From ee684d09b64c54fa010babd286fee8ccf273c781 Mon Sep 17 00:00:00 2001
From: Jonah Graham <jonah@kichwacoders.com>
Date: Sat, 28 Mar 2020 16:43:39 -0400
Subject: [PATCH] Bug 561319: Remove flickering in terminal when changing
 selection

This is done by buffering the drawing of the line of the terminal.

Change-Id: I593a3b99080d779046ea37497d93a25584c472c1
---
 .../feature.xml                               |  2 +-
 .../META-INF/MANIFEST.MF                      |  2 +-
 .../terminal/textcanvas/TextLineRenderer.java | 53 +++++++++++--------
 3 files changed, 34 insertions(+), 23 deletions(-)

diff --git a/terminal/features/org.eclipse.tm.terminal.control.feature/feature.xml b/terminal/features/org.eclipse.tm.terminal.control.feature/feature.xml
index c1966c85670..53af7622cb9 100644
--- a/terminal/features/org.eclipse.tm.terminal.control.feature/feature.xml
+++ b/terminal/features/org.eclipse.tm.terminal.control.feature/feature.xml
@@ -16,7 +16,7 @@
 <feature
       id="org.eclipse.tm.terminal.control.feature"
       label="%featureName"
-      version="4.6.0.qualifier"
+      version="4.6.1.qualifier"
       provider-name="%providerName"
       plugin="org.eclipse.tm.terminal.control"
       license-feature="org.eclipse.license"
diff --git a/terminal/plugins/org.eclipse.tm.terminal.control/META-INF/MANIFEST.MF b/terminal/plugins/org.eclipse.tm.terminal.control/META-INF/MANIFEST.MF
index 950506316f4..24d95ee2157 100644
--- a/terminal/plugins/org.eclipse.tm.terminal.control/META-INF/MANIFEST.MF
+++ b/terminal/plugins/org.eclipse.tm.terminal.control/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.tm.terminal.control; singleton:=true
-Bundle-Version: 4.6.0.qualifier
+Bundle-Version: 4.6.1.qualifier
 Bundle-Activator: org.eclipse.tm.internal.terminal.control.impl.TerminalPlugin
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
diff --git a/terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/textcanvas/TextLineRenderer.java b/terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/textcanvas/TextLineRenderer.java
index 954eeeb48fc..b45506abe13 100644
--- a/terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/textcanvas/TextLineRenderer.java
+++ b/terminal/plugins/org.eclipse.tm.terminal.control/src/org/eclipse/tm/internal/terminal/textcanvas/TextLineRenderer.java
@@ -20,6 +20,7 @@ import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Color;
 import org.eclipse.swt.graphics.Font;
 import org.eclipse.swt.graphics.GC;
+import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.tm.terminal.model.ITerminalTextDataReadOnly;
@@ -49,44 +50,54 @@ public class TextLineRenderer implements ILinelRenderer {
 
 	@Override
 	public void drawLine(ITextCanvasModel model, GC gc, int line, int x, int y, int colFirst, int colLast) {
+		int width = getCellWidth() * (colLast - colFirst);
+		int height = getCellHeight();
+		if (width <= 0 || height <= 0) {
+			return;
+		}
+		Image buffer = new Image(gc.getDevice(), width, height);
+		GC doubleBufferGC = new GC(buffer);
 		if (line < 0 || line >= getTerminalText().getHeight() || colFirst >= getTerminalText().getWidth()
 				|| colFirst - colLast == 0) {
-			fillBackground(gc, x, y, getCellWidth() * (colLast - colFirst), getCellHeight());
+			fillBackground(doubleBufferGC, 0, 0, width, height);
 		} else {
 			colLast = Math.min(colLast, getTerminalText().getWidth());
 			LineSegment[] segments = getTerminalText().getLineSegments(line, colFirst, colLast - colFirst);
 			for (int i = 0; i < segments.length; i++) {
 				LineSegment segment = segments[i];
 				Style style = segment.getStyle();
-				setupGC(gc, style);
+				setupGC(doubleBufferGC, style);
 				String text = segment.getText();
-				drawText(gc, x, y, colFirst, segment.getColumn(), text);
-				drawCursor(model, gc, line, x, y, colFirst);
+				drawText(doubleBufferGC, 0, 0, colFirst, segment.getColumn(), text);
+				drawCursor(model, doubleBufferGC, line, 0, 0, colFirst);
 			}
 			if (fModel.hasLineSelection(line)) {
-				gc.setForeground(Display.getCurrent().getSystemColor(SWT.COLOR_LIST_SELECTION_TEXT));
-				gc.setBackground(Display.getCurrent().getSystemColor(SWT.COLOR_LIST_SELECTION));
+				doubleBufferGC.setForeground(Display.getCurrent().getSystemColor(SWT.COLOR_LIST_SELECTION_TEXT));
+				doubleBufferGC.setBackground(Display.getCurrent().getSystemColor(SWT.COLOR_LIST_SELECTION));
 				Point start = model.getSelectionStart();
 				Point end = model.getSelectionEnd();
 				char[] chars = model.getTerminalText().getChars(line);
-				if (chars == null)
-					return;
-				int offset = 0;
-				if (start.y == line)
-					offset = start.x;
-				offset = Math.max(offset, colFirst);
-				int len;
-				if (end.y == line)
-					len = end.x - offset + 1;
-				else
-					len = chars.length - offset + 1;
-				len = Math.min(len, chars.length - offset);
-				if (len > 0) {
-					String text = new String(chars, offset, len);
-					drawText(gc, x, y, colFirst, offset, text);
+				if (chars != null) {
+					int offset = 0;
+					if (start.y == line)
+						offset = start.x;
+					offset = Math.max(offset, colFirst);
+					int len;
+					if (end.y == line)
+						len = end.x - offset + 1;
+					else
+						len = chars.length - offset + 1;
+					len = Math.min(len, chars.length - offset);
+					if (len > 0) {
+						String text = new String(chars, offset, len);
+						drawText(doubleBufferGC, 0, 0, colFirst, offset, text);
+					}
 				}
 			}
 		}
+		gc.drawImage(buffer, x, y);
+		doubleBufferGC.dispose();
+		buffer.dispose();
 	}
 
 	private void fillBackground(GC gc, int x, int y, int width, int height) {