1 files changed, 83 insertions, 0 deletions
diff --git a/src/device/screen.cpp b/src/device/screen.cpp
new file mode 100644
index 0000000..2857161
--- /dev/null
+++ b/src/device/screen.cpp
@@ -0,0 +1,83 @@
+#include <time.h>
+#include <stdlib.h>
+#include <string.h>
+#include <OLEDDisplay.h>
+#include <Wire.h>
+#include "screen.h"
+
+void draw_lines(OLEDDisplay *screen, struct display_status *status);
+void update_lines(struct display_status *status);
+void init_msg(char *msg, size_t size);
+
+/* Effectively const. For type safety reasons. */
+static char NOTHING[] = {'\0'};
+
+void display_status_init(OLEDDisplay *screen, struct display_status *status, char *msg)
+{
+	status->delta = 2;	/* Currently default */
+	status->screen = screen;
+	init_msg(msg, strlen(msg));
+	status->message = msg;
+	status->line_cursor = 0;
+	status->last_scroll_time = time(NULL);
+	update_lines(status);
+}
+
+/**
+ * Turns all whitespace into literal spaces to save screen real-estate and
+ * possible misinterpretation.
+ */
+void init_msg(char *msg, size_t size)
+{
+	size_t i;
+
+	for (i = 0; i < size; i++) {
+		switch (msg[i]) {
+		case '\n':
+		case '\t':
+		case '\r':
+			msg[i] = ' ';
+			break;
+		case '\0':
+			goto end;
+		default:
+			break;
+		}
+	}
+end:
+	return;
+}
+
+int display_update_scroll(struct display_status *status)
+{
+	time_t crr_time = time(NULL);
+	/* Only scroll lines once a delta, because --- duh! */
+	if (status->last_scroll_time - crr_time > status->delta) {
+		status->last_scroll_time += status->delta;
+		status->line_cursor++;
+		update_lines(status);
+		draw_lines(status->screen, status);
+	}
+	if (status->first_line == NOTHING && status->second_line == NOTHING) {
+		return END_OF_MESSAGE;
+	} else {
+		return 0;
+	}
+}
+
+void draw_lines(OLEDDisplay *screen, struct display_status *status)
+{
+	screen->clear();
+	screen->drawString(0, 0, status->first_line);
+	screen->drawString(0, SCREEN_HEIGHT / 2, status->second_line);
+}
+
+void update_lines(struct display_status *status)
+{
+	status->first_line = (status->line_cursor * SCREEN_MAX_CHARS < status->message_len)
+			? status->message + status->line_cursor * SCREEN_MAX_CHARS
+			: NOTHING;
+	status->second_line = (status->line_cursor * SCREEN_MAX_CHARS < status->message_len)
+			? status->message + (status->line_cursor + 1) * SCREEN_MAX_CHARS
+			: NOTHING;
+}