[iOS 26] Fix DisplayPromptAsync maxLength not enforced due to new multi-range delegate

[Shalini-Ashokan]

Issue Details

On iOS 26, DisplayPromptAsync ignores the maxLength parameter, allowing users to enter an unlimited number of characters beyond the specified limit.

Root Cause

iOS 26 introduced a new delegate method, ShouldChangeCharactersInRanges, which accepts multiple text ranges instead of the older ShouldChangeCharacters method. On iOS 26, the old delegate is no longer invoked, causing MAUI’s maxLength enforcement to break.

Description of Change

A runtime version check was added to use the ShouldChangeCharactersInRanges delegate on iOS 26 and later, and the ShouldChangeCharacters delegate on earlier iOS versions. The new delegate calculates the total text length by summing all range lengths and validating the result against maxLength.

Validated the behavior in the following platforms

• Android
• Windows
• iOS
• Mac

Issues Fixed

Fixes #33549

Test case

In the test for DisplayPromptAsync, there is no supported way to type text into the display prompt text fields using Appium.

Output ScreenShot

Before	After
33549-BeforeFix.mov	33549-AfterFix.mov

[dotnet-policy-service]

Hey there @@Shalini-Ashokan! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[darrabam]

@Shalini-Ashokan Thank you for taking the time to fix it, I've tested the artifact and confirm that it fixes the maxLength issue.
But there is another issue mentioned in #33549 which is the incorrect text alignment when the page/app is RightToLeft. The text will be aligned LTR even though the page/app is set to RTL. So, since you worked on this, could you please fix that issue as well?
Note that the old behavior is to have the text aligned at center regardless of page orientation.

[Shalini-Ashokan]

@Shalini-Ashokan Thank you for taking the time to fix it, I've tested the artifact and confirm that it fixes the maxLength issue. But there is another issue mentioned in #33549 which is the incorrect text alignment when the page/app is RightToLeft. The text will be aligned LTR even though the page/app is set to RTL. So, since you worked on this, could you please fix that issue as well? Note that the old behavior is to have the text aligned at center regardless of page orientation.

@darrabam, I have investigated and found that this appears to be a native-level issue. I have attached a video of a native sample for reference.

iOS26-Alignment.mov

[darrabam]

@Shalini-Ashokan fair enough, I also tried different combinations of RTL marks (\u202B , \u202E, \u2067, \u061C), but none of them forced the text to RTL. Let's hope that this is just a bug in iOS26.1 and will be resolved in further updates.

@jfversluis could you please review this PR? I've tested it and it resolves the issue, thanks!

[Copilot]

Pull request overview

This PR fixes a critical bug on iOS 26 where DisplayPromptAsync ignores the maxLength parameter, allowing users to enter unlimited characters. The issue occurs because iOS 26 introduced a new delegate method ShouldChangeCharactersInRanges that accepts multiple text ranges, replacing the older ShouldChangeCharacters method which is no longer invoked on iOS 26.

Changes:

• Added runtime version check to use the appropriate delegate method based on iOS version
• Implemented new multi-range delegate logic for iOS 26+ that sums all range lengths and validates against maxLength
• Maintained backward compatibility by keeping the old single-range delegate for iOS versions prior to 26