Bug 538612 - DateTime Spinner increment button trimmed

When the initial text is not the longest length possible for SWT.DATE or
SWT.TIME entry, the spinner buttons gets trimmed when the text is
changed to have longer length. Changed default date/time format
constants to the correct pattern. Implemented computeMaxTextSize method
to get the native text entry size corresponding to the longest possible
formatted text. Used the longest text size as the preferred width.

Tested on GTK3.22 with ControlExample->DateTime with SWT.DATE and
SWT.TIME on all styles (SHORT, MEDIUM, LONG). No cutoff with buttons or
warnings when incrementing values.

Change-Id: I1e62375f4af223d7ee1893d9789321a4805c5ff8
Signed-off-by: Xi Yan <xixiyan@redhat.com>

1 files changed, 63 insertions, 9 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/DateTime.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/DateTime.java
index d8c90b9107..7c2d2a171f 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/DateTime.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/DateTime.java
@@ -89,16 +89,21 @@ public class DateTime extends Composite {
 	Listener popupListener, popupFilter;
 
 	Point prefferedSize;
+	Locale locale;
 
 	/** Used when SWT.DROP_DOWN is set */
 	Listener mouseEventListener;
 
-	static final String DEFAULT_SHORT_DATE_FORMAT = "MM/YYYY";
-	static final String DEFAULT_MEDIUM_DATE_FORMAT = "MM/DD/YYYY";
-	static final String DEFAULT_LONG_DATE_FORMAT = "MM/DD/YYYY";
-	static final String DEFAULT_SHORT_TIME_FORMAT = "HH:MM AM";
-	static final String DEFAULT_MEDIUM_TIME_FORMAT = "HH:MM:SS AM";
-	static final String DEFAULT_LONG_TIME_FORMAT = "HH:MM:SS AM";
+	/*
+	 * Used for easier access to format pattern of DATE and TIME.
+	 * See https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html
+	 */
+	static final String DEFAULT_SHORT_DATE_FORMAT = "dd/MM/yy";
+	static final String DEFAULT_MEDIUM_DATE_FORMAT = "d-MMM-yyyy";
+	static final String DEFAULT_LONG_DATE_FORMAT = "MMMM d, yyyy";
+	static final String DEFAULT_SHORT_TIME_FORMAT = "h:mm a";
+	static final String DEFAULT_MEDIUM_TIME_FORMAT = "h:mm:ss a";
+	static final String DEFAULT_LONG_TIME_FORMAT = "h:mm:ss z a";
 	static final int MIN_YEAR = 1752; // Gregorian switchover in North America: September 19, 1752
 	static final int MAX_YEAR = 9999;
 	static final int SPACE_FOR_CURSOR = 1;
@@ -170,13 +175,11 @@ public DateTime (Composite parent, int style) {
 
 void createText() {
 	String property = System.getProperty("swt.datetime.locale");
-	Locale locale;
 	if (property == null || property.isEmpty()) {
 		locale = Locale.getDefault();
 	} else {
 		locale = Locale.forLanguageTag(property);
 	}
-
 	dateFormat = getFormat(locale, style);
 	dateFormat.setLenient(false);
 	calendar = Calendar.getInstance(locale);
@@ -259,6 +262,51 @@ protected void checkSubclass () {
 	if (!isValidSubclass ()) error (SWT.ERROR_INVALID_SUBCLASS);
 }
 
+/**
+ * Compute the native text entry size when the formatted text inside the entry
+ * is at the longest length possible. i.e. Assume DATE/HOUR field to be double digit,
+ * MONTH field for SWT.DATE | SWT.LONG is the longest text.
+ *
+ * @param wHint
+ * @param hHint
+ * @param changed
+ * @return text entry size to hold the longest possible formatted text.
+ */
+Point computeMaxTextSize (int wHint, int hHint, boolean changed) {
+	String currentText = getFormattedString();
+	String formatPattern = getComputeSizeString(style);
+
+	switch (formatPattern) {
+		case DEFAULT_MEDIUM_DATE_FORMAT:
+			// Make the DATE field a double digit
+			String longDateText = currentText.replaceFirst("\\d{1,2}", "00");
+			setText(longDateText);
+			break;
+		case DEFAULT_LONG_DATE_FORMAT:
+			// Make the MONTH field the longest length possible, the DATE field a double digit.
+			Set<String> months = calendar.getDisplayNames(Calendar.MONTH, Calendar.LONG, locale).keySet();
+			String longestMonth = Collections.max(months, (s1, s2) -> s1.length() - s2.length()); // Probably September
+			String doubleDigitDate = currentText.replaceFirst("\\d{1,2}", "00");
+			String longText = doubleDigitDate.replaceFirst("[^\\s]+", longestMonth);
+			setText(longText);
+			break;
+		case DEFAULT_SHORT_TIME_FORMAT:
+		case DEFAULT_MEDIUM_TIME_FORMAT:
+		case DEFAULT_LONG_TIME_FORMAT:
+			// Make the HOUR field a double digit
+			String longTimeText = currentText.replaceFirst("\\d{1,2}", "00");
+			setText(longTimeText);
+			break;
+		default:
+			// Fixed length for DEFAULT_SHORT_DATE_FORMAT, no need to adjust text length.
+	}
+
+	Point textSize = computeNativeSize (textEntryHandle, wHint, hHint, changed);
+	// Change the text back to match the current calendar
+	updateControl();
+	return textSize;
+}
+
 @Override
 Point computeSizeInPixels (int wHint, int hHint, boolean changed) {
 	checkWidget ();
@@ -277,7 +325,13 @@ Point computeSizeInPixels (int wHint, int hHint, boolean changed) {
 			width = size.x;
 			height = size.y;
 		} else {
-			Point textSize = computeNativeSize (textEntryHandle, wHint, hHint, changed);
+			/*
+			 * Bug 538612: Computing the native size for textEntry when the current text
+			 * is not the longest length possible causes sizing issues when the entry text
+			 * is changed. Fix is to always allocate enough size to hold the longest possible
+			 * formatted text.
+			 */
+			Point textSize = computeMaxTextSize (wHint, hHint, changed);
 			Rectangle trim = computeTrimInPixels (0,0, textSize.x,textSize.y);
 			if (isDateWithDropDownButton ()){
 				Point buttonSize = down.computeSizeInPixels (SWT.DEFAULT, SWT.DEFAULT, changed);