设置可拖动线段的限制

huangapple
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英文:

To set limit to draggable line segments

问题

在mouseMoveEvent中的这个条件检查有一个问题。您可以尝试以下更改：

  1. if (dragging)
  2. {
  3.     if (CurPoint1->y() > 50 && CurPoint1->y() < 150)
  4.     {
  5.         changeP1value(event->y());
  6.     }
  7.     else
  8.     {
  9.         // 如果超出了高度限制，您应该更新CurPoint1的y坐标，而不是忽略它
  10.         if (CurPoint1->y() <= 50)
  11.         {
  12.             CurPoint1->setY(51); // 或者您可以设置为50，根据需要
  13.             CurPoint2->setY(51); // 这将使线保持在50以上
  14.         }
  15.         else if (CurPoint1->y() >= 150)
  16.         {
  17.             CurPoint1->setY(149); // 或者您可以设置为150，根据需要
  18.             CurPoint2->setY(149); // 这将使线保持在150以下
  19.         }
  20.         update();
  21.     }
  22. }

这样，如果线的高度超出了50到150的限制，它将被设置回这些边界，从而允许您再次向下拖动。

英文:

I'm trying to implement segments that can be draggable by mouse between two points (shown below where green and red lines must be draggable between black dash lines).

sample image

设置可拖动线段的限制

I can drag the lines by mouse.

As a next step I want to set a limit to this draggable area, which I'm having issues to implement with. I really appreciate if someone can help me to do this. I now explain the situation in a bit detail:

.h is:

  1. public:
  2.     MainWindow(QWidget *parent = nullptr);
  3.     ~MainWindow();
  4.      void paintEvent(QPaintEvent *e);
  6. public slots:
  8.       void changeP1value(int);
  11. private:
  12.     Ui::MainWindow *ui;
  13.      bool dragging = false; 
  14.      QPoint p1 = QPoint(400,100);
  15.      QPoint p2 = QPoint(450,100);
  16.      QPoint p3 = QPoint(450,100);
  17.      QPoint p4 = QPoint(500,100);
  19.      QPoint *CurPoint1=nullptr;
  20.      QPoint *CurPoint2=nullptr;
  22. protected:
  23.      virtual void mousePressEvent(QMouseEvent *event) override;
  24.      virtual void mouseReleaseEvent(QMouseEvent *event) override;
  25.      virtual void mouseMoveEvent(QMouseEvent *event) override;
  26. };
  27. #endif // MAINWINDOW_H

and in .cpp file:

  1. // small helper to give us the distance
  2. int distance(QPoint x1, QPoint x2)
  3. {
  4.     return abs(x2.y() - x1.y());
  5. }
  7. // the Paint event to draw lines
  8. void MainWindow::paintEvent(QPaintEvent *e)
  9. {
  10.     QPainter painter1(this);
  12.     QPen pointpen(Qt::black);
  13.     pointpen.setWidth(5);
  14.     QPen linepen1(Qt::red);
  15.     linepen1.setWidth(2);
  16.     QPen linepen2(Qt::green);
  17.     linepen2.setWidth(2);
  19.     painter1.setPen(linepen1);
  20.     painter1.drawLine(p1,p2);
  21.     painter1.setPen(linepen2);
  22.     painter1.drawLine(p3,p4);
  24. }
  26. // when user clicks
  27. void MainWindow::mousePressEvent(QMouseEvent *event)
  28. {
  29.     QPoint mp = event-&gt;pos(); // where is mouse
  30. // test if we hit the line. give user 20 pixels slack as its hard to hit one pixel
  31.     if (distance ( mp, p1) &lt; 20 &amp;&amp; ( mp.x() &gt; p1.x() &amp;&amp; mp.x() &lt; p2.x() ) ) {
  32.         dragging = true; // flag we are dragging
  33.         
  34.         
  35.         CurPoint1 = &amp;p1;
  36.         CurPoint2 = &amp;p2;
  37.     }
  38.     else if (distance ( mp, p3) &lt; 20 &amp;&amp; ( mp.x() &gt; p3.x() &amp;&amp; mp.x() &lt; p4.x() ) ) {
  39.         dragging = true;
  40.         CurPoint1 = &amp;p3;
  41.         CurPoint2 = &amp;p4;
  42.     }
  43. }
  45. void MainWindow::mouseReleaseEvent(QMouseEvent *event)
  46. {
  47.     dragging = false; // if user release mouse we are not draggign anymore
  48. }
  50. // then when mouse move
  51. void MainWindow::mouseMoveEvent(QMouseEvent *event)
  52. {
  53.  // If we are dragging, call your normal slider changed function to update your points.
  55.     if (dragging)
  56.     {
  57.       if(CurPoint1-&gt;y()&gt;50 &amp;&amp; CurPoint1-&gt;y()&lt;150) 
  58.         {
  59.         changeP1value(event-&gt;y());
  60.         }
  61.       else
  62.       update();
  63.     }
  65. }
  67. void MainWindow::changeP1value(int value)
  68. {
  70.     CurPoint1-&gt;setY(value);
  71.     CurPoint2-&gt;setY(value);
  72.     update();
  74. }

In the mouseMoveEvent, I've condition to check if I'm dragging a line and if the hight is between 50 and 150:

  1.  if (dragging)
  2.     {
  3.       if(CurPoint1-&gt;y()&gt;50 &amp;&amp; CurPoint1-&gt;y()&lt;150) //----&gt; it get stucked and cannot be dragged down again 
  4.         {
  5.         changeP1value(event-&gt;y());
  6.         }
  7.       else
  8.       update();
  9.     }

In this case I can drag , the line stops at the set limits but I cant drag down again. Can you spot an issue?

Thanks in advance

答案1

得分: 1

你需要检查新的y值，而不是当前值：

  1. void MainWindow::mouseMoveEvent(QMouseEvent *event)
  2. {
  3.   if (dragging)
  4.   {
  5.     if(event->y() > 50 && event->y() < 150) 
  6.     {
  7.       changeP1value(event->y());
  8.     }
  9.     else
  10.       update();
  11.   }
  12. }
英文:

You need to check the new y value, not the current value:

  1. void MainWindow::mouseMoveEvent(QMouseEvent *event)
  2. {
  3.   if (dragging)
  4.   {
  5.     if(event-&gt;y() &gt; 50 &amp;&amp; event-&gt;y() &lt; 150) 
  6.     {
  7.       changeP1value(event-&gt;y());
  8.     }
  9.     else
  10.       update();
  11.   }
  12. }

huangapple
  • 本文由 发表于 2020年1月6日 23:03:57
  • 转载请务必保留本文链接：https://go.coder-hub.com/59614385.html
  • c++
  • qt
  • qtgui
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