Saturday, May 10, 2014

(De-) Bug wars - A new hope

 "This are not the bugs you are looking for"

Well hopefully in future it will get easier to find those parts of your code, that joined the dark side.
The Lazarus Team is currently working on improving the Debugger in the IDE. And not just improving, but adding an all new shiny debugger.
In fact not just one either.

Here is what we are currently working on. In future we will offer 3 kind of debuggers in the IDE.

  1. The existing gdb based debugger: "GdbmiDebugger".
    And it's variations for gdbserver, and gdb over ssh.
    We will continue to maintain them, as they support additional targets (arm, powerppc, ...) that the new debuggers do not (or not yet) have.

  2. A gdb free debugger: "FpDebugger".
    This is still in its very early alpha stage. So far it will be for Intel targets only. And initial work concentrates on supporting Mac (which no longer comes with GDB, and urgently needs a replacement), and Windows 32 bits. But Win64 and Linux are planned too.

  3. A hybrid: "FpGdbmiDebugger".
    Like the existing GdbmiDebugger it uses GDB. In fact it inherits much of the functionality from GdbmiDebugger.
    But it will have its own routines to evaluate watches itself (without GDB). So it will be able to deal better with Pascal data. As a side effect watch evaluation will also be faster.
    Other debugging tasks, such as running or stepping the exe, and handling breakpoints are handled by the GdbmiDebugger code using GDB.

    But why this one at all?
    The same watch evaluation is available when using FpDebugger?
    Well, with FpGdbmiDebugger being GDB based, it will be easier to support more of the targets that GDB can support (like arm). It will still need some additions (e.g. a reader for arm executables, to read debug info) in order to do this. And FpGdbmiDebugger also has the potential to be extended to be gdbserver based and support remote debugging in future.

    The progress of FpGdbmiDebugger can be watched on its wiki page: FpGdbmiDebugger on our wiki.
    A page for FpDebugger does not yet exist.

The two new debuggers are developed in our SVN version (1.3). And if all goes to plan, then they will be part of Lazarus 1.4 (Probably sometime in 2015)

May Pascal live long and prosper (Oops wrong source).
May the force be with Pascal.

Sunday, August 25, 2013

Threads with Lazarus

It seems every time I use threads in a program I make, I need to lookup again how threads work. So if you're like me perhaps this will help you.

Here's a more complete tutorial to read.

Threads are a great way to do a large amount of processing in your program while allowing the visual part of your program to remain responsive. If you can split up the processing into several threads you can take advantage of modern processors multi core capability and complete a job in a fraction of the time.

Lazarus programs can use threads in GUI and Console programs. If you use threading in your program you should define the compiler option -dUseCThreads. This can be done in Project->Options->Compiler Options->Other - Custom Options. This does nothing under Windows but on any *nix it includes a needed threadmanager. If your program crashes with the first use of thread.Start; then this is probably your problem.

Now that your program is thread enabled here's some basic information about threads. You must subclass the TThread type and make your own thread type and override the Execute method.

The Execute method is never called directly in your program. It is the method the thread will run on it's own when it is started. If you are using MyThread.Execute then you are making a mistake.

Here's a basic example of a new thread type

  TFooThread = class(TThread) 
    procedure Execute; override;



procedure TFooThread.Execute;
  // do stuff 

To create an instance of your thread you can use

FooThread := TFooThread.Create(True);

The argument True creates the thread in suspended state, meaning the OS thread is created but not yet run. If you use False then the thread begins and Execute is called immediately.  You can of course make your own constructor with whatever parameters you need and use inherited Create(False) there.

To start a thread you should use FooThread.Start. FooThread.Resume is deprecated as well as .Suspend which is not reliable on *nix's and can cause your program to hang.

Now your thread is running and working and making your life easier. Your program is snappier and you decide that you need to make your program display the progress your thread is making processing some data.

So in TFooThread.Execute you add Form1.ProgressBar1.Position := SomeValue.
Bad idea. It may work or your program could immediately crash or it might cause some other harder to find error that happens later. Never ever do this.

The reason this is so bad is because the GUI part of your program is run in a separate thread (duh!) and has it's own memory area. Changing the memory in one thread from another needs to be coordinated carefully. You should never change a LCL control value from a thread other than the main process.

A way to update the main thread from another thread is the Synchronize(@SomeProc) method. The Syncronize method, which is called within a created thread, causes the thread to pause and wait for the main thread to call a procedure. Also see CritialSections from the link at the beginning of this article

When your thread terminates you should assume that any code in it's destructor may be called a thread other than your main process thread, especially if you set FreeOnTerminate to True. If you assign a handler for the OnTerminate property then that procedure will be run in the main thread.

After all the code in the Execute method is run your thread cannot be restarted. You will have to free and create another instance of the thread type you need. It's common to include while not Terminated do begin ... end around the code inside the Execute method in order to use a thread multiple times without having to recreate it.

Most of the basic stuff I have run into is now covered. Go code, or read some more: Threading Tutorial on the Wiki

Tuesday, August 28, 2012

Gtk3, GObject Introspection and Free Pascal

A while back the Gtk community started a project called GObject Introspection. In short it exports the Gtk and Glib api, as well as many others, to an easily parsed xml format.

The result is gir2pascal.

gir2pascal can create bindings to pascal from any library that supports gobject introspection in just a few moments! The result is that Gtk3 bindings have been created fairly easily for pascal and can easily be updated simply by running gir2pascal against the latest version.

Here is part of the XML code from the Gtk3.gir file relating to the caption of the button:

<class name="Button"
      <implements name="Atk.ImplementorIface"/>
      <implements name="Actionable"/>
      <implements name="Activatable"/>
      <implements name="Buildable"/>
      <constructor name="new" c:identifier="gtk_button_new">
        <return-value transfer-ownership="none">
          <type name="Widget" c:type="GtkWidget*"/>
      <method name="get_label" c:identifier="gtk_button_get_label">
        <return-value transfer-ownership="none">
          <type name="utf8" c:type="gchar*"/>
      </method>      <method name="set_label" c:identifier="gtk_button_set_label">
        <return-value transfer-ownership="none">
          <type name="none" c:type="void"/>
          <parameter name="label" transfer-ownership="none">
            <type name="utf8" c:type="gchar*"/>
      <property name="label"                construct="1"
        <type name="utf8"/>
One improvement over the current (Gtk2) bindings in use is that Pascal objects (not classes) have been used in place of records. The advantage is that GObjects, a C style quasi-object, can be accessed in an object oriented way instead of the flat C functions we use currently.

Here is the corresponding generated pascal code from the XML above:

  TGtkButton = object(TGtkBin)
    priv3: PGtkButtonPrivate; 
    function new: PGtkButton; cdecl; inline; static;
    function get_label: Pgchar; cdecl; inline;
    procedure set_label(label_: Pgchar); cdecl; inline;
    property label_: Pgchar read get_label write set_label;

function gtk_button_new: PGtkButton; cdecl; external;
function gtk_button_get_label(AButton: PGtkButton): Pgchar; cdecl; external;
procedure gtk_button_set_label(AButton: PGtkButton; label_: Pgchar); cdecl; external;


function PGtkButton; cdecl;
  Result := Gtk3.gtk_button_new();

function TGtkButton.get_label: Pgchar; cdecl;
  Result := Gtk3.gtk_button_get_label(@self);

procedure TGtkButton.set_label(label_: Pgchar); cdecl;
  Gtk3.gtk_button_set_label(@self, label_);

You can see that we are using objects instead of records, compare this to the current Gtk2 bindings:

  PGtkButton = ^TGtkButton;
  TGtkButton = record
    bin : TGtkBin;
    event_window : PGdkWindow;
    label_text : Pgchar;
    activate_timeout : guint;
    flag0 : word;

function gtk_button_new:PGtkWidget; cdecl; external gtklib;
procedure gtk_button_set_label(button:PGtkButton; _label:Pgchar); cdecl; external gtklib;
function gtk_button_get_label(button:PGtkButton):Pgchar; cdecl; external gtklib;

Before, our code would look like this:

procedure Foo;
  Button: PGtkWidget;
  Button := gtk_button_new;
  gtk_button_set_label(PGtkButton(Button), 'Hello World!');

But now it's possible to use this instead:

procedure Foo;
  Button: PGtkButton;
  Button :=;
  Button^.label_ := 'Hello World!';

As you see it's a bit shorter to type the second way. Although either will work since the 'flat' functions are still available to use.

Using objects instead of records it is of course possible to access inherited methods and properties with greater ease than before, especially when using the code completion feature of Lazarus (which is extremely close to 1.0 now!). Button in the example above descends from GtkWidget which has the property tooltip_text.

This can be accessed with
Button^.tooltip_text := 'Don''t click me unless you want to!';
whereas before you had to do
gtk_widget_set_tooltip_text(PGtkWidget(Button) ,'Don''t click me unless you want to!');  

Here's the HelloWorld example included with the bindings, modified to have a tooltip.

 The Pascal Gtk3 bindings are not yet well tested. There are a couple of examples in the Lazarus-ccr repository in the folder /bindings/gtk3/examples/ including an example of GtkWebkit.

Perhaps you would like to try it out :)

Thursday, August 2, 2012

Preparing for Lazarus 1.0 (RC1)

Just to announce: Lazarus is preparing to go 1.0.

The first release candidate for the new Version has just been made public on sourceforge. Please test it.

You can find the announcement for the RC here:,17717
And a list of what changed is here:

Friday, February 17, 2012

Pascal does a strong showing in the Linux Questions Members Choice

Of course that internet quiz is not something scientific but it is nevertheless good news. Both Pascal and Lazarus made a strong showing in the Linux Questions Annual Members Choice Awards, competing with software sponsored by huge corporations. Other software written in Lazarus also appeared in the show, such as Double Commander and LazPaint.

Let's start with Lazarus itself running against other IDEs:

And how Pascal / Object Pascal as a language fared well too (despite someone mistakenly having added it as "Free Pascal"). It is pretty hard to see because of so many multiple lines, so I added a bigger line connector, but anyone can check in the full description of the results here:

See also how Double Commander fared:

And LazPaint:

If there was a category for Accessibility probably the Virtual Magnifying Glass would appear =)

Felipe Monteiro de Carvalho

Wednesday, February 15, 2012

Exploring the iPhone

As all should know, since my previous post I managed to finish off all the missing bits and get a decent initial support for Android in the LCL. But of course we are not stopping there, so I started exploring the iPhone. I haven't yet done any programming, but I already found a lot of interesting thing. Many good things, but also many bad things.

So let's start with the good things:

I was expecting something similar to Android, just more expensive, but while the user interface is remarkably similar, I must say that Apple has an extremely good taste for designing things. Everything in the iPhone is just beautiful. Each small detail seams well though out to look good, while in Android everything exists in a similar shape, it just looks OK in Android while it look great in the iPhone. Sure that some manufacturer like HTC and Sony Ericsson changes radically the user interface and even UI widgetset look, but in all cases they don't come close to looking as good as the iPhone.

The available RAM in the iPhone is pretty excellent. The iPhone 4 comes with 512MB of RAM of which aprox. 300MB are free for user applications. That's a huge amount in comparison to Android devices where you might even have 300MB or RAM, but the system is already eating 250MB =( The iPhone is also free of all that crapware which manufacturers like to fill the scarce ROM memory of Android phones, and the iPhone has a huge common memory for both media files and applications, which makes it able to run bigger apps without problems.

Now some things which are different:

The start screen is nearly identical with horizontal scrolling except that the iPhone home screen is much less configurable. You cannot place those nice widgetset to turn on/off mobile network or WiFi on a single click. The iPhone is also not very intuitive to use at times, with only icons and no perceived way for me to find out what an icon does except by guessing or testing, while in Android text labels are used much more often. There are no hints either.

And now the bad:

Frankly I am appalled that I have never heard of the evil side of the iPhone before. Why is nobody commenting that?? Am I the only one deeply bothered by this!? For me this was so terrible that I will never buy an iPhone again, for sure my next smartphone will be Android again. The iPhone is just the most restricted device, the most DRM filled, the most anti-freedom, the most monopolist, the most anti file owning device I have seen in my life. Let's start with the basic. On Android you put a SDCard in the phone and then you connect it with a USB cable to the computer and voilà! It opens as a mass media device with zero drivers installation in *any* operating system. Windows, Linux, Mac, works just as great in all! Then you can copy your music there, copy APK packages, you can copy your personal documents, you can copy source code, I don't know, you can do whatever you want! Sadly Android doesn't come with a File Browser but you can easily install the "OI File Browser" and then with it you see all your files on the phone and manage them. You can install any app to read your files. You can use the phone as a pen drive, you can create a new application to open, view and modify any file extension in the world and share that application. You can share your files. That's freedom! That's general computing! The freedom that any computer should offer.

And the iPhone!? Where are the file managers? I haven't yet found a single one which will show my photos, movies and music. WTF!?!? There are some file managers which require installing extra programs in the desktop and essentially are a sort of hack around the limitations imposed by Apple. Is music just a product you consume from bigshot producers? Can you even run you own music there? Where is my freedom to run my MP3 which I generated myself from a CD I bought in Paraguay? Those guys are not in the iTunes Mr. Jobs and I don't want to restrict myself to your iWorld. Cloud storage as an extra option, OK, but ban file owning, copying and sharing!? That's the evil dream of any monopolist. I don't want to be part of that evil iWorld, I want a general computer. But that's what the iPhone certainly does not want to be.

So, well, let's say you are conformed with the iPhone having zero file owning capabilities. What's next? It only docks to your computer via the iTunes after installing a plethora of drivers and does not work at all in Linux. You cannot freely install applications which you wrote yourself without joining the Apple Developer Program and go through a complicated process. In Android you can write apps and share them easily without any of this non-sense.

And to make it worse: Apple is monopolistic. It banned 3rd party browsers. Where is the freedom? I don't want to be stuck with Safari. I already like Opera Mobile, but they banned it. Sure there is Opera Mini, but Mobile is much more what I want.

So here we are: A superb phone, the best looking GUI and design I have ever seen. Excellent quality of the touch screen. All ruined by monopolistic, anti-freedom non-sense! All ruined by a company which wants to ban people from owning files.

Felipe Monteiro de Carvalho

Friday, November 25, 2011

LCL for Android

As the maintainer of LCL-WinCE of course I was quite shocked when Microsoft dropped Windows Mobile into the limbo and announced that native applications would be restricted to a very small list of favorite partners. Because of this, since almost 1 year now I have been trying to port the LCL for Android.

My first success was in 19th January 2011 when I first built a good x86-linux -> arm-linux cross-compiler which I have been using ever since and I hosted here:

After that I slowly started exploring Android and the SDK with many pauses. My free time floats a lot depending on the work load, my mood and my current interests. I have other hobbies which alternate as my biggest interest from time to time. The most important ones are: trains (reading news and discussing in skyscrapercity as well as travelling), politics (I'm right wing / conservative), keyboard playing and Pascal programming.

Ok, so next thing around in August I got some bounties which motivated me to make a good push. When I started we were in Android 2.2 still, and I bought a HTC Wildfire which came with 2.1 and can be upgraded only up to 2.2. At this time the perspectives for native applications were quite doomed, you had to interface with Java via the horrible JNI, I got pissed off by that and I developed an alternative system which worked by running a native executable and communicating with pipes with a Java machine. I posted about it in the android-ndk Google group and the Google guys hated my idea, they told me to buy and iPhone and try programming for that instead =D Well, I could do that, but seriously the Lazarus community is on a high mood for Android support, I don't remember yet anyone asking about iPhone support ... even requests of WebOS and Bada were heard. My hacky development strategy might sound like a bad idea, but I had many motivators for it:
1> If you can only have a library then the way LCL applications work changes dramatically =( I'm not sure yet how this will be worked around. You cannot keep the same main project file if Android requires a library and you also need changes in the project code flow.
2> FPC has a lot more bugs for library development then for executable development, specially in ARM-Linux
3> Using my method I could access the entire SDK without JNI! A true blessing. So I could quickly push some controls and get things working.
4> I also hoped that if people pushed then Google would flexibilize and support executables, but now I think I was too optimistic. At that time Android 2.3 was released and it brought a lot of improvements for native applications, but ever since there were very few changes in the NDK, so I lost my hope that Google would support native executables.

The alternative way would be creating a native library which draws all controls, and there are enourmous challanges in doing this. So, fast forwarding a bit into the future, after a bounty I got some expertise in NDK development with OpenGL so I got quite animated and I started a huge push to see how far I can push LCL-CustomDrawn until I run out of steam.

These days I feel like soldiers must have felt in the Market Garden operation, running against time to take all bridges in the way. I am not trying to consolidate the entire area, I just need to make as many breakthroughs as possible in as many key areas as possible to make sure that my development strategy works. Every time that we start doing something which was never done before, like LCL in Android you have a huge uncertainty about whether or not it will actually be possible to work, or if I will face a huge wall somewhere, like a compiler bug or a problem which needs a lot more steam then I got to solve ... so I want to clear the way and establish that my strategy indeed will work.

So far I have already taken the following bridges:

1> Lazarus Custom Drawn Controls - The first one to be tackled, it is far from complete, but I advanced it so well and so fast that it is clearly proven that we can have our own set of custom drawn controls inside Lazarus


2> Developing the major structure of LCL-CustomDrawn to allow painting with a non-native Canvas into a native surface. I already implemented this for Win32, X11 and Cocoa, so we are quite advanced here.

3> Develop a system to clip the painting of sub-controls and also clip events from sub-controls inside a form. In LCL-CustomDrawn TWinControl will be non-native, because some platforms like the Android surface do not support it. I have achieved success here too.

Now I am trying to push into a last bridge, which is resisting heavily:

4> Achieving a minimal LCL-CustomDrawn application which can run in Android and paint at least a rectangle or something.

I am facing big challanges in this task, the major ones being that when I simply include the LCL the application starts to crash, even if I don't call anything from it =( I have narrowed down to cwstrings, which is a major source of crashes, so I disabled it, but now the application crashes when clicking on it. I tryed to comment out all initialization sections in the LCL, but it didn't help. My greatest fear is a compiler bug somewhere which would reproduce only in big programs like LCL apps and stop me =( But so far it appears that I am going well, let's hope we will succeed here and clear 1 more obstacle in this difficult road.

Edit: I managed to get it working now, the second problem was introduced while debugging the cwstring issue. Now it works fine =) So we are each day closer to have LCL-CustomDrawn running in Android. From what I can see my snapshot compiler has no bug which could defeat us, so the path is ready =)

Edit2: Now it loads the application and it can draw some green stuff =D Really exciting days for LCL-CustomDrawn-Android. It still doesn't do anything useful, but the entire fact that it loads without crashing and can render something is excellent.