never mind, only commit for test by Yukun Chen.

src/TextRenderer.cpp

@@ -35,32 +35,59 @@ void TextRenderer::update(std::string newText) {
     int fontNumbersInOneLine = windowWidth / (fontWidth + left_margin);
     std::vector<std::vector<bool>> characterBitmap;
 
-    if(newText.size() < oldTextsize) {
-        clear();
-    }
-
     for(i = 0; i < newText.size(); i++) {
         if(i > oldText.size() || oldText[i] != newText[i]) {
             if(newText[i] == '\n') {
                 space += (fontNumbersInOneLine - ((i + space) % fontNumbersInOneLine) - 1);
+
+                if(newText.size() < oldTextsize) {
+                    clear(currentX, currentY, fontWidth, currentY + fontHeight);
+                }
             } else {
 
                 currentX = ((i + space) % fontNumbersInOneLine) * (fontWidth + left_margin);
                 currentY = ((i + space) / fontNumbersInOneLine) * (fontHeight + bottom_margin);
 
+                if(newText[i] == -127) {
+                    blinkX = currentX;
+                    blinkY = currentY + fontWidth - 1;
+                    space -= 1;
+                } else {
                     characterBitmap = getCharacter(newText[i], font);
 
 //            fontProcessing(characterBitmap);
                     translateToSharedMemory(characterBitmap, currentX, currentY);
                 }
-
             }
         }
+    }
+
+    if(newText.size() < oldTextsize) {
+        clear(currentX, currentY, fontWidth, currentY + fontHeight);
+    }
 
     oldTextsize = newText.size();
     setOldText(newText);
 }
 
+void TextRenderer::blink() {
+    bool signal;
+
+    while(true) {
+        for(int y = 0; y < fontHeight; y++) {
+            if(signal)
+                vkvm::setPixel(blinkX, blinkY + y, backgroundColor);
+            else
+                vkvm::setPixel(blinkX, blinkY + y, fontColor);
+        }
+        signal = !signal;
+
+        std::this_thread::sleep_for(std::chrono::seconds(1));
+    }
+
+}
+
+
 void TextRenderer::clear() {
     int x, y;
     for(y = 0; y < windowHeight; y++) {

src/TextRenderer.h

@@ -13,6 +13,7 @@
 #include <Color.hpp>
 #include <vkvm.hpp>
 #include <iostream>
+#include <thread>
 #include "Font.h"
 
 /**
@@ -41,6 +42,8 @@ public:
     int getWindowHeight();
 
 private:
+    std::mutex mutex;
+
     std::string oldText;
     vkvm::Color backgroundColor;
     vkvm::Color fontColor;
@@ -56,12 +59,15 @@ private:
     int currentX;
     int currentY;
     int oldTextsize;
+    int blinkX = 0;
+    int blinkY = 0;
     bool isBold();
     bool isItalics();
     bool isUnderline();
     void fontProcessing(std::vector<std::vector<bool>> characterBitmap);
     void translateToSharedMemory(std::vector<std::vector<bool>> characterBitmap, int startX, int startY);
     void checkWindowSize();
+    void blink();
 
     void checkFontColor();