Some documentation.

ISHelp/isetup.xml

@@ -1554,7 +1554,8 @@ Source: "README.TXT"; DestDir: "{app}"; Flags: isreadme
 <param name="Source" required="yes">
 <p>The name of the <i>source file</i>. The compiler will prepend the path of your installation's <link topic="sourcedirectorynotes">source directory</link> if you do not specify a fully qualified pathname.</p>
 <p>This can be a wildcard to specify a group of files in a single entry. When a wildcard is used, all files matching it use the same options.</p>
-<p>When the flag <tt>external</tt> is specified, <tt>Source</tt> must be the full pathname of an existing file (or wildcard) on the distribution media or the user's system (e.g. "{src}\license.ini").</p>
+<p>When the flag <tt>external</tt> is specified but the flag <tt>download</tt> is not, <tt>Source</tt> must be the full pathname of an existing file (or wildcard) on the distribution media or the user's system (e.g. "{src}\license.ini").</p>
+<p>When the flag <tt>external</tt> is specified and the flag <tt>download</tt> is also, <tt>Source</tt> must be the URL of the file to download.</p>
 <p>Constants may only be used when the <tt>external</tt> flag is specified, because the compiler does not do any constant translating itself.</p>
 <examples>
 <pre>
@@ -1665,6 +1666,16 @@ ExternalSize: 1048576; Flags: external
 <p>This parameter is ignored if the <tt>extractarchive</tt> flag isn't also specified.</p>
 </param>
 
+<param name="DownloadUserName">
+<p>Specifies the basic authentication username to use for the file download.</p>
+<p>This parameter is ignored if the <tt>download</tt> flag isn't also specified.</p>
+</param>
+
+<param name="DownloadPassword">
+<p>Specifies the basic authentication password to use for the file download. Please be aware that this password is stored in an unencrypted form in the resulting Setup file(s), even if you have enabled encryption (using the [Setup] section directive <tt>Encryption</tt>).</p>
+<p>This parameter is ignored if the <tt>download</tt> flag isn't also specified.</p>
+</param>
+
 <param name="Flags">
 <p>This parameter is a set of extra options. Multiple options may be used by separating them by spaces. The following options are supported:</p>
 
@@ -1708,14 +1719,23 @@ Instructs Setup to proceed to comparing time stamps (last write/modified time) i
 <p>Prevents Setup from verifying the file checksum after extraction. Use this flag on files you wish to modify while already compiled into Setup.</p>
 <p>Must be combined with <tt>nocompression</tt>.</p>
 </flag>
+<flag name="download">
+<p>This flag instructs Setup not to copy an existing file, but instead to download it. Optionally use the <tt>DownloadUserName</tt> and <tt>DownloadPassword</tt> parameters to specify a basic authentication username and password.</p>
+<p>This flag must be combined with the <tt>DestName</tt> and <tt>ExternalSize</tt> parameters.</p>
+<p>This flag also must be combined with the <tt>external</tt> and <tt>ignoreversion</tt> flags, meaning it should only be used on files private to your application, <i>never</i> on shared system files.</p>
+<p>This flag cannot be combined with the <tt>comparetimestamp</tt>, <tt>extractarchive</tt>, and <tt>recursesubdirs</tt> flags.</p>
+<p>Supports HTTPS (but not expired or self-signed certificates) and HTTP. Redirects are automatically followed and proxy settings are automatically used. Safe to use from services.</p>
+</flag>
 <flag name="external">
 <p>This flag instructs Inno Setup not to statically compile the file specified by the <tt>Source</tt> parameter into the installation files, but instead to copy from an existing file on the distribution media or the user's system. See the <tt>Source</tt> parameter description for more information.</p>
+<p>When combined with the <tt>download</tt> or <tt>extractarchive</tt> flags, Setup does not copy the file, but instead downloads or extracts it.</p>
 </flag>
 <flag name="extractarchive">
-<p>This flag instructs Inno Setup not to copy an existing archive file, but instead to extract it. Optionally use the <tt>ExtractArchivePassword</tt> parameter to specify a password.</p>
+<p>This flag instructs Setup not to copy an existing archive file, but instead to extract it. Optionally use the <tt>ExtractArchivePassword</tt> parameter to specify a password.</p>
 <p>The supported archive formats, beyond .7z, and the support for password-protected archives, depend on the <link topic="setup_archiveextraction">ArchiveExtraction</link> [Setup] section directive, that must not be set to <tt>basic</tt>.</p>
 <p>This flag must be combined with the <tt>external</tt> and <tt>ignoreversion</tt> flags, meaning it should only be used on files private to your application, <i>never</i> on shared system files.</p>
 <p>This flag is usually combined with the <tt>recursesubdirs</tt> and <tt>createallsubdirs</tt> flags.</p>
+<p>This flag cannot be combined with <tt>download</tt>.</p>
 <p>Using a solid archive is not recommended; extraction performance may degrade depending on the solid block size.</p>
 </flag>
 <flag name="fontisnttruetype">
@@ -1814,6 +1834,7 @@ Instructs Setup to proceed to comparing time stamps (last write/modified time) i
 </flag>
 <flag name="skipifsourcedoesntexist">
 <p>This flag instructs the compiler -- or Setup, if the <tt>external</tt> flag is also used -- to silently skip over the entry if the source file does not exist, instead of displaying an error message.</p>
+<p>When combined with the <tt>download</tt> flag, this flag instructs Setup to skip if the download fails for any reason.</p>
 </flag>
 <flag name="solidbreak">
 <p>When <link topic="setup_solidcompression">solid compression</link> is enabled, this flag instructs the compiler to finalize the current compression stream and begin a new one before compressing the file(s) matched by <tt>Source</tt>. This allows Setup to seek to the file instantly without having to decompress any preceding files first. May be useful in a large, multi-component installation if you find too much time is being spent decompressing files belonging to components that weren't selected.</p>