LCD Screen Driver Analysis (Part 1): How to Draw Points and Lines on an LCD Screen

============= Objective =====================

How to draw points and lines on an LCD screen

=======================================

I. Learning Insights

How to write a test program? How to integrate it with a Makefile to compile a program (only include what's necessary—create your own project)
1. LCDSetColor(WHITE,UNSET); // Setting color is a fundamental task, including line color, font color, and background color
2. DispSetPointDirect(6, 10); // Set position
3. LCDSetLine()
I need to create a Makefile and a main.c file.
The key is the initialization process—understanding the correct initialization sequence.
Random trial and error won't work anymore. I need to understand and experiment purposefully.
Right now, I want to understand xadd() and yadd().
Actually, I still don't grasp how it works internally.
Finally realized: At the beginning, things shouldn't be too complex—three-dimensional arrays <drawing points and lines, Chinese character font, BMP images> 【simplify】. Combining these three forms a complete screen driver. For beginners, it's better to break it down.

Learning approach: Set a clear goal (e.g., implement point and line drawing, enable Chinese text display), achieve it as quickly as possible (via targeted searching, prioritizing speed over completeness) + ensure theoretical understanding in mind.

II. Question Collection:

1. // LightAdjust color adjustment, value range -16 (to ColorR) ~ +16 (to ColorL), 0 means original color. void LCDSetColorAdjust(char *cBGRPix,int ColorAdjust) What's the meaning of ±16 here?
2. void Lcd_Test(void){
   int i;   
   Xadd(0x00,0x7F);                        // Does Xadd(startx,endx) mean drawing a line from startx to endx?
                                                // Need to verify through programming
   Yadd(0x00,0x7F);
   LCDCOM_MASTER(0x2C);    
   for(i=0;i<128*128;i++)                 // Why 128*128 instead of using nested for-loops?
  	{                                  // Does it automatically wrap lines?
	    LCDDATA_MASTER(0x00);
	    LCDDATA_MASTER(0x1f);   
  	}
}
【Question】: How do I call lcd_test in the main program main.c?

3. LCDSetButton(0,16,128,112,0,TRANSB);  // What is this function for? I don't see any button on the screen.

4. void Xadd(char startx,char endx)      // Should this be understood as defining a line between two points, or as a single coordinate point?
{
    LCDCOM_MASTER(0x2A);
    LCDDATA_MASTER(startx);
    LCDDATA_MASTER(endx);
}

void Yadd(char starty, char endy)
{
    LCDCOM_MASTER(0x2B);
    LCDDATA_MASTER(starty);                   // This function needs further study—it should be one of the few
    LCDDATA_MASTER(endy);                     // functions directly interacting with hardware. Data is written directly, then hardware takes over?
}

5. What do colorl, colorm, colorr mean?

6. BYTE cDispBatCap[MAXBATCAPNUM][32]        // What is its purpose? Defined in disp.c
   BYTE cDispSigValue[MAXSIGNUM][32]

7. What does LCDDATA_MASTER(0) mean?

Welcome to discuss!

*Append a 16x16 character*/

void DispAddChinesCharFuSe(DWORD dwQuNum,DWORD dwWeiNum) // What does "Fuse" mean? What do "qu" and "wei" mean?
{ 
   // What is GBquwei[] used for?
   unsigned int uiCurrentXY,i; 
   DWORD dwPotsIndex; 
   if(dwQuNum > 15) 
   { 
       dwPotsIndex = ((dwQuNum - 2) * 94 + dwWeiNum - 1) * 32; // Where does this index calculation formula come from?
   } 
   else 
   { 
       dwPotsIndex = ((dwQuNum - 1) * 94 + dwWeiNum - 1) * 32; 
   } 
   for(i = 0; i < 32; i++) 
   { 
       cChineseFuSe[i] = ~(hanzi1616[dwPotsIndex + i]); // Also refers to char16*8fuse[]
   } 
   uiCurrentXY = LCDdisplay1616((BYTE)(dwDispCurrentX),(BYTE)(dwDispCurrentY),cChineseFuSe); 
   dwDispCurrentY = (DWORD)(uiCurrentXY & 0xff); // Why extract the lower 8 bits?
   dwDispCurrentX = ((DWORD)(uiCurrentXY >> 8) & 0xff); // Why shift left and then mask?
}

Position calculation related functions, common numeric operations:
dwDispCurrentY -= 2;
dwDispCurrentX = 112;
setpoint()