gg: fix .char event handling for backspace, delete, tab and enter for linux/x11 (send appropriate .char codes to the apps, similar to macos)

Author: spytheman

vlib/gg/gg.c.v

@@ -468,6 +468,28 @@ fn gg_event_fn(ce voidptr, user_data voidptr) {
 			// dump(e)
 		}
 	}
+	$if linux {
+		if e.typ == .key_down && e.key_code in [.backspace, .delete, .enter, .tab] {
+			// with X11, sokol does not send .char events for some keys; we will emulate them for consistency here:
+			e.char_code = match e.key_code {
+				.backspace { u32(8) }
+				.tab { 9 }
+				.enter { 13 }
+				.delete { 127 }
+				else { u32(e.key_code) }
+			}
+			e.key_code = .invalid
+			e.typ = .char
+			if ctx.config.event_fn != unsafe { nil } {
+				ctx.config.event_fn(e, ctx.config.user_data)
+			} else if ctx.config.on_event != unsafe { nil } {
+				ctx.config.on_event(ctx.config.user_data, e)
+			}
+			if ctx.config.char_fn != unsafe { nil } {
+				ctx.config.char_fn(e.char_code, ctx.config.user_data)
+			}
+		}
+	}
 }
 
 fn gg_cleanup_fn(user_data voidptr) {