text: // MIT License, Copyright (c) 2021 Marvin Borner
  
  #include <libgui/gui.h>
  
  #define COLOR_SIZE 50
  #define TOOLBAR_MARGIN 2
  
  static const u32 colors[] = { COLOR_BLACK, COLOR_RED,	  COLOR_GREEN, COLOR_YELLOW,
  			      COLOR_BLUE,  COLOR_MAGENTA, COLOR_CYAN,  COLOR_WHITE };
  static u32 current_color = COLOR_BLACK;
  static u32 size = 5;
  
  static void mousemove(struct gui_event_mouse *event)
  {
  	static vec2 last = { 0 };
  
  	if (event->scroll && !(event->scroll == -1 && size <= 1))
  		size += event->scroll;
  
  	if (event->but.left) {
  		gui_draw_line(event->win, event->widget, GUI_LAYER_FG, last, event->pos, size,
  			      current_color);
  		gui_widget_redraw(event->win, event->widget);
  	}
  	last = event->pos;
  }
  
  static void color_click(struct gui_event_mouse *event)
  {
  	current_color = colors[event->widget - 2];
  }
  
  // TODO: Simplify using predefined widgets and utilities
  // TODO: Fix and improve paint without KVM
  int main(void)
  {
  	u32 win = gui_window(APPNAME);
  	vec2 win_size = gui_window_size(win);
  
  	gui_widget_margin(win, gui_widget_main(win), vec2(0, 0));
  	gui_widget_layout(win, gui_widget_main(win), GUI_VLAYOUT);
  
  	u32 toolbar = gui_widget(win, gui_widget_main(win),
  				 vec2(win_size.x, COLOR_SIZE + 2 * TOOLBAR_MARGIN));
  	gui_fill(win, toolbar, GUI_LAYER_BG, COLOR_WHITE);
  
  	u32 color_count = COUNT(colors);
  	for (u32 i = 0; i < color_count; i++) {
  		u32 color = gui_widget(win, toolbar, vec2(COLOR_SIZE, COLOR_SIZE));
  		gui_fill(win, color, GUI_LAYER_FG, colors[i]);
  		gui_draw_border(win, color, GUI_LAYER_FG, 2, COLOR_BLACK);
  		gui_widget_listen(win, color, GUI_LISTEN_MOUSECLICK, (u32)color_click);
  	}
  
  	u32 canvas = gui_widget(win, gui_widget_main(win),
  				vec2(win_size.x, win_size.y - (COLOR_SIZE + 2 * TOOLBAR_MARGIN)));
  	gui_fill(win, canvas, GUI_LAYER_BG, COLOR_WHITE);
  	gui_widget_listen(win, canvas, GUI_LISTEN_MOUSEMOVE, (u32)mousemove);
  
  	gui_window_redraw(win);
  	gui_loop();
  	return 0;
  }
  