C++ refactoring, plus low-power support, plus software-based SPI CS

I'm backlogged.

DisplayDriver.h

@@ -0,0 +1,84 @@
+/*
+ * 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.
+ */
+
+#pragma once
+
+#include "Task.h"
+#include "SpiDriver.h"
+#include "font.h"
+
+namespace BSP {
+
+class DisplayDriver  : public Common::Schedule::Task {
+public:
+    DisplayDriver(Common::Schedule::TaskScheduler &scheduler, SpiDriver &spi);
+
+    static constexpr uint8_t DISPLAY_WIDTH = 144;
+    static constexpr uint8_t DISPLAY_HEIGHT = 168;
+
+
+    /**
+     * Common::Schedule::Task
+     */
+    Common::ReturnCode init();
+    Common::Schedule::NextTime execute() override;
+
+    /**
+     * DisplayDriver
+     */
+    void set_bit(unsigned int x, unsigned int y, uint8_t val);
+    void set_byte(unsigned int x, unsigned int y, uint8_t val);
+    void char_at(int *x_off, int y_off, char c, const struct font *font);
+    void string_at(int x_off, int y_off, const char *string, const struct font *font);
+    void refresh();
+    void clear();
+
+private:
+    void buffer_init();
+    void set_dirty(unsigned int y);
+    const struct glyph *glyph_for_char(const struct font *font, char c);
+
+    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;
+    };
+
+
+    Common::Schedule::TaskScheduler &m_scheduler;
+    SpiDriver &m_spi;
+
+    struct display_buffer m_buffer;
+
+    bool m_is_dirty;
+    uint8_t m_dirty_line_min;
+    uint8_t m_dirty_line_max;
+
+};
+
+}