Wiki page about pgAdmin Internals

A few days ago, create a wiki page about pgAdmin internals, it's only a stub right now, but I want this page become a quick introduction guide for all new developers at pgAdmin.

Wiki it's located at:

http://wiki.postgresql.org/wiki/PgAdmin_Internals

Studying Cross-Platform GUI Programming with wxWidgets

This last two weeks I have been learning all about wxWidgets library, but until a few days ago I discover this wonderful book:

Cross-Platform GUI Programming with wxWidgets

This book is available from several sources like amazon, informit and others but in my country (Venezuela) there is a limit in a year (400$ a year) for internet buying (using foreing currency as $), and I already reached my limit, because this I only have access to sample chapter, but I found a wonderful thing:

If I do click in downloads there is available the full version of the book in pdf for free, this is great, and I'm going to use it in this way for this year, but the next year (the limit is for each year) I'm going to buy it to support the authors of the book.

Don't worry book is free because it's part of Bruce Perens' Open Source Series:

http://www.informit.com/imprint/series_detail.aspx?ser=335494

In this series the electronic versions will be made available at no cost several months after each book's publication.

;)

Here it's the full download url:

http://www.informit.com/content/images/0131473816/downloads/0131473816_book.pdf

Update #1: Other useful book found: "Subversion Version Control: Using the Subversion Version Control System in Development Projects"
url: http://www.informit.com/store/product.aspx?isbn=0131855182 [Downloads Area]

WxOGL vs WxDC vs WxArt2D

This Week I was working in the graphical part of the Query Builder and search for all possible options to implement it using wxWidgets, as part of my research I found only three probably options (there are more options but only take in count this by now) where I run and write some test application for evaluation purposes:


1. WxArt2D: is a graphical library for 2D, the drawing document can be made hierarchical by adding child primitives to a parent primitive, everything that is drawn from within a document, is done by calling drawing methods via a a2dCanvasView through it's device context a2dDrawer2D. A document can have several views open at the same time. And each view can display whatever part of the document. Source: http://wiki.wxwidgets.org/WxArt2d

Pros:

• It's a multi-document framework.
• Can draw complex objects in a easy way.
• Can exists several views of objects in hierarchy.
• Can save image to svg format.
• Allow to handled events in graphical objects.
• It's Highly optimized.
• Good community support.
  

Cons:

• The only way to use it, is downloading directly from CVS.
• Configuration, Compilation and use can be difficult for begginners because cmake haven't a useful way of explain errors and their solutions (even the simplest).
• Adds a new level of complexity in a project when the learning curve of understanding of source code grows because use it.
• If a error related to the library is raised when you use an application (that happens to me with the examples) only have two options: fix by myself (I don't want to do it ) or ask for help (can take long time).
• I try a demo of electronic parts diagram and I catch a lot of problems and exceptions only testing, without really using it, this don't give me a good advice about stability.

2. WxOGL: it's a good graphical library written when dinosaurs ruled the world :), but in my own words is a very good objects graphical library written in C++ that allow to create some simple and complex objects given to it the possibility of add events & properties.

Pros:

• Very easy to use.
• Configuration and use is very simple.
• Used by pgAdmin right now, not new dependencies needed.
• Good Stability.

Cons:

• Poor documented.
• Doesn't have support of a community.
• Development status dead.
• Don't give all control I want from my graphical objects.
• Library is not good for and architectural pattern like Model View Controller (MVC).
• Adds an extra overhead for simple graphics needed, forcing to create complex objects that some times are not needed.
• Use wxDC as their drawing method, not really a cons but an interesting afirmation.

3. WxDC: device context graphic library, allows you to draw stuff manually.

Pros:

• Have a lot of flavors: wxPaintDC for paint events, wxClientDC can be used outside paint events, wxBufferedDC for flickerless Drawing, Can paint into postscript files with wxPostScriptDC .
• Give all control to implement the design pattern that I want to use (MVC).
• It's very stable because their operations are very simple.
• Allow full control over the way stuff will be painted.
• Very simple to learn and use.
• It's integrated with the wxWidgets library not need aditional steps or configurations.
• Because their simplicity and integration with wx library, it's most probably don't have any issues when compiling source code in different plataforms
• Very well documented WxWidgets Book Chapter Sample
  

Cons:

• It's not as powerful as WxArt2D or WxOGL.
• All drawing stuff are now responsability of programmer.
• A bad implementation of drawing maybe can finish with a buggy application.
• A functional application can take a little more time (not too much) to be completed that using WxOGL or WxArt2D.

My Choice until now it's: WxDC because their simplicity and the full control that give to programmer of doing almost all things needed for a graphical query builder only using graphics primitives (in a pattern like MVC).

I create a very little (and not optimized or good programmed, just functional) hello graphic world proof of concept for a diagram of tables, you can drag and drop tables (just simple squares with text) around application only:

#include "wx/wxprec.h"

#ifdef __BORLANDC__
#pragma hdrstop
#endif

#ifndef WX_PRECOMP
#endif

#include "wx/wx.h"

class MyApp: public wxApp
{
virtual bool OnInit();
};


IMPLEMENT_APP(MyApp)



class MyFrame: public wxFrame
{
public:

MyFrame(const wxString& title,
const wxPoint& pos, const wxSize& size);

void OnQuit(wxCommandEvent& event);
void OnAbout(wxCommandEvent& event);
void MyFrame::OnPaint(wxPaintEvent& event);
void MyFrame::OnMotion(wxMouseEvent& event);
wxRect rectToDraw;
wxRect rectToDraw2;
int xx, xx2;
int yy, yy2;
int pressed;
DECLARE_EVENT_TABLE()
};


bool MyApp::OnInit()
{
MyFrame *frame = new MyFrame( wxT("Hello World"),
wxPoint(50,50), wxSize(800,600) );
frame->Show(TRUE);
SetTopWindow(frame);
frame->xx=10;
frame->yy=10;
frame->xx2=35;
frame->yy2=35;
frame->pressed=0;
return TRUE;
}


enum
{
ID_Quit = 1,
ID_About = 0,

};

BEGIN_EVENT_TABLE(MyFrame, wxFrame)
EVT_MENU(ID_Quit, MyFrame::OnQuit)
EVT_MENU(ID_About, MyFrame::OnAbout)
EVT_PAINT(MyFrame::OnPaint)
EVT_MOTION(MyFrame::OnMotion)
EVT_LEFT_DOWN(MyFrame::OnMotion)
EVT_LEFT_UP(MyFrame::OnMotion)
END_EVENT_TABLE()



void MyFrame::OnPaint(wxPaintEvent& event)
{
wxPaintDC dc(this);
dc.SetPen(*wxBLACK_PEN);

wxRect tmp(wxPoint(xx, yy), wxSize(70,70));
rectToDraw = tmp;

wxRect tmp2(wxPoint(xx2, yy2), wxSize(70,70));
rectToDraw2 = tmp2;
//Do not draw if not exposed
if (IsExposed(rectToDraw)){
//draw object 1
dc.SetBrush(*wxBLUE_BRUSH);
dc.DrawRectangle(rectToDraw);
dc.DrawText(wxT("Table 1"),xx,yy);
dc.DrawText(wxT("Col1"),xx,yy+12); //use font metrics here
//draw object 2
dc.SetBrush(*wxWHITE_BRUSH);
dc.DrawRectangle(rectToDraw2);
dc.DrawText(wxT("Table 2"),xx2,yy2);
dc.DrawText(wxT("Col1"),xx2,yy2+12);
}
}


MyFrame::MyFrame(const wxString& title,
const wxPoint& pos, const wxSize& size)
: wxFrame((wxFrame *)NULL, -1, title, pos, size)
{
wxMenu *menuFile = new wxMenu;
menuFile->Append( ID_About, wxT("&About..." ));
menuFile->AppendSeparator();
menuFile->Append( ID_Quit, wxT("E&xit" ));

wxMenuBar *menuBar = new wxMenuBar;
menuBar->Append( menuFile, wxT("&File") );

SetMenuBar( menuBar );

CreateStatusBar();
SetStatusText( wxT("Proof of Concept drawing moving objects, just click one and drag & drop [flicker can be eliminated with buffering]") );
}


void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
{
Close(TRUE);
}

void MyFrame::OnAbout(wxCommandEvent& WXUNUSED(event))
{

wxMessageBox(wxT("This is a Hello Direct Contex Application in wxWidgets"),
wxT("About Hello DC"), wxOK | wxICON_INFORMATION, this);
}


//Change position of objects when mouse is dragged & refresh painting
void MyFrame::OnMotion(wxMouseEvent& event)
{
if(event.ButtonDown()&&pressed==0){
pressed=1;
}
if(event.ButtonUp()){
pressed=0;
}

if (event.Dragging())
{
wxClientDC dc(this);
wxPen pen(*wxRED, 1); // red pen of width 1
dc.SetPen(pen);
dc.DrawPoint(event.GetPosition());
dc.SetPen(wxNullPen);
int posx=event.GetPosition().x;
int posy=event.GetPosition().y;
if(pressed==1 &&( posx-xx>0 && xx+50>posx ) && (posy-yy>0 && yy+50>posy)){
pressed=2;
}else if(pressed==1 &&( posx-xx2>0 && xx2+50>posx ) && (posy-yy2>0 && yy2+50>posy)){
pressed=3;
}

if(pressed==2){
xx=posx-25;
yy=posy-25;
}else if (pressed==3){
xx2=posx-25;
yy2=posy-25;
}

this->Refresh();
}
}

Electricity Blackout

Yesterday an electricity blackout don't let me work, I go back to 1800 way of life for about nine hours (a little more), mainly because all my stuff that works with electricity don't works and the electronics that uses batteries were uncharged like my NDS or my laptop. I only learn one thing: Charge all my electronics things all days, never left without charges :(

More information can read here: Major blackout hits most regions in Venezuela
Note: Near reality but the time of blackout in my city was from 1:00 p.m. to about 10:30 p.m.


Update #1: On 01-05-2005 Another Blackout from 8:00 a.m to 4:00 p.m.
Update #2: On 04-05-2005 Again a Blackout from 7:00 p.m. to 10:00 p.m.

A week ago, I began to work on my proposal at GSoC 2008 ...

I have been a little busy, the first week after my proposal was accepted (http://wiki.postgresql.org/wiki/Gsoc08-querybuilder), my mentor it's Dave Page (http://people.planetpostgresql.org/dpage/) he contact me yet and looks like a good person, very busy but with well define goals about the proposal.

About last week, I have done not so much things as I like it, but I should improve this week and to do a better performance.

The goals of the week #1 were:
======================
0. Planning my development infrastructure with thing like blog, what wiki pages to build, etc.
1. Formatting my machine because some problems at my operative systems.

• Linux : I have 64 bits versions of ubuntu but was not stable as I want it, and because that I'm going to install 32 bits version (and try it if don't like I return to debian :) ).
  
• Win: I don't need to explain why I should format a machine with windows every certain time (1 year or less), because it's windows it just begin to do crazy things, and when this happen it's time to reinstall a fresh copy of it.

2. Installing the development environment for win / linux:

• Linux: As usual I don't have any big troubles, nothing out of common.
• Win: On this plataform :( my sad face said everything, I have installed windows vista 32 bits or probably it's should be rename to windows BUGista, I have a lot of problems, nothing works, windows said about patches that I must install, I try to install windows patches and then said me "we don't detect any application that need this patch". Well after a lot of research (because M$ is not clear in their problems with his patches), my operating system my s.o. reboot endless (a bug found about 4 months ago) but today they force you to install the update that causes that bug :( , then after install all patches, the patches solve problem partially. FINAL SOLUTION: create a need partition, install my old copy of windows XP, and then everything works fine after loosing almost 3 days trying to fix vista, which I strongly believe it's impossible. And after all this problem I read an article from M$ saying that they users wants Windows Vista.... I Want... but I Want to burn my copy of it... after a M$ refund... :)
  

3. Use a SVN client like Tortoise SVN to access pgadmin sourcecode: Done, Tortoise SVN it's a wonderful client for the M$ plataform, on Linux I use my old command line tools :)

4. Planning to do fix a bug (a very easy bug not big ones) hunting on the project.
This was my self-imposed homework, but I can do it because all problems on my development enviroment configuration, and because the bug that dave send me, cannot be reproduced by me... :( I was needing a bug but I cannot find it... Well this requiere a new point of View, I'm going to study and document part of the internal function of pgAdmin to start to get deeper into the source code.

5. I assist to an installfest at my city.

Finally my original proposal for GSoC 2008 can be located at:

http://code.google.com/soc/2008/postgres/about.html

The name it's Graphical SQL Query Builder Improvement for pgAdmin III and if you check the google map you can see my house :)