Review Request 126308: KPushButton: respect SH_DialogButtonBox_ButtonsHaveIcons, also when drawing

Thomas Lübking thomas.luebking at gmail.com
Thu Dec 17 15:36:18 UTC 2015 


> On Dec. 11, 2015, 1:55 p.m., Thomas Lübking wrote:
> > src/kdeui/kdialogbuttonbox.cpp, line 39
> > <https://git.reviewboard.kde.org/r/126308/diff/5/?file=421661#file421661line39>
> >
> >     QDialogButtonBox::addButton should do correctly anyway, so please don't workaround things that are not broken.
> 
> René J.V. Bertin wrote:
>     No, I've looked at Qt 5.5.1 . The only QDialogButtonBox::addButton that "does correctly" is the one that takes a StandardButton. I haven't had time to test this (will need to rebuild QtBase first) but I'm pretty sure that that method creates a button with an icon with its sequence
>     
>     ```
>         QPushButton *button = new QPushButton(text, this);
>         d->addButton(button, role);
>     ```
>     
>     My approach here is to avoid adding an icon if ButtonsHaveIcons is false, or remove the icon if one was already added. That's what QDB does with its ::addButton(StandardButton btn) method (calling a private createButton() method). Any other approach is useless without a style supporting and enforcing ButtonsHaveIcons, but which such a style KDialogButtonBox doesn't need to be fixed in the first place...
> 
> Thomas Lübking wrote:
>     ::addButton(text, role) creates "new QPushButton(text, this)" - those should seriously not have any icons.
>     
>     > whith such a style KDialogButtonBox doesn't need to be fixed in the first place
>     
>     If it's broken, it needs to be fixed - you cannot bail out with "the style is correcting that for us" (I've been fixing far too many kdelibs/qtgui bugs in the style ;-)
> 
> René J.V. Bertin wrote:
>     > ::addButton(text, role) creates "new QPushButton(text, this)" - those should seriously not have any icons.
>     
>     Agreed, they shouldn't *show* any if the user doesn't want to see them. AFAIC they can have a whole bunch of icons as long as they're not displayed. 
>     
>     This argument is a bit useless as long as we don't know if an interface should stop showing icons the moment the user unticks the corresponding setting in systemsettings (and start showing them again when the setting is ticked). If it's ok to tell the user that "the new setting will only be respected after an application restart", then fine, let's simply not add icons when they're not wanted. In all those countless places where the setting will have to be applied.
>     
>     But didn't you point out yourself that the style is in the best position to avoid drawing any unwanted icons?

If you create a PushButton with this constructor, the button has at this point no icon assigned. This has absolutely nothing to do with some setting or the display of anything - where should the button have obtained an icon? None is set here in the first place. QPushButton::icon().isNull()


> On Dec. 11, 2015, 1:55 p.m., Thomas Lübking wrote:
> > src/kdeui/kdialogbuttonbox.cpp, line 57
> > <https://git.reviewboard.kde.org/r/126308/diff/5/?file=421661#file421661line57>
> >
> >     you can completely spare this, there's no reason to manipulate a copy of the GuiItem, just burns CPU
> 
> René J.V. Bertin wrote:
>     In that case I'll have to remove the `const` from guiitem, meaning a change to the API.
> 
> Thomas Lübking wrote:
>     No, you do not touch the KGuiItem that comes (it's not yours!) and it's pointless to create a copy, strip the icon from that, assign it to the button (and maybe even strip the icon from the button) - you just apply the GuiItem that enters and strip the icon from the button. The interim (deep) GuiItem copy is just detour in the path to remove the icon from the button.
> 
> René J.V. Bertin wrote:
>     I must be getting on with other real-life stuff now; I agree with not touching the incoming item of course. I'll see if there isn't a way to avoid adding the unwanted icon at all, to avoid the icon deep copy as well (probably the most expensive part of a GuiItem deep copy, no?)

There's no deep copy of an icon, it's implicitly shared. And if there was, copying the KGuiItem would still only make things worse ...


> On Dec. 11, 2015, 1:55 p.m., Thomas Lübking wrote:
> > src/kdeui/kdialogbuttonbox.cpp, line 61
> > <https://git.reviewboard.kde.org/r/126308/diff/5/?file=421661#file421661line61>
> >
> >     unrelated and it won't leak, since the cleanup is done by the parent/child relation ("this" passed to KPushButton)
> 
> René J.V. Bertin wrote:
>     Maybe it won't leak, but the question remains why what buttons with an invalid role are good for.
> 
> Thomas Lübking wrote:
>     Did you see such role being used? It would be a client code bug (the symbol is juts for completeness sake, so that you can eg. assign it to a role, pipe that to some transformation functions, check whether it's still invalid and then react to that)
> 
> René J.V. Bertin wrote:
>     No, I haven't seen such a role (and client code bug, agreed on that). I did see however that there is no trivial way to check for it; you apparently have to look at the role before adding the button, or else query the KDialogButtonBox if it owns the button (if that's even possible).

Look, there's no problem here - the enum simply knows a value that says "invalid".
Whoever wants to add a button with a variable role is supposed to check that it's not invalid - otherwise *that* particular client code has a bug.


> On Dec. 11, 2015, 1:55 p.m., Thomas Lübking wrote:
> > src/kdeui/kdialogbuttonbox.cpp, line 70
> > <https://git.reviewboard.kde.org/r/126308/diff/5/?file=421661#file421661line70>
> >
> >     Setting the icon is sufficient, please do not mess around with other attributes.
> 
> René J.V. Bertin wrote:
>     Are you sure? setIcon() doesn't call setIconSize() nor does it reset any size information already present. Is it a good idea to replace an icon and leaving the size information from the previous icon)? NB: should the icon from the KGuiItem override the role's standard icon or should it be the other way round (provided icon as a default when the role doesn't provide an icon, for instance)?
> 
> Thomas Lübking wrote:
>     setIcon *shall* not setIconSize, the two values are completely orhtogonal. Dropping the size information will just get you into trouble when you should require it again.
>     If eg. a style would reserve icon space of iconSize despite there actually is no icon to paint, the style is simply broken.
>     
>     The icon size refers to the wanted size in the widget, not what the icon provides. Resolving that is job of the icon loader (or painting routine, eg. the style)
>     
>     About GuiItem ./. StdRole: FIFO, ie. the last setter should usually win (if you've a button with a dedicated icon and role "ok" and switch the role to "delete", the "ok" icon is most certainly no longer correct ;-)
> 
> René J.V. Bertin wrote:
>     OK for iconSize ... but how should the user know the order of precedence in this case?

> how should the user know the order of precedence in this case

Hah? By "user" you likely mean "client code developer" and he's in charge to get his calls in proper order and the buttonbox just operates fifo. That's a completely natural and expectable behavior.


- Thomas


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On Dec. 11, 2015, 4:26 p.m., René J.V. Bertin wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/126308/
> -----------------------------------------------------------
> 
> (Updated Dec. 11, 2015, 4:26 p.m.)
> 
> 
> Review request for KDE Software on Mac OS X, KDE Frameworks, Qt KDE, Hugo Pereira Da Costa, and Yichao Yu.
> 
> 
> Repository: kdelibs4support
> 
> 
> Description
> -------
> 
> KF5 applications have long had a habit of drawing icons on buttons even when this feature was turned off in the user's setting. This was mostly noticeable in applications built on kdelibs4support.
> 
> It seems that the actual culprit is in Qt's QPushButton implementation (https://bugreports.qt.io/browse/QTBUG-49887), but it is possible to work around it in `KPushButton::paintEvent`, by removing the icon (forcing it to the null icon) in the option instance, before handing off control to the painter.
> 
> 
> Diffs
> -----
> 
>   src/kdeui/kdialogbuttonbox.cpp 0f6649b 
>   src/kdeui/kpushbutton.cpp 98534fa 
> 
> Diff: https://git.reviewboard.kde.org/r/126308/diff/
> 
> 
> Testing
> -------
> 
> On Kubuntu 14.04 and OS X 10.9.5 with Qt 5.5.1 and KF5 frameworks 5.16.0 .
> 
> I have not yet verified if there are other classes where this modification would be relevant too.
> 
> 
> Thanks,
> 
> René J.V. Bertin
> 
>

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