil;
 import com.intellij.openapi.util.SystemInfo;
+import com.intellij.openapi.util.registry.Registry;
 
 import javax.swing.*;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicTextAreaUI;
-import javax.swing.text.BadLocationException;
-import javax.swing.text.DefaultEditorKit;
-import javax.swing.text.JTextComponent;
-import javax.swing.text.Position;
+import javax.swing.text.*;
 import java.awt.event.KeyEvent;
 
 public class DarculaTextAreaUI extends BasicTextAreaUI{
@@ -51,4 +49,9 @@ public class DarculaTextAreaUI extends BasicTextAreaUI{
     int position = DarculaUIUtil.getPatchedNextVisualPositionFrom(t, pos, direction);
     return position != -1 ? position : super.getNextVisualPositionFrom(t, pos, b, direction, biasRet);
   }
+
+  @Override
+  protected Caret createCaret() {
+    return Registry.is("ide.text.mouse.selection.new") ? new TextFieldWithPopupHandlerUI.MyCaret(getComponent()) : super.createCaret();
+  }
 }

platform/platform-impl/src/com/intellij/ide/ui/laf/darcula/ui/TextFieldWithPopupHandlerUI.java

@@ -36,10 +36,7 @@ import javax.swing.event.DocumentListener;
 import javax.swing.plaf.FontUIResource;
 import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicTextFieldUI;
-import javax.swing.text.BadLocationException;
-import javax.swing.text.Document;
-import javax.swing.text.JTextComponent;
-import javax.swing.text.Position;
+import javax.swing.text.*;
 import java.awt.*;
 import java.awt.event.*;
 import java.beans.PropertyChangeEvent;
@@ -201,6 +198,11 @@ public abstract class TextFieldWithPopupHandlerUI extends BasicTextFieldUI imple
     return position != -1 ? position : super.getNextVisualPositionFrom(t, pos, b, direction, biasRet);
   }
 
+  @Override
+  protected Caret createCaret() {
+    return Registry.is("ide.text.mouse.selection.new") ? new MyCaret(getComponent()) : super.createCaret();
+  }
+
   @Override
   public boolean value(Object o) {
     if (o instanceof MouseEvent) {
@@ -632,4 +634,24 @@ public abstract class TextFieldWithPopupHandlerUI extends BasicTextFieldUI imple
       return "clear";
     }
   }
+
+  static class MyCaret extends BasicCaret {
+    private final JTextComponent myComponent;
+
+    public MyCaret(JTextComponent component) {
+      myComponent = component;
+    }
+
+    @Override
+    public void mouseDragged(MouseEvent e) {
+      if (e.getID() == MouseEvent.MOUSE_DRAGGED && !myComponent.getText().contains("\n")) {
+        boolean consumed = e.isConsumed();
+        e = new MouseEvent(e.getComponent(), e.getID(), e.getWhen(), e.getModifiers() | e.getModifiersEx(), e.getX(),
+                           myComponent.getHeight() / 2,
+                           e.getClickCount(), e.isPopupTrigger(), e.getButton());
+        if (consumed) e.consume();
+      }
+      super.mouseDragged(e);
+    }
+  }
 }

platform/util/resources/misc/registry.properties

@@ -1079,6 +1079,8 @@ ide.text.effect.new.scale=true
 ide.text.effect.new.scale.description=Enables scalable effect painter for text
 ide.text.effect.new.metrics=true
 ide.text.effect.new.metrics.description=Use line metrics to calculate text offset in the effect painter
+ide.text.mouse.selection.new=true
+ide.text.mouse.selection.description=Use improved mouse-drag processing in single-line text components when mouse pointer is out of area
 
 ide.intellij.laf.win10.ui=true
 ide.intellij.laf.win10.restartRequired=true