Fix: show the date a picker is set to

Source/NSDatePickerCell.m

@@ -35,6 +35,10 @@
 #import "AppKit/NSDatePickerCell.h"
 #import "AppKit/NSColor.h"
 
+@interface NSDatePickerCell (Private)
+- (void) _updateDateFormat;
+@end
+
 @implementation NSDatePickerCell
 
 - (void) dealloc
@@ -60,11 +64,119 @@ - (id) initTextCell: (NSString*)aString
       [self setBezeled: YES];
       _datePickerElements = NSYearMonthDayDatePickerElementFlag
         | NSHourMinuteSecondDatePickerElementFlag;
+      [self _updateDateFormat];
     }
 
   return self;
 }
 
+/* The template holds one letter per element the picker shows.  The pattern
+   generator turns it into the pattern the locale writes those elements in.
+   'j' stands for the hour in the clock the locale uses, twelve or twenty
+   four.
+*/
+- (NSString *) _dateFormatTemplate
+{
+  NSMutableString *template = [NSMutableString stringWithCapacity: 8];
+  NSDatePickerElementFlags elements = _datePickerElements;
+
+  if (elements & NSEraDatePickerElementFlag)
+    {
+      [template appendString: @"G"];
+    }
+  if (elements & NSYearMonthDatePickerElementFlag)
+    {
+      [template appendString: @"yM"];
+    }
+  if ((elements & NSYearMonthDayDatePickerElementFlag)
+    == NSYearMonthDayDatePickerElementFlag)
+    {
+      [template appendString: @"d"];
+    }
+  if (elements & NSHourMinuteDatePickerElementFlag)
+    {
+      [template appendString: @"jm"];
+    }
+  if ((elements & NSHourMinuteSecondDatePickerElementFlag)
+    == NSHourMinuteSecondDatePickerElementFlag)
+    {
+      [template appendString: @"s"];
+    }
+  if (elements & NSTimeZoneDatePickerElementFlag)
+    {
+      [template appendString: @"z"];
+    }
+
+  return template;
+}
+
+/* Used when the pattern generator is unavailable, which is the case in a
+   build without ICU.
+*/
+- (NSString *) _fallbackDateFormat
+{
+  NSMutableString *format = [NSMutableString stringWithCapacity: 24];
+  NSDatePickerElementFlags elements = _datePickerElements;
+
+  if (elements & NSYearMonthDatePickerElementFlag)
+    {
+      [format appendString: @"y-MM"];
+      if ((elements & NSYearMonthDayDatePickerElementFlag)
+        == NSYearMonthDayDatePickerElementFlag)
+        {
+          [format appendString: @"-dd"];
+        }
+    }
+  if (elements & NSHourMinuteDatePickerElementFlag)
+    {
+      if ([format length] > 0)
+        {
+          [format appendString: @" "];
+        }
+      [format appendString: @"HH:mm"];
+      if ((elements & NSHourMinuteSecondDatePickerElementFlag)
+        == NSHourMinuteSecondDatePickerElementFlag)
+        {
+          [format appendString: @":ss"];
+        }
+    }
+  if (elements & NSTimeZoneDatePickerElementFlag)
+    {
+      [format appendString: @" zzz"];
+    }
+  if (elements & NSEraDatePickerElementFlag)
+    {
+      [format appendString: @" G"];
+    }
+
+  return format;
+}
+
+- (void) _updateDateFormat
+{
+  NSDateFormatter *formatter = (NSDateFormatter *)[self formatter];
+  NSString *template;
+  NSString *format = nil;
+
+  if (![formatter isKindOfClass: [NSDateFormatter class]])
+    {
+      return;
+    }
+
+  template = [self _dateFormatTemplate];
+  if ([template length] > 0)
+    {
+      format = [NSDateFormatter dateFormatFromTemplate: template
+                                               options: 0
+                                                locale: [formatter locale]];
+      if (format == nil)
+        {
+          format = [self _fallbackDateFormat];
+        }
+    }
+  [formatter setDateFormat: (format == nil) ? (NSString *)@"" : format];
+}
+
 - (NSColor *) backgroundColor
 {
   return _backgroundColor;
@@ -93,6 +205,7 @@ - (NSDatePickerElementFlags) datePickerElements
 - (void) setDatePickerElements: (NSDatePickerElementFlags)flags
 {
   _datePickerElements = flags;
+  [self _updateDateFormat];
 }
 
 - (NSDatePickerMode) datePickerMode
@@ -142,6 +255,25 @@ - (void) setDateValue: (NSDate *)date
   [self setObjectValue: [self _clampedDate: date]];
 }
 
+/* NSCell keeps the text its formatter made when the value was set, which is
+   stale once the elements or the locale change, and -stringForObjectValue:
+   builds that text from a %-style format rather than from the pattern.
+*/
+- (NSString *) stringValue
+{
+  NSDateFormatter *formatter = (NSDateFormatter *)[self formatter];
+  id value = [self objectValue];
+
+  if ([value isKindOfClass: [NSDate class]]
+    && [formatter isKindOfClass: [NSDateFormatter class]]
+    && [[formatter dateFormat] length] > 0)
+    {
+      return [formatter stringFromDate: (NSDate *)value];
+    }
+
+  return [super stringValue];
+}
+
 - (id) delegate
 {
   return _delegate;
@@ -170,6 +302,7 @@ - (NSLocale *) locale
 - (void) setLocale: (NSLocale *)locale
 {
   [[self formatter] setLocale: locale];
+  [self _updateDateFormat];
 }
 
 - (NSDate *) maxDate
@@ -242,6 +375,13 @@ - (id) initWithCoder: (NSCoder *)aDecoder
 {
   if ((self = [super initWithCoder: aDecoder]))
     {
+      if (![[self formatter] isKindOfClass: [NSDateFormatter class]])
+        {
+          NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
+
+          [self setFormatter: formatter];
+          RELEASE(formatter);
+        }
       if ([aDecoder allowsKeyedCoding])
         {
           [self setTimeInterval: [aDecoder decodeDoubleForKey: @"NSTimeInterval"]];

Tests/gui/NSDatePicker/display.m

@@ -0,0 +1,123 @@
+/* The text a date picker shows follows the elements it is configured with,
+   in the order and the form its locale writes them, and in its own time zone.
+   The assertions look for the parts of the date rather than a whole string,
+   so that they hold for the pattern any CLDR version produces.  A build
+   without ICU has no pattern generator and falls back to a fixed order, so
+   the one assertion that compares two locales is made only when the
+   generator answers.  The picker uses the theme and font backend, so the set
+   is skipped when the backend is unavailable.
+*/
+#include "Testing.h"
+
+#include <Foundation/NSAutoreleasePool.h>
+#include <Foundation/NSDate.h>
+#include <Foundation/NSDateFormatter.h>
+#include <Foundation/NSGeometry.h>
+#include <Foundation/NSLocale.h>
+#include <Foundation/NSString.h>
+#include <Foundation/NSTimeZone.h>
+
+#include <AppKit/NSApplication.h>
+#include <AppKit/NSDatePicker.h>
+#include <AppKit/NSDatePickerCell.h>
+
+static BOOL
+has(NSString *string, NSString *part)
+{
+  return [string rangeOfString: part].length > 0;
+}
+
+int
+main(int argc, char **argv)
+{
+  NSDatePicker *dp;
+  NSString *text;
+  NSString *american;
+  NSDate *date;
+  BOOL generator;
+
+  START_SET("NSDatePicker display")
+
+  NS_DURING
+    {
+      [NSApplication sharedApplication];
+    }
+  NS_HANDLER
+    {
+      if ([[localException name] isEqualToString: NSInternalInconsistencyException])
+        SKIP("It looks like GNUstep backend is not yet installed")
+    }
+  NS_ENDHANDLER
+
+  NS_DURING
+    {
+      generator = ([NSDateFormatter dateFormatFromTemplate: @"yMd"
+                                                   options: 0
+                                                    locale: [NSLocale localeWithLocaleIdentifier: @"en_US"]]
+                    != nil);
+
+      /* 8 March 2023, 20:26:40 GMT. */
+      date = [NSDate dateWithTimeIntervalSinceReferenceDate: 700000000.0];
+      dp = AUTORELEASE([[NSDatePicker alloc]
+        initWithFrame: NSMakeRect(0, 0, 260, 26)]);
+      [dp setLocale: [NSLocale localeWithLocaleIdentifier: @"en_US"]];
+      [dp setTimeZone: [NSTimeZone timeZoneWithName: @"GMT"]];
+      [dp setDateValue: date];
+
+      text = [[dp cell] stringValue];
+      PASS(has(text, @"2023") && has(text, @":26:") && has(text, @"40"),
+           "the default elements show the date and the time to the second");
+      PASS(!has(text, @"+0000") && ![text isEqualToString: [date description]],
+           "the shown text is not the description of the date");
+
+      [dp setDatePickerElements: NSYearMonthDayDatePickerElementFlag];
+      text = [[dp cell] stringValue];
+      PASS(has(text, @"2023") && !has(text, @":26"),
+           "the year-month-day elements drop the time");
+
+      [dp setDatePickerElements: NSHourMinuteSecondDatePickerElementFlag];
+      text = [[dp cell] stringValue];
+      PASS(has(text, @":26:") && has(text, @"40") && !has(text, @"2023"),
+           "the hour-minute-second elements drop the date");
+
+      [dp setDatePickerElements: NSHourMinuteDatePickerElementFlag];
+      text = [[dp cell] stringValue];
+      PASS(has(text, @":26") && !has(text, @":26:"),
+           "the hour-minute elements drop the seconds");
+
+      [dp setDatePickerElements: NSYearMonthDatePickerElementFlag];
+      text = [[dp cell] stringValue];
+      PASS(has(text, @"2023") && !has(text, @":"),
+           "the year-month elements drop the day and the time");
+
+      /* The time zone the picker is set to decides the hour it shows. */
+      [dp setDatePickerElements: NSHourMinuteSecondDatePickerElementFlag];
+      text = [[dp cell] stringValue];
+      [dp setTimeZone: [NSTimeZone timeZoneForSecondsFromGMT: 3600 * 5]];
+      PASS(![[[dp cell] stringValue] isEqualToString: text],
+           "the shown time follows the time zone of the picker");
+
+      [dp setTimeZone: [NSTimeZone timeZoneWithName: @"GMT"]];
+      [dp setDatePickerElements: NSYearMonthDayDatePickerElementFlag];
+      american = [[dp cell] stringValue];
+      [dp setLocale: [NSLocale localeWithLocaleIdentifier: @"de_DE"]];
+      if (generator)
+        {
+          PASS(![[[dp cell] stringValue] isEqualToString: american],
+               "the shown date follows the locale of the picker");
+        }
+    }
+  NS_HANDLER
+    {
+      if ([[localException name] isEqualToString: NSInternalInconsistencyException]
+        || [[localException name] isEqualToString: @"NSWindowServerCommunicationException"])
+        SKIP("No display available")
+      else
+        [localException raise];
+    }
+  NS_ENDHANDLER
+
+  END_SET("NSDatePicker display")
+
+  return 0;
+}