RT#7741: Bug: Touch device: Menu's always expand left, even with mouse control

[rakunavi]

Hello all,

I am writing to report a significant UX inconsistency regarding how menus are displayed in PDF-XChange Editor, particularly on stylus-enabled devices.

The Problem: "Zigzag" Mouse Movement

In standard Windows applications, all menus—including the main menu and context menus—are designed to expand to the bottom-right of the cursor or the anchor point. Submenus also naturally expand to the right as you navigate the hierarchy.

• notepad.png

However, in PDF-XChange Editor, with the default Windows settings on stylus-enabled devices, all menus and submenus will expand to the bottom-left unless constrained by the display space. This behavior occurs regardless of whether it is a context menu or a dropdown from the main UI. This is the exact opposite of the standard Windows UX.

• pdfxce.png

This forced “leftward” expansion creates unnatural and inefficient mouse movement paths. For example, changing text size from the Bookmarks pane's context menu proceeds as follows:

1. Right-click in the Bookmarks pane to display the context menu.
2. The context menu will appear below and to the left of the mouse cursor.
3. Move the mouse left to hover over “View Options”.
4. Move the mouse right to hover over the submenu “Text Size”.
5. Move the mouse left to select the text size option.

• figure1.png
  
  
  video1.webm

If the Bookmarks pane is positioned on the left edge by default, this “Zigzag” motion is typically forced upon you. This isn't limited to context menus; the deeper the menu hierarchy—such as in Classic Toolbars menus—the more likely such operations become necessary.

In almost every other Windows application, the movement is a predictable "left-to-right" flow. PDF-XChange Editor’s current behavior forces users to move against their muscle memory. Furthermore, even when menus expand to the left, the ">" indicator remains on the right edge of the menu item, which is visually inconsistent with the expansion direction.

• video2.webm

The Technical Root Cause:

After a thorough investigation, I discovered that PDF-XChange Editor is strictly adhering to the Windows "Handedness" (MenuDropAlignment) flag.

• Registry path: HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows
• On stylus-enabled devices, Windows sets this to "Right-handed" by default to prevent menus from being hidden by the user's hand during pen input.
• This setting is linked to “Choose which hand you write with” in Windows Settings under “Bluetooth & devices > Pen & Windows Ink”. “Right” is the default, and in that case, “MenuDropAlignment” is set to 1. If you select ‘Left’, “MenuDropAlignment” is set to 0.
  figure2.png

PDF-XChange Editor lacks a pop-up menu for stylus use, making the context menu the only alternative. In this case, setting your dominant hand to right-handed can make it slightly more usable by preventing the context menu from appearing under your hand. However, once you make this setting, PDF-XChange Editor will expand all menu items to the left side, not only when using a stylus but also when using a mouse. Other modern apps (Explorer, Notepad, Office, etc.) ignore this flag when a mouse is used to maintain UI consistency.

The following video demonstrates whether the direction in which the context menu expands changes when you modify the “Choose which hand you write with” option from the default ‘Right’ to “Left” in both PDF-XChange Editor and Notepad. As you can see, PDF-XChange Editor changes direction based on the setting, while Notepad always expands and displays on the right side.

• video3.webm

My Request:

As a heavy stylus user, keeping the Windows settings for "Choose which hand you write with" option as “Right” makes sense, even if it's just to display the context menu on the left side of the pen when using the stylus. Also, since I understand all the circumstances, I can somehow tolerate the zigzag mouse movements. However, not all users of stylus-enabled PCs in the world are like that. For users who only use a mouse despite having a stylus enabled, the behavior of menus expanding on the left side must feel extremely strange.

Could you consider the following improvements?

1. Input Detection: Distinguish between mouse and stylus input, and default to "expand-to-right" when a mouse is detected.
2. Manual Toggle: Provide an option in the Preferences (e.g., under "Customize UI") to force menus to expand to the right, regardless of the system's Handedness setting.

I believe this adjustment would significantly improve the professional workflow for users who switch between stylus and mouse.

Hoping that the above information will be of some help to you.
Thank you so much for your continued support.

Best regards,
rakunavi

- PDF-XChange Editor PRO Version: 10.8.2 build 407
- OS Version: Windows 11 Pro / Home 25H2 Build 26200.7623
- PC Model: GMKtec Nucbox M7 Pro with HUION Kamvas Pro 19 / Lenovo IdeaPad C340-15IWL

[EDIT] Since a ticket has been officially issued for this matter, I have changed the topic title as follows. 2026-2-5 6:00 JST (UTC+9)

• Previous Title: All menus expand to the left on stylus-enabled devices, causing poor UX during mouse operation
• New Title: RT#7741: Bug: Touch device: Menu's always expand left, even with mouse control

[Daniel - PDF-XChange]

Hello, rakunavi

Thank you for the report, I have reproduced this and raised it to the Dev team. Hopefully we can see a resolution in the future.

RT#7741: Bug: Touch device: Menu's always expand left, even with mouse control

Kind regards,

[rakunavi]

Thank you, Daniel, for creating the ticket!

Thank you for taking time out of your busy schedule.
Please give my best regards to developers.

Best regards,
rakunavi

[Daniel - PDF-XChange]