mirror of https://github.com/texmacs/doc.git
135 lines
5.4 KiB
Tcl
135 lines
5.4 KiB
Tcl
<TeXmacs|1.0.6.10>
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<style|tmdoc>
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<\body>
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<tmdoc-title|Graphics interface between C++ and <value|scheme>>
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<paragraph*|Rationale>
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<TeXmacs> both implements a low-level part of the graphics in C++ and the
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high-level user interface in <value|scheme>. This API describes how both
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parts interact.
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The low-level C++ mainly takes care of transforming the graphical markup in
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a typesetted box. It also provides routines for translating between
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physical coordinates (relative to the window) into logical coordinates (the
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local coordinate system of the graphics) and routines for interacting with
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the typesetted boxes (finding the closest objects to a given point or
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region or projecting a point on a grid).
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<paragraph*|Definitions>
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<\description>
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<item*|Editor coordinates>The coordinates of the outermost typesetted
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box. Mouse events are typically passed in these coordinates. The
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corresponding data type is <verbatim|SI>.
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<item*|Graphics coordinates>The coordinates of the innermost graphics
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corresponding to the current cursor position.
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<item*|Grid>The current grid relative to the graphics for editing objects
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(this grid may theoretically be different from the grid which is
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displayed). The current grid consists both of a mathematical type of grid
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(no grid, cartesian grid, polar grid, etc.), together with special points
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which correspond either to control points, intersections of curves with
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the grid, intersections of curves, or self-intersections of curves.
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<item*|Grid point>A point on the grid is a triple <scm|(<scm-arg|p>
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<scm-arg|distance> <scm-arg|type>)>, where <scm-arg|p> is a point in
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graphics coordinates, <scm-arg|distance> its distance to the point which
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was projected on the grid (see <verbatim|grid-project> below) and
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<scm-arg|type> the type of grid point with a potential origin. For
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instance, <scm-arg|type> can be <verbatim|plain> or someting like
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<verbatim|(control t)> for a control point corresponding to the tree
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<scm|t> in the document.
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</description>
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<paragraph*|Coordinate transformations>
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<\explain>
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<scm|(editor-\<gtr\>graphics <scm-arg|p>)><explain-synopsis|get graphics
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coordinates>
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<|explain>
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Transform a point <scm-arg|p> of the form <scm|(<scm-arg|x> <scm-arg|y>)>
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from the editor coordinates into the graphics coordinates.
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</explain>
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<\explain>
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<scm|(graphics-\<gtr\>editor p)><explain-synopsis|get editor coordinates>
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<|explain>
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Transform a point <scm-arg|p> of the form <scm|(<scm-arg|x> <scm-arg|y>)>
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from the graphics coordinates into the editor coordinates.
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</explain>
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<paragraph*|Grid routines>
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<\explain>
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<scm|(grid-project <scm-arg|p>)><explain-synopsis|project point on grid>
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<|explain>
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Given a point <scm-arg|p> (in graphics coordinates), find its projection
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on \ the current grid, the <scm-arg|distance> part of the projection
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being the distance between <scm-arg|p> and its projection.
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Note: the routine grid-project can also be used in order to find editable
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shapes and groups close to the current pointer position. Indeed, the
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corresponding control points are understood to lie on the grid in our
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sense.
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</explain>
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<\explain>
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<scm|(grid-point-pertinence\<less\>? <scm-arg|p> <scm-arg|q>)>
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<scm|(grid-point-pertinence\<less\>=? <scm-arg|p>
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<scm-arg|q>)><explain-synopsis|order by pertinence>
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<|explain>
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Grid points are ordered by pertinence as a function of type and distance.
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For instance, control points have higher pertinence than plain grid
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points and closer grid points are considered better than farther ones.
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</explain>
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<paragraph*|Selection of shapes>
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<\explain>
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<scm|(graphics-find-disk <scm-arg|p> <scm-arg|r>)><explain-synopsis|search
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shapes in disk>
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<|explain>
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Return the list of all trees in the graphics which intersect a disk with
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center <scm-arg|p> and radius <scm-arg|r> (in graphics coordinates).
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</explain>
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<\explain>
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<scm|(graphics-find-rectangle <scm-arg|p>
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<scm-arg|q>)><explain-synopsis|search shapes in rectangle>
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<|explain>
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Return the list of all trees in the graphics which intersect a rectangle
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with corners <scm-arg|p> and <scm-arg|q> (in graphics coordinates).
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</explain>
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<paragraph*|Computations with shapes>
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<\explain>
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<scm|(box-info t)><explain-synopsis|get bounding box for a shape>
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<|explain>
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\ Get a bounding box (and other information) about a shape <scm-arg|t>.
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<scm-arg|t> can be a tree or a scheme tree.
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</explain>
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<\remark>
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This section might be extended, since a lot of the graphical intelligence
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is implemented in the C++ code. For instance, we might want to compute
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the intersections of two curves inside the Scheme code. Also, when we
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will allow for user macros, we might want routines which return the
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graphical expansion of the macro (the constituent elementary shapes, i.e.
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polylines, splines, etc.).
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</remark>
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<tmdoc-copyright|2005|Joris van der Hoeven>
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<tmdoc-license|Permission is granted to copy, distribute and/or modify this
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document under the terms of the GNU Free Documentation License, Version 1.1
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or any later version published by the Free Software Foundation; with no
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Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
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Texts. A copy of the license is included in the section entitled "GNU Free
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Documentation License".>
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</body> |