Standardized message boxes so they appear similarly on all platforms. This shafts Windows because primary/secondary text message boxes were only added in Windows Vista, but at least MSDN provides discourse.

dialog.go

@@ -2,16 +2,19 @@
 package ui
 
 import (
-	"fmt"
+	// ...
 )
 
-
 // MsgBox displays an informational message box to the user with just an OK button.
-func MsgBox(title string, textfmt string, args ...interface{}) {
+// primaryText should be a short string describing the message, and will be displayed with additional emphasis on platforms that support it.
-	msgBox(title, fmt.Sprintf(textfmt, args...))
+// secondaryText can be used to provide more information.
+// On platforms that allow for the message box window to have a title, os.Args[0] is used.
+func MsgBox(primaryText string, secondaryText string) {
+	msgBox(primaryText, secondaryText)
 }
 
 // MsgBoxError displays a message box to the user with just an OK button and an icon indicating an error.
-func MsgBoxError(title string, textfmt string, args ...interface{}) {
+// Otherwise, it behaves like MsgBox.
-	msgBoxError(title, fmt.Sprintf(textfmt, args...))
+func MsgBoxError(primaryText string, secondaryText string) {
+	msgBoxError(primaryText, secondaryText)
 }

dialog_darwin.go

@@ -26,14 +26,13 @@ var (
 	_runModal = sel_getUid("runModal")
 )
 
-func _msgBox(title string, text string, style uintptr, button0 string) {
+func _msgBox(primarytext string, secondarytext string, style uintptr, button0 string) {
 	ret := make(chan struct{})
 	defer close(ret)
 	uitask <- func() {
 		box := objc_new(_NSAlert)
-		// TODO is this appropriate for title?
+		C.objc_msgSend_id(box, _setMessageText, toNSString(primarytext))
-		C.objc_msgSend_id(box, _setMessageText, toNSString(title))
+		C.objc_msgSend_id(box, _setInformativeText, toNSString(secondarytext))
-		C.objc_msgSend_id(box, _setInformativeText, toNSString(text))
 		objc_msgSend_uint(box, _setAlertStyle, style)
 		C.objc_msgSend_id(box, _addButtonWithTitle, toNSString(button0))
 		C.objc_msgSend_noargs(box, _runModal)
@@ -42,11 +41,11 @@ func _msgBox(title string, text string, style uintptr, button0 string) {
 	<-ret
 }
 
-func msgBox(title string, text string) {
+func msgBox(primarytext string, secondarytext string) {
 	// TODO _NSInformationalAlertStyle?
-	_msgBox(title, text, _NSWarningAlertStyle, "OK")
+	_msgBox(primarytext, secondarytext, _NSWarningAlertStyle, "OK")
 }
 
-func msgBoxError(title string, text string) {
+func msgBoxError(primarytext string, secondarytext string) {
-	_msgBox(title, text, _NSCriticalAlertStyle, "OK")
+	_msgBox(primarytext, secondarytext, _NSCriticalAlertStyle, "OK")
 }

dialog_unix.go

@@ -16,15 +16,15 @@ import (
 // GtkWidget *gtkNewMsgBox(GtkMessageType type, GtkButtonsType buttons, char *title, char *text) { GtkWidget *k = gtk_message_dialog_new(NULL, GTK_DIALOG_MODAL, type, buttons, "%s", (gchar *) title); gtk_message_dialog_format_secondary_text((GtkMessageDialog *) k, "%s", (gchar *) text); return k; }
 import "C"
 
-func _msgBox(text string, title string, msgtype C.GtkMessageType, buttons C.GtkButtonsType) (result C.gint) {
+func _msgBox(primarytext string, secondarytext string, msgtype C.GtkMessageType, buttons C.GtkButtonsType) (result C.gint) {
 	ret := make(chan C.gint)
 	defer close(ret)
 	uitask <- func() {
-		ctitle := C.CString(title)
+		cprimarytext := C.CString(primarytext)
-		defer C.free(unsafe.Pointer(ctitle))
+		defer C.free(unsafe.Pointer(cprimarytext))
-		ctext := C.CString(text)
+		csecondarytext := C.CString(secondarytext)
-		defer C.free(unsafe.Pointer(ctext))
+		defer C.free(unsafe.Pointer(csecondarytext))
-		box := C.gtkNewMsgBox(msgtype, buttons, ctitle, ctext)
+		box := C.gtkNewMsgBox(msgtype, buttons, cprimarytext, csecondarytext)
 		response := C.gtk_dialog_run((*C.GtkDialog)(unsafe.Pointer(box)))
 		C.gtk_widget_destroy(box)
 		ret <- response
@@ -32,11 +32,11 @@ func _msgBox(text string, title string, msgtype C.GtkMessageType, buttons C.GtkB
 	return <-ret
 }
 
-func msgBox(title string, text string) {
+func msgBox(primarytext string, secondarytext string) {
 	// TODO add an icon?
-	_msgBox(text, title, C.GtkMessageType(C.GTK_MESSAGE_OTHER), C.GtkButtonsType(C.GTK_BUTTONS_OK))
+	_msgBox(primarytext, secondarytext, C.GtkMessageType(C.GTK_MESSAGE_OTHER), C.GtkButtonsType(C.GTK_BUTTONS_OK))
 }
 
-func msgBoxError(title string, text string) {
+func msgBoxError(primarytext string, secondarytext string) {
-	_msgBox(text, title, C.GtkMessageType(C.GTK_MESSAGE_ERROR), C.GtkButtonsType(C.GTK_BUTTONS_OK))
+	_msgBox(primarytext, secondarytext, C.GtkMessageType(C.GTK_MESSAGE_ERROR), C.GtkButtonsType(C.GTK_BUTTONS_OK))
 }

dialog_windows.go

@@ -3,6 +3,7 @@ package ui
 
 import (
 	"fmt"
+	"os"
 	"syscall"
 	"unsafe"
 )
@@ -73,23 +74,25 @@ var (
 	_messageBox = user32.NewProc("MessageBoxW")
 )
 
-func _msgBox(lpText string, lpCaption string, uType uint32) (result int) {
+func _msgBox(primarytext string, secondarytext string, uType uint32) (result int) {
+	// http://msdn.microsoft.com/en-us/library/windows/desktop/aa511267.aspx says "Use task dialogs whenever appropriate to achieve a consistent look and layout. Task dialogs require Windows Vista® or later, so they aren't suitable for earlier versions of Windows. If you must use a message box, separate the main instruction from the supplemental instruction with two line breaks."
+	text := primarytext + "\n\n" + secondarytext
 	r1, _, err := _messageBox.Call(
 		uintptr(_NULL),
-		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(lpText))),
+		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(text))),
-		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(lpCaption))),
+		uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr(os.Args[0]))),
 		uintptr(uType))
 	if r1 == 0 {		// failure
-		panic(fmt.Sprintf("error displaying message box to user: %v\nstyle: 0x%08X\ntitle: %q\ntext:\n%s", err, uType, lpCaption, lpText))
+		panic(fmt.Sprintf("error displaying message box to user: %v\nstyle: 0x%08X\ntitle: %q\ntext:\n%s", err, uType, os.Args[0], text))
 	}
 	return int(r1)
 }
 
-func msgBox(title string, text string) {
+func msgBox(primarytext string, secondarytext string) {
 	// TODO add an icon?
-	_msgBox(text, title, _MB_OK)
+	_msgBox(primarytext, secondarytext, _MB_OK)
 }
 
-func msgBoxError(title string, text string) {
+func msgBoxError(primarytext string, secondarytext string) {
-	_msgBox(text, title, _MB_OK | _MB_ICONERROR)
+	_msgBox(primarytext, secondarytext, _MB_OK | _MB_ICONERROR)
 }

test/main.go

@@ -40,7 +40,7 @@ var macCrashTest = flag.Bool("maccrash", false, "attempt crash on Mac OS X on de
 func invalidTest(c *Combobox, l *Listbox, s *Stack, g *Grid) {
 	x := func(what string ) {
 		if j := recover(); j == nil {
-			MsgBoxError("test", "%s: no panic", what)
+			MsgBoxError("test", fmt.Sprintf("%s: no panic", what))
 			panic("invalid test fail")
 		} else {
 			println("got", j.(error).Error())
@@ -200,12 +200,16 @@ mainloop:
 				lb2.Delete(4)
 			}
 		case <-b3.Clicked:
-			MsgBox("List Info",
+			f := MsgBox
-				"cb1: %d %q (len %d)\ncb2: %d %q (len %d)\nlb1: %d %q (len %d)\nlb2: %d %q (len %d)",
+			if c.Checked() {
+				f = MsgBoxError
+			}
+			f("List Info",
+				fmt.Sprintf("cb1: %d %q (len %d)\ncb2: %d %q (len %d)\nlb1: %d %q (len %d)\nlb2: %d %q (len %d)",
 				cb1.SelectedIndex(), cb1.Selection(), cb1.Len(),
 				cb2.SelectedIndex(), cb2.Selection(), cb2.Len(),
 				lb1.SelectedIndices(), lb1.Selection(), lb1.Len(),
-				lb2.SelectedIndices(), lb2.Selection(), lb2.Len())
+				lb2.SelectedIndices(), lb2.Selection(), lb2.Len()))
 		case <-incButton.Clicked:
 			prog++
 			if prog > 100 {

todo.md

@@ -22,9 +22,6 @@ so I don't forget:
 	- should message box text be selectable on all platforms or only on those that make it the default?
 - Listbox/Combobox.Index(n)
 	- Index(n) is the name used by reflect.Value; use a different one?
-- message boxes need cleanup:
-	- Windows: title: titlebar; text: message box text; no such thing as secondary text
-	- GTK+ AND Cocoa: title: message box text; text: secondary text; nothing: titlebar
 - change sysData.make() so it does not take the initial window text as an argument and instead have the respective Control/Window.make() call sysData.setText() expressly; this would allow me to remove the "no such concept of text" checks from the GTK+ and Mac OS X backends
 
 important things: