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<title>02-03滑鼠的处理的加强</title>
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<p align="left"><font SIZE="2" color="#FF0000">·02-03滑鼠的处理的加强</font></p>
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<p>前面的程式对於滑鼠的移动处理有部份考虑的不够周详，因为它在滑鼠移动时不分青红皂白就将线画在萤慕上，造成萤幕上的线条混乱，这并不是正规的处理方法，正确的处理方法应该如下：</p>
<p>
<font SIZE="2">(1) </font>滑鼠键按下时，将记录滑鼠按下的旗标设为<font SIZE="2">True.</font>同时将该点记录下来，谓之原点。
<ol START="2">
<li>滑鼠移动时，判断滑鼠按下的旗标是否设为<font SIZE="2"> True</font>，若为<font SIZE="2"> True</font>，则移动至原点，并画一条由原点至目前所在点的线。同时更新原点位置至目前所在之点。</li>
<li VALUE="3">滑鼠放开时，将记录滑鼠按下的旗标设为<font SIZE="2">False</font>。</li>
</ol>
<p>以下就是关於叁个滑鼠事件的处理程式码。</p>
<p>
<font SIZE="2">// </font>滑鼠按下的事件处理函式</p>
<p>
<font SIZE="2">// 1. </font>将旗标设为<font SIZE="2">True</font></p><p>
<font SIZE="2">// 2. </font>记录原点位置</p>
<font SIZE="2">
<p>void __fastcall TForm1::FormMouseDown(TObject *Sender, TMouseButton Button,</p>
</font>
<p><font SIZE="2">TShiftState Shift, int X, int Y)</font></p>
<p>{</p>
<p> m_bDraw = TRUE;</p>
<p> m_nOrgX=X;</p>
<p> m_nOrgY=Y;</p>
<p>}</p>
<p>
<font SIZE="2">// </font>滑鼠移动的事件处理函式</p>
<p>
<font SIZE="2">// 1. </font>判断旗标是否为<font SIZE="2">True</font>。若是则进行以下动作。</p>
<p>
<font SIZE="2">// 2. </font>移动至原点。</p>
<p>
<font SIZE="2">// 3. </font>画一条由原点至目前所在点的线条。</p>
<p>
<font SIZE="2">// 4. </font>更改原点位置。</p>
<font SIZE="2">
<p>void __fastcall TForm1::FormMouseMove(TObject *Sender, TShiftState Shift,</p>
</font>
<p><font SIZE="2">int X, int Y)</font></p>
<p>{</p>
<p> if (m_bDraw)</p>
<p> {</p>
<p> Canvas->MoveTo(m_nOrgX,m_nOrgY);</p>
<p> Canvas->LineTo(X,Y);</p>
<p> m_nOrgX = X;</p>
<p> m_nOrgY = Y;</p>
<p> }</p>
<p>}</p>
<p>
<font SIZE="2">// </font>滑鼠放开的事件处理函式</p>
<p>
<font SIZE="2">// 1. </font>判断旗标是否为<font SIZE="2">True</font>。若是则进行以下动作。</p>
<p>
<font SIZE="2">// 1. </font>将旗标设为<font SIZE="2"> False</font>。</p>
<p>
<font SIZE="2">// 2. </font>画线并记录原点位置（非必要）。</p>
<font SIZE="2">
<p>void __fastcall TForm1::FormMouseUp(TObject *Sender, TMouseButton Button,</p>
</font>
<p><font SIZE="2">TShiftState Shift, int X, int Y)</font></p>
<p>{</p>
<p> if (m_bDraw)</p>
<p> {</p>
<p> m_bDraw=FALSE;</p>
<p> Canvas->MoveTo(m_nOrgX,m_nOrgY);</p>
<p> Canvas->LineTo(X,Y);</p>
<p> m_nOrgX = X;</p>
<p> m_nOrgY = Y;</p>
<p> }</p>
<p>}</p>
<p>将滑鼠事件处理函式做以上的修改之後，我们就完成了一个基本的涂鸦程式的雏形了。我将此表格的背景设为黑色，笔的状态设为<font SIZE="2">2</font>单位宽度的红色笔，就得到以下的输出结果：</p>
<p><img SRC="Image10.gif" WIDTH="463" HEIGHT="356"></p>
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<p> <font SIZE="2"><small><a href="../../../index.htm">首页</a> >> <a href="../../program.htm">程序设计</a>
>> <a href="../cbuilder.htm">C++ Builder</a> >> </small><font>具体而微的绘图程式</font></font>·02-03<font SIZE="2">滑鼠的处理的加强</font></p>
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