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Martin Hope
rikimaru2013
Asked: 2020-01-29 23:51:43 +0000 UTC
  • 9

函数是函子吗？

函数可以在STL算法中用作函子，但出于某种原因书籍固执地证明函数是函数，函子只是对象

c++
Martin Hope
Vadim Prokopchuk
Asked: 2020-01-25 04:11:10 +0000 UTC
  • 9

为什么在有构造函数的情况下还要初始化C#值类型中的所有字段？

例如，下面的代码将不会编译

struct AAA
{
    public int A;
    public string C;

    public AAA(int a)
    {
        A = a;
    }
}

AAA.C 字段必须在控制返回到调用方法之前完全限定。

但是如果我们删除构造函数，那么一切都会编译

struct AAA
{
    public int A;
    public string C;
}
c#
Martin Hope
Yuri
Asked: 2020-01-18 23:41:07 +0000 UTC
  • 9

有一天，我在没有使用脚本的情况下绘制了顶级菜单的代码。一切顺利，但对吗？事实上，我用于造型input type="checkbox"等等pointer-events: none;。项目中有这样的实现吗，还是这种情况还是用JS比较好？

菜单代码：

body {
  font-family: Tahoma, Arial
}
.topbar {
  display: flex;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 40px;
  background-color: white;
  border-bottom: 2px solid rgba(0, 0, 0, 0.08);
}
.topbar__button-open-leftmenu {
  display: block;
  width: 24px;
  height: 24px;
  padding: 8px;
  cursor: pointer;
}
.topbar__button-open-leftmenu:hover {
  border-bottom: 2px solid #1C90F3;
}
.topbar__button-open-leftmenu svg path {
  fill: #333;
}
.topbar__button-open-leftmenu:hover svg path {
  fill: #000;
}
.topbar__memu {
  display: flex;
  list-style: none;
  padding: 0;
  margin: 0 auto 0 0;
  opacity: 1;
  transform: translateX(0);
  transition: all 0.4s ease;
  pointer-events: auto;
}
.topbar__memu li {
  transform: scale(1);
  transition: all 0.6s ease;
  opacity: 1;
}
.topbar__memu li:nth-child(1) {
  transition-delay: 0s;
}
.topbar__memu li:nth-child(2) {
  transition-delay: 0.1s;
}
.topbar__memu li:nth-child(3) {
  transition-delay: 0.2s;
}
#topbar__checked-search:checked ~ .topbar__memu li:nth-child(1) {
  transform: scale(0);
  transition-delay: 0.2s;
  opacity: 0;
  pointer-events: none;
}
#topbar__checked-search:checked ~ .topbar__memu li:nth-child(2) {
  transform: scale(0);
  transition-delay: 0.1s;
  opacity: 0;
  pointer-events: none;
}
#topbar__checked-search:checked ~ .topbar__memu li:nth-child(3) {
  transform: scale(0);
  transition-delay: 0s;
  opacity: 0;
  pointer-events: none;
}
.topbar__memu-item {
  display: block;
  height: 40px;
  padding: 0 10px;
  line-height: 40px;
  font-size: 0.8rem;
  color: #333;
  text-decoration: none;
}
.topbar__memu-item:hover {
  color: #000;
  border-bottom: 2px solid #1C90F3;
}
.topbar__button-open-search {
  display: block;
  position: relative;
  width: 40px;
  height: 40px;
}
.topbar__button-open-search:hover {
  background-color: #f5f5f5;
}
.topbar__button-open-search svg {
  position: absolute;
  top: 10px;
  left: 10px;
  width: 20px;
  height: 20px;
}
.topbar__button-open-search svg path {
  fill: #333;
}
.topbar__button-open-search:hover svg path {
  fill: #000;
}
.topbar__button-open-search svg#icon-serach-close {
  opacity: 1;
  transition: all 0.4s ease;
}
.topbar__button-open-search svg#icon-serach-open {
  opacity: 0;
  transition: all 0.4s ease;
}
#topbar__checked-search:checked ~ .topbar__button-open-search svg#icon-serach-close {
  opacity: 0;
  transition: all 0.4s ease;
}
#topbar__checked-search:checked ~ .topbar__button-open-search svg#icon-serach-open {
  opacity: 1;
  transition: all 0.4s ease;
}
#topbar__checked-search {
  display: none;
}
.topbar__search {
  display: block;
  position: absolute;
  left: 50%;
  top: 0;
  width: 60%;
  height: 30px;
  padding: 5px;
  opacity: 0;
  transform: translateX(-50%);
  transition: opacity 0.4s ease;
  pointer-events: none;
}
#topbar__checked-search:checked ~ .topbar__search {
  transition-delay: 0.6s;
  opacity: 1;
  pointer-events: auto;
}
.topbar__search-input {
  display: block;
  width: calc(100% - 40px);
  height: 30px;
  padding: 0 30px 0 10px;
  border: none;
  border-radius: 3px;
  background-color: #f4f4f4;
  font-family: inherit;
  outline: none;
  transition: background 0.2s ease;
}
.topbar__search-input:focus {
  background-color: #eeeeee;
}
.topbar__search-button {
  display: block;
  position: absolute;
  top: 11px;
  right: 12px;
  width: 18px;
  height: 18px;
  padding: 0;
  background: none;
  border: none;
  cursor: pointer;
}
.topbar__search-button svg path {
  fill: #333;
}
.topbar__search-button:hover svg path {
  fill: #000;
}
.topbar__search-panel {
  display: block;
  position: fixed;
  top: 42px;
  left: 0px;
  width: 100%;
  height: calc(100vh - 42px);
  background-color: rgba(0, 0, 0, 0.6);
  opacity: 0;
  pointer-events: none;
  transition: opacity 1s ease;
}
#topbar__checked-search:checked ~ .topbar__search-panel {
  opacity: 1;
  pointer-events: auto;
}
.topbar__search-panel-list {
  display: block;
  position: absolute;
  top: 10px;
  left: 50%;
  width: 60%;
  padding: 5px 0;
  border-radius: 2px;
  transform: translateX(-50%) translateY(-20%);
  background-color: white;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
  transition: transform 0.4s ease, opacity 0.4s ease;
  opacity: 0;
}
#topbar__checked-search:checked ~ .topbar__search-panel .topbar__search-panel-list {
  transition-delay: 0.6s;
  transform: translateX(-50%) translateY(0%);
  opacity: 1;
}
.topbar__search-panel-list:before {
  display: block;
  content: 'Результаты поиска:';
  font-size: 0.8rem;
  padding: 3px 10px;
  margin: 0 0 5px 0;
  color: #acacac;
  border-bottom: 1px solid #f2f2f2;
}
.topbar__search-panel-list-item {
  display: block;
  font-size: 0.8rem;
  padding: 3px 10px;
  color: #333;
  text-decoration: none;
}
.topbar__search-panel-list-item:hover {
  background-color: #f4f4f4;
}
/* Leftmenu */

.leftmenu {
  display: block;
  position: fixed;
  top: 42px;
  left: 0px;
  width: 100%;
  height: calc(100vh - 42px);
  background-color: rgba(0, 0, 0, 0.6);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.4s ease;
}
#topbar__checked-leftmenu:checked + .leftmenu {
  opacity: 1;
  pointer-events: auto;
}
.leftmenu__list {
  display: block;
  position: absolute;
  left: -200px;
  width: 200px;
  height: 100%;
  margin: 0;
  padding: 0;
  background-color: white;
  transition: left 0.4s ease;
}
#topbar__checked-leftmenu:checked + .leftmenu .leftmenu__list {
  left: 0;
}
.leftmenu__list-item {
  display: block;
  padding: 6px 12px;
  font-size: 0.8rem;
  color: #333;
  text-decoration: none;
}
.leftmenu__list-item:hover {
  background-color: #f4f4f4;
}
.leftmenu__hidemenu {
  display: block;
  position: absolute;
  left: 200px;
  top: 0;
  width: calc(100% - 200px);
  height: 100%;
}
<div class="topbar">
  <label for="topbar__checked-leftmenu" class="topbar__button-open-leftmenu">
    <svg viewBox="0 0 32 32">
      <path d="M 16 6 C 14.895431 6 14 6.8954305 14 8 C 14 9.1045695 14.895431 10 16 10 C 17.104569 10 18 9.1045695 18 8 C 18 6.8954305 17.104569 6 16 6 z M 16 14 C 14.895431 14 14 14.895431 14 16 C 14 17.104569 14.895431 18 16 18 C 17.104569 18 18 17.104569 18 16 C 18 14.895431 17.104569 14 16 14 z M 16 22 C 14.895431 22 14 22.895431 14 24 C 14 25.104569 14.895431 26 16 26 C 17.104569 26 18 25.104569 18 24 C 18 22.895431 17.104569 22 16 22 z"></path>
    </svg>
  </label>
  <input type="checkbox" id="topbar__checked-search">
  <ul class="topbar__memu">
    <li><a href="" class="topbar__memu-item">Пункт 1</a>
    </li>
    <li><a href="" class="topbar__memu-item">Пункт 2</a>
    </li>
    <li><a href="" class="topbar__memu-item">Пункт 3</a>
    </li>
  </ul>
  <div class="topbar__search">
    <input type="text" class="topbar__search-input" placeholder="Найти...">
    <button class="topbar__search-button">
      <svg version="1" viewBox="0 0 24 24" enable-background="new 0 0 24 24">
        <path d="M 9 2 C 5.1 2 2 5.1 2 9 C 2 12.9 5.1 16 9 16 C 10.722428 16 12.28779 15.386196 13.5 14.375 L 14 14.875 L 14 15.6875 L 20.3125 22 L 22 20.3125 L 15.6875 14 L 14.8125 14 L 14.34375 13.53125 C 15.372135 12.314388 16 10.738606 16 9 C 16 5.1 12.9 2 9 2 z M 9 4 C 11.8 4 14 6.2 14 9 C 14 11.8 11.8 14 9 14 C 6.2 14 4 11.8 4 9 C 4 6.2 6.2 4 9 4 z"></path>
      </svg>
    </button>
  </div>
  <label for="topbar__checked-search" class="topbar__button-open-search">
    <svg id="icon-serach-close" version="1" viewBox="0 0 24 24" enable-background="new 0 0 24 24">
      <path d="M 9 2 C 5.1 2 2 5.1 2 9 C 2 12.9 5.1 16 9 16 C 10.722428 16 12.28779 15.386196 13.5 14.375 L 14 14.875 L 14 15.6875 L 20.3125 22 L 22 20.3125 L 15.6875 14 L 14.8125 14 L 14.34375 13.53125 C 15.372135 12.314388 16 10.738606 16 9 C 16 5.1 12.9 2 9 2 z M 9 4 C 11.8 4 14 6.2 14 9 C 14 11.8 11.8 14 9 14 C 6.2 14 4 11.8 4 9 C 4 6.2 6.2 4 9 4 z"></path>
    </svg>
    <svg id="icon-serach-open" viewBox="0 0 32 32">
      <path style="text-indent:0;text-align:start;line-height:normal;text-transform:none;block-progression:tb;-inkscape-font-specification:Bitstream Vera Sans" d="M 8.71875 7.28125 L 7.28125 8.71875 L 14.5625 16 L 7.28125 23.28125 L 8.71875 24.71875 L 16 17.4375 L 23.28125 24.71875 L 24.71875 23.28125 L 17.4375 16 L 24.71875 8.71875 L 23.28125 7.28125 L 16 14.5625 L 8.71875 7.28125 z"
      color="#000" overflow="visible" font-family="Bitstream Vera Sans"></path>
    </svg>
  </label>
  <div class="topbar__search-panel">
    <div class="topbar__search-panel-list">
      <a href="#" class="topbar__search-panel-list-item">Обои для рабочего стола</a>
      <a href="#" class="topbar__search-panel-list-item">Новости</a>
      <a href="#" class="topbar__search-panel-list-item">StackOverflow</a>
    </div>
  </div>
</div>
<input type="checkbox" id="topbar__checked-leftmenu">
<div class="leftmenu">
  <ul class="leftmenu__list">
    <li><a href="#" class="leftmenu__list-item">Пункт 1</a>
    </li>
    <li><a href="#" class="leftmenu__list-item">Пункт 2</a>
    </li>
    <li><a href="#" class="leftmenu__list-item">Пункт 3</a>
    </li>
  </ul>
  <label for="topbar__checked-leftmenu" class="leftmenu__hidemenu"></label>
</div>

如果有人知道如何更好地实现这一点，我将很高兴学习:)

css
Martin Hope
Alexandr_TT
Asked: 2020-01-14 19:26:52 +0000 UTC
  • 9

这个问题已经被问过很多次了，使用 有很好的解决方案javascript，比如这段代码：

var shapeClick = document.getElementById("shape").addEventListener("click", changeColor);
var clicks = 0;
function changeColor(){
  if (shape.style.fill == "rgb(29, 172, 249)")
  {
    shape.style.fill = "rgb(255, 0, 0)";
  }
  else {
    shape.style.fill = "rgb(29, 172, 249)";
  }
}
<div>  
<svg version="1.1" xmlns="http://www.w3.org/2000/svg" 
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:ev="http://www.w3.org/2001/xml-events"
 width="250" height="250" viewBox="0 0 250 250" 
> 
         <circle id="shape" class="seat" cx="120" cy="125" r="50" style="fill: #1dacf9" stroke="black" stroke-width="2" />>
 
   </svg> 
   </div>

一切正常，在脚本的帮助下你可以做很多事情。

注意问题

如何在SVG (SMIL)不使用javascriptand的情况下在 pure 上做同样的事情CSS。

只需在点击时更改颜色很容易：

<svg id="svg1" version="1.1" xmlns="http://www.w3.org/2000/svg" 
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:ev="http://www.w3.org/2001/xml-events"
 width="250" height="250" viewBox="0 0 250 250" 
> 
         <circle  cx="120" cy="125" r="50" style="fill: dodgerblue; stroke:black; stroke-width:2;" >
		 <animate attributeName="fill" from="dodgerblue" to="red" fill="freeze" begin="svg1.click" dur="0.1s" calcMode="discrete"/>
			 </circle>
	 
   </svg>

但是我并没有想到如何通过反复点击对象来改变颜色。

javascript
Martin Hope
Vyacheslav Potseluyko
Asked: 2020-01-09 17:19:06 +0000 UTC
  • 9

clip-path: polygon()需要特定点。下面代码中的某种示例。

.wrapper {
  width: 960px;
  height: 720px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto;
  background-image: url(http://beerhold.it/960/722);
  background-repeat: no-repeat;
  backgorund-position: center center;
  position: relative;
}

.key {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
  width: 10em;
  height: 10em;
  border: 2em solid rgba(255, 255, 255, .3);
  border-radius: 10em;
}

.block1,
.block2 {
  position: absolute;
  top: 0;
  width: 480px;
  height: 720px;
}

.block1 {
  left: 0;
  background-color: rgba(255, 0, 0, .2);
}

.block2 {
  right: 0;
}
.block3 {
  top: 0;
  width: 100%;
  height: calc(50% - 7em);
  background: rgba(0, 0, 0, 0.7);
  
}
.block4 {
  top: calc(50% - 7em);
  background: rgba(0, 0, 0, 0.7);
  width: 100%;
  height: 14em;
  clip-path: polygon(1% 0%, 100% 0%, 100% 100%, 0% 100%, 8% 94%, 15% 88%, 22% 78%, 29% 69%, 34% 60%, 34% 48%, 33% 36%, 30% 22%, 23% 14%, 12% 7%);
}
.block5 {
  bottom: 0;
  height: calc(50% - 7em);
  width: 100%;
  background: rgba(0, 0, 0, 0.7);
}
<div class="wrapper">
  <div class="block1"></div>
  <div class="block2">
    <div class='block3'></div>
    <div class='block4'></div>
    <div class='block5'></div>
    <div class='block6'></div>
  </div>
  <div class="key"></div>
</div>

如您所见，此刻它只是一条曲线，凹进了图形。任务是画一个半圆（或尽可能接近它），凹入一个图形。在我的理解中，这需要less，sass依此类推。还有sin，cos。我不知道从哪里开始，如何开始，我没有遇到过。感谢@AndreyFedorov 在这里使用他的代码片段

(!) 我同意给出相同结果的任何其他选项。

在此处输入图像描述

svg
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