Source code for cairotft.tft

# Copyright (c) 2015, Thomas Chiroux - Link Care Services
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#   this software without specific prior written permission.

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"""Class for display on tft using linuxfb."""
import asyncio
import cairocffi as cairo

from cairotft import linuxfb


class TftDisplay():

    """Display class for the tft display."""

    def __init__(self, interface='/dev/fb0', cairo_format=cairo.FORMAT_ARGB32):
        """Initialisation of the class.

        :param str interface: framebuffer interface name
        :param int cairo_format: the pixel format.
            see: https://pythonhosted.org/cairocffi/api.html#pixel-format
        """
        self.fb_interface = interface
        self.cairo_format = cairo_format

        # two memory buffers:
        #     * fbmem for direct draw on the screen
        #     * buffermem: memory buffer for double buffering.
        self.fbmem = linuxfb.open_fbmem(self.fb_interface)
        self.buffermem = linuxfb.memory_buffer(self.fbmem.fix_info.smem_len)

        # two cairo surface, directly on the screen and in the memory buffer.
        self.surf = linuxfb.cairo_surface_from_fbmem(
            self.fbmem,
            self.fbmem.mmap,
            cairo_format)
        self.buffer_surf = linuxfb.cairo_surface_from_fbmem(
            self.fbmem,
            self.buffermem,
            cairo_format)

        # calculates width and height of the screen
        self.width, self.height = self.surf.get_width(), self.surf.get_height()
        self.size_per_pixel = self.fbmem.fix_info.smem_len / (self.width *
                                                              self.height)
        # by default we write only in buffer using self.ctx
        self.ctx = cairo.Context(self.buffer_surf)

        # cairo context for direct rendering on the screen.
        # normaly only used with blit.
        self.screen_ctx = cairo.Context(self.surf)

        # async io loop
        self.io_loop = asyncio.get_event_loop()

    def blit(self):
        """Display the buffer in the screen.

        Take the content of the memory buffer and draw it on the screen.
        """
        self.screen_ctx.set_source_surface(self.buffer_surf)
        self.screen_ctx.paint()

    def close(self):
        """Close the interface."""
        # Back to black background
        self.blank_screen(self.ctx)
        linuxfb.close_fbmem(self.fbmem)

    def blank_screen(self, ctx, color=(0, 0, 0, 1), blit=True):
        """Blank the screen with the given color.

        :param ctx: cairocffi context
        :type ctx: :class:`cairocffi.Context`
        :param color: 4 int tuple reprensentig the rgba color.
        """
        ctx.set_source_rgba(*color)
        ctx.rectangle(0, 0, self.width, self.height)
        ctx.fill()
        if blit:
            self.blit()

    def draw_interface(self, ctx):
        """Method that should be overriden by subclasses."""
        raise NotImplementedError

    def run(self):
        """main loop."""
        # just afer loop is started, draw the interface
        self.io_loop.call_soon(self.draw_interface, self.ctx)
        try:
            self.io_loop.run_forever()
        except KeyboardInterrupt:
            pass
        finally:
            self.io_loop.close()
            self.close()