Myanmar Language font changed after iOS 18.4

It would help to see the relevant code for this, as it might be that something related to something you've coded has changed between the two versions.

I notice you have 18.2 and 18.4. Is it broken on 18.3, too?

This is my code and I haven't changed it. This is used to run on both 18.2 and 18.4. Also it didn't happened on 18.3. I have provided a screenshot also.

struct PracticeScreen: View {
    @EnvironmentObject private var vm: HomeViewModel
    @AppStorage("count") private var count = 0
    @AppStorage("round") private var round = 0
    @State private var showDialog = false
    @State private var showComplete = false
    private let totalCount = 108
 
    var body: some View {
        ZStack {
            Color(UIColor.systemGroupedBackground)
                .ignoresSafeArea()
 
            if case .active = vm.status, !vm.todayCompleted {
                VStack {
                    Text(vm.currentPrayer?.day.desc ?? "")
                        .font(.title3)
                        .fontWeight(.medium)
                        .foregroundStyle(.accent)
                        .padding(.bottom, 4)
 
                    Text(vm.currentPrayer?.mantra ?? "")
                        .lineLimit(2, reservesSpace: true)
                        .multilineTextAlignment(.center)
                        .font(.system(size: 40, weight: .bold, design: .rounded))
 
                    Spacer()
 
                    // clipped number text
                    Text("\(count.toMyanmarDigits())")
                        .font(.system(size: 40, weight: .bold, design: .rounded))
                        .monospaced()
                        .foregroundStyle(.accent)
 
                    Button {
                        addCount()
                    } label: {
                        ZStack {
                            Circle()
                                .stroke(.accent, lineWidth: 10)
                                .frame(width: 250, height: 250)
 
                            Circle()
                                .fill(
                                    .accent.opacity(0.5)
                                )
                                .frame(width: 230, height: 230)
 
                            Text("Count")
                                .font(.system(size: 36, weight: .bold))
                                .foregroundStyle(.accent)
                        }
                    }
                    .buttonStyle(PressableButtonStyle())
 
                    Spacer()
 
                    HStack(spacing: 20) {
                        Text("အပတ်ရေ: \(round.toMyanmarDigits()) /\((vm.currentPrayer?.rounds ?? 0).toMyanmarDigits())")
                            .font(.footnote)
                            .foregroundStyle(.white)
                            .padding(.horizontal, 10)
                            .padding(.vertical, 12)
                            .frame(maxWidth: .infinity)
                            .background(
                                Capsule()
                                    .fill(.accent)
                            )
 
                        Button {
                            showDialog.toggle()
                        } label: {
                            Image(systemName: "arrow.clockwise")
                                .font(.footnote)
                                .foregroundStyle(.white)
                                .padding(12)
                                .background(
                                    Circle()
                                        .fill()
                                )
                        }
 
                        Text("Count: \(count.toMyanmarDigits()) /\(totalCount.toMyanmarDigits())")
                            .font(.footnote)
                            .foregroundStyle(.white)
                            .padding(.horizontal, 10)
                            .padding(.vertical, 12)
                            .frame(maxWidth: .infinity)
                            .background(
                                Capsule()
                                    .fill(.accent)
                            )
                    }
                }
                .padding()
                .padding(.bottom)
            } else {
                NoticeCard(status: vm.status)
            }
        }
        .confirmationDialog("အဓိဌာန် အစမှ ပြန်စမလား?", isPresented: $showDialog, titleVisibility: .visible) {
            Button("အစမှ ပြန်စမည်။", role: .destructive, action: resetCount)
            Button("မလုပ်တော့ပါ", role: .cancel, action: {})
        }
        .alert("ဒီနေ့ အဓိဌာန် ပြီးဆုံးပါပြီ", isPresented: $showComplete) {
            Button("ပြီးဆုံးပါပြီ") {
                vm.markTodayComplete()
            }
 
            Button("မလုပ်တော့ပါ", role: .destructive, action: {})
        }
        .navigationTitle("ဒီနေ့ အဓိဌာန်")
        .navigationBarTitleDisplayMode(.inline)
        .toolbar {
            if case .active = vm.status, !vm.todayCompleted {
                ToolbarItem(placement: .topBarTrailing) {
                    Button("ပြီးဆုံးပါပြီ") {
                        showComplete.toggle()
                    }
                }
            }
        }
    }
}

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What happens if you set the frame height ?

Text("\(count.toMyanmarDigits())")
    .frame(height: 50)  // or even 60
    .font(.system(size: 40, weight: .bold, design: .rounded))
    .monospaced()
    .foregroundStyle(.accent)
 

Unfortunately setting the frame height to 60 or may be 100 doesn't fix it. It still clipped the Myanmar's number both on top and bottom.

The problem could come from the baseline offset:

https://stackoverflow.com/questions/69760382/how-do-i-fix-clipped-ascenders-and-descenders-in-a-custom-font

See more here: https://medium.com/mobimeo-technology/what-if-your-designers-want-a-baseline-grid-on-ios-d5234c7b52c0

Here on how to change offset (through attributes): https://developer.apple.com/forums/thread/124799

Why did it change in iOS 18.4 is another question…