add example which generates a pdf

examples/generate_pdf/main.py

@@ -0,0 +1,51 @@
+from io import BytesIO
+from pathlib import Path
+
+import cairo
+
+from nicegui import ui
+
+
+def generate_svg() -> str:
+    output = BytesIO()
+    surface = cairo.SVGSurface(output, 200, 150)
+    draw(surface)
+    surface.finish()
+    return output.getvalue().decode('utf-8')
+
+
+def generate_pdf() -> bytes:
+    output = BytesIO()
+    surface = cairo.PDFSurface(output, 200, 150)
+    draw(surface)
+    surface.finish()
+    return output.getvalue()
+
+
+def draw(surface: cairo.SVGSurface):
+    context = cairo.Context(surface)
+
+    context.select_font_face("Arial", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
+    context.set_font_size(20)
+    context.move_to(10, 40)
+    context.show_text(f"{name_input.value}")
+    context.move_to(10, 80)
+    context.show_text(f"{email_input.value}")
+
+
+def update():
+    preview.content = generate_svg()
+    Path('output.pdf').write_bytes(generate_pdf())
+
+
+with ui.row().classes('items-stretch gap-12'):
+    with ui.column():
+        name_input = ui.input("Name", placeholder="Enter your name", on_change=update)
+        email_input = ui.input("E-Mail", placeholder="Enter your E-Mail address", on_change=update)
+    with ui.column():
+        preview = ui.html().classes('w-[400px] h-[300px] border-2 border-gray-500')
+    with ui.column():
+        ui.button("Download PDF", on_click=lambda: ui.download('output.pdf'))\
+            .bind_visibility_from(preview, 'content')
+
+ui.run()

examples/generate_pdf/requirements.txt

@@ -0,0 +1,2 @@
+pycairo
+nicegui

main.py

@@ -342,6 +342,7 @@ async def index_page(client: Client) -> None:
                          'Demonstrate using the official '
                          '[zauberzeug/nicegui](https://hub.docker.com/r/zauberzeug/nicegui) docker image')
             example_link('Download Text as File', 'providing in-memory data like strings as file download')
+            example_link('Generate PDF', 'create SVG preview and PDF download from input form elements')
 
     with ui.row().classes('dark-box min-h-screen mt-16'):
         link_target('why')