Fix: Fl_Native_File_Chooser::filter_value() [Kdialog] always returns 0 (#899)

- remove build option FLTK_USE_KDIALOG replaced by an Fl::option() option
- new run-time option OPTION_FNFC_USES_KDIALOG
- make options OPTION_FNFC_USES_KDIALOG and OPTION_FNFC_USES_ZENITY
false by default
- add mention of new program fltk-options in the doc of Fl::option()
- change logic of choice of the native file chooser under X11/Wayland:
the zenity and kdialog choosers are opt-in; otherwise the GTK file chooser
is used, unless opted out with  OPTION_FNFC_USES_GTK
- document that zenity may be interesting for sandboxed apps
- document that both zenity and kdialog make member functions
Fl_Native_File_Chooser::filter_value() inoperable

1 files changed, 6 insertions, 7 deletions

diff --git a/FL/Fl_Native_File_Chooser.H b/FL/Fl_Native_File_Chooser.H
index 92e21a98e..726a34636 100644
--- a/FL/Fl_Native_File_Chooser.H
+++ b/FL/Fl_Native_File_Chooser.H
@@ -105,11 +105,12 @@ class Fl_Native_File_Chooser_Driver;
 
  - Under X11/Wayland the dialog is chosen as follows:
  -# If command \p zenity is available at run-time and if \p Fl::option(OPTION_FNFC_USES_ZENITY) is
- not turned off, the \p zenity -based dialog opens. This is expected to be more appropriate
- than other dialog forms for sandboxed apps.
- -# Else if the app runs under the KDE desktop and if command \p kdialog is available at run-time
- and if the library was not built with <tt>cmake -D FLTK_USE_KDIALOG=OFF</tt>, the
- \p kdialog -based dialog opens.
+ turned on, the \p zenity -based dialog opens. This is expected to be more appropriate
+ than other dialog forms for sandboxed apps, but member function filter_value() is not effective.
+ -# Else if the app runs under the KDE desktop
+ and if \p Fl::option(OPTION_FNFC_USES_KDIALOG) is turned on,
+ and if command \p kdialog is available at run-time, the \p kdialog -based dialog opens.
+ Member function filter_value() is not effective with this dialog.
  -# Else if the GTK library is available at run-time on the computer and if \p Fl::option(OPTION_FNFC_USES_GTK) is
  not turned off, the GTK-styled dialog opens. Call fl_register_images() to add  a "Preview" button to this dialog.
  Use the static public attributes of class Fl_File_Chooser to localize the browser.
@@ -119,8 +120,6 @@ class Fl_Native_File_Chooser_Driver;
  at the start of main(), to enable the nicer looking file browser widgets.
  Use the static public attributes of class Fl_File_Chooser to localize the browser.
 
- \todo Improve documentation about selection of native file choosers on X11/Wayland.\n
-
  - Some operating systems support certain OS specific options; see
  Fl_Native_File_Chooser::options() for a list.