No flash when play lightgun games

[beudbeud]

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Platform / OS / Hardware: Linux / Recalbox / Raspberry Pi 5

Flycast version: 2.4 libretro

Hardware:

Description of the Issue

When i watch let's play on House of the dead 2 on Dreamcast hardware there are flash when peaple shoot.
So i wanna know if it will be possible to add this flash for play with a real lightgun like goncon2 on CRT with Flycast

exemple https://youtu.be/IK19TayAH5o?t=322

Debugging Steps Tested

• Play House of the Dead 2
• Trigger the shoot
• No flash coming

[flyinghead]

This works in Flycast but you need to have a window wider than 4:3 to see the flashes. The flashes are produced by changing the color of the screen border, which is invisible on 4:3 window. Obviously this is different on real CRT screen depending on its settings.