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How to define external stubs to implement your CommLCD engine and Comm IAL engine outside MiniGUI Core.

Table of Contents

• Introduction
• Key Points
• Functions to be Implemented
  • CommLCD NEWGAL engine
    • Initializing the engine
    • Setting video mode
    • Setting palette
    • Update method
    • Releasing the engine
  • Comm IAL engine
• Summary
• References

Introduction

Since MiniGUI 3.2.2, you can use MiniGUI's built-in CommLCD NEWGAL engine and Comm IAL engine to support your video output device and input device.

By using these two engines, you do not need to change the source code of MiniGUI core. Instead, you implement the engines outside the MiniGUI core by defining some external functions.

In this document, we describe the usage and the interfaces about these two engines.

Key Points

• Use MiniGUI 3.2.2 or later.
• Enable the engines when configuring MiniGUI:
  • --enable-videocommlcd: enable CommLCD NEWGAL engine.
  • --enable-commial: enable Comm IAL engine.
  • --with-targetname=external: define target name to be external.
• Implement the external stubs in your app side:
  • #include <minigui/exstubs.h>
• Specify the following runtime configuration options:
  • gal_engine=commlcd: use CommLCD NEWGAL engine.
  • ial_engine=comm: use comm IAL engine.
• Sample code: comm-engines in mg-tests

Functions to be Implemented

In MiniGUI header file <minigui/exstubs.h>, we declare the function prototypes you need to implement for these two engines. You must include this header in your C source file(s), and implement all of the functions correctly.

In the commlcd sample of mg-samples package, the file commlcd_ops.c implements the functions for CommLCD NEWGAL engine, and the file comminput_ops.c implements the functions for Comm IAL engine:

• commlcd_ops.c
• comminput_ops.c

The former implementation does not connect to any real device; it creates an anonymous memory map and returns the address of the memory map as the frame buffer to MiniGUI. However, when there is a update, this engine will save the whole frame buffer content to a Windows bitmap file. So you can observe the behaviors of the engine.

The latter implementation gives you a sample which gets input events from a touch screen on Linux, and passed the events to MiniGUI. If you have no such device, the engine will fails to initialize.

CommLCD NEWGAL engine

Initializing the engine

__commlcd_drv_init will be called when initializing your CommLCD engine implementation. In the commlcd sample, it does nothing and just returns zero:

int __commlcd_drv_init (void)
{
    return 0;
}

Note that, all external methods for CommLCD engine should return zero for success.

Setting video mode

__commlcd_drv_getinfo will be called when MiniGUI tries to set the video mode according to your settings in the MiniGUI runtime configuration, e.g., defaultmode=240x320-32bpp.

In our sample, it creates the anonymous memory map by calling mmap system call and returns the video information via struct commlcd_info* li:

int __commlcd_drv_getinfo (struct commlcd_info *li, int width, int height, int depth)
{
    sg_fb = (BYTE*) mmap (0, FB_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
    if (sg_fb == MAP_FAILED) {
        perror ("Failed calling __commlcd_drv_getinfo: ");
        return -1;
    }

    li->type = COMMLCD_TRUE_ARGB8888;
    li->height = SCREEN_HEIGHT;
    li->width = SCREEN_WIDTH;
    li->bpp = COLOR_DEPTH;
    li->pitch = SCREEN_WIDTH * BYTES_PER_PIXEL;
    li->update_method = COMMLCD_UPDATE_ASYNC;
    li->fb = sg_fb;
    return 0;
}

You need fill the all fields of struct commlcd_info* li with the correct values:

• type: The video mode type. Currently, CommLCD supports the following modes:
  • COMMLCD_PSEUDO_RGB332: 256-color video mode.
  • COMMLCD_TRUE_RGB555: RGB555 15-bit video mode.
  • COMMLCD_TRUE_RGB565: RGB565 16-bit video mode.
  • COMMLCD_TRUE_RGB888: RGB888 24-bit video mode.
  • COMMLCD_TRUE_RGB0888: RGB0888 32-bit video mode (without alpha component).
  • COMMLCD_TRUE_ARGB1555: RGB1555 16-bit video mode (the alpha component use 1 bit only).
  • COMMLCD_TRUE_ARGB8888: RGB8888 32-bit video mode (the alpha, red, green, blue components all use 8 bits).
• height: The vertical resolution in pixels.
• width: The horizontal resolution in pixels.
• bpp: The color depth in bits per pixels. Actually, this field is a redundancy, because the type already contains the depth information.
• pitch: The length in bytes of one scan line. Generally, it should be a times of 4, i.e., the address of each scan line should be 4-byte aligned.
• update_method: The update method when there is a dirty rectangle, can be one of the following values:
  • COMMLCD_UPDATE_NONE: do not call __commlcd_drv_update (see below).
  • COMMLCD_UPDATE_SYNC: call __commlcd_drv_update synchronously.
  • COMMLCD_UPDATE_ASYNC: call __commlcd_drv_update asynchronously.
• fb: The address of the frame buffer.

Setting palette

If the color depth of the video mode is less than 15 (COMMLCD_PSEUDO_RGB332), __commlcd_drv_setclut function will be called to set the palette.

In our sample, this method does nothing and returns zero:

int __commlcd_drv_setclut (int firstcolor, int ncolors, GAL_Color *colors)
{
    return 0;
}

In practice, you should set the hardware palette (color look up table) in this method if the color depth of your video device is only 256-color.

The arguments of this function have the following meanings:

• firstcolor: The first color index (the palette entry index) should be set.
• ncolors: The number of palette entries should be set.
• colors: The array of GAL_Color which define the RGB triples for each palette entries will be set.

GAL_Color is a structure defined in MiniGUI header:

typedef struct _GAL_Color
{
    /**
     * The red component of a RGBA quarter.
     */
    gal_uint8 r;
    /**
     * The green component of a RGBA quarter.
     */
    gal_uint8 g;
    /**
     * The blue component of a RGBA quarter.
     */
    gal_uint8 b;
    /**
     * The alpha component of a RGBA quarter.
     */
    gal_uint8 a;
} GAL_Color;

Update method

If you specify the update_method to be COMMLCD_UPDATE_SYNC or COMMLCD_UPDATE_ASYNC, the update method __commlcd_drv_update will be called frequently or periodically.

In our sample, this method saves the whole frame buffer content to Windows bitmap files by calling MiniGUI function:

int __commlcd_drv_update (const RECT* rc_dirty)
{
    char filename [PATH_MAX + 1];
    struct timeval tv;

    MYBITMAP my_bmp = {
        flags: MYBMP_TYPE_RGB | MYBMP_FLOW_DOWN,
        frames: 1,
        depth: 32,
        w: SCREEN_WIDTH,
        h: SCREEN_HEIGHT,
        pitch: PITCH,
        size: FB_SIZE,
        bits: sg_fb
    };

    printf ("__commlcd_drv_update called (%d, %d, %d, %d)\n",
            rc_dirty->left, rc_dirty->top,
            rc_dirty->right, rc_dirty->bottom);

    gettimeofday (&tv, NULL);
    sprintf (filename, "screenshot-%d.%d.bmp", (int)tv.tv_sec, (int)tv.tv_usec);
    SaveMyBitmapToFile (&my_bmp, NULL, filename);
    return 0;
}

Note that, you can not call MiniGUI GDI functions here to draw something to screen.

In practice, you may need to send an ioctl command to your video device driver to update the content in our frame buffer to the real LCD controller.

For example, if you use SPI to connect a LCD screen, you may create an off-screen frame buffer in memory, and transfer the pixels to the LCD controller via SPI.

The argument rc_dirty contains the dirty rectangle, i.e., the rectangle need to be updated to the real frame buffer or LCD controller.

Generally, you should set update_mothod to be COMMLCD_UPDATE_ASYNC in __commlcd_drv_init method, and the method will be called asynchronously in a different thread, about 20 times per second.

If you set update_mothod to be COMMLCD_UPDATE_SYNC, this update method will be called synchronously when there is any update of the frame buffer. For example, you call the MiniGUI function SetPixel to draw just one pixel on the screen. Therefore, this will reduce the refresh performance of the entire system. However, if you use MiniGUI's Synchronous Update Mechanism, it will be better to set update_mothod to be COMMLCD_UPDATE_SYNC.

If you can access the LCD frame buffer directly, and your LCD screen do not need a refresh/update operation, you do not need to implement the update method, and the function can just return zero:

int __commlcd_drv_update (const RECT* rc_dirty)
{
    return 0;
}

If you specify the update_mothod to be COMMLCD_UPDATE_NONE in __commlcd_drv_init method, this function will be never called.

Releasing the engine

When MiniGUI quits, it will call __commlcd_drv_release to release the resource allocated or created by the engine.

In our sample, it destroys the anonymous memory map and returns zero:

int __commlcd_drv_release (void)
{
    munmap (sg_fb, FB_SIZE);
    return 0;
}

Comm IAL engine

Summary

References

• GAL and IAL Engines