📄 4.2.4 事件方式.htm
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<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312
size=4>get_locator(x,y)<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312
size=4>下述的一段程序是用await_event、get_locator命令从1号工作站的图形输入板上输入一个点集，并用直线段连接这些点：<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1">
</SPAN>set_stroke_mode(1,2,event);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1">
</SPAN>if(device_class==stroke) {<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 2">
</SPAN>await_event(60,device_class,ws,device_code);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1">
</SPAN>}<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1">
</SPAN>get_stroke(n,xa,ya);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1">
</SPAN>polyline(n,xa,ya);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN
style="mso-fareast-language: ZH-CN"><FONT face=楷体_GB2312 size=4>这里<SPAN
lang=EN-US>IF条件循环为了把从其它设备来的在队列中的数据滤掉；设置的等待时间为1分钟，以保证输入数据接收完毕。当然在事件方式下，若只有这台图形输入板处于激活状态，那么这个IF条件循环就不要了。<o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN style="mso-fareast-language: ZH-CN"><FONT
face=楷体_GB2312
size=4>在事件方式下，同时可应用多台输入设备以加快交互处理。下面的程序是从键盘输入属性和从图形输入板输入数据画折线。<SPAN
lang=EN-US><o:p></o:p></SPAN></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312
size=4>set_ployline_index(1);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312
size=4>set_stroke_mode(1,2,event);(把图形输入板设成笔划设备)<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312
size=4>set_choice_mode(1,7,event);(把键盘设成选择设备)<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4>do
{<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 2">
</SPAN>await_event(60,device_class,ws,device_code);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 2">
</SPAN>if(device_class==choice) then {<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 3">
</SPAN>get_choice(option);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 3">
</SPAN>set_polyline_index(option);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 2">
</SPAN>}<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 2"> </SPAN>else
<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 3">
</SPAN>if(device_class==stroke) then {<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 4">
</SPAN>get_stroke(n,xa,ya);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 4">
</SPAN>polyline(n,xa,ya);<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><SPAN
style="mso-tab-count: 3">
</SPAN>}<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent style="TEXT-INDENT: 0cm"><SPAN lang=EN-US><FONT
face=楷体_GB2312 size=4><SPAN style="mso-tab-count: 1"> </SPAN>}
while(device_class)<o:p></o:p></FONT></SPAN></P>
<P class=MsoBodyTextIndent><SPAN style="mso-fareast-language: ZH-CN"><FONT
face=楷体_GB2312 size=4>在此例中通过将<SPAN
lang=EN-US>device_class设成空来终止此过程。若等待1分钟后，还没有新事件进入事件队列，即会发生终止的情况。在事件方式下，还需应用其它一些命令，如清事件队列等。<o:p></o:p></SPAN></FONT></SPAN></P>
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<P class=MsoNormal><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">图</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt"> 4.2.3 </SPAN><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'; mso-ascii-font-family: 'Times New Roman'">事件方式的输入过程</SPAN></P></DIV><![if !mso]></TD></TR></TBODY></TABLE><![endif]></v:textbox><w:wrap
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style="mso-fareast-language: ZH-CN"><FONT face=楷体_GB2312 size=4><![if !supportEmptyParas]> </FONT></SPAN><FONT face=楷体_GB2312
size=4><IMG height=54 alt="文本框: 图 4.2.3 事件方式的输入过程" hspace=12
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<P class=MsoBodyTextIndent></P>
<P class=MsoBodyTextIndent><SPAN style="mso-fareast-language: ZH-CN"><FONT
face=楷体_GB2312 size=4>事件方式的输入过程见图<SPAN
lang=EN-US>4.2.3所示。在事件模式数据输入过程中，输入设备和程序分别各自运行。输入设备所产生的数据被组织成事件结点，排入事件队列中等待程序的处理。程序运行到事件处理语句时，就从事件队列中取出队首事件予以处理。如果事件队空，程序则等待一定的时间片，等待事件的发生。</SPAN></FONT></SPAN><FONT
face=楷体_GB2312 size=4><SPAN lang=EN-US
style="FONT-SIZE: 10pt; mso-fareast-language: ZH-CN"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><SPAN lang=EN-US><FONT face=楷体_GB2312 size=4><![if !supportEmptyParas]><![endif]> <o:p></o:p></FONT></SPAN></P>
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