Start beautifying the code

* Split out SPI and display (a little)
* Use more of the common Macros
* Remove wasted bytes from notomono font
* Create a mock "menu"

display.h

@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) 2019  Max Regan
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef _DISPLAY_H_
+#define _DISPLAY_H_
+
+#include <stdint.h>
+#include <stddef.h>
+#include <assert.h>
+
+#include "spi.h"
+#include "font.h"
+
+#define DISPLAY_WIDTH 144
+#define DISPLAY_HEIGHT 168
+
+struct display_line
+{
+    uint8_t mode;
+    uint8_t line;
+    uint8_t data[DISPLAY_WIDTH / 8];
+};
+
+struct display_buffer
+{
+    struct display_line lines[DISPLAY_HEIGHT];
+    uint16_t dummy;
+};
+
+static_assert(sizeof(struct display_buffer) == (DISPLAY_WIDTH / 8 + 2) * DISPLAY_HEIGHT + 2,
+    "The display buffer structure must be packed");
+
+struct display
+{
+    SPI_TypeDef *spi;
+    struct display_buffer buffer;
+};
+
+
+void display_init(struct display *display, SPI_TypeDef *spi);
+
+void display_set_bit(struct display *display, unsigned int x, unsigned int y, uint8_t val);
+
+void display_set_byte(struct display *display, unsigned int x, unsigned int y, uint8_t val);
+
+void display_char_at(struct display *display, int *x_off, int y_off, char c, const struct font *font);
+
+void display_string_at(struct display *display, int x_off, int y_off, const char *string, const struct font *font);
+
+void display_refresh(struct display *display);
+
+// TODO
+void display_clear(struct display *display);
+
+#endif