mirror of
https://github.com/python/cpython.git
synced 2024-11-24 18:34:43 +08:00
73 lines
4.9 KiB
HTML
73 lines
4.9 KiB
HTML
<HTML><HEAD><TITLE>Using WASTE</TITLE></HEAD>
|
|
<BODY>
|
|
<H1>Using WASTE</H1>
|
|
<HR>
|
|
|
|
WASTE is an almost-compatible TextEdit replacement which overcomes
|
|
some of the limitations of it (like the 32K limit) and provides some extensions
|
|
(drag and drop, images, undo support). Moreover, it has a much cleaner interface
|
|
and is therefore easier integrated in Python. <p>
|
|
|
|
WASTE is written by Marco Piovanelli, <A HREF="mailto:piovanel@kagi.com"><piovanel@kagi.com></A>,
|
|
and copyrighted by him. You can always obtain the latest version (for use in C
|
|
or Pascal programs) and the documentation from
|
|
<A HREF="ftp://ftp.dsi.unimi.it/DSI/piovanel/WASTE"><ftp://ftp.dsi.unimi.it/DSI/piovanel/WASTE></A>.
|
|
|
|
We explain the useage of waste here by showing how to modify the TextEdit based
|
|
<A HREF="textedit/ped.py">ped.py</A> of the
|
|
<A HREF="textedit.html">previous example</A> into the waste-based <A HREF="waste/wed.py">wed.py</A>,
|
|
so you should have both sources handy. <p>
|
|
|
|
Functionally, <code>wed.py</code> provides three new things: resizable windows, a horizontal
|
|
scroll bar and undo. <p>
|
|
|
|
Let us look at the code, first at the application class <code>Wed</code>. The only real change is that
|
|
we now handle <code>undo</code>. Aside from enabling it in the creation routine and the addition of
|
|
a callback routine there is a bit of new code in <code>updatemenubar</code>: Waste not only handles
|
|
the full details of implementing undo, it will also tell us what the next undo operation will undo
|
|
(or redo). We use this to our advantage by changing the undo menu label to tell the user. <p>
|
|
|
|
The <code>WasteWindow</code> has seen a bit more change. Initialization of the waste data structure is
|
|
a bit different, in that we can specify some options at creation time. Also, waste has no <code>SetText</code>
|
|
method but a <code>UseText</code> which expects a handle as parameter. We have to be <EM>very</EM> careful
|
|
that we keep this handle around, because Python will happily free the handle if we have no more references
|
|
to it (and I doubt that Waste would like this:-). A final difference in <code>open</code>
|
|
is that we use a large number for the destination rectangle width, because we will use a horizontal scroll
|
|
bar. <p>
|
|
|
|
The <code>idle</code> method is a bit more involved, since we also call <code>WEAdjustCursor</code> to
|
|
provide the correct cursor based on mouse-position. Users like this. <p>
|
|
|
|
<code>Getscrollbarvalues</code> is simpler than its' TextEdit counterpart because Waste correctly
|
|
updates the destination rectangle when the document changes. Also note that waste uses accessor functions
|
|
to get at internal values, as opposed to direct struct access for TextEdit. <p>
|
|
|
|
<code>Scrollbar_callback</code> on the other hand is more elaborate (but also provides more functionality).
|
|
It also handles horizontal scrolls (scrolling one-tenth and half a screenful with the buttons). This
|
|
function is also "multi-font-ready" in that scrolling one line will do the expected thing in case of multiple
|
|
fonts. We will implement a multi-font editor later. A minor annoyance of Waste is that is does not provide
|
|
a pinned scroll, so at the end of our callback routine we have to check that we have not scrolled past the
|
|
beginning or end of the document, and adjust when needed. <p>
|
|
|
|
<code>do_update</code> is also changed, because Waste is completely region-based (as opposed to rect-based).
|
|
Hence, we erase regions here and we can also return immedeately if there is nothing to update. <p>
|
|
|
|
<code>Do_postresize</code> is new: because Waste uses accessor functions we can now modify the viewRect from
|
|
Python, which is impossible in the Python TextEdit interface, and hence we can implement resize. The
|
|
<code>do_key</code> and <code>do_contentclick</code> methods have also seen minor changes, because the
|
|
corresponding waste routines need a bit more information than their TextEdit counterparts. The Cut/copy/paste
|
|
code is simplified, because Waste uses the normal desktop scrap. <p>
|
|
|
|
Implementing undo is a wonder of simplicity: Waste handles all the details for us. Also, the new
|
|
<code>can_paste</code> method (which controls greying out of the paste menu entry) is an improvement
|
|
over what <code>ped</code> did: in ped it was possible that paste was enabled but that the data on the
|
|
scrap was incompatible with TextEdit. No more such problems here. <p>
|
|
|
|
That is all for now. There is an undocumented extended version of wed, <a href="waste/swed.py">swed.py</a>,
|
|
which supports multiple fonts, sizes and faces, and uses Waste's tab-calculation to do tab characters "right".
|
|
There is also an even more elaborate example, <a href="waste/htmled.py">htmled.py</a> which extends swed with
|
|
the ability to import html files, showing the use of color and how to use embedded object (rulers, in this case).
|
|
These two programs have not been documented yet, though, so you will have to look at them without guidance. <p>
|
|
<hr>
|
|
Back to the <A HREF="index.html">index</A> to pick another example.
|