SwtMisc.systemFontWidth now returns double instead of int`.

Author: nedtwigg

CHANGES.md

@@ -2,7 +2,9 @@
 
 ## [Unreleased]
 ### Changed
-- **BREAKING** remove RxJava completely in favor of Kotlin Flow 
+- **BREAKING** `SwtMisc.systemFontWidth` now returns `double` instead of `int`.
+  - added new methods `systemFontWidthTimes(int)` and `systemFontWidthTimes(String)` to make this easier to deal with
+- **BREAKING** remove RxJava completely in favor of Kotlin Flow.
 - Bump required java from 11 to 17.
 
 ## [4.3.1] - 2024-07-05

durian-swt/src/main/java/com/diffplug/common/swt/SwtMisc.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 DiffPlug
+ * Copyright (C) 2020-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,7 +15,6 @@
  */
 package com.diffplug.common.swt;
 
-
 import com.diffplug.common.base.Box;
 import com.diffplug.common.base.Errors;
 import com.diffplug.common.base.Preconditions;
@@ -358,7 +357,7 @@ public static int blockForMessageBox(String title, String message, int style) {
 	///////////////////
 	/** The cached height of the system font. */
 	static int systemFontHeight = 0;
-	static int systemFontWidth = 0;
+	static double systemFontWidth = 0;
 
 	/** Populates the height and width of the system font. */
 	private static void populateSystemFont() {
@@ -368,7 +367,7 @@ private static void populateSystemFont() {
 
 		FontMetrics metrics = gc.getFontMetrics();
 		systemFontHeight = metrics.getHeight();
-		systemFontWidth = metrics.getAverageCharWidth();
+		systemFontWidth = metrics.getAverageCharacterWidth();
 		if (OS.getNative().isMac()) {
 			// add 20% width on Mac
 			systemFontWidth = (systemFontWidth * 12) / 10;
@@ -387,26 +386,34 @@ public static int systemFontHeight() {
 	}
 
 	/** Returns the width of the system font. */
-	public static int systemFontWidth() {
+	public static double systemFontWidth() {
 		if (systemFontWidth == 0) {
 			populateSystemFont();
 		}
 		return systemFontWidth;
 	}
 
+	public static int systemFontWidthTimes(int numChars) {
+		return (int) Math.round(systemFontWidth() * numChars);
+	}
+
+	public static int systemFontWidthTimes(String str) {
+		return systemFontWidthTimes(str.length());
+	}
+
 	/** Returns a distance which is a snug fit for a line of text in the system font. */
 	public static int systemFontSnug() {
 		return systemFontHeight() + Layouts.defaultMargin();
 	}
 
 	/** Returns the default width of a button, scaled for the system font. */
 	public static int defaultButtonWidth() {
-		return systemFontWidth() * "   Cancel   ".length();
+		return systemFontWidthTimes("   Cancel   ");
 	}
 
 	/** Returns the default width of a dialog. */
 	public static int defaultDialogWidth() {
-		return 50 * systemFontWidth();
+		return systemFontWidthTimes(50);
 	}
 
 	/** Returns a size which is scaled by the system font's height. */
@@ -421,7 +428,7 @@ public static int scaleByFontHeight(int rows) {
 
 	/** Returns a point that represents the size of a (cols x rows) grid of characters printed in the standard system font. */
 	public static Point scaleByFont(int cols, int rows) {
-		return new Point(cols * systemFontWidth(), rows * systemFontHeight());
+		return new Point(systemFontWidthTimes(cols), rows * systemFontHeight());
 	}
 
 	/** Returns a dimension which is guaranteed to be comfortable for the given string. */

durian-swt/src/main/java/com/diffplug/common/swt/widgets/ScaleCtl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 DiffPlug
+ * Copyright (C) 2020-2025 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,7 +15,6 @@
  */
 package com.diffplug.common.swt.widgets;
 
-
 import com.diffplug.common.base.Preconditions;
 import com.diffplug.common.rx.RxBox;
 import com.diffplug.common.swt.ControlWrapper;
@@ -136,7 +135,7 @@ public ScaleCtl(Composite parent, Builder builder, RxBox<Double> box) {
 		}
 
 		text = new Text(wrapped, SWT.BORDER | SWT.SINGLE);
-		Layouts.setGridData(text).grabHorizontal().widthHint(SwtMisc.systemFontWidth() * 4);
+		Layouts.setGridData(text).grabHorizontal().widthHint(SwtMisc.systemFontWidthTimes(4));
 
 		SwtExec.async().guardOn(text).execute(text::selectAll);
 		Listener selectAllListener = SwtMisc.asListener(SwtExec.async().guardOn(text).wrap(text::selectAll));