From 1f90a60db1a7b5f7d98e5d11af9c7d13e0c25d9a Mon Sep 17 00:00:00 2001
From: Tuukka Lehtonen <tuukka.lehtonen@semantum.fi>
Date: Mon, 9 Mar 2020 18:11:02 +0200
Subject: [PATCH] Fixed StyledtextContentAdapter to overwrite existing content
 properly

gitlab #492

Change-Id: I58e4feb40b13f8a9c6b0619776cf496d5f21a80b
---
 .../ui/assist/StyledTextContentAdapter.java   | 62 +++++++++++++------
 1 file changed, 44 insertions(+), 18 deletions(-)

diff --git a/bundles/org.simantics.scl.ui/src/org/simantics/scl/ui/assist/StyledTextContentAdapter.java b/bundles/org.simantics.scl.ui/src/org/simantics/scl/ui/assist/StyledTextContentAdapter.java
index dd71e323b..899b9e731 100644
--- a/bundles/org.simantics.scl.ui/src/org/simantics/scl/ui/assist/StyledTextContentAdapter.java
+++ b/bundles/org.simantics.scl.ui/src/org/simantics/scl/ui/assist/StyledTextContentAdapter.java
@@ -10,6 +10,7 @@
  *******************************************************************************/
 package org.simantics.scl.ui.assist;
 
+import org.eclipse.jface.fieldassist.ContentProposalAdapter;
 import org.eclipse.jface.fieldassist.IControlContentAdapter;
 import org.eclipse.jface.fieldassist.IControlContentAdapter2;
 import org.eclipse.swt.custom.StyledText;
@@ -69,26 +70,51 @@ public class StyledTextContentAdapter implements IControlContentAdapter, IContro
 	public void insertControlContents(Control control, String contents, int cursorPosition) {
 		StyledText text = ((StyledText)control);
 		cursorPosition = Math.min(cursorPosition, contents.length());
-		int caretEndRange = text.getCaretOffset();
+
+		int caretOffset = text.getCaretOffset();
 		String currentText = text.getText();
-		
-		int offset = caretEndRange;
-        int length = currentText.length();
-        while (--offset >= 0 && (Character.isJavaIdentifierPart(currentText.charAt(offset)) && !Character.isWhitespace(currentText.charAt(offset))))
-            length--;
-		
-		int nameSpaceBeginRange = currentText.lastIndexOf(".", caretEndRange - 1); //$NON-NLS-1$
-		if (nameSpaceBeginRange > length)
-		    length = nameSpaceBeginRange;
-		int endRange = currentText.length();
-		if (caretEndRange < endRange)
-		    endRange = caretEndRange;
-		text.setSelection(length, endRange);
+		int replacementOffset = findPrefixMatchOffset(currentText, caretOffset, contents);
+
+//		System.out.println("text: " + currentText);
+//		System.out.println("proposal to fill: " + contents);
+//		System.out.format("longest match of proposed contents found from text @ offset %d: \"%s[%s]%s\"%n",
+//				replacementOffset,
+//				currentText.substring(0, replacementOffset),
+//				currentText.substring(replacementOffset, caretOffset),
+//				currentText.substring(caretOffset));
+
+		// The text between [replaceOffset, caretOffset) will be replaced with `contents`
+		text.setSelection(replacementOffset, caretOffset);
 		text.insert(contents);
-		// calculate the initial count of letters that was typed when the proposal was accepted to insert the caret
-		// at the right position
-		int proposalFirstLettersCount = endRange - (length);
-		text.setCaretOffset(caretEndRange + cursorPosition - proposalFirstLettersCount);
+		text.setSelection(replacementOffset + contents.length());
+	}
+
+	/**
+	 * Find offset of longest prefix match of <code>match</code> in
+	 * <code>text</code> ending at offset <code>endOffset</code>.
+	 * 
+	 * Example:
+	 * <pre>
+	 * ...  res (=text)
+	 * resource (=match)
+	 *  resourc
+	 *   resour
+	 *    resou
+	 *     reso
+	 *      res match! return endOffset - 3
+	 * </pre>
+	 * 
+	 * @param text the text from which to find the match
+	 * @param endOffset endOffset until which to search for the longest match
+	 * @param match the text to prefix-match
+	 * @return
+	 */
+	private static int findPrefixMatchOffset(String text, int endOffset, String match) {
+		for (int i = match.length(); i >= 0; --i) {
+			if (text.regionMatches(true, endOffset - i, match, 0, i))
+				return endOffset - i;
+		}
+		return 0;
 	}
 
 	/*
-- 
2.43.2