Add drawing buttons

include/button.h

@@ -0,0 +1,16 @@
+#ifndef BUTTON_H
+#define BUTTON_H
+
+#include "window.h"
+
+#define BUTTON_WIDTH 100
+#define BUTTON_HEIGHT 40
+
+typedef struct button button_t;
+struct button {
+  rect_t rect;
+};
+
+void draw_button(const window_t *wnd, const button_t *button);
+
+#endif // !BUTTON_H

src/button.c

@@ -0,0 +1,10 @@
+#include "button.h"
+#include "window.h"
+
+#define BUTTON_FILL_COLOUR ((colour_t){.abgr = 0xff89a83c})
+#define BUTTON_BORDER_COLOUR ((colour_t){.abgr = 0xff768432})
+
+void draw_button(const window_t *wnd, const button_t *button) {
+  fill_rect(wnd, &(button->rect), BUTTON_FILL_COLOUR);
+  draw_rect(wnd, &(button->rect), BUTTON_BORDER_COLOUR);
+}