198 lines
8.5 KiB
Plaintext
198 lines
8.5 KiB
Plaintext
This file gives some information about the code in edit.c. If you want to
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change, add, or fix code, please read this text. If you're not interested
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in doing actual work on edit.c only C & D will be of interest to you.
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A) basic policy
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B) special functions
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C) not implemented / implementation ideas / implementation problems
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D) known bugs / features
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A) Basic Policy
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All messages are handled by EditWndProc(), which is the only external
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function call. All other functions are static (local to edit.c).
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All Windows Messages (WM_XXX) are 32-bit, since the edit control is now a
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32-bit registered class. The message are dealt with through the helper
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functions EDIT_WM_XXX().
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The edit control messages can be either 16 or 32 bit, depending on the type
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of application that sends the message. Wherever possible EditWndProc()
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converts the 16-bit message parameters to parameters corresponding to their
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32-bit counterparts. The message is then handled by the appropriate
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EDIT_EM_XXX() helper function. Sometimes it is not possible to handle the
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16-bit and 32-bit versions in the same way, in which case both helper
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functions EDIT_EM_XXX16() and EDIT_EM_XXX() are defined.
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All other functions are called EDIT_XXX().
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Note: Sometimes a function is internally used a bit different than the specs
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of a similar function. For instance EDIT_SetSel() is used internally and
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should not be mixed up with EDIT_EM_SetSel(), a message handler that _does_
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conform to the specs of EM_SETSEL.
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The code has been made in such a way, that functions try to call other
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(documented) functions if that is sufficient. This might sometimes not be
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the most efficient way, but it keeps the code clear. This way I tried to
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keep the number of functions that rely on the internal EDITSTATE structure
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as low as possible. For instance EDIT_WM_Cut() simply calls EDIT_WM_Copy()
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and EDIT_WM_Clear(). The latter two are well documented message handlers,
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so as long as they are right EDIT_WM_Cut() will never have to change again.
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Example:
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The best thing to do, when you want to know the offset of line 3, is calling
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EDIT_EM_LineIndex(). Again this is a well documented message handler.
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Don't look at es->LineDefs[2].offset. It would just be another reference to
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the internal structure, and that would make it more difficult to change
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things. Refer to EDIT_WM_???? and EDIT_EM_????? functions as much as
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possible.
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The WND * pointer is used internally whenever possible. Although it is not
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the real HWND, it improves performance enough to use it.
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All displaying is done by invalidating regions / rects. Only
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EDIT_EM_LineScroll() uses direct painting. This way things become much
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faster. Although sometimes the response time might appear to be slow, it
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would be much slower even, when everything would be painted instantly. This
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is especially true for scrollbar tracking and selection changes..
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The text buffer is a kind of tricky. Initially the edit control allocates a
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HLOCAL32 buffer (32 bit linear memory handler). However, 16 bit application
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might send a EM_GETHANDLE message and expect a HLOCAL16 (16 bit SEG:OFF
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handler). From that moment on we have to keep using this 16 bit memory
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handler, because it is supposed to be valid at all times after EM_GETHANDLE.
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What we do is create a HLOCAL16 buffer, copy the text, and do pointer
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conversion.
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B) Special functions
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Several helper functions try to make your life easier when dealing with the
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allocated buffer. In principle Windows can move memory blocks around unless
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they are locked. Currently, WINE doesn't do this, but it might in the
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future.
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For this reason there is a nice EDIT_GetPointer() function, which locks the
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heap buffer *only once*, no matter how often it is called. It then returns a
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nice 32-bit pointer to linear memory. Calling EDIT_GetPointer() is very fast
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if the buffer is already locked, so you can call it whenever you feel it
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*might* be useful.
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At the end of EditWndProc(), EDIT_ReleasePointer() is automatically called
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which cleans up the initialized pointer. So you don't have to worry about
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unlocking the memory block. This way, the buffer gets locked / unlock only
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once every message, although EDIT_GetPointer() may actually have been called
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a hundred times. Only when the actual HLOCAL is needed (for example to
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ReAlloc), an extra call (besides the cleanup at the end of EditWndProc()) to
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EDIT_ReleasePointer() is needed. Look for instance in EDIT_MakeFit().
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This brings us to EDIT_MakeFit(). It automatically re-allocates the buffer
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if the size parameter > buffersize. If everything is successful TRUE is
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returned, otherwise FALSE. Only when the buffer contents may grow you need
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to call EDIT_MakeFit(). Currently this is only in EDIT_ReplaceSel() and
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EDIT_WM_SetText().
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EDIT_GetPointer(), EDIT_ReleasePointer and EDIT_MakeFit() are aware of the
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HLOCAL32 / HLOCAL16 business.
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EDIT_BuildLineDefs() is the most important function in edit.c. It builds
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the internal EDITSTATE structure. As soon as text *might* have changed, or
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when the appearance of the text on the screen *might* have changed, call
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this function ! This includes changes of screen size, change of the font,
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clipboard actions, etc. etc. Most other functions that rely on EDITSTATE,
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rely on the stuff this function builds.
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C) Not Implemented / Implementation Ideas / Implementation Problems
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Styles:
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- ES_CENTER
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- ES_RIGHT
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- ES_NUMBER (new since win95)
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- ES_OEMCONVERT
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- ES_WANTRETURN
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None of these should be difficult to include. I just didn't have the time
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yet. Feel free ...
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- ES_AUTOVSCROLL (every multi line control *is* auto vscroll)
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- ES_AUTOHSCROLL (every single line control *is* auto hscroll)
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(for multi line controls it works : wordwrap)
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Much, much more difficult. It comes down to this: When there is no
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autoscrolling, the edit control should first check whether the new text
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(after a typed key for instance) would fit. If not, an EN_MAXTEXT should be
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sent. However, currently this would require the actual change to be made,
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then call EDIT_BuildLineDefs() and then find out that the new text doesn't
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fit. After all this, things should be put back in the state before the
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changes. Given the fact that even normal UNDO doesn't work ...
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Messages:
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- EM_SETRECT
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- EM_SETRECTNP
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- EM_SETMARGINS (new since win95)
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- EM_FMTLINES
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These shouldn't be really difficult either. They just confine the visual
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output to something different than the client rectangle. Currently the
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client area is used everywhere in the code. At some points this should
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really be so (GetClientRect32()), whereas at other points it should be the
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format rectangle (EDIT_EM_GetRect()). Both functions are now used, but
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inconsistently and mixed up ! If you implement the formatting rectangle /
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margins, be sure to check all references to RECT's, and how they are /
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should be obtained.
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- EM_FMTLINES
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This means: insert or remove the soft linebreak character (\r\r\n). Probably
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invented by MS to suit their implementation of the edit control. However,
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with WINE's implementation I've never come up with occasions where it is
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actually useful (we never insert \r\r\n, and applications always request
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removal). If you are a purist ... implementation shouldn't be difficult.
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Take care to check if the text still fits the buffer after insertion. If
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not, notify with EN_ERRSPACE.
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- WM_UNDO (=EM_UNDO)
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I'm working on it. It is, however, not trivial. Luckily the only function
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where actual text changes is EM_REPLACESEL, so this is the only spot where
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we have to worry about UNDO capabilities. Before you try: contact me. I
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already have ideas and might start implementing it myself really soon.
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- EM_SETWORDBREAKPROC
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Not really difficult. It used to work, but since we moved to 32 bits there
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are now two kinds of callback functions. And I don't know the 32-bit specs
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for the WordBreakProc() ... Look it up and uncomment the code that is still
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there for 16 bit callback.
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- EM_SCROLL
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Supposed to be the same as WM_VSCROLL, but not quite. In other words:
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poorly documented. Somebody that knows ?
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D) Known bugs / Features
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- The control still calls GetTabbedTextExtent() and TabbedTextOut() in
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their 16 bit version (since the 32 bit versions don't yet exist).
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Therefore the tab list is 16 bits (should be 32).
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- Scrollbar tracking is broken.
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- Lots of API calls are to 16 bit functions, because their 32 bit
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versions haven't been implemented yet (e.g. clipboard).
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- Turning on WordWrap with 16-bit Notepad leaves part of the horizontal
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scrollbar visible (problem with WM_ERASEBKGND ???).
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- FIXME's (grep for them).
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I am working on Undo capabilities. If you want to do things, other than bug
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fixes, please mail me so we can synchronize.
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Frans van Dorsselaer
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dorssel@rulhm1.LeidenUniv.nl
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