Weidongshan digital photo frame project learning (IV) simple TXT document display (e-paper book)

Weidong mountain Digital photo frame Project learning （ Four ） Simple TXT Document display （ Electronic paper book ）

With the previous about LCD、freetype Learning from , It's ready to start TXT The preparation of document display . The whole implementation process is not complicated , What must be made clear is freetype Library usage , Chinese character dot matrix LCD The transformation of coordinates and Cartesian coordinates and in LCD Processing of some details when displaying on .

Experimental results

This time, only the most basic functions are realized , stay LCD Displayed on the UTF-8 Coded txt file , Let's look at the experimental results first

GIF The picture effect of has been cut , The actual effect will refresh a page every two seconds .

Application framework

The following figure is a simple TXT The frame of the document display , It's simple , It is mainly to master the idea of stratification , Familiar with the basic framework .

The framework of the whole program is divided into three parts ： Show 、 typeface 、 File encoding

Display management

disp_manager It abstracts a layer , Extract the commonness of display devices , On the next floor framebuffer Or other display devices , Just use disp_manager Functions provided by layer , Distribute 、 Set up 、 Sign up for a T_DispOpr Just the structure , Here is given T_DispOpr Structure code

typedef struct T_DispOpr {
    
	char 	*name;
	int 	iXres;
	int 	iYres;
	int		iBpp;
	int 	(*DeviceInit)(void);
	int		(*ScreenClean)(unsigned int dwBackColor);
	int		(*DrawPixel)(int iX, int iY, unsigned int dwColor);

	struct T_DispOpr *ptNext;
}T_DispOpr, *PT_DispOpr;

Is it simple , Function currently has only three functions , Initialization 、 Clear the screen 、 And the point function , With these three functions , The most important thing is to describe the point function , With the point function , We can expand other interesting functions based on it .
Underlying code , Just assign 、 Set up 、 By registering your own structure, you can add devices to our framework .
Distribute 、 Setting up a structure is simple , So how to register ？
The answer is the following function

int RegisterDispOpr(PT_DispOpr ptDispOpr);

This function is in the disp_manager.c To implement inside , It mainly calls the underlying application , Register the underlying application's own structure to disp_manager Maintain a linked list , To put it bluntly, it is the addition of linked list nodes .

int RegisterDispOpr(PT_DispOpr ptDispOpr)
{
    
	if(!ptDispOpr)
	{
    
		DBG_PRINT("ptDispOpr is NULL\n");
		return -1;
	}

	ptDispOpr->ptNext = g_tDispOprs;
	g_tDispOprs = ptDispOpr;
	return 0;
}

This function is very simple , First, judge whether the structure to be registered is empty , Then add the newly registered item to the front of the linked list .
Then our application can use disp_manager Functions provided by this layer , Register to... Through the underlying application disp_manager The structure of this layer accesses the services provided by the underlying application , Here is framebuffer Displayed services .
Do this when modifying the underlying application , There is no need to make too many changes to the code of the upper application .

Font management

font_manager here , We mainly extract freetype And Chinese character library （HZK16） Commonalities of lattice provided , Abstract out such a structure ----T_FontBitmap, This structure is the information description of a text lattice

typedef struct T_FontBitmap {
    
	int	iXLeft;			/* LCD coordinate , top left corner x coordinate  */
	int iYTop;			/* LCD coordinate , top left corner x coordinate  */
	int iXMax;			/* LCD coordinate ,x Axis width  */
	int iYMax;			/* LCD coordinate ,y Axis width  */
	int	iBpp; 			/*  How many bits are used to represent a pixel  */
	int iPitch; 		/*  The spacing of each line of the dot matrix of a character  */
	int iCurOriginX; 	/*  The input variable  */
	int iCurOriginY; 	/*  The input variable  */
	int iNextOriginX;	/*  Output variables  */
	int iNextOriginY;	/*  Output variables  */
	unsigned char 	*pucBuffer;
}T_FontBitmap, *PT_FontBitmap;

Every variable here is and LCD Coordinate related , because freetype according to unicode The lattice data returned by the code is the data in Cartesian coordinates , stay LCD When it is shown on the screen , Some details need to be handled . This is an interesting place .

Code management

stay encoding_manager here , I only achieved the right UTF-8 Parsing and output of , Get to know UTF-8 The encoding format of can be quickly obtained from the file data unicode code . Here I have learned a lot about the coding of files ,UTF-8 The documents are divided into UTF-8 And belt BOM Of UTF-8, We have to choose to take BOM Of UTF-8, Because I didn't bring it BOM Of UTF-8 There are three files without the beginning of the file UTF-8 logo
There's another problem that hasn't been solved , It's about the compatibility between the big and small ends , I am here Windows It was edited on UTF-8 The file is in big end format , Upload to ubuntu It becomes a small end mode , stay 157 It is also a small end format storage , But I don't know why , Later, it was successful to read and write files in big format , I hope you can give me some advice .

Complete code

The complete code is given in the form of a compressed package
Full code link （ No points required ）： Complete code