# FORMS

This version (0.83) of PgAccess has changed a little the visual form builder introduced since 0.82 version : variable handling, query results interface and control bindings naming convention. Please read it carefully, download the database demo and practice a while before trying to design your own forms.

For the moment, it has only some basic widgets : labels, entries, buttons , listboxes , checkboxes and radiobuttons.

Also there is a pseudo query widget that allows you yo have access to a query results.

How do you generate widgets :

1. select a widget from the toolbox by clicking the appropriate radiobutton
2. move to the canvas , point with the mouse at the desired location and click the mouse button to begin
3. keeping the mouse-button pressed move the mouse in order to draw a rectangle that will hold the widget
4. release the mouse-button

In the rectangle that you have designed it will appear the selected object.
Move now to the attribute window to change some of its properties.

Renaming, resizing items are possible (for the moment) only by modifying appropriate parameters in attribute window. You must press Enter in the edit field after changing a value in order to be accepted.

You can also move items by dragging them or delete them by pressing Del key after selecting them.

In attribute window, there are some fields named `Command` and `Variable`.

The field `Command` have meaning only for Button widgets and holds the command that will be invoked when the button is pressed.

The field `Variable` have meaning only for EditField , Label widgets , checkboxes and radiobuttons and it is the name of the global variable that will hold the value for that widget. For checkboxes the values are t and f (from true and false) in order to simplify binding to logical data fields (PgAccess 0.82 used 0 and 1).

For radiobuttons, it is usual to assign the same variable to the same radiobuttons within the same group. That variable will contain the name of the widget of the radiobutton that has been pressed. Let's presume that you have entered 3 radiobuttons named red, green and blue, all of them having the same variable named color. If you will press them, they will assign their names to global variable.

In order to make a simple test, put an entry field and set it's variable to v1 and a button who's command is "set v1 whisky". Press the button "Test form" and click on the button. In that entry should appear whisky.
Another test is defining in Script module a script called "My first script" having the following commands:
`tk_messageBox -title Warning -message "This is my first message!"`
and then define a button who's command is `execute_script "My first script"`.

## Database manipulation

Let's presume that our form have the internal name `mf` (my form). He will be referred inside the Tcl/Tk source as `.mf`
If you want to close the form in run-time you have to issue the command `destroy .mf`

Also, any widget will have the name prefixed by `.mf` We will have `.mf.button1` or `.mf.listbox1` .

We can name the query widget `qry` for example. The complete name will be `.mf.qry` then.
The `Command` property of the query widget must contain the SQL command that will be executed.
When the form will be in run-time, automatically you will have access to the following procedures and functions :

`.mf.qry:open` - opens the connection and execute the query (returns nothing)
`.mf.qry:setsql newsql` - set the command query that will be executed at the next `.mf.qry:open`
`.mf.qry:nrecords` - returns the number of records in the selected query
`.mf.qry:crtrecord` - returns the current record number inside the query result
`.mf.qry:fields` - returns a list of the fields in the result set
`.mf.qry:movefirst` - move the cursor to the first record in the recordset
`.mf.qry:movelast``, .mf.qry:movenext , .mf.qry:moveprevious` - moves the cursor there
`.mf.qry:moveto newrecno` - move the cursor to that new record number (first is 0)
`.mf.qry:updatecontrols` - update the variables inside the designed form that have a particular name (I'll explain later)
`.mf.qry:clearcontrols` - clear the variables inside the designed form binded to a query result
`.mf.qry:fill listbox field``` - fill the named listbox (whole widget name as `.mf.listbox1`) with the all the values of that field in the current queryresult
`.mf.qry:close` - close the connection (if you don't close the query result, you will loose some memory)

It's no need to close a query-result if you want to assign it a new SQL command and open it again. That will be done automatically.

If you want to bound some controls to the fields of the recordset, you will have to name their associate variable like that :

`mfqry(salary)` to get the "salary" field , or `mfqry(name)` to get the "name" field. So, you take the internal name of the form (without the leading point) and merge it with the query-widget name and you will get a associative array name. The values are given using the field name as a key in this associative array.
* WARNING * The naming style has been changed from 0.82 version of PgAccess and I cannot guarantee that it not be changed again in the future. I'm just trying to make it as simple it could be. The old style naming convention had some incompatibilities with Tcl/Tk syntax.

QUESTION : Do you think that it would be more clear if the above functions and procedures regarding a query-widget would be named in a similar manner as binded variable controls ? That mean, `mfqry:open` and `mfqry:updatecontrols` instead of `.mf.qry:open` and `.mf.qry:updatecontrols` ?

The only advantage of `.mf.qry:open` is that is much closer to the Tk method of referring objects within a window and it may give to the programmer the feeling that he is using a object-oriented widget. Since I cannot use further for naming binded variables a similar manner (`.mf.qry.salary)` it might be possible to abandon that naming convention .

Here it is a dumped sample database that contains a demo database. What should you do ?
Shift-click the above URL in order to download that tiny file (4 Kb). Create a empty database and `psql yourdatabase <formdemo.sql`

You should find a single table called "phonebook" a form called "Phone book" and another "A simple demo form".

First of all enter and view the phonebook table in table view. Note the fields and their values.
Open the "Phone book" form and enter a letter (a, e or i) in the field to the left of "Find" button then press Find. It's fine to enter one letter in order to get more records in query result. You will get information about the number of records selected, in the listbox you will see all the values of field "name" from the current data set. Use buttons to move to first, next, previous or last record within the record set.

In order to add a new record, press the "New" button in order to get new, clean entries. Fill them with your data and press "Add new" button. A new phonebook record will be added. Also, if you want to update a record, change it's values in the displayed fields after finding it and press "Update" button. The values will be updated in the database BUT NOT IN THE CURRENT QUERY RESULT . If you want to see them modified, make a new query trying to find it again.

Before using the results from a query you should know that the information that has been retrieved could be found only in your computer client memory. It has no live connection to the data from the database. That's why it isn't possible to develop a simple update function as interface to that query-result widget. More than that : a query result could be obtained from a SQL command that return a non-updatable data set !!! For example fields gathered from multiple tables or summary fields. It isn't just simple to make an automatic update procedure. The programmer must know how to make the update or the append procedure, sometimes using key fields to point to the desired record or an OID. There are examples in the demo database in "Phone book" form. It may be possible that in the future, I will develop another pseudo-widget describing a table. It would be more simple than to implement an update or append or even a delete procedure.

There is in the demo database also another simple form called "A simple demo form". It will show you how to handle variables from checkboxes, radiobuttons, how to use listboxes, open another forms and so on. I think they will help you.

In order to avoid naming user defined forms with a particular name of another PgAccess form, I would recommend naming them as udf0, udf1 (user defined form 0 , 1 )

Please feel free to send me your opinion at teo@flex.ro on forms designing and usage.

KEEP IN MIND ! THE FORM API WILL CHANGE IN ORDER TO BE MORE SIMPLE AND BETTER! SEND ME YOUR WISHES, YOUR IDEAS, YOUR OPINIONS !
ALSO ... DON'T BLAME ME IF YOU WILL HAVE TO RE-DESIGN YOUR OLD FORMS DUE TO SOME INCOMPATIBILITIES WITH NEWER PGACCESS VERSIONS.