docs(data_binding): move the data binding docs to to the given widget's page

docs/src/details/auxiliary-modules/observer/observer.rst

@@ -361,13 +361,9 @@ integer value:
 
 - flag (or OR-ed combination of flags) from from the ``LV_OBJ_FLAG_...`` enumeration values;
 - state (or OR-ed combination of states) from the ``LV_STATE_...`` enumeration values;
-- text value for
+- text and/or integer values for
-
     - Label
     - Span;
-
-- integer value for these Widget types:
-
     - Arc
     - Drop-Down
     - Roller
@@ -457,141 +453,11 @@ Subject's value to be set to ``1`` or ``0`` respectively.
 
 - :cpp:expr:`lv_obj_bind_checked(widget, &subject)`
 
+Specific Widget Types
+~~~~~~~~~~~~~~~~~~~~~
 
-Label Widgets
+To learn how to bind subjects to Arcs, Labels, Slider, etc. visit the "Data binding"
-~~~~~~~~~~~~~
+section of the given widget's documentation. For example: :ref:`Data binding for lv_label <lv_label_data_binding>`.
-
-.. |deg|    unicode:: U+000B0 .. DEGREE SIGN
-
-This method of subscribing to an integer Subject affects a Label Widget's
-``text``.  The Subject can be an STRING, POINTER or INTEGER type.
-
-When the subscribing occurs, and each time the Subject's value is changed thereafter,
-the Subject's value is used to update the Label's text as follows:
-
-:string Subject:    Subject's string is used to directly update the Label's text.
-
-:pointer Subject:   If NULL is passed as the ``format_string`` argument when
-                    subscribing, the Subject's pointer value is assumed to point to a
-                    NUL-terminated string. and is used to directly update the Label's
-                    text.  See :ref:`observer_format_string` for other options.
-
-:integer Subject:   Subject's integer value is used with the ``format_string`` argument.
-                    See See :ref:`observer_format_string` for details.
-
-Note that this is a one-way binding (Subject ===> Widget).
-
-- :cpp:expr:`lv_label_bind_text(label, &subject, format_string)`
-
-.. _observer_format_string:
-
-The ``format_string`` Argument
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-The ``format_string`` argument is optional and if provided, must contain exactly 1
-printf-like format specifier and be one of the following:
-
-:string or pointer Subject:  "%s" to format the new pointer value as a string or "%p"
-                             to format the pointer as a pointer (typically the
-                             pointer's address value is spelled out with 4, 8 or 16
-                             hexadecimal characters depending on the platform).
-
-:integer Subject:            "%d" format specifier (``"%" PRIdxx`` --- a
-                             cross-platform equivalent where ``xx`` can be ``8``,
-                             ``16``, ``32`` or ``64``, depending on the platform).
-
-:float Subject:              "%f" format specifier, or e.g. "%0.2f" to display two digits after the decimal point.
-
-
-If ``NULL`` is passed for the ``format_string`` argument:
-
-:string or pointer Subject:  Updates expect the pointer to point to a NUL-terminated string.
-:integer Subject:            The Label will simply display the number. Equivalent to "%d".
-:float Subject:            The Label will display the value with "%0.1f" format string.
-
-**Example:**  "%d |deg|\C"
-
-
-Spangroup's Span
-~~~~~~~~~~~~~~~~
-
-Very similar to Label-text binding, a Span's text can be bound to a subject as well.
-
-The only difference is that in the bind function both the Spangroup and the Span need to be specified:
-
- :cpp:expr:`lv_spangroup_bind_span_text(spangroup, span1, &subject, format_string)`
-
-Note that before calling :cpp:expr:`lv_spangroup_delete_span` :cpp:expr:`lv_observer_remove`
-needs to be called manually as LVGL can't remove the binding automatically.
-
-Arc Widgets
-~~~~~~~~~~~
-
-This method of subscribing to an integer Subject affects an Arc Widget's integer
-value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
-user's direct interaction with the Arc Widget updates the Subject's value and vice
-versa.  (Requires :c:macro:`LV_USE_ARC` to be configured to ``1``.)
-
-It support integer and float subjects.
-
-
-- :cpp:expr:`lv_arc_bind_value(arc, &subject)`
-
-
-Slider Widgets
-~~~~~~~~~~~~~~
-
-This method of subscribing to an integer Subject affects a Slider Widget's integer
-value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
-user's direct interaction with the Slider Widget updates the Subject's value and vice
-versa.  (Requires :c:macro:`LV_USE_SLIDER` to be configured to ``1``.)
-
-It support integer and float subjects.
-
-- :cpp:expr:`lv_slider_bind_value(slider, &subject)`
-
-
-Roller Widgets
-~~~~~~~~~~~~~~
-
-This method of subscribing to an integer Subject affects a Roller Widget's integer
-value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
-user's direct interaction with the Slider Widget updates the Subject's value and vice
-versa.  (Requires :c:macro:`LV_USE_ROLLER` to be configured to ``1``.)
-
-It support only integer subjects.
-
-- :cpp:expr:`lv_roller_bind_value(roller, &subject)`
-
-
-Drop-Down Widgets
-~~~~~~~~~~~~~~~~~
-
-This method of subscribing to an integer Subject affects a Drop-Down Widget's integer
-value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
-user's direct interaction with the Drop-Down Widget updates the Subject's value and
-vice versa.  (Requires :c:macro:`LV_USE_DROPDOWN` to be configured to ``1``.)
-
-It support only integer subjects.
-
-- :cpp:expr:`lv_dropdown_bind_value(dropdown, &subject)`
-
-Scale's Section
-~~~~~~~~~~~~~~~
-
-This method of subscribing to an integer Subject affects a Section of a Scale Widget's integer
-minimum or maximum values directly.  Note that this is a one-way binding (Subject ==> Widget)
-as the Scale Section's boundaries are not interactive.
-(Requires :c:macro:`LV_USE_SCALE` to be configured to ``1``.)
-
-It supports only integer subjects.
-
-- :cpp:expr:`lv_scale_bind_section_min_value(scale, section1, &subject)`
-- :cpp:expr:`lv_scale_bind_section_max_value(scale, section1, &subject)`
-
-
-.. _change_subject_on_event:
-
 
 Change Subject on Event
 -----------------------

docs/src/details/widgets/arc.rst

@@ -141,6 +141,22 @@ used to rotate the Widget to the current value of the Arc.
 A typical use case is to call these functions in the ``VALUE_CHANGED``
 event of the Arc.
 
+Data binding
+------------
+
+To get familiar with observers, subjects, and data bindings in general visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to an integer Subject affects an Arc Widget's integer
+value directly.  Note that this is a two-way binding (Subject <===> Widget), so an end
+user's direct interaction with the Arc Widget updates the Subject's value and vice
+versa.
+
+It support integer and float subjects.
+
+
+- :cpp:expr:`lv_arc_bind_value(arc, &subject)`
+
 
 .. _lv_arc_events:
 

docs/src/details/widgets/dropdown.rst

@@ -132,6 +132,21 @@ To programmatically open or close the Drop-Down List use
 :cpp:expr:`lv_dropdown_open(dropdown)` or :cpp:expr:`lv_dropdown_close(dropdown)`.
 
 
+Data binding
+------------
+
+To get familiar with observers, subjects, and data bindings in general visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to an integer Subject affects a Drop-Down Widget's integer
+value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
+user's direct interaction with the Drop-Down Widget updates the Subject's value and
+vice versa.
+
+It support only integer subjects.
+
+- :cpp:expr:`lv_dropdown_bind_value(dropdown, &subject)`
+
 
 .. _lv_dropdown_events:
 

docs/src/details/widgets/image.rst

@@ -194,7 +194,19 @@ To automatically scale or tile the image, pass one of these ``align`` values:
 - :cpp:enumerator:`LV_IMAGE_ALIGN_CONTAIN` The image keeps its aspect ratio, but is resized to the maximum size that fits within the Widget's area.
 - :cpp:enumerator:`LV_IMAGE_ALIGN_COVER` The image keeps its aspect ratio and fills the Widget's area.
 
+Data binding
+------------
 
+To get familiar with observers, subjects, and data bindings in general visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to a pointer Subject affects an Image Widget's source (``src``)
+value directly.  Note that this is a one-way binding (Subject ==> Widget) so when
+the subject changes the Image will be update too.
+
+It support only pointer subjects.
+
+- :cpp:expr:`lv_image_bind_src(slider, &subject)`
 
 .. _lv_image_events:
 

docs/src/details/widgets/label.rst

@@ -155,6 +155,7 @@ Note that this has a visible effect only if:
 - the Label Widget's width is larger than the width of the longest line of text, and
 - the text has multiple lines with different line lengths.
 
+
 .. _lv_label_very_long_texts:
 
 Very long text
@@ -185,6 +186,69 @@ the :ref:`font` section to learn more about symbols.
 
 
 
+.. _lv_label_data_binding:
+
+Data binding
+------------
+
+.. |deg|    unicode:: U+000B0 .. DEGREE SIGN
+
+To get familiar with observers, subjects, and data bindings in general visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to a Subject affects a Label Widget's
+``text``.  The Subject can be an STRING, POINTER or INTEGER type.
+
+When the subscription occurs, and each time the Subject's value is changed thereafter,
+the Subject's value is used to update the Label's text as follows:
+
+:string Subject:    Subject's string is used to directly update the Label's text.
+
+:pointer Subject:   If NULL is passed as the ``format_string`` argument when
+                    subscribing, the Subject's pointer value is assumed to point to a
+                    NUL-terminated string and is used to directly update the Label's
+                    text.  See :ref:`observer_format_string` for other options.
+
+:integer Subject:   Subject's integer value is used with the ``format_string`` argument.
+                    See :ref:`observer_format_string` for details.
+
+Note that this is a one-way binding (Subject ===> Widget).
+
+- :cpp:expr:`lv_label_bind_text(label, &subject, format_string)`
+
+.. _observer_format_string:
+
+The ``format_string`` Argument
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The ``format_string`` argument is optional and if provided, must contain exactly 1
+printf-like format specifier and be one of the following:
+
+:string or pointer Subject:  "%s" to format the new pointer value as a string or "%p"
+                             to format the pointer as a pointer (typically the
+                             pointer's address value is spelled out with 4, 8 or 16
+                             hexadecimal characters depending on the platform).
+
+:integer Subject:            "%d" format specifier (``"%" PRIdxx`` --- a
+                             cross-platform equivalent where ``xx`` can be ``8``,
+                             ``16``, ``32`` or ``64``, depending on the platform).
+
+:float Subject:              "%f" format specifier, or e.g. "%0.2f" to display two digits after the decimal point.
+
+
+If ``NULL`` is passed for the ``format_string`` argument:
+
+:string or pointer Subject:  Updates expect the pointer to point to a NUL-terminated string.
+:integer Subject:            The Label will simply display the number. Equivalent to "%d".
+:float Subject:            The Label will display the value with "%0.1f" format string.
+
+**Example:**  "%d |deg|\C"
+
+As usual with format strings, ``%%`` shall be used to get ``%``. For example ``%d%%``
+
+
+
+
 .. _lv_label_events:
 
 Events

docs/src/details/widgets/roller.rst

@@ -76,6 +76,21 @@ This function calculates the height with the current style. If the font,
 line space, border width, etc. of the Roller changes, this function needs
 to be called again.
 
+Data binding
+------------
+
+To get familiar with observers, subjects, and data bindings in general visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to an integer Subject affects a Roller Widget's integer
+value directly.  Note that this is a two-way binding (Subject <===> Widget) so an end
+user's direct interaction with the Roller Widget updates the Subject's value and vice
+versa.
+
+It supports only integer subjects.
+
+- :cpp:expr:`lv_roller_bind_value(roller, &subject)`
+
 
 
 .. _lv_roller_events:

docs/src/details/widgets/scale.rst

@@ -184,6 +184,25 @@ range.  If a Section's range is not within the Scale's range at all, it will not
 used in drawing.  That can be useful to temporarily "disable" a Section, e.g.
 :cpp:expr:`lv_scale_section_set_range(section, 0, -1)`.)
 
+Data binding
+~~~~~~~~~~~~
+
+To get familiar with observers, subjects, and data bindings in general, visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to an integer Subject affects a Section of a Scale Widget's integer
+minimum or maximum values directly.  Note that this is a one-way binding (Subject ==> Widget)
+as the Scale Section's boundaries are not interactive.
+
+
+It supports only integer subjects.
+
+- :cpp:expr:`lv_scale_bind_section_min_value(scale, section1, &subject)`
+- :cpp:expr:`lv_scale_bind_section_max_value(scale, section1, &subject)`
+
+
+.. _change_subject_on_event:
+
 
 .. _scale_styling_sections:
 

docs/src/details/widgets/slider.rst

@@ -93,6 +93,20 @@ feature is enabled by adding the :cpp:enumerator:`LV_OBJ_FLAG_ADV_HITTEST` flag:
 Any extended click area (set by :cpp:expr:`lv_obj_set_ext_click_area(slider, value)`)
 increases the knob's click area.
 
+Data binding
+------------
+
+To get familiar with observers, subjects, and data bindings in general, visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+This method of subscribing to an integer Subject affects a Slider Widget's integer
+value directly.  Note that this is a two-way binding (Subject <===> Widget), so an end
+user's direct interaction with the Slider Widget updates the Subject's value and vice
+versa.
+
+It supports integer and float subjects.
+
+- :cpp:expr:`lv_slider_bind_value(slider, &subject)`
 
 
 .. _lv_slider_events:

docs/src/details/widgets/spangroup.rst

@@ -146,6 +146,20 @@ of lines to be displayed in :cpp:enumerator:`LV_SPAN_MODE_BREAK` mode. A negativ
 value indicates no limit.
 
 
+Data binding
+------------
+
+To get familiar with observers, subjects, and data bindings in general, visit the
+:ref:`Observer <observer_how_to_use>` page.
+
+Very similar to Label-text binding, a Span's text can be bound to a subject as well.
+
+The only difference is that in the bind function both the Spangroup and the Span need to be specified:
+
+:cpp:expr:`lv_spangroup_bind_span_text(spangroup, span1, &subject, format_string)`
+
+Note that before calling :cpp:expr:`lv_spangroup_delete_span`, :cpp:expr:`lv_observer_remove`
+needs to be called manually as LVGL can't remove the binding automatically.
 
 .. _lv_spangroup_events:
 

src/others/xml/parsers/lv_xml_bar_parser.c

@@ -67,10 +67,19 @@ void lv_xml_bar_apply(lv_xml_parser_state_t * state, const char ** attrs)
             bool anim = anim_str ? lv_xml_to_bool(anim_str) : false;
             lv_bar_set_start_value(item, v, anim);
         }
-        if(lv_streq("min_value", name)) lv_bar_set_min_value(item, lv_xml_atoi(value));
+        else if(lv_streq("min_value", name)) lv_bar_set_min_value(item, lv_xml_atoi(value));
-        if(lv_streq("max_value", name)) lv_bar_set_max_value(item, lv_xml_atoi(value));
+        else if(lv_streq("max_value", name)) lv_bar_set_max_value(item, lv_xml_atoi(value));
-        if(lv_streq("orientation", name)) lv_bar_set_orientation(item, orientation_text_to_enum_value(value));
+        else if(lv_streq("orientation", name)) lv_bar_set_orientation(item, orientation_text_to_enum_value(value));
-        if(lv_streq("mode", name)) lv_bar_set_mode(item, mode_text_to_enum_value(value));
+        else if(lv_streq("mode", name)) lv_bar_set_mode(item, mode_text_to_enum_value(value));
+        else if(lv_streq("bind_value", name)) {
+            lv_subject_t * subject = lv_xml_get_subject(&state->scope, value);
+            if(subject) {
+                lv_bar_bind_value(item, subject);
+            }
+            else {
+                LV_LOG_WARN("Subject \"%s\" doesn't exist in bar bind_value", value);
+            }
+        }
     }
 }