fix margin-element node and make margin_top optional

CHANGELOG.md

@@ -10,6 +10,8 @@
   https://github.com/anvilistas/anvil-extras/pull/121
 * storage - update and clear were missing from the documented api
   https://github.com/anvilistas/anvil-extras/pull/125
+* PageBreak - fix margin_top property and make it optional
+  https://github.com/anvilistas/anvil-extras/pull/137
 
 ## Updates
 * Slider Component - bump javascript dependency and refactor. No changes to the component's public API.

client_code/PageBreak/__init__.py

@@ -13,7 +13,7 @@
 
 
 class PageBreak(PageBreakTemplate):
-    def __init__(self, margin_top, **properties):
+    def __init__(self, margin_top=0, **properties):
         self.margin_node = _S(anvil.js.get_dom_node(self)).find(".margin-element")
         self.margin_top = margin_top
         self.init_components(**properties)

client_code/PageBreak/form_template.yaml

@@ -3,11 +3,12 @@ container:
   properties: {tooltip: '', background: '', foreground: '', border: '', visible: true,
     role: null, html: "<!--\nBased on the snippet at https://anvil.works/forum/t/plots-in-pdf-being-divided-between-two-pages/7774/5\n\
       -->\n<div class=\"break-container\" style=\"overflow: hidden;\">\n  <div style=\"\
-      page-break-after:always;\"/>\n  <div style=\"margin-top: 0px;\"/>\n</div>\n\n\
-      <style>\n  .break-container {\n    border: 1px solid grey;\n  }\n  @media print\
-      \ {\n    .break-container {\n      border: none;\n    }\n  }\n</style>"}
+      page-break-after:always;\"/>\n  <div class=\"margin-element\" style=\"margin-top:\
+      \ 0px;\"/>\n</div>\n\n<style>\n  .break-container {\n    border: 1px solid grey;\n\
+      \  }\n  @media print {\n    .break-container {\n      border: none;\n    }\n\
+      \  }\n</style>"}
 components: []
 is_package: true
 custom_component: true
 properties:
-- {name: margin_top, type: number, default_value: 0, default_binding_prop: true}
+- {name: margin_top, type: number, default_value: 0, default_binding_prop: true, description: Use to adjust whitespace at the top of each page in the generated pdf. This is an optional property and defaults to 0. Can be positive or negative. Negative numbers will reduce whitespace in the generated pdf.}

docs/guides/components/page_break.rst

@@ -1,3 +1,7 @@
 PageBreak
 =========
 For use in forms which are rendered to PDF to indicate that a page break is required.
+
+The ``margin_top`` property is optional. In the generated pdf you may want more or less white space at the top of the page.
+You can set the ``margin_top`` property to a positive/negative number to adjust the whitespace.
+Most of the time this is unnecessary. This won't have any effect on the designer only the generated pdf.