 原文： 11.6. How do I use the Canvas as a geometry manager? In a call to create a window (or anything) on your Canvas you need to specify its position - this is in part how a Canvas can be used as a geometry manager. e.g.: my($bittag) = $canvar->create(’bitmap’,10,10, -bitmap=>’hourglass’); Specifies the x=10, y=10 screen pixel location (from the upper left). Other possible units are: tag unit example pixels 25,50 # i.e. no unit tag at all m milliimeters 10c,20c c centimeters 1c,2c p points (1/72") 35p,70p There can be a great deal more to it than just units, however. Note the following question posed and answered by Eric J. Bohm. Eric J. Bohm Following up to my own message here. All right, after several false leads, I spent 3 hours fighting a canvas widget and pounding my head against the canvas.html doc, until I finally understood how to include my entries in a frame in a window in the canvas and get things to scroll nicely. Turns out that the whole thing isn’t all that hard to do once I understood how canvas widgets work. Not sure if its of general interest, but here’s the snippet, which was stolen from the items demo inside the widget_lib and then brutally hacked. Perhaps a simpler demo would have been easier to use as a guide, but I got there eventually, so my thanks for the widget demo. #---------------------------------------- my $c = $w_frame->Canvas(); $c->configure( -height => ’300’, -width => ’600’, -relief => ’sunken’, -bd => 2, ); my $w_frame_vscroll = $w_frame->Scrollbar( -command => [’yview’, $c] ); my $w_frame_hscroll = $w_frame->Scrollbar( -orient => ’horiz’, -command => [’xview’, $c] ); $c->configure(-xscrollcommand => [’set’, $w_frame_hscroll]); $c->configure(-yscrollcommand => [’set’, $w_frame_vscroll]); $w_frame_hscroll->pack(-side => ’bottom’, -fill => ’x’); $w_frame_vscroll->pack(-side => ’right’, -fill => ’y’); $c->pack(-expand => ’yes’, -fill => ’both’,-side=>’top’); my $entryframe=$c->Frame; my $c_win= create $c ’window’,’0’,’0’, -window=>$entryframe, -anchor=>’nw’; #---------------------------------------- Where $c -> configure( -scrollregion => [$top, $left, $right, $bottom]) can be used to size things nicely once you find out how big it’ll be. And the widgets you want scrolled should be slaves of $entryframe. Vastly more robust than anything I had running in the BLT Table. EJB 译文： 11.6. 怎样把画布作为布局管理器？ 当您在画布里创建一个窗口（或任何其他元件）时，都需要设定他们的位置，而这正是画布作为布局管理器的作用。例如： my($bittag) = $canvar->create(’bitmap’,10,10, -bitmap=>’hourglass’); 这里，就指定了这个位图在屏幕上的坐标（象素）是x=10，y=10（从左上角开始）。 其他可能的坐标单位更有： 符号 单位 例子 象素 25,50 #也就是不用写任何单位量 m 毫米 10m,20m c 厘米 1c,2c p 点（1/72英寸） 35p,70p 当然，作为布局管理器，绝不但仅是坐标的单位而已。让我们看看下面的这个由Eric J. Bohm提出并回答的问题： Eric J. Bohm写到： ！我在一个框架中配置了一列连续的输入框，自上而下排列。 ！这样，当删除了其中的一个时，下面的会自动的冒上来。 ！这个工作实在是太好了，我要感谢咱们积极勇敢的pTk研发小组！ ！ ！现在我碰到的麻烦是，我应该把我设计的这套东西放在什么组件中， ！才能使得当我有很多行，超出了屏幕的范围时，他能够带有滚动条？ [细节和抱怨……] 下面是我自己的解决方案：（译者注：这里的“我”还是指Eric J. Bohm） 经过几次失败的尝试，我又花了3个小时研究了画布组件和canvas.html的文档，直到我最后终于明白了怎样把我的一系列输入框放入到一个框架中，然后作为一个窗口放入画布里，这样就能够让他滚动起来了。 现在我感觉其实这个事情并没有那么困难，只要我们理解了画布组件是怎样工作的。 虽然我还是不太确定是否会有很多人对这个感兴趣，但我还是在这里放了一个小片断??是从widget_lib里的演示脚本中摘录下来的。 也许假如有个简单些的演示程式来作为向导会让这些变得更容易一些吧，但是我最终还是找到了，所以还是要感谢widget演示程式。 #---------------------------------------- my $c = $w_frame->Canvas(); $c->configure( -height => ’300’, -width => ’600’, -relief => ’sunken’, -bd => 2, ); my $w_frame_vscroll = $w_frame->Scrollbar( -command => [’yview’, $c] ); my $w_frame_hscroll = $w_frame->Scrollbar( -orient => ’horiz’, -command => [’xview’, $c] ); $c->configure(-xscrollcommand => [’set’, $w_frame_hscroll]); $c->configure(-yscrollcommand => [’set’, $w_frame_vscroll]); $w_frame_hscroll->pack(-side => ’bottom’, -fill => ’x’); $w_frame_vscroll->pack(-side => ’right’, -fill => ’y’); $c->pack(-expand => ’yes’, -fill => ’both’,-side=>’top’); my $entryframe=$c->Frame; my $c_win= create $c ’window’,’0’,’0’, -window=>$entryframe, -anchor=>’nw’; #---------------------------------------- 这里$c -> configure( -scrollregion => [$top, $left, $right, $bottom])能够用来在您知道了组件的大小以后来配置其尺寸。 这样，您想要能够滚动的组件必须是从属于$entryframe的。 很好用，比我曾用过的BLT Table要强壮的多。 EJB |
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