Handle CR without NL printed in EditorConsole

Previously, any CR without NL was treated just like a NL. For tools that
used single CRs to update a progress bar (such as dfu-util), this would
end up printing the subsequent versions of the progress bar below each
other, instead of updating a single line as intended. Additionally,
since ConsoleOutputStream only scrolled the view on \n, these updates
would end up outside of the main view, making the upload progress quite
unclear.

This commit makes EditorConsole support lone CRs by resetting the insert
position to the start of the current line, so subsequent writes
overwrite existing content. If subsequent lines are shorter than an
earlier line, only part of the earlier line will be overwritten (this
mimics what terminal emulators do).

Author: matthijskooijman

Diff for: app/src/processing/app/EditorConsole.java

@@ -27,6 +27,8 @@
 import javax.swing.text.*;
 import java.awt.*;
 import java.io.PrintStream;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import static processing.app.Theme.scale;
 
@@ -37,6 +39,8 @@ public class EditorConsole extends JScrollPane {
 
   private static ConsoleOutputStream out;
   private static ConsoleOutputStream err;
+  private static int startOfLine = 0;
+  private static int insertPosition = 0;
 
   public static synchronized void setCurrentEditorConsole(EditorConsole console) {
     if (out == null) {
@@ -161,6 +165,8 @@ public void applyPreferences() {
   public void clear() {
     try {
       document.remove(0, document.getLength());
+      startOfLine = 0;
+      insertPosition = 0;
     } catch (BadLocationException e) {
       // ignore the error otherwise this will cause an infinite loop
       // maybe not a good idea in the long run?
@@ -176,10 +182,48 @@ public boolean isEmpty() {
     return document.getLength() == 0;
   }
 
-  public void insertString(String line, SimpleAttributeSet attributes) throws BadLocationException {
-    line = line.replace("\r\n", "\n").replace("\r", "\n");
-    int offset = document.getLength();
-    document.insertString(offset, line, attributes);
+  public void insertString(String str, SimpleAttributeSet attributes) throws BadLocationException {
+    // Separate the string into content, newlines and lone carriage
+    // returns.
+    //
+    // Doing so allows lone CRs to return the insertPosition to the
+    // start of the line to allow overwriting the most recent line (e.g.
+    // for a progress bar). Any CR or NL that are immediately followed
+    // by another NL are bunched together for efficiency, since these
+    // can just be inserted into the document directly and still be
+    // correct.
+    //
+    // This regex is written so it will necessarily match any string
+    // completely if applied repeatedly. This is important because any
+    // part not matched would be silently dropped.
+    Matcher m = Pattern.compile("([^\r\n]*)([\r\n]*\n)?(\r+)?").matcher(str);
+    while (m.find()) {
+      String content = m.group(1);
+      String newlines = m.group(2);
+      String crs = m.group(3);
+
+      // Replace (or append if at end of the document) the content first
+      int replaceLength = Math.min(content.length(), document.getLength() - insertPosition);
+      document.replace(insertPosition, replaceLength, content, attributes);
+      insertPosition += content.length();
+
+      // Then insert any newlines, but always at the end of the document
+      // e.g. if insertPosition is halfway a line, do not delete
+      // anything, just add the newline(s) at the end).
+      if (newlines != null) {
+        document.insertString(document.getLength(), newlines, attributes);
+        insertPosition = document.getLength();
+        startOfLine = insertPosition;
+      }
+
+      // Then, for any CRs not followed by newlines, move insertPosition
+      // to the start of the line. Note that if a newline follows before
+      // any content in the next call to insertString, it will be added
+      // at the end of the document anyway, as expected.
+      if (crs != null) {
+        insertPosition = startOfLine;
+      }
+    }
   }
 
   public String getText() {