andlabs-ui/dialog_windows.go

// 7 february 2014

package ui

import (
	"fmt"
	"os"
)

var (
	_messageBox = user32.NewProc("MessageBoxW")
)

func _msgBox(parent *Window, primarytext string, secondarytext string, uType uint32) (result chan 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
	if secondarytext != "" {
		text += "\n\n" + secondarytext
	}
	ptext := toUTF16(text)
	ptitle := toUTF16(os.Args[0])
	parenthwnd := _HWND(_NULL)
	if parent != dialogWindow {
		parenthwnd = parent.sysData.hwnd
		uType |= _MB_APPLMODAL // only for this window
	} else {
		uType |= _MB_TASKMODAL // make modal to every window in the program (they're all windows of the uitask, which is a single thread)
	}
	retchan := make(chan int)
	go func() {
		ret := make(chan int)
		defer close(ret)
		uitask <- func() {
			r1, _, err := _messageBox.Call(
				uintptr(parenthwnd),
				utf16ToArg(ptext),
				utf16ToArg(ptitle),
				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, os.Args[0], text))
			}
			ret <- int(r1)		// so as to not hang up uitask
		}
		retchan <- <-ret
	}()
	return retchan
}

func (w *Window) msgBox(primarytext string, secondarytext string) (done chan struct{}) {
	done = make(chan struct{})
	go func() {
		<-_msgBox(w, primarytext, secondarytext, _MB_OK)
		done <- struct{}{}
	}()
	return done
}

func (w *Window) msgBoxError(primarytext string, secondarytext string) (done chan struct{}) {
	done = make(chan struct{})
	go func() {
		<-_msgBox(w, primarytext, secondarytext, _MB_OK|_MB_ICONERROR)
		done <- struct{}{}
	}()
	return done
}