Fix widgets not updating with parent's widget

Implement the twin_widget_children_paint function to repaint all the
box's widgets. The issue arises when the spline updates the pixmap
beneath the button widget, the pixmap of the button isn't triggered
to repaint. To solve this, we call the twin_widget_paint function after
the spline update to ensure the related widget will be repainted.

Signed-off-by: Wei-Hsin Yeh <weihsinyeh168@gmail.com>

Author: weihsinyeh

apps/spline.c

@@ -129,6 +129,7 @@ static twin_dispatch_result_t _apps_spline_update_pos(apps_spline_t *spline,
     spline->points[spline->which].y = twin_sfixed_to_fixed(
         _twin_matrix_y(&(spline->inverse_transition), x, y));
     _twin_widget_queue_paint(&spline->widget);
+    twin_widget_children_paint((spline->widget).parent);
     return TwinDispatchDone;
 }
 

include/twin.h

@@ -1124,6 +1124,9 @@ twin_angle_t twin_acos(twin_fixed_t x);
  * widget.c
  */
 
+/* Paint the widget children of the box. */
+void twin_widget_children_paint(twin_box_t *box);
+
 twin_widget_t *twin_widget_create(twin_box_t *parent,
                                   twin_argb32_t background,
                                   twin_coord_t width,

src/widget.c

@@ -200,6 +200,13 @@ void _twin_widget_bevel(twin_widget_t *widget, twin_fixed_t b, bool down)
     }
 }
 
+void twin_widget_children_paint(twin_box_t *box)
+{
+    /* Paint the widget children of the box. */
+    for (twin_widget_t *child = box->children; child; child = child->next)
+        _twin_widget_queue_paint(child);
+}
+
 twin_widget_t *twin_widget_create(twin_box_t *parent,
                                   twin_argb32_t background,
                                   twin_coord_t width,