Romance of the Three Kingdoms X with Power Up Kit (628060) display/mouse mismatch

Compatibility Report

• Name of the game with compatibility issues: Romance of the Three Kingdoms X with Power Up Kit
• Steam AppID of the game: 628060

System Information

• GPU: Intel Open Source Technology Center Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2) x86/MMX/SSE2
• Driver/LLVM version: 3.0 Mesa 18.3.6
• Kernel version: 5.1.6-300.fc30.x86_64
• Link to full system information report as Gist: https://gist.github.com/cheese/24cf55e75b8b51f034259f1e9bb7495f
• Proton version: 4.2-6

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

Symptoms

The game window starts from the top-left of the display monitor. But the mouse movable area is at the center of the display monitor. So coordinates are mismatched between display and mouse that the game is not playable.

Reproduction

Always. Also tested on another system with AMD GPU.

Start by reproducing the issue with Romance of the Three Kingdoms X with Power Up Kit (Steam AppID 628060) under Proton 4.2-6 on Linux, using the reported display and mouse behavior as the baseline. Review the compatibility report and system information, then verify that the mouse coordinates align with the game window and the game becomes playable.