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

MoveToEx and LineTo doesnt draw using MAKEPOINTS stored in vertices(push_back) win32 c++

本文关键字：c++ win32 back 中的 MAKEPOINTS 绘制 push LineTo 存储 顶点 MoveToEx      更新时间：2023-10-16

除非我设置了LineTo(hdc，50，50(，否则它将从点(50，50

请帮助

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头

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;

顶点标头

#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;
};

顶点标头

#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，它不想取"x"answers"y"，但我只对这个有计算的程序有这个问题，它的工作原理很有魅力。

感谢的帮助

在代码中，行的起点和终点在同一点。所以你们没能划清界限。如果你的Vertex类函数是这样的：

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

点击鼠标绘制一个连续线段，你可以这样编码：

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;

如果你需要保存鼠标点击的位置，你需要自己添加。这里提供了一个使用鼠标绘制的示例，但变量应该是static变量。

试试类似的东西：

vector<Vertex> connectLines;
void addClickPoint(HWND hWnd, int X, int Y)
{
connectLines.push_back(Vertex(X, Y));
InvalidateRect(hWnd, NULL, TRUE);
}
...
case WM_LBUTTONDOWN:
{
POINTS clickPoint = MAKEPOINTS(lParam);
addClickPoint(hWnd, clickPoint.x, clickPoint.y);
/* alternatively:
addClickPoint(hWnd, GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
*/
}
break;
// optionally:
case WM_MOUSEMOVE:
{
if (wParam & MK_LBUTTON)
{
POINTS clickPoint = MAKEPOINTS(lParam);
addClickPoint(hWnd, clickPoint.x, clickPoint.y);
/* alternatively:
addClickPoint(hWnd, GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
*/
}
}
break;
//
case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
...
if (connectLines.size() > 1)
{
MoveToEx(hdc, connectLines[0].GetX(), connectLines[0].GetY(), NULL);
for(size_t i = 1; i < connectLines.size(); ++i)
LineTo(hdc, connectLines[i].GetX(), connectLines[i].GetY());
}
...
EndPaint(hWnd, &ps);
}
break;
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