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diff --git a/files/zh-cn/web/api/canvasrenderingcontext2d/textalign/index.html b/files/zh-cn/web/api/canvasrenderingcontext2d/textalign/index.html new file mode 100644 index 0000000000..bfeb7c5a73 --- /dev/null +++ b/files/zh-cn/web/api/canvasrenderingcontext2d/textalign/index.html @@ -0,0 +1,180 @@ +--- +title: CanvasRenderingContext2D.textAlign +slug: Web/API/CanvasRenderingContext2D/textAlign +translation_of: Web/API/CanvasRenderingContext2D/textAlign +--- +<div>{{APIRef}}</div> + +<p><code><strong>CanvasRenderingContext2D</strong></code><strong><code>.textAlign</code></strong> 是 Canvas 2D API 描述绘制文本时，文本的对齐方式的属性。注意，该对齐是基于CanvasRenderingContext2D.fillText方法的x的值。所以如果textAlign="center"，那么该文本将画在 x-50%*width。</p> + +<blockquote> +<p>译者注：这里的textAlign="center"比较特殊。textAlign的值为center时候文本的居中是基于你在fillText的时候所给的x的值，也就是说文本一半在x的左边，一半在x的右边（可以理解为计算x的位置时从默认文字的左端，改为文字的中心，因此你只需要考虑x的位置即可）。所以，如果你想让文本在整个canvas居中，就需要将fillText的x值设置成canvas的宽度的一半。</p> +</blockquote> + +<h2 id="语法">语法</h2> + +<pre class="syntaxbox"><var><em>ctx</em>.textAlign = "left" || "right" || "center" || "start" || "end";</var> +</pre> + +<h3 id="选项">选项</h3> + +<p>有效值：</p> + +<dl> + <dt>left</dt> + <dd>文本左对齐。</dd> + <dt>right</dt> + <dd>文本右对齐。</dd> + <dt>center</dt> + <dd>文本居中对齐。</dd> + <dt>start</dt> + <dd>文本对齐界线开始的地方 （左对齐指本地从左向右，右对齐指本地从右向左）。</dd> + <dt>end</dt> + <dd>文本对齐界线结束的地方 （左对齐指本地从左向右，右对齐指本地从右向左）。</dd> +</dl> + +<p>默认值是 <code>start。</code></p> + +<blockquote> +<p><code>译者注：direction属性会对此属性产生影响。如果direction属性设置为ltr，则left和start的效果相同，right和end的效果相同；如果direction属性设置为rtl，则left和end的效果相同，right和start的效果相同。</code></p> +</blockquote> + +<h2 id="示例">示例</h2> + +<h3 id="Using_the_textAlign_property" name="Using_the_textAlign_property">使用 <code>textAlign</code> 属性</h3> + +<p>这是一段简单的代码片段，使用 <code>textAlign</code> 属性设置文本的不同对齐方式。</p> + +<h4 id="HTML">HTML</h4> + +<pre class="brush: html"><canvas id="canvas"></canvas> +</pre> + +<h4 id="JavaScript">JavaScript</h4> + +<pre class="brush: js">var canvas = document.getElementById("canvas"); +var ctx = canvas.getContext("2d"); + +ctx.font = "48px serif"; +ctx.textAlign = "left"; +ctx.strokeText("Hello world", 0, 100); +</pre> + +<p>修改下面的代码并在线查看 canvas 的变化：</p> + +<div class="hidden"> +<h6 id="Playable_code" name="Playable_code">Playable code</h6> + +<pre class="brush: html"><canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas> +<div class="playable-buttons"> + <input id="edit" type="button" value="Edit" /> + <input id="reset" type="button" value="Reset" /> +</div> +<textarea id="code" class="playable-code"> +ctx.font = "48px serif"; +ctx.textAlign = "left"; +ctx.strokeText("Hello world", 0, 100);</textarea> +</pre> + +<pre class="brush: js">var canvas = document.getElementById("canvas"); +var ctx = canvas.getContext("2d"); +var textarea = document.getElementById("code"); +var reset = document.getElementById("reset"); +var edit = document.getElementById("edit"); +var code = textarea.value; + +function drawCanvas() { + ctx.clearRect(0, 0, canvas.width, canvas.height); + eval(textarea.value); +} + +reset.addEventListener("click", function() { + textarea.value = code; + drawCanvas(); +}); + +edit.addEventListener("click", function() { + textarea.focus(); +}) + +textarea.addEventListener("input", drawCanvas); +window.addEventListener("load", drawCanvas); +</pre> +</div> + +<p>{{ EmbedLiveSample('Playable_code', 700, 360) }}</p> + +<h2 id="规范描述">规范描述</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-textalign", "CanvasRenderingContext2D.textAlign")}}</td> + <td>{{Spec2('HTML WHATWG')}}</td> + <td> </td> + </tr> + </tbody> +</table> + +<h2 id="浏览器兼容性">浏览器兼容性</h2> + +<p>{{ CompatibilityTable() }}</p> + +<div id="compat-desktop"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Chrome</th> + <th>Firefox (Gecko)</th> + <th>Internet Explorer</th> + <th>Opera</th> + <th>Safari</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatGeckoDesktop("1.9.1") }}</td> + <td>{{ CompatIE(9) }}</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatVersionUnknown() }}</td> + </tr> + </tbody> +</table> +</div> + +<div id="compat-mobile"> +<table class="compat-table"> + <tbody> + <tr> + <th>Feature</th> + <th>Android</th> + <th>Chrome for Android</th> + <th>Firefox Mobile (Gecko)</th> + <th>IE Mobile</th> + <th>Opera Mobile</th> + <th>Safari Mobile</th> + </tr> + <tr> + <td>Basic support</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatGeckoMobile("1.9.1") }}</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatVersionUnknown() }}</td> + <td>{{ CompatVersionUnknown() }}</td> + </tr> + </tbody> +</table> +</div> + +<h2 id="参见">参见</h2> + +<ul> + <li>接口定义， {{domxref("CanvasRenderingContext2D")}}.</li> +</ul> |