Document the new signature of the `CreateCustomForm()` function (#573)

911edd7e (Resize before page initialization., 2025-10-23) changed the
signature, but did not adjust the documentation.

Signed-off-by: Johannes Schindelin <[email protected]>

ISHelp/isxclasses.footer

@@ -1,5 +1,5 @@
 <p><b>See also:</b><br />
-<tt>function <link topic="isxfunc_CreateCustomForm">CreateCustomForm</link>: TSetupForm;</tt><br />
+<tt>function <link topic="isxfunc_CreateCustomForm">CreateCustomForm</link>(const ClientWidth, ClientHeight: Integer; const KeepSizeX, KeepSizeY: Boolean): TSetupForm;</tt><br />
 <tt>function <link topic="isxfunc_CreateCustomPage">CreateCustomPage</link>(const AfterID: Integer; const ACaption, ADescription: String): TWizardPage;</tt><br />
 <tt>function <link topic="isxfunc_CreateDownloadPage">CreateDownloadPage</link>(const ACaption, ADescription: String; const OnDownloadProgress: TOnDownloadProgress): TDownloadWizardPage;</tt><br />
 <tt>function <link topic="isxfunc_CreateInputDirPage">CreateInputDirPage</link>(const AfterID: Integer; const ACaption, ADescription, ASubCaption: String; AAppendDir: Boolean; ANewFolderName: String): TInputDirWizardPage;</tt><br />

ISHelp/isxfunc.xml

@@ -2807,7 +2807,7 @@ Page := CreateOutputMsgMemoPage(wpWelcome,
     <subcategory>
       <function>
         <name>CreateCustomForm</name>
-        <prototype>function CreateCustomForm: TSetupForm;</prototype>
+        <prototype>function CreateCustomForm(const ClientWidth, ClientHeight: Integer; const KeepSizeX, KeepSizeY: Boolean): TSetupForm;</prototype>
         <description><p>Creates a form. The form is empty by default; you have to create your own controls afterward and place them on the form (by setting their Parent properties to the <link topic="scriptclasses" anchor="TSetupForm">TSetupForm</link> instance returned by this function).</p></description>
         <remarks><p>You should call this function instead of creating <link topic="scriptclasses" anchor="TForm">TForm</link> or <link topic="scriptclasses" anchor="TSetupForm">TSetupForm</link> instances directly. This function automatically initializes the font and other properties of the created form to be like Setup's other dialogs.</p>
 <p>The <tt>[LangOptions]</tt> section's <tt>DialogFontName</tt> and <tt>DialogFontSize</tt> directives determine the font used by the form and, by default, any child controls created on the form.</p></remarks>