ardupilot/libraries/AP_OSD/AP_OSD_Backend.h

/*
 * This file is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#pragma once

#include <AP_HAL/HAL.h>
#include <AP_OSD/AP_OSD.h>
#include <AP_Filesystem/AP_Filesystem.h>


class AP_OSD_Backend
{

public:
    //constructor
    AP_OSD_Backend(AP_OSD &osd): _osd(osd) {};

    //destructor
    virtual ~AP_OSD_Backend(void) {}

    //draw given text to framebuffer
    virtual void write(uint8_t x, uint8_t y, const char* text) = 0;

    //draw formatted text to framebuffer
    virtual void write(uint8_t x, uint8_t y, bool blink, const char *fmt, ...) FMT_PRINTF(5, 6);

    //initilize framebuffer and underlying hardware
    virtual bool init() = 0;

    //update screen
    virtual void flush() = 0;

    // return a correction factor used to display angles correctly
    virtual float get_aspect_ratio_correction() const {return 1;}

    //clear screen
    //should match hw blink
    virtual void clear()
    {
        blink_phase = (blink_phase+1)%4;
    };

    AP_OSD * get_osd()
    {
        return &_osd;
    }

protected:
    AP_OSD& _osd;

    // get font choice
    uint8_t get_font_num(void) const
    {
        return (uint8_t)_osd.font_num.get();
    }

    //check option
    bool check_option(uint32_t option) const
    {
        return (_osd.options & option) != 0;
    }

    // load a font from sdcard or ROMFS
    FileData *load_font_data(uint8_t font_num);

    int8_t blink_phase;

    enum vid_format {
        FORMAT_UNKNOWN = 0,
        FORMAT_NTSC = 1,
        FORMAT_PAL = 2,
    } _format;
};