Align with doc on file_download control (Avaiga#943)

* - Add code example for the file_download control
- Doc for download()

* Better (?) doc for file_download and linters.

* Comments

* Add chart rebuild property example

---------

Co-authored-by: Fabien Lelaquais <[email protected]>

doc/examples/charts/advanced-shapes.py

@@ -13,7 +13,7 @@
 # Python environment and run:
 #     python <script>
 # -----------------------------------------------------------------------------------------
-from taipy,gui import Gui
+from taipy.gui import Gui
 
 
 # Function to plot: x^3/3-x

doc/examples/charts/candlestick-simple.py

@@ -27,7 +27,7 @@
 
 page = """
 # Candlestick - Simple
- 
+
 <|{stock}|chart|type=candlestick|x=Date|open=Open|close=Close|low=Low|high=High|>
 """
 

doc/examples/charts/continuous-error-simple.py

@@ -66,7 +66,7 @@
 
 page = """
 # Continuous Error - Simple
- 
+
 <|{data}|chart|properties={properties}|>
 """
 

doc/examples/charts/example-rebuild.py

@@ -30,4 +30,4 @@
 <|{selected_type}|toggle|lov={types}|>
 """
 
-Gui(page=page).run()
+Gui(page).run()

doc/examples/controls/file_download-dynamic-temp-file.py

@@ -0,0 +1,78 @@
+# Copyright 2023 Avaiga Private Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+# an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the License.
+# -----------------------------------------------------------------------------------------
+# To execute this script, make sure that the taipy-gui package is installed in your
+# Python environment and run:
+#     python <script>
+# -----------------------------------------------------------------------------------------
+from taipy.gui import Gui, download
+from decimal import getcontext, Decimal
+from tempfile import NamedTemporaryFile
+import os
+
+# Initial precision
+precision = 10
+# Stores the path to the temporary file
+temp_path = None
+
+
+def pi(precision: int) -> list[int]:
+    """Compute Pi to the required precision.
+
+    Adapted from https://docs.python.org/3/library/decimal.html
+    """
+    saved_precision = getcontext().prec  # Save precision
+    getcontext().prec = precision
+    three = Decimal(3)  # substitute "three=3.0" for regular floats
+    lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
+    while s != lasts:
+        lasts = s
+        n, na = n + na, na + 8
+        d, da = d + da, da + 32
+        t = (t * n) / d
+        s += t
+    digits = []
+    while s != 0:
+        integral = int(s)
+        digits.append(integral)
+        s = (s - integral) * 10
+    getcontext().prec = saved_precision
+    return digits
+
+
+# Remove the temporary file
+def clean_up(state):
+    os.remove(state.temp_path)
+
+
+# Generate the digits, save them in a CSV temporary file, then trigger a download action
+# for that file.
+def download_pi(state):
+    digits = pi(state.precision)
+    with NamedTemporaryFile("r+t", suffix=".csv", delete=False) as temp_file:
+        state.temp_path = temp_file.name
+        temp_file.write("index,digit\n")
+        for i, d in enumerate(digits):
+            temp_file.write(f"{i},{d}\n")
+    download(state, content=temp_file.name, name="pi.csv", on_action=clean_up)
+
+
+page = """
+# File Download - Dynamic content
+
+Precision:
+
+<|{precision}|slider|min=2|max=10000|>
+
+<|{None}|file_download|on_action=download_pi|label=Download Pi digits|>
+"""
+
+Gui(page).run()

doc/examples/controls/file_download-dynamic.py

@@ -0,0 +1,69 @@
+# Copyright 2023 Avaiga Private Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+# the License. You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+# an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the License.
+# -----------------------------------------------------------------------------------------
+# To execute this script, make sure that the taipy-gui package is installed in your
+# Python environment and run:
+#     python <script>
+# -----------------------------------------------------------------------------------------
+from taipy.gui import Gui, download
+from decimal import getcontext, Decimal
+import io
+
+# Initial precision
+precision = 10
+
+
+def pi(precision: int) -> list[int]:
+    """Compute Pi to the required precision.
+
+    Adapted from https://docs.python.org/3/library/decimal.html
+    """
+    saved_precision = getcontext().prec  # Save precision
+    getcontext().prec = precision
+    three = Decimal(3)  # substitute "three=3.0" for regular floats
+    lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
+    while s != lasts:
+        lasts = s
+        n, na = n + na, na + 8
+        d, da = d + da, da + 32
+        t = (t * n) / d
+        s += t
+    digits = []
+    while s != 0:
+        integral = int(s)
+        digits.append(integral)
+        s = (s - integral) * 10
+    getcontext().prec = saved_precision
+    return digits
+
+
+# Generate the digits, save them in a CSV file content, and trigger a download action
+# so the user can retrieve them
+def download_pi(state):
+    digits = pi(state.precision)
+    buffer = io.StringIO()
+    buffer.write("index,digit\n")
+    for i, d in enumerate(digits):
+        buffer.write(f"{i},{d}\n")
+    download(state, content=bytes(buffer.getvalue(), "UTF-8"), name="pi.csv")
+
+
+page = """
+# File Download - Dynamic content
+
+Precision:
+
+<|{precision}|slider|min=2|max=10000|>
+
+<|{None}|file_download|on_action=download_pi|label=Download Pi digits|>
+"""
+
+Gui(page).run()

src/taipy/gui/gui_actions.py

@@ -24,9 +24,33 @@ def download(
 
     Arguments:
         state (State^): The current user state as received in any callback.
-        content: File path or file content.
+        content: File path or file content. See below.
         name: File name for the content on the client browser (defaults to content name).
-        on_action: Callback function to call when the download ends.
+        on_action: Callback function (or callback name) to call when the download ends. See below.
+
+    ## Notes:
+
+    - *content*: this parameter can hold several values depending on your use case:
+        - a string: the value must be an existing path name to the file that gets downloaded or
+          the URL to the resource you want to download.
+        - a buffer (such as a `bytes` object): if the size of the buffer is smaller than
+           the [*data_url_max_size*](../../gui/configuration/#p-data_url_max_size) configuration
+           setting, then the [`python-magic`](https://pypi.org/project/python-magic/) package is
+           used to determine the [MIME type](https://en.wikipedia.org/wiki/Media_type) of the
+           buffer content, and the download is performed using a generated "data:" URL with
+           the relevant type, and a base64-encoded version of the buffer content.<br/>
+           If the buffer is too large, its content is transferred after saving it in a temporary
+           server file.
+      - *on_action*: TODO CHECK<br/>
+           this callback is triggered when the transfer of the content is achieved.</br>
+           In this function, you can perform any clean up operation that could be required after
+           the download is performed.<br/>
+           This callback expects [] paramters:
+        - *state*: the `State^` instance of the caller.
+        - *id* (optional): a string representing the identifier of the caller. If this function is
+          called directly, this will always be "Gui.download". Some controls may also trigger
+          download actions, then *id* would reflect the identifier of those controls.
+        - *payload* (optional): an optional payload from the caller.
     """
     if state and isinstance(state._gui, Gui):
         state._gui._download(content, name, on_action)

src/taipy/gui/viselements.json

@@ -515,8 +515,8 @@
           {
             "name": "content",
             "default_property": true,
-            "type": "dynamic(url|path|file|ReadableBuffer)",
-            "doc": "The content of the file.<br/>If a buffer is provided (string, array of bytes...), and in order to prevent the bandwidth to be consumed too much, the way the data is transferred depends on the the <i>data_url_max_size</i> parameter of the application configuration (which is set to 50kB by default):\n<ul>\n<li>If the size of the buffer is smaller than this setting, then the raw content is generated as a data URL, encoded using base64 (i.e. <code>\"data:&lt;mimetype&gt;;base64,&lt;data&gt;\"</code>).</li>\n<li>If the size of the buffer is greater than this setting, then it is transferred through a temporary file.</li>\n</ul>"
+            "type": "dynamic(path|file|URL|ReadableBuffer|None)",
+            "doc": "The content to transfer.<br/>If this is a string, a URL, or a file, then the content is read from this source.<br/>If a readable buffer is provided (such as an array of bytes...), and to prevent the bandwidth from being consumed too much, the way the data is transferred depends on the <i>data_url_max_size</i> parameter of the application configuration (which is set to 50kB by default):\n<ul>\n<li>If the buffer size is smaller than this setting, then the raw content is generated as a data URL, encoded using base64 (i.e. <code>\"data:&lt;mimetype&gt;;base64,&lt;data&gt;\"</code>).</li>\n<li>If the buffer size exceeds this setting, then it is transferred through a temporary file.</li>\n</ul>If this property is set to None, that indicates that dynamic content is generated. Please take a look at the examples below for details on dynamic generation."
           },
           {
             "name": "label",
@@ -526,7 +526,7 @@
           {
             "name": "on_action",
             "type": "Callback",
-            "doc": "The name of a function that is triggered when the download is terminated (or on user action if content is None).<br/>All the parameters of that function are optional:\n<ul>\n<li>state (<code>State^</code>): the state instance.</li>\n<li>id (optional[str]): the identifier of the button.</li>\n<li>action (optional[str]): the name of the action that provoked the change.</li>\n<li>payload (dict): the details on this callback's invocation.<br/>\nThis dictionary has the following keys:\n<ul>\n<li>args: A list of two elements: <i>args[0]</i> reflects the <i>name</i> property and <i>args[1]</i> holds the file URL.</li>\n</ul>\n</li>\n</ul>",
+            "doc": "The name of a function that is triggered when the download is terminated (or on user action if <i>content</i> is None).<br/>All the parameters of that function are optional:\n<ul>\n<li>state (<code>State^</code>): the state instance.</li>\n<li>id (optional[str]): the identifier of the button.</li>\n<li>action (optional[str]): the name of the action that provoked the change.</li>\n<li>payload (dict): the details on this callback's invocation.<br/>\nThis dictionary has a single key:\n<ul>\n<li>args: A list of two elements: <i>args[0]</i> reflects the <i>name</i> property and <i>args[1]</i> holds the file URL.</li>\n</ul>\n</li>\n</ul>",
             "signature": [["state", "State"], ["id", "str"], ["action", "str"], ["payload", "dict"]]
           },
           {
@@ -612,8 +612,8 @@
           {
             "name": "content",
             "default_property": true,
-            "type": "dynamic(url|path|file|ReadableBuffer)",
-            "doc": "The image source.<br/>If a buffer is provided (string, array of bytes...), and in order to prevent the bandwidth to be consumed too much, the way the image data is transferred depends on the the <i>data_url_max_size</i> parameter of the application configuration (which is set to 50kB by default):\n<ul>\n<li>If the size of the buffer is smaller than this setting, then the raw content is generated as a\n  data URL, encoded using base64 (i.e. <code>\"data:&lt;mimetype&gt;;base64,&lt;data&gt;\"</code>).</li>\n<li>If the size of the buffer is greater than this setting, then it is transferred through a temporary\n  file.</li>\n</ul>"
+            "type": "dynamic(path|URL|file|ReadableBuffer)",
+            "doc": "The image source.<br/>If a buffer is provided (string, array of bytes...), and in order to prevent the bandwidth to be consumed too much, the way the image data is transferred depends on the <i>data_url_max_size</i> parameter of the application configuration (which is set to 50kB by default):\n<ul>\n<li>If the size of the buffer is smaller than this setting, then the raw content is generated as a\n  data URL, encoded using base64 (i.e. <code>\"data:&lt;mimetype&gt;;base64,&lt;data&gt;\"</code>).</li>\n<li>If the size of the buffer is greater than this setting, then it is transferred through a temporary\n  file.</li>\n</ul>"
           },
           {
             "name": "label",
@@ -1127,7 +1127,7 @@
           {
             "name": "page",
             "type": "dynamic(str)",
-            "doc": "The page to show as the content of the block (page name if defined or an URL in an <i>iframe</i>).<br/>This should not be defined if <i>partial</i> is set."
+            "doc": "The page to show as the content of the block (page name if defined or a URL in an <i>iframe</i>).<br/>This should not be defined if <i>partial</i> is set."
           },
           {
             "name": "height",