GNUe Traffic #112 For 17 Apr 

Editor: Peter Sullivan

By Peter Sullivan

Table Of Contents

• Standard Format
• Text Format
• XML Source
• Introduction
• Threads Covered

  1.	12 Apr		Designer for Forms and Application Server
  2.	12 Apr  - 14 Apr		Requerying on a commit in Forms
  3.	13 Apr		Menu tags and triggers within Forms
  4.	13 Apr		Forms approaching version 1.0?
  5.	14 Apr  - 15 Apr		Trigger namespace in Forms

Introduction

1. Designer for Forms and Application Server

12 Apr  Archive Link: "[IRC] 12 Apr 2006"

Summary By Peter Sullivan

Topics: Designer, Forms, Application Server

People: Jan Ischebeck, Jason Cater

Jan Ischebeck (siesel) asked "how is designer improving?" Jason Cater (jcater) said "it requires wx2.6 now - so the first change was getting it stable on 2.6. Then I stopped using GNUe Form's ui drivers to draw widgets in real-time on the layout canvas - I now draw my own objects on my own canvas object - this gave me a tremendous amount of control over the canvas - so things "just work" on it now - like rubberband boxes, etc. I also reworked the property editor - which as it turns out - was solely responsible for the 2+ second delay between clicking on a widget, and having designer actually select that widget. Actually, that will be the extent of the changes before I declare designer "stable" again - but there's a lot of under the hood cleaning (comments, better variable naming, etc)" .

Jan said that he was "thinking how to enable designer to create appserver designs" , alongside its current role as a designer for Forms and Reports. Jason said he definantly wanted "to tackle that after I get forms support stable again" but he had not given much thought to how an Appserver Designer would actually work yet - it needed to be a tool for end users who were not programmers but who understood the business process they were trying to model.

For the current (Forms-related) version of Designer, Jason was "not *that* far away from wanting alpha testers - if I can get in a couple of solid days of programming, I think it'd be where I want it at" .

2. Requerying on a commit in Forms

12 Apr  - 14 Apr  Archive Link: "[IRC] 12 Apr 2006"

Summary By Peter Sullivan

Topics: Forms

People: Reinhard Müller, Jason Cater, James Thompson, Bajusz Tamás

Referring back to Issue #111, Section #2  (5 Apr : Behaviour of Clear button) , Reinhard Müller (reinhard) noted the consensus that "it would be logical if after a commit the complete result set would be queried again" , but added several further issues: "1. actually the starting point was the "undo" function (that we came up with a different name afterwards), that this function should do the query again - it was me who extrapolated that to the commit - is this really desired to after commit see changes done by different users? and 2. doing the complete query again after commit would mean newly inserted records being sorted to the place they belong instead of the place they were originally inserted, so it would look to the user as if the record "jumped" to a different place" . Also, "3. what about those records that were inserted or changed in a way that they don't match the query? would they disappear after the commit?" .

Jason Cater (jcater) noted that "the last query is already saved" since "if you press the "Query" button twice, the previous query is brought back up" , so users could re-run the query manually to see what had changed if they wanted to. On the more general issue, "my personal feeling is in several key forms, my users will get disoriented if the resultset changes on them - but I can see where it would be useful/desirable too. Certainly it wouldn't be hard to add a requery-on-commit attribute to datasources or blocks (is there not one now?). But even then, the question becomes "what is the default?"" .

James Thompson (jamest) said "what's the advantage to the requery of the whole result set? (other than it would make our record tracking and removal code go away :)" But Jason was not sure of this last point - "as even on requery, wouldn't you want it to still try to make a best-effort to go back to the same record" ? Reinhard said that the "advantage would be that you see other records that other users have added meanwhile - or changes from other users - (current requery logic only requeries those records that had changes on commit)" . James wondered "if that shouldn't be a separate feature - like in postgresql's case it allows you to register for notifications of table updates" .

Reinhard was "also interested in what you think about this "revert" function: should it revert to the original state of the db, or should it fetch changes from other transactions? I think new records popping up on revert might not disorient as much as it would on commit" but worried "*sigh* why does it happen so often that I start implementing something and after that, I find out that I'm not even sure what exactly I want to implement..." ..

Two days later (http://www.gnuenterprise.org/irc-logs/gnue-public.log.2006-04-14) , Bajusz Tamás (btami) explained that some of his users were having problems adjusting to using a legacy application, now translated to use GNUe Forms, because of the behaviour of the 'Clear' button. The 'clear' button threw away all changes since the last commit, not just on the current record. Also, it did not re-query the data, leaving the user looking at a blank form. Reinhard Müller (reinhard) noted that "both issues are actually related to the "undo" function, and not to commit in any way" . This meant that the behaviour of commit could stay as it was as of time of writing, avoiding some of the potential problems previously discussed. The main outstanding issue was whether the 'undo' function should "revert to the state of the result set before any change was made - or should it refresh data from the backend - risking that, for example, the current record suddenly disappears because another user has just deleted it - or records "jumping around" because somebody changed a record in a way relevant for the sort order" .

3. Menu tags and triggers within Forms

13 Apr  Archive Link: "[IRC] 13 Apr 2006"

Summary By Peter Sullivan

Topics: Forms

People: Reinhard Müller, James Thompson, Jason Cater

Reinhard Müller (reinhard) noted that the <menu> tag "seems to fulfill both fuctions: menu and menuitem - is that on purpose?" James Thompson (jamest) confessed "not a lot was done in menus beyond playing around - there is a pretty complete dynamic menu system in designer fwiw - that I was going to rip out and put into common to replace the stuff started there" . Reinhard looked at this, and noted that it "seems to deal with the UI creation for the menu - which leads to the question - does the menu handling actually belong to common or to forms?" James thought that "the toolbar and menu logic for setting up menus belongs in common" , or even in his new, proposed, GNUe Application Platform (GAP), as discussed in Issue #109, Section #5  (27 Mar : GNUe Application Platform to replace Navigator?) - "as it should be the same code in all our gui apps" . It had been a while since he had looked at this code, but "i think the addFoo methods built a in memory representation of a menu - and then the finialize method mapped it to the UI widget set. what I was hoping for in common was a set of classes/methods that let us build a logical menu in memory" . Just like a GNUe form definition, this would not be specific to any particular user interface. The idea would be that "the UI would register to listen for menu update events" , thus completely isolating the menu logic from whatever user interface the user happened to be using.

Reinhard asked whether this would also apply to the 'standard' menu items that were actually part of the base Forms application, as well as to additional menu items defined by a forms developer. James thought so - this would mean that "1) a form could extend a menu or remove items or hide them via startup triggers - 2) it may be possible for an application like navigator to adjust it's menu dynamically based upon the forms loaded in memory" . Reinhard understood - the issue then was whether to implement this as UI events or as function calls by the menu code - "my experience so far is that events add complexity and eat performance" . James agreed, and although he had been thinking originally in terms of events, could see no reason not to do this as function calls instead.

Reinhard liked James' idea of allowing triggers to be switched on and off. Jason Cater (jcater) wondered what should then happen "if a disabled trigger is called - does it just not run? - throw an exception?" He felt the latter option might be better - it represented "a developer error" . James suggested "you could flip optional processing on/off via a checkbox on a form via a trigger disabling another named trigger" . Reinhard felt this was bad style - it was better to keep the trigger active, but make it "check the value of the check box in the trigger code" and simply do nothing if that was what was required.

Later, Reinhard added "the more I think about menus and toolbars, the more I see them bound rather tightly to triggers - they will fire triggers, they will follow trigger's enabling/disabling ... they might even get label and help text from triggers (so a menu item and its corresponding toolbar button will get the same label/tooltip). So I'm starting to think if implementation of GMenu, GMenuItem and GToolButton would feel well in the logic/ subdirectory" . Jason noted that "fwiw, this is how designer does it - and how I was moving forms to do it" . And user interface systems such as QT did something similar - "except they all have "Events" instead of "Triggers"" - "so I think having one object that represents any type of such "action" makes sense" . This would also automatically handle the different ways of selecting something in a typical graphical user interface - pressing a hot key, selecting a menu option or clicking a toolbar icon "are all the same object - my only concern is are we overloading triggers too much" . In particular, all of the GNUe Tools had the concept of triggers, but this more specific use of them "for the menu/toolbar/ui stuff" really only made sense in "forms (and maybe navigator)" .

Jason and Reinhard swapped some sample XML to try to clarify what they each meant. Jason suggested "what I now wish we had done (and might could still do without any breakage)" was that triggers could just be stand-alone pieces of python code with a name, which could be called either by another trigger bound to an object (what GNUe had, up until now, considered a trigger) or called by an action. This would simplify Reinhard's suggested treatment of menu items, in that these would just be a specific type of action.

Reinhard set out the options - either "a) a menu item has an ON-ACTIVATE trigger that is fired when the item is clicked, and that trigger is just a trigger like all other triggers, or b) there are <action>s, and a menu item is bound to an action, and gets info like icon, label, help text from that action element, and an action is, while in implementation closely related to a trigger, something completely different in philosophy. The more I think about it the more it seems to me these are diametral concepts." . Jason liked this second option - "it seems like a clean distiction as far as the definition of our markup" .

4. Forms approaching version 1.0?

13 Apr  Archive Link: "[IRC] 13 Apr 2006"

Summary By Peter Sullivan

Topics: Forms

People: Jason Cater, Reinhard Müller

Jason Cater (jcater) asked "how far are we featurewise from considering a 1.0 release" for GNUe Forms. "I only ask because I see so many projects where our 0.6 is comparable to their 1.6 or even 2.6" . This made no difference to him, but it maybe affected others' willingness to use GNUe. Reinhard Müller (reinhard) said "there is one psychological thing here for me - as long as we are 0.x I feel like having the right to break compatibility - as soon as we are 1.0 I think we morally have the obligation to stay compatible with every single feature or misfeature that is in the code. I seriously would like to see a 0.9 or comparable being in use for > 6 months without much happening - so we know it's stable enough" , both in terms of bugs and in terms of not needing new features that would break backward-compatability.

5. Trigger namespace in Forms

14 Apr  - 15 Apr  Archive Link: "[IRC] 14 Apr 2006"

Summary By Peter Sullivan

Topics: Forms

People: Reinhard Müller, James Thompson

Reinhard Müller (reinhard) noted that "each object in the trigger namespace has a _parent property - do you make use of that in any way?" James Thompson (jamest) said that he did not use this when coding his triggers - "i believe i always use absolute reference from form" in the format "form.block.field" . Reinhard also asked "I figure that you also don't make use of the _object property of trigger objects that let you directly access the GObj object that should actually be hidden behind it" . James confirmed this - he personally had never been keen on this, but it had been "added for papo folks" , as previously discussed in several threads, including Issue #63, Section #1  (1 Jan 2003: Project PAPO and GNUe) .

James explained that "i see the trigger namespace as ideally being a restricted python environment with control over imports" , with code for triggers "having no access to the GObjs, only to instances of the class that implements the namespace representation of that object in the trigger" . He added "there is a class that maps a var name in the trigger to an object - and controlls access to that object via the exposed properties - methods, etc" . Reinhard identified this as "GObjNamespace - exactly the class I'm cleaning up" as of time of writing - "thus all these questions" .

The next day (http://www.gnuenterprise.org/irc-logs/gnue-public.log.2006-04-15) , Reinhard noted that, previously, "any trigger got a copy of the __dict__ of the "self" object into its local namespace - so for a block trigger, you could do either self.firstRecord() or just firstRecord(). I removed that as I considered it a bug, but now I'm not sure if it is wanted behaviour. In any case I don't like it very much as it allows for sloppy programming - and it will most probably hurt the "support for self in named triggers" todo item. Anyway, if anybody knows some background why this was done, I'd be happy to know :)"

Sharon And Joy