Added old abandoned KDE3 version of koffice

git-svn-id: svn://anonsvn.kde.org/home/kde/branches/trinity/applications/koffice@1077364 283d02a7-25f6-0310-bc7c-ecb5cbfe19da

1 files changed, 297 insertions, 0 deletions

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+
+                        The design of kformula
+                          (as we imagine it)
+
+The core of kformula is a tree of element objects that make up the
+formula which is beeing edited.
+
+The element tree itself
+#######################
+
+BasicElement
+------------
+
+All element classes are derived from this one.
+So it provides the interface that is common to all elements.
+BasicElement itself is an abstract class. You never want to create
+objects from it.
+
+Responsebilities
+(This goes for every derived element and therefore for each one.)
+
+- knows its children. Actually BasicElement doesn't have any. But it
+  already defines that children must be known by their parent.
+- knows its bounding rectangle (its size.) The children are included
+  in this rect. (Only width and height are needed. Positions are
+  handled by the parent)
+//- knows its middle line. (for alignment)
+- knows it's zero point for midline (vertical alignment) and 
+  keep open the possibility of negative positions (out of bounding rect)
+- draws itself (given a painter); children are drawn, too
+- knows all positions where the cursor is allowed to be. (see below)
+- knows its parent; The topmost element has no parent; there is a
+  implicit garantie that the topmost element is always a
+  SequenceElement.
+- can save and load itself. different formates. (see below)
+- all children must be a SequenceElement. Except for SequenceElement's
+  children that might be of any type.
+- might have its own color.
+- might have its own font size (see below).
+
+
+SequenceElement from BasicElement
+---------------
+
+Manages a list of children. The children are aligned horizontally at
+one middle line. No gaps, no overlaps.
+
+Has no own look. It just draws all its children and is done. Except if
+its empty. It looks like an empty space then (i.e. a little square)
+
+Has n+1 valid cursor positions where n is the number of
+children. These are before, between and after the children.
+
+May contain any (type of) element as child 
+
+except SequenceElements if they contains a SequenceElement they merge 
+it in the list
+
+They can handle splitting of the sequence to allow "select an put selected item
+between parenthesis" i.e. as content child of a delimiterelement) 
+
+
+FormulaElement from SequenceElement
+--------------
+
+The only element those parent is null. The root of the element object
+tree.
+
+This is the element that is created by the KFormulaDoc and that knows
+about it. As every other element knows its parent and therefore the
+FormulaElement we get a chance to pass messages to the outside world.
+
+
+RootElement from BasicElement
+-----------
+
+contains two children. content and index. index is optional.
+
+
+IndexElement from BasicElement
+------------
+
+contains five children. content and four indexes. all indexes are
+optional. If there is no index the element might be replaced by its content.
+
+
+TextElement from BasicElement
+-----------
+
+contains one char and no children at all.
+
+
+Might have its own font and size. But preferes to use a reasonalbe
+font and size that are calculated from its parents font and a given
+scheme (see below).
+
+
+DelimiterElement from BasicElement
+----------------
+
+contains one child and draws delimiters around it. You are free to
+choose with.
+
+
+FractionElement from BasicElement
+---------------
+
+2 children: numerator, denominator
+
+
+DecorationElement from BasicElement
+-----------------
+
+A piece of art. It has one child and decorates it above (or below or
+both) with some nice decor. Some decor might be required to be as
+width as the content. There is a way to guarantee this.
+
+We could even add yet another child that can optionally be shown at
+the other side of the decoration.
+
+
+SumIntegralElement from BasicElement  //PrefixedElement
+------------------
+
+draws all sorts of mathematical symbols with three children. Above,
+below (or whereever the indices and limits go)and to the right.
+
+
+GeometryElement from BasicElement
+---------------
+
+One child.
+Draw it at a fixed position relative to parent or absolute.
+This is to do dirty things.
+
+This element must not be used, kformula will provide you everything
+without the use of this kind of element, any way for strange reasons
+you want to do things that are not usually allowed and that are not
+typical of a math formula.
+[We will decide if implement this element or not]
+
+
+MatrixElement from BasicElement
+-------------
+
+A matrix of children.
+With all align stuff, internal borders etc, matrix dots handling (i.e.
+those dots or lines that complete the matrix, not well handled in TeX),
+etc..
+
+SpaceElement from BasicElement
+------------
+
+No children at all. Provides the facility to insert horizontal spaces
+in the formula. (therefore it is similar to TextElement.)
+
+
+OperatorElement from TextElement
+---------------
+
+The element to be used for all kinds of operators. It needed because
+operators require some space before and after and are therefore no
+simple text.
+
+They can you pixamps inestead of fonts, the use of pixmaps is needed only 
+to give the user the possibilty of introduce its strange operator that we 
+do not provide as a font. There problems with the scalability but we will
+include as fonts (or vectorial images) in kformula all TeX operators so we
+hope there is no need to use pixamps for a standard use of KFormula
+
+Navigation
+##########
+
+There is a class Cursor that implements a pointer to a valid cursor
+position inside the formula structure. Each kformula view needs to
+have its own object of this class.
+
+The Cursor class uses the elements facility to travel throught the
+structure. (It gives the key to the current element and asks for the
+new position.)
+
+If the cursor points into an element this element is said to own the
+cursor. There are a few rules that describe how new cursor positions
+are calculated given the current key:
+
+- An elements cursor positions are its children. The element might not
+own the cursor except when it is owned by one of its children. The
+only exception is SequenceElement which has valid cursor positions
+before, between and after its children, too.
+
+(Therefore the cursor is always owned by a SequenceElement.)
+
+- Each element's children are ordered. If the cursor leaves one child
+the next child it. The direction depends on the key that moved the
+cursor. If there is child left the cursor is passed to the parent.
+
+- If the cursor comes from our parent the first or the last child gets
+it. Depending on the direction in which the cursor moved.
+
+Please note that because each element knows its own cursor positions
+and how to behave, it is possible for each combination of elements to
+work together correctly.
+
+
+
+Save and Load (Import/Export)
+#############################
+
+there are quite a few formats we want to read and write:
+
+Built in:
+- native koffice xml
+
+Import/Export filters
+- MathML 
+- C like math strings 
+- LaTeX
+
+
+
+Element templates
+#################
+
+example: you can create a template to write limits:
+it is a "lim ( )" string over 2 empty elements with an arrows that separe
+them
+
+
+
+"Look" templates
+################
+
+There need to be templates that tell which font to use, how the sizes
+differ among different elements and what spaces are to be
+included. (And much more.)
+
+Your only need to choose one of them to get a reasonable good look.
+
+
+
+Interface templates 
+###################
+
+Decide what KAction have to be toolbars,
+what element templates must be loaded, what toolbar display....
+There will be predefined (sorry for the spelling error) templates for 
+-General...
+-Physics (Vectors , integral, partial derivative etc are preferred..)
+-Analysis (Integral and diff equation stuff)
+-Geometry (Tensor product etc)
+-Chemistry (Arrows, Periodic table external toolbar)
+-Computer science (...)
+-????
+
+
+
+Context sensibility
+###################
+
+We want a formula to look different according to its
+surroundings. (Most obviosly according to the available height and/or width.)
+
+It would be great to get something like automatic operator
+alignment. So if you type some formulas each on its own line the
+assigment operators should be automatically in a column. (If the user
+turns this on.)
+
+
+
+Fonts and font size (2 ideas)
+###################
+
+1)
+Each element know its font family (also if it is not a text element) so that it 
+can give this font to its children.
+
+The font size is calculated starting from a global scale factor and appling to it
+a local size modifier (like HTML -2, -1,+3,etc..), this also calculate the 
+QPen width for vector drawn stuff (like root symbol etc) and it gives a scale
+factor for pixmap.
+
+2)
+When it comes to drawing we pass a StyleContext to the
+FormulaElement. The StyleContext contains the font family to use, the
+normal font size, the spaces to include between certain elements and
+all sorts of context information that is needed to draw the
+formula. As it is passed down the tree it also counts the current level
+so it can tell each element the font size it is supposed to use.
+
+The elements use this information to calculate their sizes and to draw
+themselves. Each element is allowed to choose different settings for
+whatever reason. But if the formula looks ugly then its the elements
+blame.
+
+
+Andrea Rizzi <[email protected]>
+Ulrich Kuettler <[email protected]>