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@u-fischer
u-fischer committed Mar 2, 2021
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126 changes: 104 additions & 22 deletions newpackages/l3pdffield-checkbox.dtx
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%
% \maketitle
% \begin{documentation}
% The implementation of form fields in hyperref is in part faulty, see for example
% The implementation of form fields in hyperref has some bugs, see for example
% \url{https://github.com/latex3/hyperref/issues/94}. This package is a first step
% toward the goal to review and improve the code of form fields.
% towards the goal to review and improve the code of form fields.
%
% It handles \emph{only} checkboxes, other form fields like radio buttons or
% textfields will follow later. It relies on the hyperref code
% It handles for now \emph{only} checkboxes, other form fields like radio buttons or
% text fields will follow later. It relies on the hyperref code
% to initialize the form and it requires the new PDF management code.
% The package will suppress the deprecated /NeedAppearances setting.
%
% So typical use will look like this
% So a typical use will look like this
%
% \begin{verbatim}
% \RequirePackage{pdfmanagement-testphase}
Expand All @@ -77,28 +77,107 @@
% \Form
% \end{verbatim}
%
% \section{Some background}
% Form fields consist of a field object and number of instances of the field:
% A checkbox can appear on more than one page or location and if one instances
% is checked all other instances follows and are checked too.
%
% All instances are widget annotations and are referenced in the Kid array of the field
% object. This means that the code has to collect all the children and write
% All instances are in this case widget annotations and are referenced in the Kid array of the field
% object\footnote{Fields can actually build a tree: between the root field and
% widget annotations there can be more fields. The last one before the widget is
% the \emph{terminal} field, but unless a sensible
% use case comes up, I will assume that the widget annotations are direct children of
% the root and that the root field is the terminal field.}.
% This means that the code has to collect all the children and write
% out the field object at the end of the document.
%
% If a field has only one children the content of the field dictionary and the
% widget annotation dictionary can be merged---some examples in the PDF reference
% show such merged dictionaries---but the code here keeps them separate, at the end
% this is clearer.
%
% All the root field objects must be referenced in the AcroForm dictionary in the
% Fields entry. This can be done with
%
% \begin{verbatim}
% \pdfmanagement_add:nnx{Catalog/AcroForm}{Fields}{<obj ref>}
% \end{verbatim}
%
% A checkbox has two different looks: checked and unchecked. The current hyperref
% implementation uses symbolic names for the two states and lets the PDF viewer
% create a look from them. But this doesn't work reliably. Newer PDF versions require
% that such a look, an \enquote{appearance}, are XObjects: such XObjects are like small
% pictures stored in the PDF.
% create a look from them. But this doesn't work reliably. Also newer PDF versions
% require that such a look, an \enquote{appearance}, are given as form XObjects:
% such form XObjects are like small pictures stored in the PDF, they can be
% created with the commands of the \pkg{l3pdfxform} package.
%
% The checkbox instances, the widget annotations, cover a rectangular area on
% the page, the XObjects are fit into this rectangle. So for the best result
% The checkbox instances---the widget annotations---cover a rectangular area on
% the page, the XObjects are squeezed into this rectangle. So for the best result
% both should have the same ratio of width and height.
% XObjects used as appearances can not be rotated, if needed one has to
% create a new appearance.
%
%
% \subsection{The Field dictionary}
%
% The field dictionary shall or can have the following entries
%
% \begin{description}
% \item[FT] required for terminal fields (here for the root field),
% the value is always \texttt{Btn}, so this entry is set by the code.
% \item[Parents] currently irrelevant as we don't have a field hierarchy.
% \item[Kids] an array. Contains references to the children, in our case to
% the widget annotations. The array is build by the code.
%
% \item[T] required, the name, a (unique) text string without a period.
% This field is a mandatory argument which must be given by the user.
% The value should be passed through a suitable string conversion and periods should
% be removed.
%
% \item[TU,TM] optional, alternative names for user messages (TU) and export (TM).
% As these fields are optional they should be set by some key-val option.
%
% \item[Ff] A bitset, two flags must be unset for a checkbox (Radio and Pushbotton),
% for the rest we need a keyval interface.
%
% \item[V] describes the initial value, for checkboxes is should be either |/Yes|
% or |/Off|. The initial value will be |/Yes|, keys are need to set both the local
% and the default value.
%
% \item[DV] optional, the default value after a reset. Should be her like |V| be either
% |/Yes| or |/Off|.
%
% \item[AA] An action dictionary. For this we need a special command to setup such
% dictionaries, so that they then can be used in various places.
%
% \end{description}
%
% \subsection{The widget annotation dictionary}
%
% \begin{description}
% \item[Type] Value: |/Annot|, set automatically
% \item[Subtype] Value: |/Widget| if we use the command from l3pdfannot which use
% the |l__pdfannot/widget| dictionary this is added automatically.
% Then one has to fill the rest of the entries with |\pdfannot_dict_put:nnn{widget}...|
% \item[Parent] The reference to the field, automatically added.
% \item[Rect] the size, calculated from the box size
% \item[Contents] a text string, not really need but an optional key should allow to
% set it,
% \item[AP] the appearance dictionary. It should look like this
% |/AP <</N <</Yes 17 0 R/Off 15 0 R>>>>|. I need to test if it makes sense here to
% have a |/R| and |/D| entry too. The objects refer to suitable xforms.
% \item[AS] should be either |/Yes| or |/Off|, and sensibly by default be
% the same as the V entry in the field dictionary. If they differ the AS entry wins.
%
% \item[A] Action, this must be checked.
% \item[AA] additional actions. This must be checked too.
%
% \item[Border, C, OC, AF, BM, Lang, P, NM, M, F, BS, H]: These are not specifically
% needed for checkbox. An interface to add something to the used annot dictionary
% is needed (or already there), but probably no special key-val support for now.
%
% \item[MK] this is what hyperref uses to set the appearance, but I
% explicitly leave it out and use |AP|.
%
% \end{description}
% \end{documentation}
% \begin{implementation}
% \begin{macrocode}
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% A bitset for the field flag Ff:
% Not yet decided if this should public or not ...
% \begin{macrocode}
\bitset_new:Nn \l__pdffield_Ff_bitset
\bitset_new:Nn \l_pdffield_Ff_bitset
{
ReadOnly = 0,
Required = 1,
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\cs_generate_variant:Nn \pdfxform_dp:n {e}
\cs_generate_variant:Nn \pdfxform_ref:n{e}

\pdfdict_new:n {l_pdffield/checkbox/Field}
\pdfdict_new:n {l_pdffield/checkbox/Annot}
% \end{macrocode}
% Like in the l3pdfannot module, we hide the dictionaries
% and will offer an interface if needed.
% \begin{macrocode}
\pdfdict_new:n {l__pdffield/checkbox/Field}
\pdfdict_new:n {l__pdffield/checkbox/Annot}


\tl_new:N \g__pdffield_normal_off_default_tl
Expand Down Expand Up @@ -328,12 +411,12 @@
{
\pdf_object_ref:n {pdffield/checkbox/Field/Btn/#1/Kids}
}
\bitset_set_false:Nn \l__pdffield_Ff_bitset {Radio}
\bitset_set_false:Nn \l__pdffield_Ff_bitset {Pushbutton}
\bitset_set_true:Nn \l__pdffield_Ff_bitset {NoExport}
\bitset_set_false:Nn \l_pdffield_Ff_bitset {Radio}
\bitset_set_false:Nn \l_pdffield_Ff_bitset {Pushbutton}
%\bitset_set_true:Nn \l_pdffield_Ff_bitset {NoExport} %?
\pdfdict_put:nnx {l_pdffield/checkbox/Field}
{Ff}
{\bitset_to_arabic:N \l__pdffield_Ff_bitset }
{\bitset_to_arabic:N \l_pdffield_Ff_bitset }
\pdf_object_write:nx {pdffield/checkbox/Field/Btn/#1} { \pdfdict_use:n {l_pdffield/checkbox/Field} }
\pdfmanagement_add:nnx
{ Catalog / AcroForm }
Expand All @@ -351,8 +434,7 @@
{
\rule
[-\l__pdffield_field_dp_dim]{0pt}{\dim_eval:n{\l__pdffield_field_ht_dim+\l__pdffield_field_dp_dim}}
\pdfannot_box:nnnnn
{widget}
\pdfannot_widget_box:nnnn
{ \dim_use:N \l__pdffield_field_wd_dim }
{ \dim_use:N \l__pdffield_field_ht_dim }
{ \dim_use:N \l__pdffield_field_dp_dim }
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