将带有glut的点击的坐标添加到向量的链接列表中 [英] Adding coordinates of clicks with glut to a linked list of vectors

问题描述

我想创建矢量的链接列表，并借助GLUT库获取点击位置并将其附加到链接列表中.

I want to create a linked list of vectors and with the help of GLUT library get the positions of the clicks and append them to the linked list.

这些是我写的结构.

typedef struct vector{int x;int y;}Vector;
typedef struct VectorList{Vector X; struct VectorList*next; }node_v;

我全局定义了一个P向量和上一个向量的链接列表.

I globally defined a P vector and linked list of vectors prev.

Vector P;
node_v * prev=NULL;

每次单击鼠标左键时，都在鼠标回调函数_mouse_CB中，我想用当前的x和y值更新P向量，并将它们附加到链接列表中.

Inside the mouse callback function _mouse_CB everytime left mouse button is clicked, i want to update the P vector with the current x and y values and append them to the linked list.

这是代码的一部分.

static void _mouse_CB(int button, int state, int x, int y)
{
    if(state==GLUT_DOWN)
    {
        switch(button)
        {
        case GLUT_LEFT_BUTTON :
            px=x;py=y;
            P.x=x;
            P.y=y;
            prev=VL_new1(P);

            append(&prev,P);
            break;

我在这里用geeksforgeeks编写的append函数，并在末尾添加了while循环，以检查值是否正确添加，但是我越来越溢出.

the append function here i wrote from geeksforgeeks and added a while loop at the end to check if the values are added correctly, but i am getting overflow.

void append(node_v** head_ref, Vector A)
{ 
    node_v* new_node = (node_v*) malloc(sizeof(node_v)); 

    node_v *last = *head_ref;  

    new_node->X.x  = A.x; 
      new_node->X.y  = A.y; 
    new_node->next = NULL; 

    if (*head_ref == NULL) 
    { 
       *head_ref = new_node; 
       return; 
    }   
    while (last->next != NULL) 
        last = last->next; 
    last->next = new_node; 
    last = *head_ref;
    while(last){
      printf("%d %d\n", last->X.x,last->X.y);
      last = last->next;
    }
    return;     
} 

要创建一个节点，我编写了此函数

To create a node i wrote this function

node_v* VL_new1(Vector A){
        node_v *new = (node_v*)malloc(sizeof(node_v));
        if(new==NULL){exit(1);}
        else{
            new->X.x  = A.x; 
            new->X.y  = A.y; 
            new->next = NULL;
        }
        return new;
}

每次我运行该程序并单击出现的窗口时，在终端上，appendf里面的printf都会输出此

Each time i run this program and click on the appeared window, on the terminal the printf inside append function outputs this

-732680176 -729092496
0 -1344244448

我应该进行哪些更改以免溢出并成功添加当前值?

What changes should i make to not get overflow and successfully add the current values?

推荐答案

新节点在函数append中创建:

node_v* new_node = (node_v*) malloc(sizeof(node_v));

指令prev=VL_new1(P);生成一个新的列表头.每次执行代码时，都会设置prev，并且prev的先前内容会丢失.

The instruction prev=VL_new1(P); generates a new list head. Every time when the code is executed, then prev is set and the previous content of prev is lost.

删除是否:

case GLUT_LEFT_BUTTON :
    px=x;py=y;
    P.x=x;
    P.y=y;
    append(&prev,P);

请注意，函数VL_new1可以在append中调用，而不是:

Note, the function VL_new1 can be called in append, instead:

void append(node_v** head_ref, Vector A)
{ 
    node_v *last = *head_ref;
    node_v* new_node = VL_new1(A); 

    if (*head_ref == NULL) 
    { 
       *head_ref = new_node; 
       return; 
    }

    while (last->next != NULL) 
        last = last->next; 
    last->next = new_node;
}

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