diff --git a/examples/users_gui/users.v b/examples/users_gui/users.v
index e9faeebf04..d839d8e548 100644
--- a/examples/users_gui/users.v
+++ b/examples/users_gui/users.v
@@ -2,10 +2,10 @@ import ui
 import gx
 
 const (
-	NR_COLS     = 3
-	CELL_HEIGHT = 25
-	CELL_WIDTH  = 100
-	TABLE_WIDTH = CELL_WIDTH * NR_COLS
+	NrCols     = 3
+	CellHeight = 25
+	CellWidth  = 100
+	TableWidth = CellWidth * NrCols
 )
 
 struct User {
@@ -38,15 +38,14 @@ fn main() {
 	ctx.last_name = ctx.add_textbox('Last name')
 	ctx.age = ctx.add_textbox('Age')
 	mut btn := ui.new_button('Add user', ctx.window, btn_click)
-	btn.widget.set_pos(TABLE_WIDTH + 50, ctx.txt_pos)
+	btn.widget.set_pos(TableWidth + 50, ctx.txt_pos)
 	for {
 		ui.wait_events()
 	}
 }
 
 // TODO replace with `fn (ctx mut Context) btn_click() {`
-fn btn_click(_ctx *Context) {
-	mut ctx = _ctx// TODO hack
+fn btn_click(btn voidptr, ctx mut Context) {
 	ctx.users << User {
 		first_name: ctx.first_name.text()
 		last_name: ctx.last_name.text()
@@ -59,23 +58,23 @@ fn btn_click(_ctx *Context) {
 fn draw(ctx *Context) {
 	for i, user in ctx.users {
 		x := 10
-		y := 10 + i * CELL_HEIGHT
+		y := 10 + i * CellHeight
 		// Outer border
-		gx.draw_empty_rect(x, y, TABLE_WIDTH, CELL_HEIGHT, gx.GRAY)
+		ui.draw_empty_rect(x, y, TableWidth, CellHeight, gx.GRAY)
 		// Vertical separators
-		gx.draw_line(x + CELL_WIDTH, y, x + CELL_WIDTH, y + CELL_HEIGHT)
-		gx.draw_line(x + CELL_WIDTH * 2, y, x + CELL_WIDTH * 2, y + CELL_HEIGHT)
+		ui.draw_line(x + CellWidth, y, x + CellWidth, y + CellHeight)
+		ui.draw_line(x + CellWidth * 2, y, x + CellWidth * 2, y + CellHeight)
 		// Text values
-		gx.draw_text_def(x + 5, y + 5, user.first_name)
-		gx.draw_text_def(x + 5 + CELL_WIDTH, y + 5, user.last_name)
-		gx.draw_text_def(x + 5 + CELL_WIDTH * 2, y + 5, user.age.str())
+		ui.draw_text_def(x + 5, y + 5, user.first_name)
+		ui.draw_text_def(x + 5 + CellWidth, y + 5, user.last_name)
+		ui.draw_text_def(x + 5 + CellWidth * 2, y + 5, user.age.str())
 	}
 }
 
 fn (ctx mut Context) add_textbox(placeholder string) ui.TextBox {
 	mut txt_box := ui.new_textbox(ctx.window, false)
 	txt_box.set_placeholder(placeholder)
-	txt_box.widget.set_pos(TABLE_WIDTH + 50, ctx.txt_pos)
+	txt_box.widget.set_pos(TableWidth + 50, ctx.txt_pos)
 	ctx.txt_pos += 30
 	return txt_box
 }