Trim console output before processing it console document

When processing large amounts of console output of a process,
its possible that the Eclipse UI will freeze.
E.g. on Linux, very long lines (> 1 million symbols) result in such freezes.

Using the console limit preference doesn't help preventing this freeze,
despite limitting the contents seen in the console.

This change adjusts IOConsolePartitioner.QueueProcessingJob.processPendingPartitions()
to trim pending console output before setting this output in the console document,
if a console limit is set in the Eclipse preferences.

See: #2283

Author: trancexpress

debug/org.eclipse.ui.console/src/org/eclipse/ui/internal/console/IOConsolePartitioner.java

@@ -784,7 +784,7 @@ public boolean shouldRun() {
 		 * update partitioning.
 		 */
 		private void processPendingPartitions() {
-			final List<PendingPartition> pendingCopy = new ArrayList<>();
+			List<PendingPartition> pendingCopy = new ArrayList<>();
 			// draining the whole buffer here is important - this way we get as much data as
 			// available and may skip to draw text that exceeds the Console buffer size
 			// anyway (see checkBufferSize()).
@@ -800,6 +800,36 @@ private void processPendingPartitions() {
 				}
 				sizeHint += p.text.length();
 			}
+			/*
+			 * Check if the output we want to process is over the console limit. If so, trim
+			 * the output before passing it to SWT.
+			 */
+			int hwm = highWaterMark;
+			if (hwm > 0 && sizeHint > hwm) {
+				List<PendingPartition> copy = new ArrayList<>();
+				List<PendingPartition> trimmedCopy = new ArrayList<>();
+				for (PendingPartition p : pendingCopy) {
+					if (p.stream != stream) {
+						break;
+					}
+					copy.add(p);
+				}
+				sizeHint = 0;
+				int index = 0;
+				for (int i = copy.size() - 1; i >= 0; --i) {
+					PendingPartition p = copy.get(i);
+					sizeHint += p.text.length();
+					index = i;
+					if (sizeHint > hwm) {
+						break;
+					}
+				}
+				for (int i = index; i < copy.size(); ++i) {
+					PendingPartition p = copy.get(i);
+					trimmedCopy.add(p);
+				}
+				pendingCopy = trimmedCopy;
+			}
 			synchronized (partitions) {
 				if (document != null) {
 					applyStreamOutput(pendingCopy, sizeHint);