Hi Thierry,
By default, buttons include the "btn-outline-secondary" class
If I want to change, for example: "btn-outline-light", I add this instruction in wCSSclassAdd.
This works, but the class is overloaded like this:

Hi Vincent,
What the VFP BaseClass of your 'button'? Commandbutton
or Image
?
Hi Thierry,
Commandbutton
For memory, there is this code in commandbutton.Init()
if wlWeb()
store 4 to this.PictureMargin, this.PictureSpacing
*!* if File(ForceExt(this.Picture, CPNG))
*!* this.Picture = ForceExt(this.Picture, CPNG)
*!* endif
*!* if File(ForceExt(this.DisabledPicture, CPNG))
*!* this.DisabledPicture = ForceExt(this.DisabledPicture, CPNG)
*!* endif
*!* if File(ForceExt(this.DownPicture, CPNG))
*!* this.DownPicture = ForceExt(this.DownPicture, CPNG)
*!* endif
if Type('thisForm.wBSlHTMLgen') == 'L' and thisForm.wBSlHTMLgen
this.wCSSclassAdd = cListEdit(this.wCSSclassAdd;
, c2Words(Iif(.F.;
or 'btn-secondary' $ this.wCSSclassAdd;
or 'btn-primary' $ this.wCSSclassAdd;
or 'btn-success' $ this.wCSSclassAdd;
or 'btn-info' $ this.wCSSclassAdd;
or 'btn-warning' $ this.wCSSclassAdd;
or 'btn-danger' $ this.wCSSclassAdd;
or 'btn-link' $ this.wCSSclassAdd;
, '';
, 'btn-secondary';
);
, ' ';
, ''; && doo-btn-responsive && 2016-12-23 thn -- {FiC V 2.23.1-beta.1} {en} removed
);
, ;
, ' ';
)
endif
endif
return DoDefault()

FoxInCloud does not force this CSS class… perhaps somewhere in your code?
Vincent,
For memory, there is this code in
commandbutton.Init()
Does not seem to execute as btn-secondary
is not in your <button class="…"…>
, or is modified by a child class' .Init()
In the posted example, I'm using the commandbutton base class.
Sorry, but I don't see where I could have added code...
I found the culprit:
In xxxServer.prg I have this code:
* ===========================================
DEFINE CLASS xxxHTMLgen as awHTMLgen of awHTML.prg
* ----------------------------------------------------
protected function getHTML_cnt && {fr} HTML par défaut d'un objet contenant
lparameters tlInnerHTML && [.F.] {fr} Rendre l'intérieur du conteneur seulement {en} Render contained objects only
LOCAL lcResult as String
lcResult = DoDefault(m.tlInnerHTML)
return Iif(m.this.cBaseClass == 'form' and m.this.BSlHTMLgen, Strtran(m.lcResult, 'btn-secondary', 'btn-outline-secondary'), m.lcResult)
endfunc
ENDDEFINE && class snoHTMLgen
* ===========================================
Yet with this addition in awHTML.prg, "btn-secondary" (replaced by "btn-outline-secondary" in xxxServer.prg) should not be added in the button code
or 'btn-outline-' $ m.lcResult; && 2021-11-04 thn -- {FiC V 3.0.0-beta.5} {en} added