You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
104 lines
4.8 KiB
104 lines
4.8 KiB
Coordinate systems
|
|
==================
|
|
|
|
This is fun; brace yourself
|
|
|
|
Document:
|
|
All objects have a position on the page which is described in the typographic units
|
|
named points.
|
|
There are 72 points to the inch, and these absolute coordinates simply place your
|
|
objects on the page.
|
|
An example; a frame is positioned on paper some 35mm from the left border of the paper and
|
|
some 35mm from the top of the first page. the absolute position of that frame is 100, 100
|
|
since 100pt equals 35mm.
|
|
Note that positioning is done from page 1, so when a frame is moved from page 1 to page 2 it
|
|
simply gets a higher Y coordinate.
|
|
|
|
Zoomed: (aka Normal)
|
|
Every object on screen has a size, and at different zoom levels we use a different amount
|
|
of pixels to display the same object.
|
|
Our object above has a top-left position of document:(100,100). To determine where
|
|
this is on screen we call KoZoomHander::zoomItX(xPos) and KoZoomHander::zoomItY(yPos) to
|
|
retrieve the pixel positioning on screen at the current zoom level. The zoom level
|
|
is stored only in the zoomhandler, which is in KWord the document (an instance of KWDocument).
|
|
Since we are using pixel values all these values are stored in integers, they should not
|
|
be used to move something around, the absolute coordinate system has to be used for that.
|
|
|
|
Internal:
|
|
The former two were mostly for objects like frames etc, not for text. Text (the individual
|
|
words and characters) are positioned with the layout coordinates. Layout is similar to the
|
|
Zoomed system, but always uses the same resolution. This resolution is sufficiently high to
|
|
do the layout in integers, and not really lose info.
|
|
|
|
This is the high-resolution unit in which the text layout is done,
|
|
currently set to 1440 DPI. Everything known the QRT classes will be in
|
|
this coordinate system (including the QTextFormats). When painting, we apply
|
|
the current zoom and resolution to find the right font size to use, and we
|
|
have to catch up with rounding differences. However the position of the words
|
|
(i.e. layout) is the one determined previously in layout units. KoZoomHandler
|
|
offers methods for converting between layout units and zoom-dependent points
|
|
and pixels.
|
|
|
|
Note that the Internal coordinate system starts at the topleft corner of
|
|
the first text frame, (whereas the other coordinate systems start at the
|
|
topleft corner of the first page).
|
|
Also, Internal coordinates only exists within the text frames.
|
|
Internal coordinates can be converted to Document coordinates with
|
|
KWTextFrameSet::internalToDocument(), and the other way round with documentToInternal().
|
|
|
|
View:
|
|
The same as the zoomed coordinate system, but this one can use multiple pages next to each
|
|
other. So 3 pages horizontal in preview mode is no problem. A frame on page 3
|
|
then has a higher X coordinate then the same frame on page 1 (and e.g. the same Y).
|
|
When converting to Zoomed the X coordinates are equals, but the Y of the frame on page
|
|
3 is higher than the Y of the frame on page 1.
|
|
|
|
|
|
Document (pt values, in double, KoPoint, KoRect.)
|
|
| |
|
|
| |--KoZoomHander::zoomIt[XY] and unzoomIt[XY]
|
|
| |
|
|
| V
|
|
| Zoomed coordinates (pixel values, in int, QPoint, QRect)
|
|
| This is also called the "Normal" coordinate system.
|
|
| |
|
|
| |--KWViewMode::normalToView
|
|
| V
|
|
| View Mode (pixels values, but e.g. pages are re-arranged)
|
|
| That's also the KWCanvas (scrollview)'s contents coordinates.
|
|
|
|
|
|
|
|
|
|
|
| And for text framesets, there's also :
|
|
|
|
|
|--KWTextFrameSet::documentToInternal
|
|
V
|
|
Internal coordinates (the coordinates given to QRT - in "layout units")
|
|
Note that there are pixels and pts in the layout unit system too !
|
|
There are conversions between LU points and document points,
|
|
but also direct conversions between LU pixels and view pixels.
|
|
|
|
Font sizes
|
|
==========
|
|
A 12pt font will lead to a layout font of ptToLayoutUnit(12)=20*12=240pt -
|
|
that's the value stored in the QTextFormat.
|
|
|
|
However font metrics are calculated from the 100%-zoom-level font (e.g. 12pt for a 12pt font)
|
|
and _then_ multiplied by 20, instead of loading a 240pt font for that as we did before.
|
|
This is implemented by KoTextFormat::charWidth().
|
|
|
|
On screen, at 100%, a layoutUnitToFontSize(240,false)=(240/20)*1.0=20.0pt font size will be used.
|
|
This does NOT depend on the DPI settings. TQt takes care of pt->pixel conversion for fonts.
|
|
|
|
When printing... TODO, double-check whether TQt does pt->pixel conversion correctly
|
|
|
|
QFont multiplies by 10 and stores into a 'short'... So for QFont the maximum font size
|
|
is 3276, and in KOffice the maximum font size in points is around 163.
|
|
|
|
See also
|
|
========
|
|
koffice/kword/DESIGN for more kword-specific things,
|
|
and for explanation about KoTextView (text-edit objects)
|
|
|
|
David Faure <faure@kde.org>
|