Graphic Palettes
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Graphic Palettes

Tk Canvas
TkPath
TkZinc 3.3.4

Tk Canvas

All graphical objects listed in Tk Canvas Objects can be animated. The object changes colour, or their image depending on the »state« property. Possible states are: »hidden«, »normal«, »active« and »disabled«. An image object thus may display three different icons, depending on its state.

The default palette for canvas objects is shown in Figure 6.1, “The Tk Canvas Palette”. The ellipsis (...) denotes that the item starts an »insert mode«. This insert mode is terminated either by turning it off –implemented through a checkbutton with on and off logic– or by selecting another object –auto off.

Figure 6.1. The Tk Canvas Palette


Tk Canvas Objects

Rect...

rect, a plain rectangle.

Oval

oval, a ellipse or circle.

Arc, pieslice, choord

arc, either a choord or pieslice.

The »style« property defines, whether arc displays a »pieslice« or a »choord«.

Line...

line, better known as poly-line. line is convertible into a open spline curve.

A line may have arrows.

Polygon...

polygon, a closed poly-line also featuring spline curves.

Text

text, an elaborated multi-line text object, with insert marks and edit capabilities.

text objects can be »center«, »left« and »right« aligned. This is defined through the »justify« property.

SVG Text Generation Rules

Always synchronize »anchor« and »justify«! Also use top-alignment (n) for any multi-line text.

Synchronizing alignment and anchor keeps the text position in Scalable Vector Graphics identical to the Tcl/Tk source; even when font substitution occurs in Scalable Vector Graphics.

Icon

image, a simple raster image object.

The chosen raster image is determined by the state property. For example »activeimage« is used when the cursor hovers over the object.

SVG and Line, Polygon Splines

»smooth« (splines) polygons and lines are not directly convertible into Scalable Vector Graphics. Scalable Vector Graphics does not support splines, were the control points fall onto curve -spiro, B-splines and clothoid splines.

The tclspline 1.0 extension provides access to the Tk canvas Splines functionality. The Scalable Vector Graphics code generation detects and uses tclspline 1.0 when it´s available.

TkPath is a close counterpart to Scalable Vector Graphics, written for Tcl/Tk.

Many objects inside of TkPath, replace the before mentioned Tk canvas objects. Jeszra generates Scalable Vector Graphics for both Tk canvas and TkPath, mixing objects from both is possible and recommended. The TkPath objects are however the first choice.

TkPath uses CAIRO under the X Window System. Hence TkPath objects are very fast, slick and anti-aliased.

Key Features

Figure 6.2. The TkPath 0.2 Palette


The Palette

Path...

Path, the name-giving item of TkPath. Path is an unusual flexible graphical object. It supports points, lines, arcs, closed, open shapes, cubic and quadratic bézier segments. Every other graphical object, including ptext, can be replaced through a path object.

Polyline..., Polyline

Polyline is the equivalent to a Tk canvas line.

The »Polyline« item contains predefined points, whereas »Polyline...« starts an insert mode, to interactively define its coordinates.

Line, pline

pline is a straight line defined by two points.

Polygon..., Polygon, ppolygon

ppolygon is the counterpart to the Tk canvas polygon.

Text, ptext

ptext, a single line text object.

Ellipse

ellipse is the counterpart to the Tk canvas oval.

Icon, pimage

pimage is the counterpart to the Tk canvas image.

Rectangle, prect

prect is the counterpart to canvas rectangle.

A prect rectangle may feature rounded corners.

Circle

Another counterpart to the Tk canvas oval.

Linear Gradients

»Linear LR Gradient« to »Linear TLBR Gradient«.

A collection of predefined linear gradients.

All gradients are direct editable within Jeszra.

Radial Gradient

A predefined radial gradient.

Figure 6.3. Editing the TkPath 0.3 Palette


The TkPath 0.3 palette features two new items, as shown in Figure 6.3, “Editing the TkPath 0.3 Palette”. The first new item is »tkp::canvas«, the »pathCanvas« window. »group« is the second new item.

The Extended Palette

tkp::canvas

The pathCanvas window class replaces the Tk canvas window. pathCanvas is the foundation for using TkPath objects. Starting with version 0.3 TkPath objects are no longer injected into a ordinary Tk canvas window. pathCanvas is the successor to Tk´s own canvas window and TkPath version 0.2.

»tkp« in »tkp::canvas« stands for the new TkPath namespace(tkp). That is: a pathCanvas window takes the place of a Tk canvas window whenever importing the canvas command, from the tkp namespace, in the target namespace.

Group

Group is a container object. Groups are themselves invisible. Groups are very important for structured transformations. Different transformations cannot be combined commutative onto a single graphical object. A group shall be used in order to separate multiple transformation types and to apply additional tramsformations –through a group– on the same object.

groups do not have coordinates! The coordinates originate from the grouped objects.

As the noun group implies: a group may contain multiple objects. Any transformation applied on a group is also applied onto each contained objects.

Only objects originating from TkPath (ptext, group, polyline, path, pimage, pline, ppolygon, prect, circle, ellipse) are group-able.

Groups are displayed with their parent child dependency inside of Jeszra’s hierarchy view. Groups and their visual representation inside the hierarchy view are roughly equivalent to container windows. Likewise do Drag'n'Drop operations work for groups. Of course moving, copying and dragging groups is restricted to »pathCanvas« windows and contained groups.

TkZinc 3.3.4 is the third supported vector graphics window; again TkZinc 3.3.4 is a dedicated visualization system. TkZinc 3.3.4 contains a series of air traffic control specific objects. Such as »track«, »map«, »recticle«, »waypoint« and »tabular«. These objects are only briefly mentioned herein. Neither is Scalable Vector Graphics generated for specific air traffic objects.

The common objects are however of general interest. Quit often are TkZinc 3.3.4 objects almost identical to their Tk canvas counterparts.

Key Features

Figure 6.4. The TkZinc 3.3.4 Palette


The Palette

Zinc

The »zinc« window creates the TkZinc 3.3.4 drawing area. An instance of the »zinc« window is required to use any TkZinc 3.3.4 object.

Group

Group is a container object.

Every object must be part of a group, even groups themselves. The TkZinc 3.3.4 window auto creates an initial, permanent group with ID »0«, also known as the rroot group. Only use temporal transformations on the root group, because all transformation of the root group get lost. No code will be generated for the root group.

Arc

The arc object is similar to the Tk canvas arc object. It also substitutes the Tk canvas oval.

Arc, may also resemble a rounded line. It can display individual arrows for both ends, specified through the »lastend« and »firstend« properties.

Curve...

A curve is similar to the path object from TkPath, but less complex. Only straight lines and cubic bézier segments are possible for a curve object.

In addition, a open curve object may have arrows.

Icon

The icon object is used for displaying bitmaps.

Icon objects are transformable, similar to pimage from TkPath.

Rectangle

The rectangle object.

Text

A multi-line text object, similar to Tk canvas text. Please follow the same anchor and justify rules as described in: SVG Text Generation Rules .

Map, Recticle, Tabular, Track, Triangles, Waypoint

Items dedicated to air traffic control, hence omitted.

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Chapter 6. Vector Graphics ↑ Creating Graphical Objects
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