Bug 531639 - [StyledText] Improve performance on load when

setLineSpacingProvider is called 

Change-Id: Ie26e1718b9af2cc5e008c53a4db2012684713777
Signed-off-by: angelozerr <angelo.zerr@gmail.com>

2 files changed, 27 insertions, 3 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java
index 954e6e54b3..a05e0bf0a1 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java
@@ -9381,8 +9381,32 @@ public void setLineSpacingProvider(StyledTextLineSpacingProvider lineSpacingProv
 					&& renderer.getLineSpacingProvider().equals(lineSpacingProvider)))
 		return;
 	renderer.setLineSpacingProvider(lineSpacingProvider);
-	setVariableLineHeight();
-	resetCache(0, content.getLineCount());
+	// reset lines cache if needed
+	if (lineSpacingProvider == null) {
+		if (!isFixedLineHeight()) {
+			resetCache(0, content.getLineCount());
+		}
+	} else {
+		if (isFixedLineHeight()) {
+			int firstLine = -1;
+			for (int i = 0; i < content.getLineCount(); i++) {
+				Integer lineSpacing = lineSpacingProvider.getLineSpacing(i);
+				if (lineSpacing != null && lineSpacing > 0) {
+					// there is a custom line spacing, set StyledText as variable line height mode
+					setVariableLineHeight();
+					// reset only the line size
+					renderer.reset(i, 1);
+					if (firstLine == -1) {
+						firstLine = i;
+					}
+				}
+			}
+			if (firstLine != -1) {
+				// call reset cache for the first line which have changed to recompute scrollbars
+				resetCache(firstLine, 0);
+			}
+		}
+	}
 	setCaretLocation();
 	super.redraw();
 }
diff --git a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledTextRenderer.java b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledTextRenderer.java
index 7963e3308c..d8144511b3 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledTextRenderer.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledTextRenderer.java
@@ -889,7 +889,7 @@ TextLayout getTextLayout(int lineIndex) {
 			 * resetCache, setCaretLocation, redraw methods only at the end of the compute of all lines spacing.
 			 */
 			lineSpacingComputing = true;
-			styledText.resetCache(lineIndex, styledText.getLineCount());
+			styledText.resetCache(lineIndex, 1);
 			styledText.setVariableLineHeight();
 			styledText.setCaretLocation();
 			styledText.redraw();