feat(image): add data binding to image src

docs/src/details/widgets/image.rst

@@ -200,13 +200,13 @@ 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``)
+This method of subscribing to a pointer Subject affects a 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.
+the subject changes, the Image will be updated too.
 
-It support only pointer subjects.
+It supports only pointer subjects.
 
-- :cpp:expr:`lv_image_bind_src(slider, &subject)`
+- :cpp:expr:`lv_image_bind_src(img, &subject)`
 
 .. _lv_image_events:
 

src/others/xml/parsers/lv_xml_image_parser.c

@@ -61,12 +61,21 @@ void lv_xml_image_apply(lv_xml_parser_state_t * state, const char ** attrs)
         const char * value = attrs[i + 1];
 
         if(lv_streq("src", name)) lv_image_set_src(item, lv_xml_get_image(&state->scope, value));
-        if(lv_streq("inner_align", name)) lv_image_set_inner_align(item, image_align_to_enum(value));
-        if(lv_streq("rotation", name)) lv_image_set_rotation(item, lv_xml_atoi(value));
-        if(lv_streq("scale_x", name)) lv_image_set_scale_x(item, lv_xml_atoi(value));
-        if(lv_streq("scale_y", name)) lv_image_set_scale_y(item, lv_xml_atoi(value));
-        if(lv_streq("pivot_x", name)) lv_image_set_pivot_x(item, lv_xml_to_size(value));
-        if(lv_streq("pivot_y", name)) lv_image_set_pivot_y(item, lv_xml_to_size(value));
+        else if(lv_streq("inner_align", name)) lv_image_set_inner_align(item, image_align_to_enum(value));
+        else if(lv_streq("rotation", name)) lv_image_set_rotation(item, lv_xml_atoi(value));
+        else if(lv_streq("scale_x", name)) lv_image_set_scale_x(item, lv_xml_atoi(value));
+        else if(lv_streq("scale_y", name)) lv_image_set_scale_y(item, lv_xml_atoi(value));
+        else if(lv_streq("pivot_x", name)) lv_image_set_pivot_x(item, lv_xml_to_size(value));
+        else if(lv_streq("pivot_y", name)) lv_image_set_pivot_y(item, lv_xml_to_size(value));
+        else if(lv_streq("bind_src", name)) {
+            lv_subject_t * subject = lv_xml_get_subject(&state->scope, value);
+            if(subject) {
+                lv_image_bind_src(item, subject);
+            }
+            else {
+                LV_LOG_WARN("Subject \"%s\" doesn't exist in image bind_src", value);
+            }
+        }
     }
 }
 

src/widgets/image/lv_image.c

@@ -13,8 +13,9 @@
 #include "../../draw/lv_draw_private.h"
 #include "../../core/lv_obj_event_private.h"
 #include "../../core/lv_obj_class_private.h"
-#include "../../core/lv_obj_class_private.h"
 #include "../../core/lv_obj_draw_private.h"
+#include "../../core/lv_obj_class_private.h"
+#include "../../others/observer/lv_observer_private.h"
 
 #if LV_USE_IMAGE != 0
 
@@ -39,6 +40,11 @@ static void draw_image(lv_event_t * e);
 static void scale_update(lv_obj_t * obj, int32_t scale_x, int32_t scale_y);
 static void update_align(lv_obj_t * obj);
 static void reset_image_attributes(lv_obj_t * obj);
+
+#if LV_USE_OBSERVER
+    static void image_src_observer_cb(lv_observer_t * observer, lv_subject_t * subject);
+#endif /*LV_USE_OBSERVER*/
+
 #if LV_USE_OBJ_PROPERTY
     static void lv_image_set_pivot_helper(lv_obj_t * obj, lv_point_t * pivot);
     static lv_point_t lv_image_get_pivot_helper(lv_obj_t * obj);
@@ -653,6 +659,24 @@ const lv_image_dsc_t * lv_image_get_bitmap_map_src(lv_obj_t * obj)
     return img->bitmap_mask_src;
 }
 
+
+#if LV_USE_OBSERVER
+lv_observer_t * lv_image_bind_src(lv_obj_t * obj, lv_subject_t * subject)
+{
+    LV_ASSERT_NULL(subject);
+    LV_ASSERT_OBJ(obj, MY_CLASS);
+
+    if(subject->type != LV_SUBJECT_TYPE_POINTER) {
+        LV_LOG_WARN("Incompatible subject type: %d", subject->type);
+        return NULL;
+    }
+
+    lv_observer_t * observer = lv_subject_add_observer_obj(subject, image_src_observer_cb, obj, NULL);
+    return observer;
+}
+#endif /*LV_USE_OBSERVER*/
+
+
 /**********************
  *   STATIC FUNCTIONS
  **********************/
@@ -1035,6 +1059,18 @@ static void reset_image_attributes(lv_obj_t * obj)
     lv_obj_refresh_self_size(obj);
 }
 
+
+#if LV_USE_OBSERVER
+
+static void image_src_observer_cb(lv_observer_t * observer, lv_subject_t * subject)
+{
+    if(subject->type == LV_SUBJECT_TYPE_POINTER) {
+        lv_image_set_src(observer->target, subject->value.pointer);
+    }
+}
+
+#endif /*LV_USE_OBSERVER*/
+
 #if LV_USE_OBJ_PROPERTY
 static void lv_image_set_pivot_helper(lv_obj_t * obj, lv_point_t * pivot)
 {
@@ -1049,4 +1085,5 @@ static lv_point_t lv_image_get_pivot_helper(lv_obj_t * obj)
 }
 #endif
 
+
 #endif

src/widgets/image/lv_image.h

@@ -25,6 +25,7 @@ extern "C" {
 #include "../../core/lv_obj.h"
 #include "../../misc/lv_fs.h"
 #include "../../draw/lv_draw.h"
+#include "../../others/observer/lv_observer.h"
 
 /*********************
  *      DEFINES
@@ -338,6 +339,17 @@ lv_image_align_t lv_image_get_inner_align(lv_obj_t * obj);
  */
 const lv_image_dsc_t * lv_image_get_bitmap_map_src(lv_obj_t * obj);
 
+
+#if LV_USE_OBSERVER
+/**
+ * Bind a pointer Subject to an Image's source.
+ * @param obj       pointer to Image
+ * @param subject   pointer to Subject
+ * @return          pointer to newly-created Observer
+ */
+lv_observer_t * lv_image_bind_src(lv_obj_t * obj, lv_subject_t * subject);
+#endif
+
 /**********************
  *      MACROS
  **********************/

xmls/lv_image.xml

@@ -29,5 +29,6 @@ Example
 	    <prop name="scale_y" type="int" help=""/>
     	<prop name="pivot_x" type="int" help=""/>
     	<prop name="pivot_y" type="int" help=""/>
+        <prop name="bind_src" type="subject" />
 	</api>
 </widget>