Month: May 2018

Book Review: WiX 3.6: A Developer’s Guide to Windows Installer XML by Nick Ramirez

This book was instrumental in me managing to package Dashman. It had pretty much everything I needed and most if not everything I learned from the book worked with the latest WiX 3.X.
One issue that I have with most WiX information out there is that it assumes you are working in a .Net language and using Visual Studio. I understand this is true for most WiX users but it’s not for me, as I was building a Java application. If you are in the same situation as me, I recommend reading chapter 1 and then immediately jumping to chapter 9 that explains how to use all the different parts of WiX from the command line. After that go back to chapter 2 and work yourself over to chapter 8.
I haven’t read a lot past chapter 9 because it gets into a lot of very advanced stuff that I didn’t need. I feel that a lot of computer books these days are just introductions. It’s nice to see one that goes so deep into a subject that I find myself not needing to read it, instead of wondering where’s the next more advanced book.
I wish more computer books were like this (but I do understand why they are not).

★★★★★

Buy WiX 3.6: A Developer’s Guide to Windows Installer XML in USA

Buy WiX 3.6: A Developer’s Guide to Windows Installer XML in UK

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I had to stop watching Lost in Space

I’m referring to the new series, the Netflix one. I’ve never really watched the old one but I’ve seen enough clips to know: “Danger Will Robinson”. There are several reasons why I stopped watching even though I’m starving for non-pessimistic future space science fiction.

The first one is that I don’t enjoy seeing people make obvious bad decisions. When it was the kids making bad decisions it was annoying but it made sense, they are kids after all. But when it’s adults, I can’t stand it. These are supposed to be a selection of the most intelligent and capable adults on earth, and yet, they constantly make bad decisions.

Some spoilers ahead. Stop reading here if you don’t want to be exposed to them.

For example, Maureen Robinson decided to go do an experiment with a high altitude balloon, on her own, without telling anybody, on a planet of unknown levels danger. She should have taken a few people with her and notified other people where she was going to be. This is what we do on earth when we go hiking or some other wilderness adventure. At the very least her ex-husband would have jumped into the opportunity as he’s hungry for her acceptance but also being a former military man, he’s a good asset. This almost cost her life in a very stupid way.

Ignacio Serricchio, the mechanic, not notifying everybody what happened with Dr. Smith. Judy Robinson not notifying everybody what happened with Dr. Smith. See a pattern? There’s a lot of information hoarding. When you are in a life-or-death situation in such a small community of survivals, you don’t hoard information. You share it so that if they are part of a bigger puzzle, someone can put it together.

I had to stop watching when Maureen Robinson discovered their impending doom and didn’t immediately tell everybody. I don’t know if she’ll tell them afterwards but just considering not doing was the straw that broke the camel’s back. I sort of understand keeping doom-predicting information from the general population of Earth, to avoid panic, specially if the average person can’t do anything about it. This is not the case. They are a elite, they are a small community of highly capable people that should know if they are doomed to work their asses off to solve the problem, using resources that maybe they would have been saving for the future otherwise. A future that doesn’t exist.

Oh… and electricity, physics, astrophysics and medicine are all horribly wrong. Not a little wrong, not a little exaggerated: horribly wrong.

Implementing Windows’ Restart Manager in Java

Disclaimer: I don’t know what I’m talking about, I’ve done little Win API (Win32) development and I only have a few years of Java development of which maybe 2 or 3 are developing desktop applications with JavaFX (Dashman being my first fully fledged out JavaFX app).

Disclaimer 2: I have only tested this on my own computer, running Microsoft Windows 10. I hope to soon test it in many others and over time we’ll see whether my solution was correct or not. I’ll update this blog post accordingly (or link to a newer version if necessary).

I started taking the quality of Dashman very seriously and one of the problems I found was that the running instances wouldn’t exit properly during uninstall or upgrades. And as I expected, this turned out into a head-bashing-into-brick-wall task. My solution was for a JavaFX app, but this should work for a Swing or any other kind of apps.

It all started with learning about Windows Restart Manager, something I didn’t know it even existed until a week ago. This is what allows Windows to close applications on uninstall, on reboots, etc. In the Guidelines for Applications, the crucial bit is this:

The Restart Manager queries GUI applications for shutdown by sending a WM_QUERYENDSESSION notification that has the lParam parameter set to ENDSESSION_CLOSEAPP (0x1). Applications should not shut down when they receive a WM_QUERYENDSESSION message because another application may not be ready to shut down. GUI applications should listen for the WM_QUERYENDSESSION message and return a value of TRUE if the application is prepared to shut down and restart. If no application returns a value of FALSE, the Restart Manager sends a WM_ENDSESSION message with the lParam parameter set to ENDSESSION_CLOSEAPP (0x1) and the wparam parameter set to TRUE. Applications should shut down only when they receive the WM_ENDSESSION message. The Restart Manager also sends a WM_CLOSE message for GUI applications that do not shut down on receiving WM_ENDSESSION. If any GUI application responds to a WM_QUERYENDSESSION message by returning a value of FALSE, the shutdown is canceled. However, if the shutdown is forced, the application is terminated regardless.

Simplifying it: when Windows needs your app to close, it will send a message asking if you are ready to close. Your application might respond negatively and then no application will be closed. This could happen for example if there’s some unsaved work and the app needs the consent from the user to either save or discard. This is what happens when you try to shut down your computer and Microsoft Word stops it asking whether you want to save the file or not.

After that your application can receive a message asking it to please close or telling it to close now. I’m not sure what the nuances are between these two. For Dashman I decided to just save the config and close in either of these instances.

Receiving these messages requires interfacing with Windows DLLs, for which I’m using JNA. I don’t know how JNA works, I read the code, sort-of understood it, copied and pasted it. What I think is going on is that you open the user32.dll like this:

User32 user32 = Native.loadLibrary("user32", User32.class, Collections.unmodifiableMap(options))

User32 is an interface that contains all the methods with the proper signatures to be able to call them from Java. options just makes sure we are using the Unicode version of the Win32 API calls. You can see that and all the other missing pieces on the full example at the end of the blog post.

I need a Win32 API callback that will receive the messages and actually implement the guidelines previously quoted:

StdCallLibrary.StdCallCallback proc = new StdCallLibrary.StdCallCallback() {
    public WinDef.LRESULT callback(WinDef.HWND hwnd, int uMsg, WinDef.WPARAM wParam, WinDef.LPARAM lParam) {
        if (uMsg == WM_QUERYENDSESSION && lParam.intValue() == ENDSESSION_CLOSEAPP) {
            return new WinDef.LRESULT(WIN_TRUE);
        } else if ((uMsg == WM_ENDSESSION && lParam.intValue() == ENDSESSION_CLOSEAPP && wParam.intValue() == WIN_TRUE) || uMsg == WM_CLOSE) {
            Application.exit();
            return new WinDef.LRESULT(WIN_FALSE); 
        }
        return user32.DefWindowProc(hwnd, uMsg, wParam, lParam);

    }
};

Oh! Lot’s of constants! What are they? I define them in the full example at the bottom of this post. They should be mostly self-evident what they stand for, their actual values are not that important.

Now things get tricky. Apparently Microsoft Windows send these messages to windows, not processes. Dashman can run in the tray bar, with no active window. And even if it had an active window, getting the HWND pointer for that window in JavaFX doesn’t seem trivial (I couldn’t get it to work). So, I create a size 0 invisible window to receive the message:

WinDef.HWND window = user32.CreateWindowEx(0, "STATIC", "Dashman Win32 Restart Manager Window.", WS_MINIMIZE, 0, 0, 0, 0, null, null, null, null);

Then I need to connect that window to the callback:

try {
    user32.SetWindowLongPtr(window, GWL_WNDPROC, proc);
} catch (UnsatisfiedLinkError e) {
    user32.SetWindowLong(window, GWL_WNDPROC, proc);
}

The callback is not magic though, and requires an event loop that will constantly check if there’s a message and trigger the processing when that happens:

WinUser.MSG msg = new WinUser.MSG();
while (user32.GetMessage(msg, null, 0, 0) > 0) {
   user32.TranslateMessage(msg);
   user32.DispatchMessage(msg);
}

Of course, that means you want this to run as its own daemon thread. The reason to make it a daemon thread is so that it won’t hang around preventing the JVM from exiting. 

One of my most useful sources of understanding and inspiration was the source code for Briar. I want to give credit where credit is due. I do think I spotted an issue with their source code in which they are not following the guidelines though. Also, they have a much more complex situation to handle.

And now, the full example with all my comments including links to more information explaining where all the values for constants and logic is coming from:

import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.platform.win32.WinDef;
import com.sun.jna.platform.win32.WinUser;
import com.sun.jna.win32.StdCallLibrary;
import com.sun.jna.win32.W32APIFunctionMapper;
import com.sun.jna.win32.W32APITypeMapper;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import static com.sun.jna.Library.OPTION_FUNCTION_MAPPER;
import static com.sun.jna.Library.OPTION_TYPE_MAPPER;

// Inspiration can be found at https://code.briarproject.org/akwizgran/briar
public class RestartManager {
    // https://autohotkey.com/docs/misc/SendMessageList.htm
    private static final int WM_CLOSE = 0x10; // https://msdn.microsoft.com/en-us/library/windows/desktop/ms632617
    private static final int WM_QUERYENDSESSION = 0x11; // https://msdn.microsoft.com/en-us/library/windows/desktop/aa376890
    private static final int WM_ENDSESSION = 0x16; // https://msdn.microsoft.com/en-us/library/windows/desktop/aa376889

    // https://msdn.microsoft.com/en-us/library/windows/desktop/aa376890
    // https://msdn.microsoft.com/en-us/library/windows/desktop/aa376889
    private static final int ENDSESSION_CLOSEAPP = 0x00000001;
    private static final int ENDSESSION_CRITICAL = 0x40000000;
    private static final int ENDSESSION_LOGOFF = 0x80000000;

    // https://stackoverflow.com/questions/50409858/how-do-i-return-a-boolean-as-a-windef-lresult
    private static final int WIN_FALSE = 0;
    private static final int WIN_TRUE = 1;

    // https://msdn.microsoft.com/en-us/library/windows/desktop/ms633591(v=vs.85).aspx
    private static final int GWL_WNDPROC = -4;

    // https://msdn.microsoft.com/en-us/library/windows/desktop/ms632600(v=vs.85).aspx
    private static final int WS_MINIMIZE = 0x20000000;

    public static void enable() {
        Runnable evenLoopProc = () -> {
            // Load user32.dll usi the Unicode versions of Win32 API calls
            Map options = new HashMap();
            options.put(OPTION_TYPE_MAPPER, W32APITypeMapper.UNICODE);
            options.put(OPTION_FUNCTION_MAPPER, W32APIFunctionMapper.UNICODE);
            User32 user32 = Native.loadLibrary("user32", User32.class, Collections.unmodifiableMap(options));

            // Function that handles the messages according to the Restart Manager Guidelines for Applications.
            // https://msdn.microsoft.com/en-us/library/windows/desktop/aa373651
            StdCallLibrary.StdCallCallback proc = new StdCallLibrary.StdCallCallback() {
                WinDef.LRESULT callback(WinDef.HWND hwnd, int uMsg, WinDef.WPARAM wParam, WinDef.LPARAM lParam) {
                    if (uMsg == WM_QUERYENDSESSION && lParam.intValue() == ENDSESSION_CLOSEAPP) {
                        return new WinDef.LRESULT(WIN_TRUE); // Yes, we can exit whenever you want.
                    } else if ((uMsg == WM_ENDSESSION && lParam.intValue() == ENDSESSION_CLOSEAPP
                            && wParam.intValue() == WIN_TRUE) || uMsg == WM_CLOSE) {
                        Application.exit();
                        return new WinDef.LRESULT(WIN_FALSE); // Done... don't call user32.DefWindowProc.
                    }
                    return user32.DefWindowProc(hwnd, uMsg, wParam, lParam); // Pass the message to the default window procedure

                }
            };

            // Create a native window that will receive the messages.
            WinDef.HWND window = user32.CreateWindowEx(0, "STATIC",
                    "Dashman Win32 Restart Manager Window.", WS_MINIMIZE, 0, 0, 0,
                    0, null, null, null, null);

            // Register the callback
            try {
                user32.SetWindowLongPtr(window, GWL_WNDPROC, proc); // Use SetWindowLongPtr if available (64-bit safe)
            } catch (UnsatisfiedLinkError e) {
                user32.SetWindowLong(window, GWL_WNDPROC, proc); // Use SetWindowLong if SetWindowLongPtr isn't available
            }

            // The actual event loop.
            WinUser.MSG msg = new WinUser.MSG();
            while (user32.GetMessage(msg, null, 0, 0) > 0) {
                user32.TranslateMessage(msg);
                user32.DispatchMessage(msg);
            }
        };

        Thread eventLoopThread = new Thread(evenLoopProc, "Win32 Event Loop");
        eventLoopThread.setDaemon(true); // Make the thread a daemon so it doesn't prevent Dashman from exiting.
        eventLoopThread.start();
    }

    private interface User32 extends StdCallLibrary {
        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms632680(v=vs.85).aspx
        WinDef.HWND CreateWindowEx(int dwExStyle, String lpClassName, String lpWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, WinDef.HWND hWndParent, WinDef.HMENU hMenu, WinDef.HINSTANCE hInstance, Pointer lpParam);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms633572(v=vs.85).aspx
        WinDef.LRESULT DefWindowProc(WinDef.HWND hWnd, int Msg, WinDef.WPARAM wParam, WinDef.LPARAM lParam);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms633591(v=vs.85).aspx
        WinDef.LRESULT SetWindowLong(WinDef.HWND hWnd, int nIndex, StdCallLibrary.StdCallCallback dwNewLong);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms644898(v=vs.85).aspx
        WinDef.LRESULT SetWindowLongPtr(WinDef.HWND hWnd, int nIndex, StdCallLibrary.StdCallCallback dwNewLong);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms644936(v=vs.85).aspx
        int GetMessage(WinUser.MSG lpMsg, WinDef.HWND hWnd, int wMsgFilterMin, int wMsgFilterMax);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms644955(v=vs.85).aspx
        boolean TranslateMessage(WinUser.MSG lpMsg);

        // https://msdn.microsoft.com/en-us/library/windows/desktop/ms644934(v=vs.85).aspx
        WinDef.LRESULT DispatchMessage(WinUser.MSG lpmsg);
    }
}

And now, my usual question: do you think this should be a reusable open source library? would you use it?