c++ - MoveToEx 和 LineTo 不使用存储在顶点 (push_back) win32 c++ 中的 MAKEPOINTS 绘制

Question

除非我设置，例如，LineTo(hdc,50,50) 它将从点 (50,50) 绘制，但无论我做什么，我都无法使用 MAKEPOINTS 使其工作并将其存储在 Vertex 类中(类是正确的)

请帮忙

case WM_LBUTTONDOWN:
        {
            HDC hdc = GetDC(hWnd);
            POINTS clickPoint = MAKEPOINTS(lParam); 
            connectLines.push_back(Vertex(clickPoint.x, clickPoint.y));                 
            MoveToEx(hdc, clickPoint.x, clickPoint.y, NULL);            
            LineTo(hdc, LOWORD(lParam), HIWORD(lParam));
            ReleaseDC(hWnd, hdc);
        }
        break;

编辑:我正在添加 WM_PAINT 和 Vertex 类以及 Vertex header

case WM_PAINT:
        {
            PAINTSTRUCT ps;         
            HDC hdc = BeginPaint(hWnd, &ps);
            // TODO: Add any drawing code that uses hdc here...

            for (Vertex points : connectLines) {
                HPEN pen = CreatePen(PS_SOLID, 7, RGB(255, 0, 0));
                HGDIOBJ oldPen = SelectObject(hdc, pen);
                SelectObject(hdc, oldPen);
                DeleteObject(pen);
            }
            EndPaint(hWnd, &ps);
        }
        break;

顶点标题

#pragma once
class Vertex
{
public:
    Vertex();
    Vertex(int x, int y);
    Vertex(const Vertex& other);

    // Accessors
    int GetX() const;
    void SetX(const int x);
    int GetY() const;
    void SetY(const int y);

    // Assigment operator
    Vertex& operator= (const Vertex& rhs);

    bool operator== (const Vertex& rhs) const;

    const Vertex operator+ (const Vertex& rhs) const;

private:
    int _x;
    int _y;
};

顶点标题

#include "Vertex.h"

Vertex::Vertex()
{
    _x = 0.0f;
    _y = 0.0f;
}

Vertex::Vertex(int x, int y)
{
    _x = x;
    _y = y;
}

Vertex::Vertex(const Vertex& other)
{
    _x = other.GetX();
    _y = other.GetY();
}

int Vertex::GetX() const
{
    return _x;
}

void Vertex::SetX(const int x)
{
    _x = x;
}

int Vertex::GetY() const
{
    return _y;
}

void Vertex::SetY(const int y)
{
    _y = y;
}

Vertex& Vertex::operator=(const Vertex& rhs)
{
    // Only do the assignment if we are not assigning
    // to ourselves
    if (this != &rhs)
    {
        _x = rhs.GetX();
        _x = rhs.GetY();
    }
    return *this;
}

// The const at the end of the declaration for '==' indicates that this operation does not change
// any of the member variables in this class

bool Vertex::operator==(const Vertex& rhs) const
{
    return (_x == rhs.GetX() && _y == rhs.GetY());
}

// You can see three different uses of 'const' here:
//
// The first const indicates that the method changes the return value, but it is not moved in memory
// The second const indicates that the parameter is passed by reference, but it is not modified
// The third const indicates that the operator does not change any of the memory variables in the class

const Vertex Vertex::operator+(const Vertex& rhs) const
{
    return Vertex(_x + rhs.GetX(), _y + rhs.GetY());
}

出于某种我不知道的原因它不想使用“x”和“y”但是我只有这个程序有这个问题，它的计算就像一个魅力。

谢谢你的帮助

Answer 1

在您的代码中，该行在同一点开始和结束。所以你没有画线。如果您的 Vertex 类函数如下:

void Vertex::SetX(const int x)
{
    _x = x;
}

void Vertex::SetY(const int y)
{
    _y = y;
}

根据鼠标点击绘制连续的线段，可以这样编码:

static POINT ptPrevious = { 0,0 };
static bool flag = false;
Vertex temp;
...
case WM_LBUTTONDOWN:
        HDC hdc = GetDC(hWnd);
        POINTS clickPoint = MAKEPOINTS(lParam);
        if (flag == false) {
            ptPrevious.x = clickPoint.x;
            ptPrevious.y = clickPoint.y;
            flag = true;
        }
        //store the point in connectLines
        temp.SetX(clickPoint.x);
        temp.SetY(clickPoint.y);
        connectLines.push_back(temp);

        MoveToEx(hdc, ptPrevious.x, ptPrevious.y, NULL);
        LineTo(hdc, LOWORD(lParam), HIWORD(lParam));

        //record previous point
        ptPrevious.x = clickPoint.x;
        ptPrevious.y = clickPoint.y;

        ReleaseDC(hWnd, hdc);
        break;

如果需要保存鼠标点击的位置，需要自己添加。和 here提供了一个用鼠标绘制的示例，但变量应该是 static 变量。