hotp: add code for displaying keys on screen

examples/tutorials/hotp/hotp_milestone_one/screen.c

@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include <u8g2-tock.h>
+#include <u8g2.h>
+
+#include "step0.h"
+#include "screen.h"
+
+u8g2_t u8g2;
+bool inited = false;
+
+int display_hotp_keys(hotp_key_t* hotp_key, int num_keys) {
+  // Only init if not previously init-ed.
+  if (!inited) {
+    int ret = u8g2_tock_init(&u8g2);
+    if (ret != 0) {
+      return -1;
+    }
+    inited = true;
+  }
+
+
+  // int height = u8g2_GetDisplayHeight(&u8g2);
+  int width = u8g2_GetDisplayWidth(&u8g2);
+
+  u8g2_SetFont(&u8g2, u8g2_font_profont17_tr);
+  u8g2_SetFontPosTop(&u8g2);
+
+  u8g2_ClearBuffer(&u8g2);
+
+  // Draw title.
+  u8g2_DrawStr(&u8g2, 0, 0, "HOTP App");
+
+  // Draw line below title.
+  int title_height = u8g2_GetMaxCharHeight(&u8g2);
+  u8g2_DrawHLine(&u8g2, 0, title_height , width);
+
+  // Draw for each key.
+  u8g2_SetFont(&u8g2, u8g2_font_helvR08_tr);
+  int lines_start = title_height+1;
+  int offset = u8g2_GetMaxCharHeight(&u8g2) + 1;
+
+  for (int i=0;i<num_keys;i++) {
+    char buf[100];
+
+    int y_pos = lines_start + (offset * i);
+
+    if (hotp_key[i].len == 0) {
+      snprintf(buf, 100, "Key %i: (unused)", i);
+    } else {
+      snprintf(buf, 100, "Key %i: %li", i, (uint32_t) hotp_key[i].counter);
+    }
+    u8g2_DrawStr(&u8g2, 0, y_pos, buf);
+  }
+
+  // Write to display.
+  u8g2_SendBuffer(&u8g2);
+
+
+  return 0;
+
+}

examples/tutorials/hotp/hotp_milestone_one/screen.h

@@ -0,0 +1,4 @@
+#pragma once
+
+
+int display_hotp_keys(hotp_key_t* hotp_key, int num_keys);