NTU was the initial/code name for the project (ImMobile)

Welcome to the story behind NTU (NT Universal) — my attempt to create a true universal environment that works even on the earliest Windows builds and provides a desktop-like experience on limited, often abandoned hardware.

This project is powered by C++ and ImGui — a combination chosen for raw performance and flexibility. I want to take you through the journey — the problems I faced, the technical trenches I fell into, and the solutions I came up with, often through sheer persistence rather than perfection.

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UWP has been incredibly limiting—especially on older Windows devices that were forced to use it exclusively.

Microsoft’s main direction has been pushing .NET and XAML, shifting app dependencies from OS-level libraries to frameworks. As a result, we ended up with apps that were completely incompatible with older Windows builds (14393 and below). I constantly ran into situations where even small XAML components would break entire apps, and there were no known fixes for the compatibility issues.

On C++/DirectX level most apps that designed for UWP perform general DPI calculations, which result in oversized frame rendering on weak SoCs. Porting them into a XAML-based UI made things worse. Older Windows builds had memory leaks in some components, making the app progressively heavier the longer it ran.

To make matters worse, newer XAML libraries demanded significantly more system resources.

Even more complicated was trying to port apps like WUT (Windows Universal Tool) to Windows 8.1 using C#/XAML—it was nearly impossible.

Some essential .NET libraries were simply unavailable. I couldn’t even get a basic HTTP client working. Whether that was my fault or not, I didn’t face such issues with my ImMobile project, which used C++/DirectX/ImGui.

I spent years fixing and completing UWP apps for ARM32 that were abandoned by other developers.

Some of those efforts felt like a waste of time, especially with GPL-licensed projects where some owners were skeptical, thinking I was doing it for profit.

Others, like PPSSPP, and RetroArch, had friendly owners which was worth the efforts to have ARM32 port, but yet you may spend months and users may never know your name, this one of the reasons I dropped a lot of plans to push legacy support over the official repositories.

Some project owners didn’t seem to grasp the reality of investing precious time into legacy support. It’s a huge risk—your ideas and your work are out there in public, and we have 0% protection for even a single line of it.

That’s when I started to appreciate the MIT license. It promotes transparency and goodwill, but also encourages responsibility.

So, what now? The only real solution is to build your own thing—something based solely on what’s necessary, leaving behind the outdated environment.

Originally, I never imagined it would grow this large. My initial idea was just to create a simple grid with a click-and-show window.

But it turns out, building an environment—especially using my own complex calculation methods—was far more challenging.

Since I taught myself C/C++, I knew that any project I create should be:

• C++-friendly and easy to use

• Allow others to focus on logic, while NTU handles the heavy lifting: UI, system access, and touch input

That was—and still is—the vision.

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This was the first screenshot debug test of NTU (ImMobile)

at this moment I got that dialog and touch-pad..etc I though all will be easy and quick lol.

I had 2 projects coding on them in the same time, the main one Windows 10 (WinRT) and NTU for Windows 8.1 / Mobile (CX)

devenv_Z2b8EYjFfN.mp4

Generally after setting the bases during the early development I had to put 8.1 version on hold to boost the main one

it's hard and very much time consuming.. later it took nearly 30+ days (~2 month) to port the whole thing to 8.1 with more challenging issues.

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Let me take you through the biggest pain points I encountered, the decisions I made, and the stuff that just wouldn’t work until it finally did.

Each section here is a chapter of what was happening behind the scenes.

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The first major hurdle I hit? UWP file access—especially on Windows builds older than 14393.

Microsoft only allowed HANDLE from (StorageItem) starting from build 14393. Anything older than that? You're pretty much on your own.

So I had to implement two separate code paths:

• One for builds below 14393
• Another for builds 14393 and above

And the further back you go, the worse it gets. I had to come up with some really strange workarounds. Thankfully, I had prior experience from an earlier UWP storage project—that helped a lot.

Still, of course… it never goes smoothly.

In this kind of situation, you end up doing exactly what you were trying to avoid.

What does that mean?

It means you have to fall back to the basics—the old-school, legacy way of handling files. That means using things like fopen, fread, fwrite, and other file stream functions.

Most C/C++ codebases use those anyway. Some fall back to HANDLE (like libzip), but a 90% working solution is always better than something completely broken.

So I built a full emulation layer for fopen, fread, fwrite, and more, based on a fake FILE* wrapper that behaves just like the standard C API.

It was anything but easy—especially for the functions that involve formatted output. I ran into weird issues that forced me to manually parse format strings.

This part of the project was long, difficult, and time-consuming. I had to dive deep and understand how each stream function really works—the exact kind of low-level detail I always avoided every time I saw those functions in a library.

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UWP apps have a "Pause/OnSuspending" behavior — meaning the app (and its threads/render loop) gets paused whenever something else steals focus. This includes file pickers, which suspends the app until the user selects a file (on desktop this may differ).

As you'd expect, this introduces some bugs. For example, the file picker might close unexpectedly during file selection, and if the app doesn’t handle it properly, it may crash. Good luck debugging that.

So instead of relying on external pickers, why not do it the better way? Pick files directly in place — and manage them too.

I started with ImFileDialog, but had to modify it to make it usable in a mobile UWP context:

• On vertical mobile screens, the layout was nearly unusable.

• The on-screen keyboard would pop up and cover half the interface.

• Async file loading was necessary to prevent UI freezes.

Here's what I added:

• File previews

• Asynchronous loading

• Basic file operations (copy, delete, rename)

There were many other fixes and tweaks for the environment that I cannot remember.

One particularly tricky issue was navigation. On touchscreens, I don't like tap to open files directly, user may need to scroll, select before open.

Double-tap navigation was implemented and works, but due to varying frame rates and tap speeds, it wasn’t always reliable.

The solution? I made the left-side icon act as a button that opens a context menu — much more stable and touch-friendly, in tight area with a lot of files there is no empty space for the user to show the root context, so the root folder has sub menu button at the top so you can perform few tasks.

Showcase (Click Here)

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I used to think touch input would be simple. One tap = one event, right?

Nope. It turned out to be one of the hardest parts.

Handling touch properly meant analyzing input across multiple frames. For example:

• One tap? Might be a scroll.

• Tap and hold? Maybe it's a context menu.

• Two fingers? Possibly a zoom gesture.

I had to account for delays, offsets, visibility, and even the angle of your finger — because it can block what you're interacting with.

Touch behavior became an entire engine of its own.

It’s still not perfect, but after a lot of pain, I’d say it works around 70% correctly.

I’ve always believed: there’s no magic or “universal” solution to this stuff. At some point, you have to simulate the behavior manually, and handle it case by case.

In my WUT app, I had to write deep conditional logic just to handle navigation between pages. It may sound like a bad idea, but from a user experience perspective, it’s far better than relying on standard page navigation/caching systems.

Same applies here — I’m sure platforms like Android and iOS have deeply researched and highly tuned engines to interpret touch behavior. It’s not just "tap → event" — there’s a lot going on under the hood.

Another tricky example: the touch keyboard (input pane).

In theory, when you tap an input field, it should open. And when you tap outside, it should close.

But in practice? Sometimes I don’t want it to open — like when I was scrolling and my finger just happened to lift off over an input field. Same with the start menu — I wasn’t trying to open it; I was just scrolling horizontally and landed over it by accident.

These things happen quickly, but they trigger unwanted actions. Some parts of the UI has NoInput flags to prevent them from stealing focus and for better touch control, of course, that introduced extra problems that need to be handled.

And then there's the opposite case: like in a terminal, where I want to copy text but also keep the keyboard visible because I’m still typing. So I had to write separate behavior per scenario.

Even menus and submenus caused trouble. On vertical screens, a submenu might appear directly under your finger — which just touched the parent item. Because of release-delay handling, you might accidentally trigger the submenu as well.

Honestly, I could go on forever with touch-related headaches — but these are the kinds of problems I actually enjoy solving. After a lot of work, I finally reached a touch experience that feels... well, pretty fine.

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Since this environment is becoming a standalone platform, I wanted it to feel more like a desktop experience — multiple windows, taskbar, minimize/maximize behavior, and all the management that comes with it.

That’s when you start to really appreciate how complex operating systems are when it comes to window and focus management.

Here were some key challenges I had to solve:

• Handling focus across multiple windows
• Maintaining layout integrity on mobile rotation
• Preventing minimized windows from wasting CPU by continuing to render

Each window includes a default menu system with basic controls — options like fullscreen, fit to top/bottom, and a File menu containing actions like Close (and potentially more). These controls are essential, and I decided to make them part of every window by default.

I had to manually check when a user intends to close a window, such as when they hit the back button. Only the window currently in focus should respond and close.

By default, windows should not render if they’re not active (with some exceptions), to avoid wasting resources. So every window constantly checks whether it’s allowed to render before doing so.

But here's a tricky part: when a popup dialog appears, it steals focus. That would incorrectly mark the underlying window as inactive, even though it's technically still the parent. To solve this, I track whether a popup belongs to the current window. If it does, the window stays active and continues rendering.

Another issue I ran into was with certain windows (like configuration screens). When the window was reactivated from an inactive state, the scroll position would reset to the top. To fix this, each window maintains its own state object, storing details like:

• Whether it's minimized
• Current scroll position
• Whether it's rotated
• Custom flags and rendering behavior

One more subtle bug was related to tab interactions on touch devices. I had a workaround to enable easier tab switching via touch. But it introduced a weird edge case: if the current window was touched, and another window behind it had a tab located at the exact same screen position, the tab in the inactive window could get triggered.

I fixed this by adding stricter validation in the touch resolver — ensuring that only the currently focused window can respond to input.

Implementing minimize and maximize wasn’t simple either. There were a lot of edge cases that needed special handling — window positioning, input management, and focus recalculation.

To better control performance and behavior, I also added custom ImGui flags:

• RenderAlways — forces a window to render even when inactive.
• Render30FPS — useful for heavy-content windows that don’t need 60fps updates.
• TouchPad — allows touchpad to render over a window that has this flag only.

There is also the annoying touch keyboard part.

When an input field is focused, the touch keyboard should pop up. That works perfectly — as long as the input is near the top of the screen.

But if the input is located below the center, it gets completely blocked — especially in vertical orientation (don’t even ask about horizontal mode... it's worse).

To fix this, the input field needs to be scrolled into the visible area, above the keyboard. But that’s not as straightforward as it sounds.

First, you need to resize the window layout to fit within the available space above the keyboard. Then, you have to scroll just the right amount to make the selected input fully visible — ideally, centered within the new viewable area.

After many calculations, I got this workaround to work about 90% reliably. But it was a challenge, because any interaction — even a small one — could dismiss the keyboard unexpectedly, which meant everything had to revert gracefully.

Showcase (Click Here)

This one of the reasons you would see files browser fields at the top.

On Android, this problem is often avoided by presenting the input in a dedicated fullscreen layout, showing only the keyboard and the input field. This keeps the rest of the UI untouched and predictable.

I followed a similar approach in the hex editor: when editing an input, a separate dialog pops up specifically for that field. It's much cleaner for complex input cases, and I’m considering making it the default behavior — where a floating input dialog appears when you tap to edit text, ensuring a smoother and more consistent experience.

Showcase (Click Here)

Overall, it’s been a deep dive into UI architecture. There’s no one-size-fits-all solution — everything had to be carefully calculated and emulated to achieve the desktop-style behavior I wanted, especially on mobile and touch-based platforms.

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This was the first component I started working on after resolving the main app’s rendering, rotation, and resizing behavior.

In my earlier WUT app, managing settings was frustrating. Even though I had a (partial) settings engine, all settings were manually defined. Every time I needed to add a new setting, I had to duplicate logic across both XAML and C#.

Looking back, it's clear how much easier this could have been — especially now, using ImGui for UI rendering. It allows for more streamlined and dynamic setting panels.

However, building a universal configuration engine isn’t easy. It needs to handle a wide variety of data types and support persistent storage.

Initially, I used the app’s built-in preferences storage, since at the time I didn’t know how to properly save configs to an INI file — I was still learning the depths of C++.

The basic features like saving and retrieving int, bool, and similar types were working well.

The goal of the configs engine was to allow building a settings page with minimal code. I also added helper utilities to make the process even smoother.

It was a time-consuming task — and my first serious attempt at developing a full C++ application. I learned a lot, especially about pointer-related issues, as the engine relied heavily on them for real-time synchronization of values.

Later, I got SimpleIni library added and it made the ini save/restore possible.

below example on settings pages, dynamically building/drawing:

Showcase (Click Here)

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One of the first questions I asked myself back when I used Windows Phone was: "Why is there no built-in text editor or viewer?"

Because of that, I decided to include a default text viewer in my environment — so no one else would have to ask the same question.

When I started developing apps (around late 2019), I noticed how poorly some early versions of XAML/WinUI handled text.

Specifically, large text files loaded into input text components could cause serious memory leaks and performance issues — to the point where memory usage spiked and everything slowed down dramatically.

Now, don’t get me wrong — C#/XAML has its strengths and works great in many scenarios. This isn’t a criticism of the platform itself. But coming from a C#/XAML background, it felt nearly impossible to read and interact with large text files efficiently.

That’s when I came across ImGuiColorTextEdit. I had already been planning a more advanced text utility (as part of the NTU idea), and this seemed like a potential solution. Still, I had zero expectations for how fast C++/DirectX could be in practice.

But once I got it running, I was shocked — the performance was beyond anything I anticipated.

A smooth, colored, long-text editor running at 60 FPS on an ARM SoC — it felt like magic.

It completely changed how I viewed programming languages and any future UI framework I may use.

Of course, major credit goes to BalazsJako, the developer of ImGuiColorTextEdit. If the implementation hadn’t been done so well, none of this would’ve been possible — the environment doesn’t make things "magically fast" on its own.

Example on memory usage, same file opened using ImMobile (CPP) and WUT (.NET)

beside ImMobile was having another extra file opened during the test

The XAML elements (specifically text input) demand way too much RAM that make the app lagging too much

not to mentioned the extra left over RAM that depends on the GC to clean up later,

this was very serious when we are dealing with device has limited hardware

After integrating ImGuiColorTextEdit, though, I encountered a new set of challenges — especially around mobile use cases:

• Touch input caused odd selection behavior.
• The on-screen keyboard (input pane) would cover the editor.
• Cursor visibility often required manual scrolling.

You can't always predict how users will interact with a text editor — whether for viewing or editing.

For instance, if the user was just scrolling through a file and the input pane suddenly appeared, they’d be forced to tap outside of the text box — even though the text box itself might take up 90% of the screen.

These edge cases needed careful handling to avoid frustrating user experiences.

Another challenge was screen scaling. On devices with varying DPI settings, text size wasn’t always optimal. So I had to implement:

• Zoom in/out controls in the menus,
• Additional syntax highlighting themes,
• File save/open operations (UWP-compatible),
• A quick Markdown viewer with live updates,
• Bug fixes related to ARM memory heap behavior.

Despite all of this, it's one of the components I rarely had to revisit — it just worked. Huge thanks to BalazsJako — this widget was a real game-changer.

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When I began integrating a few samples early in development, one of the first issues I encountered was that certain ImGui elements didn’t respond to tap or touch input.

After a bit of research, I found a reference from Omar (ImGui's author) explaining that tab interactions typically require a few frames of hover before a click is registered.

However, in a touch interface, there's no concept of hover. So in this context, a tab that's hovered via touch should effectively be treated as clicked.

To address this, I implemented a solution that has gradually evolved over time. It manually switches tabs as soon as they're hovered via touch.

It was a tricky workaround, especially since in many environments, the native ImGui input flow isn’t used directly—instead, input is processed and then pointer actions are simulated. This made it necessary to carefully manage the state to ensure consistent behavior.

Handling DPI scaling was one of the most important things I tackled early on—and I’m very glad I did.

Without it, things would have quickly become chaotic across different devices, each potentially using its own DPI configuration.

It became even more complex once I added the ability for users to manually adjust the DPI scale, as well as to customize font scaling. These introduced additional layers of variability.

Fortunately, because the DPI and scaling logic were addressed early, it laid a strong foundation for creating a consistent and unified UI across all device types later in development.

ImGui doesn’t officially support keeping certain windows always on top, which makes sense given the framework’s design philosophy.

However, in our case, it was critical to ensure certain elements—like toolbars or input overlays—remain above others. For example, when a user taps into a text box and needs access to copy/paste tools, those should always appear above all other windows.

Thankfully, ImGui provides an internal function to bring a window to the front without affecting input focus. But initially, I observed a flicker—when tapping, the window would briefly be pushed back, then brought forward again. This behavior was once described in an ImGui issue as “windows fighting for z-index,” and it's difficult to resolve cleanly.

Eventually, I implemented a custom solution (involving some modifications to ImGui itself) to force specific windows to stay strictly on top. It now works as intended, with zero flicker.

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TBC....