Pull Request: Fix SGR and PIXEL mouse modes blocked by mouse_event check

Summary

This PR fixes a bug where SGR (mode 1006) and PIXEL (mode 1016) mouse modes were not working in applications like less and vim due to an incorrect condition check.

The Bug

In src/tsm/tsm-vte.c, the SGR and PIXEL mode handlers check both the mouse mode AND the mouse_event flag:

} else if (vte->mouse_mode == TSM_VTE_MOUSE_MODE_SGR && vte->mouse_event) {
    // SGR handling code
}

} else if (vte->mouse_mode == TSM_VTE_MOUSE_MODE_PIXEL && vte->mouse_event) {
    // PIXEL handling code
}

Problem: When applications like less or vim activate SGR mouse mode, they don't always set vte->mouse_event first. The value remains 0, causing the condition && vte->mouse_event to evaluate to false, and the SGR/PIXEL handler never executes.

The Fix

Remove the && vte->mouse_event condition from both checks:

} else if (vte->mouse_mode == TSM_VTE_MOUSE_MODE_SGR) {
    // SGR handling code
}

} else if (vte->mouse_mode == TSM_VTE_MOUSE_MODE_PIXEL) {
    // PIXEL handling code
}

Rationale: The mouse_mode check alone is sufficient. If the mode is set to SGR or PIXEL, the handler should execute. The mouse_event flag is used internally to filter event types (press/release/motion), but shouldn't prevent the mode handler from running.

Test Cases

Before the fix:

• Run less --mouse in kmscon → mouse wheel does NOT work
• Run vim with :set mouse=a ttymouse=sgr → mouse wheel does NOT work (in some cases)

After the fix:

• Run less --mouse in kmscon → mouse wheel WORKS correctly
• Run vim with :set mouse=a ttymouse=sgr → mouse wheel WORKS correctly

Impact

This bug affects any application using libtsm that:

1. Activates SGR or PIXEL mouse modes
2. Doesn't explicitly set mouse_event before sending mouse events
3. Common examples: less, vim, emacs, nano with mouse support

Related Information

• SGR mode (1006) is the modern standard for mouse reporting in terminals
• It's supported by all major terminal emulators (xterm, gnome-terminal, etc.)
• This bug makes libtsm incompatible with standard terminal behavior

Compatibility

This change has no negative impact:

• Applications that DO set mouse_event will continue to work
• Applications that DON'T set mouse_event will now work correctly
• No API changes
• Purely a bug fix