Hello, Items specific to the Qt widget set.

In LCL we have many item containers that can have custom draw item events.

To implement this functionality I suposed it will be enough to listen painEvent and call draw item events while traversing items.

But qt suggest anther approach for that - override QAbstractItemDelegate. We already have QComboBox_setItemDelegate, QAbstractItemView_setItemDelegate and so on. We only need our own delegate.

I dont think it is not possible to subclass QAbstractItemDelegate in pascal. So we need this thing in bindings.

We only should override 2 methods: paint and sizeHint at moment to achive needed result.

We need that paint and sizeHint methods redirect calls to our own methods. We can for example use constructor and pass that methods as arguments or we can use getters and setters.

For example:

Delegate := QPascalItemDelegate_create(@PaintHook, @SizeHintHook);
QComboBox_setItemDelegate(Delegate);
...

Den, what do you think. Is it possible?

It will be even better to override QItemDelegate instead of QAbstractItemDelegate. Sice QItemDelegate already has default implementation we can turn it on if we will not process that painting ourself.

Best regards,
Paul Ishenin.

Paul Ishenin wrote

It will be even better to override QItemDelegate instead of QAbstractItemDelegate. Sice QItemDelegate already has default implementation we can turn it on if we will not process that painting ourself.

I'll prefer both in bindings.

Paul Ishenin wrote

In LCL we have many item containers that can have custom draw item events.

I see the binding for LCL needs, not for pascal Qt programming. For this indeed method overriding is lacking. For LCL it is normally not needed, almost everything can be overriden via the eventfilter (proof is CLX).

So everything needed is present.

QAbstractItemDelegate is just more abstraction, they needed something to sell Qt 4. It is not present in Qt 3. The commercial nature of Qt makes that over time it is moving from perfect lean design to big monster due to the stupid need to have something new in every release. Please do not use something so advanced in a widgetset interface.

Catching paint events and other events via event filters, void the need to derive the class. It is just catching signals. Qt is build for that. But for method overriding, you need to subclass.

Please review your request or elaborate further.

Anyhow creating a framework for method overriding is a lot of work, weeks, so perhaps it is better spent on something else.

I would prefer that the simple things work first, before we work on custom drawn combo box items. But we can also come back on this later.

Radio buttons do not work yet, even with the QT_HIDDEN_BUTTON_WORKAROUND. The horizontal positions are not correct, nor the tab order (key up/down). Could we work on such things first. I tried to read the code, but do not even find were the positions are set.

kind regards,

Den Jean

Quoting Den Jean :

I agree with you about QAbstractItemDelegate, and about QT_HIDDEN_BUTTON_WORKAROUND, my svn copy already contains some changes which fixes a lot of geometry & positioning problems, but we have to discuss about it.
eg. I don't get LCL's diff between GetClientRect() and GetClientBounds(). First one should return ClientRect() and second one BoundsRect() similar as in Delphi. Isn't it ? or I'm wrong ...
Anyway , my wiki page contains things which I changed today on the beach ;), and will be commited when you try it on your distro and when Paul try it on his WinXP. I've already tested changes on WinXP , FC3, FC4 & FC7 and it looks ok.
Pls. write me which screen resolutions and dpi settings you use on Linux. I'm using 1280x1024 96x96 dpi (WinXP & Linux).

here is my wiki link:
http://wiki.lazarus.freepascal.org/User:Zeljan

Anyway , my wiki page contains things which I changed today on the beach ;), and will be commited when you try it on your distro and when

how test something we do not have ???
commit please

Paul try it on his WinXP. I've already tested changes on WinXP , FC3, FC4 & FC7 and it looks ok. Pls. write me which screen resolutions and dpi settings you use on

1920x1200 and 1680x1050
90x89 DPI

Ok, I tell me what is:
QClxListItem_measure_Event, QClxListBoxHooks_hook_measure, QClxListItem_paint_Event, QClxListBoxHooks_hook_paint

So everything needed is present.

No. As I understand borland used same approach. They subclassed QAbstractItemDelegate or QItemDelegate and overrided sizeHint and paint. They also provided that two methods: QClxListBoxHooks_hook_measure and QClxListBoxHooks_hook_paint.

We need something about the same. We need to subclass QItemDelegate and provide 2 our own event. Measure event will be passed on QItemDelegate.sizeHint call and paint event on paint.

If that events are not processed then default behaviour should be used.

Anyhow creating a framework for method overriding is a lot of work, weeks, so perhaps it is better spent on something else.

No we doesnot need such framework. We need only one special class in bindings (written on c++) and need 2 special hook install methods. No more no less.

hope it is fixed now :)

Best regards,
Paul Ishenin.

Paul Ishenin wrote

We need something about the same. We need to subclass QItemDelegate and provide 2 our own event. Measure event will be passed on QItemDelegate.sizeHint call and paint event on paint.

I will look into it.

regards,

Den Jean

Big thanks.

Best regards,
Paul Ishenin.

Paul Ishenin wrote

We need something about the same. We need to subclass QItemDelegate and provide 2 our own event. Measure event will be passed on QItemDelegate.sizeHint call and paint event on paint.

for Zeljko too:

i just read this in
src/gui/itemviews/qitemdelegate.h.
The HMargin may be of interest.

/*!
Returns the size needed by the delegate to display the item specified by \a index, taking into account the style information provided by \a option.

When reimplementing this function, note that in case of text items, QItemDelegate adds a margin (i.e. 2 *
QStyle::PM_FocusFrameHMargin) to the length of the text. */

QSize QItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const