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130 lines
5.7 KiB
130 lines
5.7 KiB
Overall design
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==============
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* The document (KWDocument) has a list of framesets (KWFrameSet)
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* Framesets include: text frameset, picture/clipart frameset, table frameset etc.
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* A frameset has a list of frames, KWFrame. A KWFrame is basically a rectangle
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(KoRect) with a bunch of attributes.
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The frameset contains the contents, like the text or a picture.
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The frames visualize the contents of the frameset.
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Imagine a 10 pages document, with 1 text-frameset and 10 frames, because our
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example author wants to have one frame per page. This means that there is one
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text, and the frames define where on the pages this text is displayed.
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* About text framesets: they hold a text document (KWTextDocument, which is
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a QTextDocument from the KoText classes - more on KoText later).
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* About Tables; one table is a KWTableFrameset. This tableframeset contains
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all the cells as its frames. But because the cells have a different text per
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cell, we contain the cells in their own KWTextFrameset.
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KWTableFrameSet
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| TextFrames
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Cells +--------+
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+ ---> KWTextFrameSet |
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| +-> KWFrame <-+
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+ ---> KWTextFrameSet |
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| +-> KWFrame <-+
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+ ---> KWTextFrameSet |
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+-> KWFrame <-+
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* The z-order of the frames (i.e. which one is on top of which)
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is defined by m_zOrder in KWFrame. This number is relative to the other
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frames *on the same page*.
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Frame layout and pages
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======================
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Generally, the user is free to position frames where he/she wants to.
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KWTextFrameSet::slotAfterFormatting() takes care of triggering frame
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resizing (AutoExtend frames), creating a new page (AutoCreateNewFrame), etc.
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However, in Word Processing mode, some frames are special: main text frameset
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(which might include columns), headers, footers, and footnotes. All of those
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are laid out by the KWFrameLayout class, which is triggered by
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KWDocument::recalcFrames.
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When creating a new page, KWDocument::insertPage takes care of creating the
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followup frames for all frames with newFrameBehavior=Reconnect.
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The newFrameBehavior called "Copy" means "exact copy of the contents of
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the frame". This is used for headers/footers (but the user can also use
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it for logos and stuff). In such a case we don't copy anything, we simply
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paint the same contents in many pages.
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In WP mode, removing pages is automatically done by KWDocument::tryRemovingPages().
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In DTP mode pages are user-controlled (insert and delete page actions),
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but overflowing text can still create a new page as well.
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The difficulty with frame layout is that in most cases the frame size and
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number depends on the text inside, and the text layout depends on the frames
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(frame width, frames on top, etc.). This is why text layout (formatMore())
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and frame layout (e.g. KWFrameLayout) often call each other, resulting in
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infinite loops when some code goes wrong.
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Editing
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=======
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To edit the contents of a text frameset (including table cells), the user clicks on it.
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This creates an edit object for the frameset, which will be destroyed as soon as we go
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edit another frameset. This means, in a given view (canvas), there is only one edit
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object at a given moment (for text objects, it's the one with the cursor).
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There is one type of edit object per type of frameset. For instance: KWTextFrameSetEdit.
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The kotext library provides a base class for the 'text editing' object, it's KoTextView.
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Custom items
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============
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A custom item is anything (like an inline frame, a variable etc.) that
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is treated as a special character. QTextCustomItem is the base class for
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it, we have KoTextCustomItem in kotext.
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Inline frames are one kind of custom item. The frame (and its englobing
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frameset) exist as usual, but a KWAnchor instance is created, inserted
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into the text, and linked to the frame. The anchor always has the same size
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as the frame. When the text is flowed, the anchor is positioned, it tells
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the frame to move to the new position.
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Painting
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========
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Here's how the painting (drawing the stuff on screen, and on printer) works:
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Each frameset is responsible for drawing itself. The base class, KWFrameSet,
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handles the generic code for iterating through the frames, applying the
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"frame is a copy" stuff, drawing the borders, etc. So each specific frameset
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class only has to implement drawFrame (exception for KWTableFrameset though).
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Painting of text: KWTextFrameset paints the text for each frame, calling
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KoTextDocument::drawWYSIWYG (with flags for "only the changed paragraphs" etc).
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When printing this method delegates to drawWithoutDoubleBuffer.
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Both methods iterate through the paragraphs, and call drawParagWYSIWYG for each
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one to be redrawn. This method implements the double-buffering, paints the
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background color and the space on the right of the paragraph, and calls
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QTextParag::paint(). Its role is to draw series of characters with the same
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formatting at once (in one go). For each set of chars to be painted,
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KoTextParag::drawParagString is called.
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In short:
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KWFrame::drawContents -> KWTextFrameSet::drawFrame
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-> KoTextDocument::drawWYSIWYG -> KoTextDocument::drawParagWYSIWYG
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-> KoTextParag::paint -> KoTextParag::drawParagString -> KoTextParag::drawParagStringInternal
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The cursor is also drawn by KoTextParag::paint, which calls KoTextParag::drawCursor.
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The blinking cursor is implemented in KoTextView, which calls a virtual
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drawCursor() method, implemented in KWTextFrameSetEdit.
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More low-level things
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=====================
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.. such as coordinate systems, font sizes, justified spaces etc.
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See lib/kotext/DESIGN.
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Wow, you managed to read this until the end ? Good. "GOTO 10" now ;)
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David Faure <faure@kde.org>
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