improves transition to a new VL (explorer's NAD tab)

docs/user_guide/nad_widget.md

@@ -50,6 +50,7 @@ update_nad(nadwidget, svg, invalid_lf: bool = False, enable_callbacks: bool = Fa
 - invalid_lf: when True the opacity style for some of the displayed info's (e.g., active and reactive power) is decreased, making them barely visible in the diagram.
 - enable_callbacks: if True, enable the callbacks for selecting nodes (through a SHIFT+CLICK on a node) and moving nodes. Please note that this feature is working with versions of PyPowSyBl equal to or greater than v1.8.1.
 - grayout: if True, changes the diagram elements' color to gray.
+- keep_viewbox: if True, keeps the current diagram content, including pan and zoom settings.
 
 ## Customize widget's interactions
 By default, only the pan and zoom interactions with the diagram are active.

js/nadwidget.ts

@@ -77,10 +77,12 @@ function render({ model, el }: RenderProps<NadWidgetModel>) {
         model.send({ event: 'move_text_node' });
     };
 
-    function render_diagram(model: any): any {
+    function render_diagram(
+        model: any,
+        diagram_svg: string,
+        diagram_meta: string | null
+    ): any {
         const diagram_data = model.get('diagram_data');
-        const svg_data = diagram_data['svg_data'];
-        const metadata = diagram_data['metadata'];
         const is_invalid_lf = diagram_data['invalid_lf'];
         const is_grayout = diagram_data['grayout'];
         const is_enabled_callbacks = diagram_data['enable_callbacks'];
@@ -94,8 +96,8 @@ function render({ model, el }: RenderProps<NadWidgetModel>) {
 
         new NetworkAreaDiagramViewer(
             el_div,
-            svg_data,
-            metadata ? JSON.parse(metadata) : null,
+            diagram_svg,
+            diagram_meta ? JSON.parse(diagram_meta) : null,
             800,
             600,
             800,
@@ -119,12 +121,29 @@ function render({ model, el }: RenderProps<NadWidgetModel>) {
         return el_div;
     }
 
-    const diagram_element = render_diagram(model);
+    const diagram_element = render_diagram(
+        model,
+        model.get('diagram_data')['svg_data'],
+        model.get('diagram_data')['metadata']
+    );
     el.appendChild(diagram_element);
 
     model.on('change:diagram_data', () => {
+        const diagram_data = model.get('diagram_data');
+        const keep_viewbox = diagram_data['keep_viewbox'];
+        let diagram_svg = '';
+        let diagram_meta = null;
+
         const nodes = el.querySelectorAll('.svg-nad-viewer-widget')[0];
-        const new_el = render_diagram(model);
+
+        if (keep_viewbox) {
+            diagram_svg = nodes.querySelector(':scope > svg')?.outerHTML ?? '';
+        } else {
+            diagram_svg = diagram_data['svg_data'];
+            diagram_meta = diagram_data['metadata'];
+        }
+
+        const new_el = render_diagram(model, diagram_svg, diagram_meta);
         el.replaceChild(new_el, nodes);
     });
 }

src/pypowsybl_jupyter/nadwidget.py

@@ -88,7 +88,7 @@ def display_nad(svg, invalid_lf: bool = False, enable_callbacks: bool = False, g
     svg_metadata = "" if not enable_callbacks else _get_svg_metadata(svg)
     return NadWidget(diagram_data= {"svg_data": svg_value, "metadata": svg_metadata, "invalid_lf": invalid_lf, "enable_callbacks": enable_callbacks, "grayout": grayout})
 
-def update_nad(nadwidget, svg, invalid_lf: bool = False, enable_callbacks: bool = False, grayout:  bool = False):
+def update_nad(nadwidget, svg, invalid_lf: bool = False, enable_callbacks: bool = False, grayout:  bool = False, keep_viewbox: bool = False):
     """
     Updates an existing NAD widget with a new SVG content
 
@@ -98,6 +98,7 @@ def update_nad(nadwidget, svg, invalid_lf: bool = False, enable_callbacks: bool
         invalid_lf: when True the opacity style for some of the displayed info's (e.g., active and reactive power) is decreased, making them barely visible in the diagram.
         enable_callbacks: if True, enable the callbacks for moving and selecting nodes in the diagram. Please note that this feature is working with versions of PyPowSyBl equal or greater than v1.8.1.
         grayout: if True, changes the diagram elements' color to gray.
+        keep_viewbox: if True, keeps the current diagram content, including pan and zoom settings.
 
     Examples:
 
@@ -108,4 +109,4 @@ def update_nad(nadwidget, svg, invalid_lf: bool = False, enable_callbacks: bool
 
     svg_value=_get_svg_string(svg)
     svg_metadata = "" if not enable_callbacks else _get_svg_metadata(svg)
-    nadwidget.diagram_data= {"svg_data": svg_value, "metadata": svg_metadata, "invalid_lf": invalid_lf, "enable_callbacks": enable_callbacks, "grayout": grayout}
+    nadwidget.diagram_data= {"svg_data": svg_value, "metadata": svg_metadata, "invalid_lf": invalid_lf, "enable_callbacks": enable_callbacks, "grayout": grayout, "keep_viewbox": keep_viewbox}

src/pypowsybl_jupyter/networkexplorer.py

@@ -225,13 +225,13 @@ def compute_nad_data(el, depth=0):
 
     current_nad_data = compute_nad_data(None)
 
-    def update_nad_widget(new_diagram_data, enable_callbacks=True, grayout=False):
+    def update_nad_widget(new_diagram_data, enable_callbacks=True, grayout=False, keep_viewbox=False):
         nonlocal nad_widget
         if nad_widget==None:
             nad_widget=display_nad(new_diagram_data, enable_callbacks=enable_callbacks, grayout=grayout)
             nad_widget.on_select_node(lambda event : go_to_vl_from_nad(event))
         else:
-            update_nad(nad_widget,new_diagram_data, enable_callbacks=enable_callbacks, grayout=grayout)
+            update_nad(nad_widget,new_diagram_data, enable_callbacks=enable_callbacks, grayout=grayout, keep_viewbox=keep_viewbox)
 
     in_progress_widget=widgets.HTML(value=PROGRESS_EMPTY_SVG, 
                                     layout=widgets.Layout(width='30', justify_content='flex-end', margin='0px 20px 0px 0px'))
@@ -254,9 +254,9 @@ def disable_in_progress():
     def update_nad_diagram(el):
         nonlocal current_nad_data, nad_displayed_vl_id
         if nad_widget != None:
-            enable_in_progress()
-            update_nad_widget(current_nad_data, enable_callbacks=False, grayout=True)
+            update_nad_widget('', enable_callbacks=False, grayout=True, keep_viewbox=True)
             display(nad_widget)
+            enable_in_progress()
             update_sld_widget(current_sld_data, True, enable_callbacks=False)
             display(sld_widget)
             if map_widget != None: