only handle non-printables on press/release, and BS is 0x7F

src/Window.zig

@@ -598,10 +598,11 @@ fn keyCallback(
     }
 
     // Handle non-printable characters
+    if (action == .press or action == .repeat) {
         const char: u8 = switch (@bitCast(u8, mods)) {
             // No modifiers pressed at all
             0 => @as(u8, switch (key) {
-            .backspace => 0x08,
+                .backspace => 0x7F,
                 .enter => '\r',
                 .tab => '\t',
                 .escape => 0x1B,
@@ -645,6 +646,7 @@ fn keyCallback(
             win.queueWrite(&[1]u8{char}) catch |err|
                 log.err("error queueing write in keyCallback err={}", .{err});
         }
+    }
 }
 
 fn focusCallback(window: glfw.Window, focused: bool) void {