pod::Prima::Drawable(3)

NAME
Prima::Drawable - 2-D graphic interface

SYNOPSIS
   if ( $object-> isa('Prima::Drawable')) {
        $object-> begin_paint;
        $object-> color( cl::Black);
        $object-> line( 100, 100, 200, 200);
        $object-> ellipse( 100, 100, 200, 200);
        $object-> end_paint;
   }

DESCRIPTION
Prima::Drawable is a descendant of Prima::Component. It provides access to the object-bound graphic context and canvas through its methods and properties. The Prima::Drawable descendants Prima::Widget, Prima::Image, Prima::DeviceBitmap and Prima::Printer are backed by system-dependent routines that allow drawing and painting on the system objects.

USAGE
Prima::Drawable, as well as its ancestors Prima::Component and Prima::Object, is never used directly, because Prima::Drawable class by itself provides only the interface. It provides a three-state object access - when drawing and painting is enabled, when these are disabled, and the information acquisition state. By default, the object is created in paint-disabled state. To switch to the enabled state, begin_paint() method is used. Once in the enabled state, the object drawing and painting methods apply to the object-bound canvas. To return to the disabled state, end_paint() method is called. The information state can be managed by using begin_paint_info() and end_paint_info() methods pair. An object cannot be triggered from the information state to the enabled state ( and vice versa ) directly. These states differ on how do they apply to a graphic context and a canvas.

  Graphic context and canvas
The graphic context is the set of variables, that control how exactly graphic primitives are rendered. The variable examples are color, font, line width, etc. Another term used here is 'canvas' - the graphic area of a certain extent, bound to the object, where the drawing and painting methods are applied to.

In all three states a graphic context is allowed to be modified, but in different ways. In the disabled state the graphic context values form a template values; when a object enters the information or the enabled state, the values are preserved, but when the object is back to the disabled state, the graphic context is restored to the values last assigned before entering new state. The code example below illustrates the idea:

   $d = Prima::Drawable-> create;
   $d-> lineWidth( 5);
   $d-> begin_paint_info;
   # lineWidth is 5 here
   $d-> lineWidth( 1);
   # lineWidth is 1
   $d-> end_paint_info;
   # lineWidth is 5 again

( Note: "::region", "::clipRect" and "::translate" properties are exceptions. They can not be used in the disabled state; their values are neither recorded nor used as a template).

That is, in disabled state any Drawable maintains only the graphic context. To draw on a canvas, the object must enter the enabled state by calling begin_paint(). This function can be unsuccessful, because the object binds with system resources during this stage, and might fail. Only after the enabled state is entered, the canvas is accessible:

   $d = Prima::Image-> create( width => 100, height => 100);
   if ( $d-> begin_paint) {
      $d-> color( cl::Black);
      $d-> bar( 0, 0, $d-> size);
      $d-> color( cl::White);
      $d-> fill_ellipse( $d-> width / 2, $d-> height / 2, 30, 30);
      $d-> end_paint;
   } else {
      die "can't draw on image:$@";
   }

Different objects are mapped to different types of canvases - Prima::Image canvas pertains its content after end_paint(), Prima::Widget maps it to a screen area, which content is of more transitory nature, etc.

The information state is as same as the enabled state, but the changes to a canvas are not visible. Its sole purpose is to read, not to write information. Because begin_paint() requires some amount of system resources, there is a chance that a resource request can fail, for any reason. The begin_paint_info() requires some resources as well, but usually much less, and therefore if only information is desired, it is usually faster and cheaper to obtain it inside the information state. A notable example is get_text_width() method, that returns the length of a text string in pixels. It works in both enabled and information states, but code

   $d = Prima::Image-> create( width => 10000, height => 10000);
   $d-> begin_paint;
   $x = $d-> get_text_width('A');
   $d-> end_paint;

is much more 'expensive' than

   $d = Prima::Image-> create( width => 10000, height => 10000);
   $d-> begin_paint_info;
   $x = $d-> get_text_width('A');
   $d-> end_paint_info;

for the obvious reasons.

It must be noted that some information methods like get_text_width() work even under the disabled state; the object is switched to the information state implicitly if it is necessary.

  Color space
Graphic context and canvas operations rely completely on a system implementation. The internal canvas color representation is therefore system-specific, and usually could not be described in standard definitions. Often the only information available about color space is its color depth.

Therefore, all color manipulations, including dithering and antialiasing are subject to system implementation, and can not be controlled from perl code. When a property is set in the object disabled state, it is recorded verbatim; color properties are no exception. After the object switched to the enabled state, a color value is transformed to a system color representation, which might be different from Prima's. For example, if a display color depth is 15 bits, 5 bits for every component, then white color value 0xffffff is mapped to

 11111000 11111000 11111000
 --R----- --G----- --B-----

that equals to 0xf8f8f8, not 0xffffff ( See Prima::gp-problems for inevident graphic issues discussion ).

The Prima::Drawable color format is RRGGBB, with each component resolution of 8 bit, thus allowing 2^24 color combinations. If the device color space depth is different, the color is truncated or expanded automatically. In case the device color depth is small, dithering algorithms might apply.

Note: not only color properties, but all graphic context properties allow all possible values in the disabled state, which transformed into system-allowed values in the enabled and the information states. This feature can be used to test if a graphic device is capable of performing certain operations ( for example, if it supports raster operations - the printers usually do not ). Example:

  $d-> begin_paint;
  $d-> rop( rop::Or);
  if ( $d-> rop != rop::Or) { # this assertion is always false without
     ...                      # begin_paint/end_paint brackets
  }
  $d-> end_paint;

There are ( at least ) two color properties on each drawable - "::color" and "::backColor". The values they operate are integers in the discussed above RRGGBB format, however, the toolkit defines some mnemonic color constants:

  cl::Black
  cl::Blue
  cl::Green
  cl::Cyan
  cl::Red
  cl::Magenta
  cl::Brown
  cl::LightGray
  cl::DarkGray
  cl::LightBlue
  cl::LightGreen
  cl::LightCyan
  cl::LightRed
  cl::LightMagenta
  cl::Yellow
  cl::White
  cl::Gray

As stated before, it is not unlikely that if a device color depth is small, the primitives plotted in particular colors will be drawn with dithered or incorrect colors. This usually happens on paletted displays, with 256 or less colors.

There exists two methods that facilitate the correct color representation. The first way is to get as much information as possible about the device. The methods get_nearest_color() and get_physical_palette() provide possibility to avoid mixed colors drawing by obtaining indirect information about solid colors, supported by a device. Another method is to use "::palette" property. It works by inserting the colors into the system palette, so if an application knows the colors it needs beforehand, it can employ this method - however this might result in system palette flash when a window focus toggles.

Both of these methods are applicable both with drawing routines and image output. An image desired to output with least distortion is advised to export its palette to an output device, because images usually are not subject to automatic dithering algorithms. Prima::ImageViewer module employs this scheme.

  Monochrome bitmaps
A special case of "put_image" is taken where the object to be drawn is a monochrome DeviceBitmap object. This object doesn't possess the color palette, and is by definition a bitmap, where there are only two values present, 0s and 1s. When it is drawn, 0s are drawn with the color value of the target canvas "color" property, and 1s with "backColor".

This means that the following code

    $bitmap-> color(0);
    $bitmap-> line(0,0,100,100);
    $target-> color(cl::Green);
    $target-> put_image(0,0,$bitmap);

produces a green line on $target.

When using monochrome bitmaps for logical operations, note that target colors should not be explicit 0 and 0xffffff, nor "cl::Black" and "cl::White", but "cl::Clear" and "cl::Set" instead. The reason is that on paletted displays, system palette may not necessarily contain the white color under palette index (2^ScreenDepth-1). "cl::Set" thus signals that the value should be "all ones", no matter what color it represents, because it will be used for logical operations.

  Fonts
Prima maintains its own font naming convention, that usually does not conform to system's. Since its goal is interoperability, it might be so that some system fonts would not be accessible from within the toolkit.

Prima::Drawable provides property "::font", that accepts/returns a hash, that represents the state of a font in the object-bound graphic context. The font hash keys that are acceptable on set-call are:

name
    The font name string. If there is no such font, a default font name is used. To select default font, a 'Default' string can be passed with the same result ( unless the system has a font named 'Default', of course).

height
    An integer value from 1 to MAX_INT. Specifies the desired extent of a font glyph between descent and ascent lines in pixels.

size
    An integer value from 1 to MAX_INT. Specifies the desired extent of a font glyph between descent and internal leading lines in points. The relation between "size" and "height" is

                height - internal_leading
      size =  --------------------------- * 72.27
                     resolution

    That differs from some other system representations: Win32, for example, rounds 72.27 constant to 72.

width
    A integer value from 0 to MAX_INT. If greater than 0, specifies the desired extent of a font glyph width in pixels. If 0, sets the default ( designed ) width corresponding to the font size or height.

style
    A combination of "fs::" ( font style ) constants. The constants hight

       fs::Normal
       fs::Bold
       fs::Thin
       fs::Italic
       fs::Underlined
       fs::StruckOut
       fs::Outline

    and can be OR-ed together to express the font style. fs::Normal equals to 0 and usually never used. If some styles are not supported by a system-dependent font subsystem, they are ignored.

pitch
    A one of three constants:

       fp::Default
       fp::Fixed
       fp::Variable

    fp::Default specifies no interest about font pitch selection. fp::Fixed is set when a monospaced (all glyphs are of same width) font is desired. fp::Variable pitch specifies a font with different glyph widths. This key is of the highest priority; all other keys may be altered for the consistency of the pitch key.

direction
    A counter-clockwise rotation angle - 0 is default, 90 is pi/2, 180 is pi, etc. If a font could not be rotated, it is usually substituted to the one that can.

encoding
    A string value, one of the strings returned by "Prima::Application::font_encodings". Selects desired font encoding; if empty, picks the first matched encoding, preferably the locale set up by the user.

    The encodings provided by different systems are different; in addition, the only encodings are recognizable by the system, that are represented by at least one font in the system.

    Unix systems and the toolkit PostScript interface usually provide the following encodings:

       iso8859-1
       iso8859-2
       ... other iso8859 ...
       fontspecific

    Win32 returns the literal strings like

       Western
       Baltic
       Cyrillic
       Hebrew
       Symbol

A hash that "::font" returns, is a tied hash, whose keys are also available as separate properties. For example,

   $x = $d-> font-> {style};

is equivalent to

   $x = $d-> font-> style;

While the latter gives nothing but the arguable coding convenience, its usage in set-call is much more usable:

   $d-> font-> style( fs::Bold);

instead of

   my %temp = %{$d-> font};
   $temp{ style} = fs::Bold;
   $d-> font( \%temp);

The properties of a font tied hash are also accessible through set() call, like in Prima::Object:

   $d-> font-> style( fs::Bold);
   $d-> font-> width( 10);

is adequate to

   $d-> font-> set(
      style => fs::Bold,
      width => 10,
   );

When get-called, "::font" property returns a hash where more entries than the described above can be found. These keys are read-only, their values are discarded if passed to "::font" in a set-call.

In order to query the full list of fonts available to a graphic device, a "::fonts" method is used. This method is not present in Prima::Drawable namespace; it can be found in two built-in class instances, "Prima::Application" and "Prima::Printer".

"Prima::Application::fonts" returns metrics for the fonts available to a screen device, while "Prima::Printer::fonts" ( or its substitute Prima::PS::Printer ) returns fonts for the printing device. The result of this method is an array of font metrics, fully analogous to these returned by "Prima::Drawable::font" method.

family
    A string with font family name. The family is a secondary string key, used for distinguishing between fonts with same name but of different vendors ( for example, Adobe Courier and Microsoft Courier).

vector
    A boolean; true if the font is vector ( e.g. can be scaled with no quality loss ), false otherwise. The false value does not show if the font can be scaled at all - the behavior is system-dependent. Win32 can scale all non-vector fonts; X11 only the fonts specified as the scalable.

ascent
    Number of pixels between a glyph baseline and descent line.

descent
    Number of pixels between a glyph baseline and descent line.

internalLeading
    Number of pixels between ascent and internal leading lines. Negative if the ascent line is below the internal leading line.

externalLeading
    Number of pixels between ascent and external leading lines. Negative if the ascent line is above the external leading line.

              ------------- external leading line

         $    ------------- ascent line
        $ $
              ------------- internal leading line
         $
        $$$
       $   $
      $     $       $
      $$$$$$$    $$$
      $     $   $   $
      $     $   $   $
      $     $    $$$   ---- baseline
                    $
                     $
                     $
                 $$$$  ---- descent line

weight
    A font designed weight. Can be one of

       fw::UltraLight
       fw::ExtraLight
       fw::Light
       fw::SemiLight
       fw::Medium
       fw::SemiBold
       fw::Bold
       fw::ExtraBold
       fw::UltraBold

    constants.

maximalWidth
    Maximal extent of a glyph in pixels. Equals to width in monospaced fonts.

xDeviceRes
    Designed horizontal font resolution in dpi.

yDeviceRes
    Designed vertical font resolution in dpi.

firstChar
    Index of the first glyph present in a font.

lastChar
    Index of the last glyph present in a font.

breakChar
    Index of the default character used to divide words. In a typical western language font it is 32, ASCII space character.

defaultChar
    Index of a glyph that is drawn instead of nonexistent glyph if its index is passed to the text drawing routines.

  Font ABC metrics
Besides these characteristics, every font glyph has an ABC-metric, the three integer values that describe horizontal extents of a glyph's black part relative to the glyph extent:

    .  .     .  .      .  .        .  .
    .  .     $$$.      .  .        .  .
    .  .   $$.  $      .  .        .  .
    .  .   $$.  .      .  .     $$ .  .
    . $$$$$$$$$$.      .  .$$$$$   .  .
    .  .  $$ .  .      .  $    $$  .  .
    .  . $$  .  .      .  .$$$$$   .  .
    .  . $$  .  .      .  .    $$  .  .
    .  .$$   .  .      .  . $$$ $$$.  .
    $$ .$$   .  .      .  $       $$  .
    .$$$     .  .      .  .$$$$$$$$.  .
    .  .     .  .      .  .        .  .
    <A>.     .<C>      <A>.        .<C>
    .<-.--B--.->.      .  .<--B--->.  .

      A = -3                A = 3
      B = 13                B = 10
      C = -3                C = 3

A and C are negative, if a glyphs 'hangs' over it neighbors, as shown in picture on the left. A and C values are positive, if a glyph contains empty space in front or behind the neighbor glyphs, like in picture on the right. As can be seen, B is the width of a glyph's black part.

ABC metrics returned by get_font_abc() method.

  Raster operations
A drawable has two raster operation properties: "::rop" and "::rop2". These define how the graphic primitives are plotted. "::rop" deals with the foreground color drawing, and "::rop2" with the background.

The toolkit defines the following operations:

   rop::Blackness      #   = 0
   rop::NotOr          #   = !(src | dest)
   rop::NotSrcAnd      #  &= !src
   rop::NotPut         #   = !src
   rop::NotDestAnd     #   = !dest & src
   rop::Invert         #   = !dest
   rop::XorPut         #  ^= src
   rop::NotAnd         #   = !(src & dest)
   rop::AndPut         #  &= src
   rop::NotXor         #   = !(src ^ dest)
   rop::NotSrcXor      #     alias for rop::NotXor
   rop::NotDestXor     #     alias for rop::NotXor
   rop::NoOper         #   = dest
   rop::NotSrcOr       #  |= !src
   rop::CopyPut        #   = src
   rop::NotDestOr      #   = !dest | src
   rop::OrPut          #  |= src
   rop::Whiteness      #   = 1

Usually, however, graphic devices support only a small part of the above set, limiting "::rop" to the most important operations: Copy, And, Or, Xor, NoOp. "::rop2" is usually even more restricted, supports only Copy and NoOp.

The raster operations apply to all graphic primitives except SetPixel.

  Coordinates
The Prima toolkit employs a geometrical XY grid, where X ascends rightwards and Y ascends upwards. There, the (0,0) location is the bottom-left pixel of a canvas.

All graphic primitives use inclusive-inclusive boundaries. For example,

   $d-> bar( 0, 0, 1, 1);

plots a bar that covers 4 pixels: (0,0), (0,1), (1,0) and (1,1).

The coordinate origin can be shifted using "::translate" property, that translates the (0,0) point to the given offset. Calls to "::translate", "::clipRect" and "::region" always use the 'physical' (0,0) point, whereas the plotting methods use the transformation result, the 'logical' (0,0) point.

As noted before, these three properties can not be used in when an object is in its disabled state.

API

  Graphic context properties

backColor COLOR
    Reflects background color in the graphic context. All drawing routines that use non-solid or transparent fill or line patterns use this property value.

color COLOR
    Reflects foreground color in the graphic context. All drawing routines use this property value.

clipRect X1, Y1, X2, Y2
    Selects the clipping rectangle corresponding to the physical canvas origin. On get-call, returns the extent of the clipping area, if it is not rectangular, or the clipping rectangle otherwise. The code

       $d-> clipRect( 1, 1, 2, 2);
       $d-> bar( 0, 0, 1, 1);

    thus affects only one pixel at (1,1).

    Set-call discards the previous "::region" value.

    Note: "::clipRect" can not be used while the object is in the paint-disabled state, its context is neither recorded nor used as a template ( see "Graphic context and canvas").

fillWinding BOOLEAN
    Affect filling style of complex polygonal shapes filled by "fillpoly". If 1, the filled shape contains no holes; otherwise, holes are present where the shape edges cross.

    Default value: 0

fillPattern ( [ @PATTERN ] ) or ( fp::XXX )
    Selects 8x8 fill pattern that affects primitives that plot filled shapes: bar(), fill_chord(), fill_ellipse(), fillpoly(), fill_sector(), floodfill().

    Accepts either a "fp::" constant or a reference to an array of 8 integers, each representing 8 bits of each line in a pattern, where the first integer is the topmost pattern line, and the bit 0x80 is the leftmost pixel in the line.

    There are some predefined patterns, that can be referred via "fp::" constants:

      fp::Empty
      fp::Solid
      fp::Line
      fp::LtSlash
      fp::Slash
      fp::BkSlash
      fp::LtBkSlash
      fp::Hatch
      fp::XHatch
      fp::Interleave
      fp::WideDot
      fp::CloseDot
      fp::SimpleDots
      fp::Borland
      fp::Parquet

    ( the actual patterns are hardcoded in primguts.c ) The default pattern is fp::Solid.

    An example below shows encoding of fp::Parquet pattern:

       # 76543210
         84218421  Hex

       0  $ $   $  51
       1   $   $   22
       2    $ $ $  15
       3 $   $     88
       4  $   $ $  45
       5   $   $   22
       6  $ $ $    54
       7 $   $     88

       $d-> fillPattern([ 0x51, 0x22, 0x15, 0x88, 0x45, 0x22, 0x54, 0x88 ]);

    On a get-call always returns an array, never a "fp::" constant.

font \%FONT
    Manages font context. FONT hash acceptable values are "name", "height", "size", "width", "style" and "pitch".

    Synopsis:

       $d-> font-> size( 10);
       $d-> font-> name( 'Courier');
       $d-> font-> set(
         style => $x-> font-> style | fs::Bold,
         width => 22
       );

    See "Fonts" for the detailed descriptions.

    Applies to text_out(), get_text_width(), get_text_box(), get_font_abc().

lineEnd VALUE
    Selects a line ending cap for plotting primitives. VALUE can be one of

      le::Flat
      le::Square
      le::Round

      constants. le::Round is the default value.

lineJoin VALUE
    Selects a line joining style for polygons. VALUE can be one of

      lj::Round
      lj::Bevel
      lj::Miter

    constants. lj::Round is the default value.

linePattern PATTERN
    Selects a line pattern for plotting primitives. PATTERN is either a predefined "lp::" constant, or a string where each even byte is a length of a dash, and each odd byte is a length of a gap.

    The predefined constants are:

        lp::Null           #    ""              /*              */
        lp::Solid          #    "\1"            /* ___________  */
        lp::Dash           #    "\x9\3"         /* __ __ __ __  */
        lp::LongDash       #    "\x16\6"        /* _____ _____  */
        lp::ShortDash      #    "\3\3"          /* _ _ _ _ _ _  */
        lp::Dot            #    "\1\3"          /* . . . . . .  */
        lp::DotDot         #    "\1\1"          /* ............ */
        lp::DashDot        #    "\x9\6\1\3"     /* _._._._._._  */
        lp::DashDotDot     #    "\x9\3\1\3\1\3" /* _.._.._.._.. */

    Not all systems are capable of accepting user-defined line patterns, and in such situation the "lp::" constants are mapped to the system-defined patterns. In Win9x, for example, lp::DashDotDot is much different from its string definition therefore.

    Default value is lp::Solid.

lineWidth WIDTH
    Selects a line width for plotting primitives. If a VALUE is 0, then a 'cosmetic' pen is used - the thinnest possible line that a device can plot. If a VALUE is greater than 0, then a 'geometric' pen is used - the line width is set in device units. There is a subtle difference between VALUE 0 and 1 in a way the lines are joined.

    Default value is 0.

palette [ @PALETTE ]
    Selects solid colors in a system palette, as many as possible. PALETTE is an array of integer triplets, where each is R, G and B component. The call

       $d-> palette([128, 240, 240]);

    selects a gray-cyan color, for example.

    The return value from get-call is the content of the previous set-call, not the actual colors that were copied to the system palette.

region OBJECT
    Selects a clipping region applied to all drawing and painting routines. The OBJECT is either undef, then the clip region is erased ( no clip ), or a Prima::Image object with a bit depth of 1. The bit mask of OBJECT is applied to the system clipping region. If the OBJECT is smaller than the drawable, its exterior is assigned to clipped area as well. Discards the previous "::clipRect" value; successive get-calls to "::clipRect" return the boundaries of the region.

    Note: "::region" can not be used while the object is in the paint-disabled state, its context is neither recorded nor used as a template ( see "Graphic context and canvas").

resolution X, Y
    A read-only property. Returns horizontal and vertical device resolution in dpi.

rop OPERATION
    Selects raster operation that applies to foreground color plotting routines.

    See also: "::rop2", "Raster operations".

rop2 OPERATION
    Selects raster operation that applies to background color plotting routines.

    See also: "::rop", "Raster operations".

splinePrecision INT
    Selects number of steps to use for each spline segment in "spline" and "fill_spline" calls. In other words, determines smoothness of a curve. Minimum accepted value, 1, produces straight lines; maximum value is not present, though it is hardly practical to set it higher than the output device resolution.

    Default value: 24

textOpaque FLAG
    If FLAG is 1, then text_out() fills the text background area with "::backColor" property value before drawing the text. Default value is 0, when text_out() plots text only.

    See get_text_box().

textOutBaseline FLAG
    If FLAG is 1, then text_out() plots text on a given Y coordinate correspondent to font baseline. If FLAG is 0, a Y coordinate is mapped to font descent line. Default is 0.

translate X_OFFSET, Y_OFFSET
    Translates the origin point by X_OFFSET and Y_OFFSET. Does not affect "::clipRect" and "::region". Not cumulative, so the call sequence

       $d-> translate( 5, 5);
       $d-> translate( 15, 15);

    is equivalent to

       $d-> translate( 15, 15);

    Note: "::translate" can not be used while the object is in the paint-disabled state, its context is neither recorded nor used as a template ( see "Graphic context and canvas").

  Other properties

height HEIGHT
    Selects the height of a canvas.

size WIDTH, HEIGHT
    Selects the extent of a canvas.

width WIDTH
    Selects the width of a canvas.

  Graphic primitives methods

arc X, Y, DIAMETER_X, DIAMETER_Y, START_ANGLE, END_ANGLE
    Plots an arc with center in X, Y and DIAMETER_X and DIAMETER_Y axis from START_ANGLE to END_ANGLE.

    Context used: color, backColor, lineEnd, linePattern, lineWidth, rop, rop2

bar X1, Y1, X2, Y2
    Draws a filled rectangle with (X1,Y1) - (X2,Y2) extents.

    Context used: color, backColor, fillPattern, rop, rop2

chord X, Y, DIAMETER_X, DIAMETER_Y, START_ANGLE, END_ANGLE
    Plots an arc with center in X, Y and DIAMETER_X and DIAMETER_Y axis from START_ANGLE to END_ANGLE and connects its ends with a straight line.

    Context used: color, backColor, lineEnd, linePattern, lineWidth, rop, rop2

clear <X1, Y1, X2, Y2>
    Draws rectangle filled with pure background color with (X1,Y1) - (X2,Y2) extents. Can be called without parameters, in this case fills all canvas area.

    Context used: backColor, rop2

draw_text CANVAS, TEXT, X1, Y1, X2, Y2, [ FLAGS = dt::Default, TAB_INDENT = 1 ]
    Draws several lines of text one under another with respect to align and break rules, specified in FLAGS and TAB_INDENT tab character expansion.

    "draw_text" is a convenience wrapper around "text_wrap" for drawing the wrapped text, and also provides the tilde ( ~ )- character underlining support.

    The FLAGS is a combination of the following constants:

      dt::Left                  - text is aligned to the left boundary
      dt::Right                 - text is aligned to the right boundary
      dt::Center                - text is aligned horizontally in center
      dt::Top                   - text is aligned to the upper boundary
      dt::Bottom                - text is aligned to the lower boundary
      dt::VCenter               - text is aligned vertically in center
      dt::DrawMnemonic          - tilde-escapement and underlining is used
      dt::DrawSingleChar        - sets tw::BreakSingle option to
                                  Prima::Drawable::text_wrap call
      dt::NewLineBreak          - sets tw::NewLineBreak option to
                                  Prima::Drawable::text_wrap call
      dt::SpaceBreak            - sets tw::SpaceBreak option to
                                  Prima::Drawable::text_wrap call
      dt::WordBreak             - sets tw::WordBreak option to
                                  Prima::Drawable::text_wrap call
      dt::ExpandTabs            - performs tab character ( \t ) expansion
      dt::DrawPartial           - draws the last line, if it is visible partially
      dt::UseExternalLeading    - text lines positioned vertically with respect to
                                  the font external leading
      dt::UseClip               - assign ::clipRect property to the boundary rectangle
      dt::QueryLinesDrawn       - calculates and returns number of lines drawn
                                  ( contrary to dt::QueryHeight )
      dt::QueryHeight           - if set, calculates and returns vertical extension
                                  of the lines drawn
      dt::NoWordWrap            - performs no word wrapping by the width of the boundaries
      dt::WordWrap              - performs word wrapping by the width of the boundaries
      dt::Default               - dt::NewLineBreak|dt::WordBreak|dt::ExpandTabs|
                                  dt::UseExternalLeading

    Context used: color, backColor, font, rop, textOpaque, textOutBaseline

ellipse X, Y, DIAMETER_X, DIAMETER_Y
    Plots an ellipse with center in X, Y and DIAMETER_X and DIAMETER_Y axis.

    Context used: color, backColor, linePattern, lineWidth, rop, rop2

fill_chord X, Y, DIAMETER_X, DIAMETER_Y, START_ANGLE, END_ANGLE
    Fills a chord outline with center in X, Y and DIAMETER_X and DIAMETER_Y axis from START_ANGLE to END_ANGLE (see chord()).

    Context used: color, backColor, fillPattern, rop, rop2

fill_ellipse X, Y, DIAMETER_X, DIAMETER_Y
    Fills an elliptical outline with center in X, Y and DIAMETER_X and DIAMETER_Y axis.

    Context used: color, backColor, fillPattern, rop, rop2

fillpoly \@POLYGON
    Fills a polygonal area defined by POLYGON set of points. POLYGON must present an array of integer pair in (X,Y) format. Example:

       $d-> fillpoly([ 0, 0, 15, 20, 30, 0]); # triangle

    Context used: color, backColor, fillPattern, rop, rop2, fillWinding

    Returns success flag; if failed, $@ contains the error.

    See also: polyline().

fill_sector X, Y, DIAMETER_X, DIAMETER_Y, START_ANGLE, END_ANGLE
    Fills a sector outline with center in X, Y and DIAMETER_X and DIAMETER_Y axis from START_ANGLE to END_ANGLE (see sector()).

    Context used: color, backColor, fillPattern, rop, rop2

fill_spline \@POLYGON
    Fills a polygonal area defined by a curve, projected by applying cubic spline interpolation to POLYGON set of points. Number of vertices between each polygon equals to current value of "splinePrecision" property. POLYGON must present an array of integer pair in (X,Y) format. Example:

       $d-> fill_spline([ 0, 0, 15, 20, 30, 0]);

    Context used: color, backColor, fillPattern, rop, rop2, splinePrecision

    Returns success flag; if failed, $@ contains the error.

    See also: spline, splinePrecision, render_spline

flood_fill X, Y, COLOR, SINGLEBORDER = 1
    Fills an area of the canvas in current fill context. The area is assumed to be bounded as specified by the SINGLEBORDER parameter. SINGLEBORDER can be 0 or 1.

    SINGLEBORDER = 0: The fill area is bounded by the color specified by the COLOR parameter.

    SINGLEBORDER = 1: The fill area is defined by the color that is specified by COLOR. Filling continues outward in all directions as long as the color is encountered. This style is useful for filling areas with multicolored boundaries.

    Context used: color, backColor, fillPattern, rop, rop2

line X1, Y1, X2, Y2
    Plots a straight line from (X1,Y1) to (X2,Y2).

    Context used: color, backColor, linePattern, lineWidth, rop, rop2

lines \@LINES
    LINES is an array of integer quartets in format (X1,Y1,X2,Y2). lines() plots a straight line per quartet.

    Context used: color, backColor, linePattern, lineWidth, rop, rop2

    Returns success flag; if failed, $@ contains the error.

pixel X, Y, <COLOR>
    ::pixel is a property - on set-call it changes the pixel value at (X,Y) to COLOR, on get-call ( without COLOR ) it does return a pixel value at (X,Y).

    No context is used.

polyline \@POLYGON
    Draws a polygonal area defined by POLYGON set of points. POLYGON must present an array of integer pair in (X,Y) format.

    Context used: color, backColor, linePattern, lineWidth, lineJoin, lineEnd, rop, rop2

    Returns success flag; if failed, $@ contains the error.

    See also: fillpoly().

put_image X, Y, OBJECT, [ ROP ]
    Draws an OBJECT at coordinates (X,Y). OBJECT must be Prima::Image, Prima::Icon or Prima::DeviceBitmap. If ROP raster operation is specified, it is used. Otherwise, value of "::rop" property is used.

    Returns success flag; if failed, $@ contains the error.

    Context used: rop; color and backColor for a monochrome DeviceBitmap

put_image_indirect OBJECT, X, Y, X_FROM, Y_FROM, DEST_WIDTH, DEST_HEIGHT, SRC_WIDTH, SRC_HEIGHT, ROP
    Copies a OBJECT from a source rectangle into a destination rectangle, stretching or compressing the OBJECT to fit the dimensions of the destination rectangle, if necessary. The source rectangle starts at (X_FROM,Y_FROM), and is SRC_WIDTH pixels wide and SRC_HEIGHT pixels tall. The destination rectangle starts at (X,Y), and is abs(DEST_WIDTH) pixels wide and abs(DEST_HEIGHT) pixels tall. If DEST_WIDTH or DEST_HEIGHT are negative, a mirroring by respective axis is performed.

    OBJECT must be Prima::Image, Prima::Icon or Prima::DeviceBitmap.

    No context is used, except color and backColor for a monochrome DeviceBitmap

    Returns success flag; if failed, $@ contains the error.

rect3d X1, Y1, X2, Y2, WIDTH, LIGHT_COLOR, DARK_COLOR, [ BACK_COLOR ]
    Draws 3d-shaded rectangle in boundaries X1,Y1 - X2,Y2 with WIDTH line width and LIGHT_COLOR and DARK_COLOR colors. If BACK_COLOR is specified, paints an inferior rectangle with it, otherwise the inferior rectangle is not touched.

    Context used: rop; color and backColor for a monochrome DeviceBitmap

rect_focus X1, Y1, X2, Y2, [ WIDTH = 1 ]
    Draws a marquee rectangle in boundaries X1,Y1 - X2,Y2 with WIDTH line width.

    No context is used.

rectangle X1, Y1, X2, Y2
    Plots a rectangle with (X1,Y1) - (X2,Y2) extents.

    Context used: color, backColor, linePattern, lineWidth, rop, rop2

sector X, Y, DIAMETER_X, DIAMETER_Y, START_ANGLE, END_ANGLE
    Plots an arc with center in X, Y and DIAMETER_X and DIAMETER_Y axis from START_ANGLE to END_ANGLE and connects its ends and (X,Y) with two straight lines.

    Context used: color, backColor, lineEnd, linePattern, lineWidth, rop, rop2

spline \@POLYGON
    Draws a cubic spline defined by set of POLYGON points. Number of vertices between each polygon equals to current value of "splinePrecision" property. POLYGON must present an array of integer pair in (X,Y) format.

    Context used: color, backColor, linePattern, lineWidth, lineEnd, rop, rop2

    Returns success flag; if failed, $@ contains the error.

    See also: fill_spline, splinePrecision, render_spline.

stretch_image X, Y, DEST_WIDTH, DEST_HEIGHT, OBJECT, [ ROP ]
    Copies a OBJECT into a destination rectangle, stretching or compressing the OBJECT to fit the dimensions of the destination rectangle, if necessary. If DEST_WIDTH or DEST_HEIGHT are negative, a mirroring is performed. The destination rectangle starts at (X,Y) and is DEST_WIDTH pixels wide and DEST_HEIGHT pixels tall.

    If ROP raster operation is specified, it is used. Otherwise, value of "::rop" property is used.

    OBJECT must be Prima::Image, Prima::Icon or Prima::DeviceBitmap.

    Returns success flag; if failed, $@ contains the error.

    Context used: rop

text_out TEXT, X, Y
    Draws TEXT string at (X,Y).

    Returns success flag; if failed, $@ contains the error.

    Context used: color, backColor, font, rop, textOpaque, textOutBaseline

  Methods

begin_paint
    Enters the enabled ( active paint ) state, returns success flag; if failed, $@ contains the error. Once the object is in enabled state, painting and drawing methods can perform write operations on a canvas.

    See also: "end_paint", "begin_paint_info", "Graphic context and canvas"

begin_paint_info
    Enters the information state, returns success flag; if failed, $@ contains the error. The object information state is same as enabled state ( see "begin_paint"), except painting and drawing methods do not change the object canvas.

    See also: "end_paint_info", "begin_paint", "Graphic context and canvas"

end_paint
    Exits the enabled state and returns the object to a disabled state.

    See also: "begin_paint", "Graphic context and canvas"

end_paint_info
    Exits the information state and returns the object to a disabled state.

    See also: "begin_paint_info", "Graphic context and canvas"

font_match \%SOURCE, \%DEST, PICK = 1
    Performs merging of two font hashes, SOURCE and DEST. Returns the merge result. If PICK is true, matches the result with a system font repository.

    Called implicitly by "::font" on set-call, allowing the following example to work:

       $d-> font-> set( size => 10);
       $d-> font-> set( style => fs::Bold);

    In the example, the hash 'style => fs::Bold' does not overwrite the previous font context ( 'size => 10' ) but gets added to it ( by font_match()), providing the resulting font with both font properties set.

fonts <FAMILY = "", ENCODING = "">
    Member of "Prima::Application" and "Prima::Printer", does not present in "Prima::Drawable".

    Returns an array of font metric hashes for a given font FAMILY and ENCODING. Every hash has full set of elements described in "Fonts".

    If called without parameters, returns an array of same hashes where each hash represents a member of font family from every system font set. It this special case, each font hash contains additional "encodings" entry, which points to an array of encodings available for the font.

    If called with FAMILY parameter set but no ENCODING is set, enumerates all combinations of fonts with all available encodings.

    If called with FAMILY set to an empty string, but ENCODING specified, returns only fonts that can be displayed with the encoding.

    Example:

      print sort map {"$_->{name}\n"} @{$::application-> fonts};

get_bpp
    Returns device color depth. 1 is for black-and-white monochrome, 24 for true color, etc.

get_font_abc FIRST_CHAR = -1, LAST_CHAR = -1, UNICODE = 0
    Returns ABC font metrics for the given range, starting at FIRST_CHAR and ending with LAST_CHAR. If parameters are -1, the default range ( 0 and 255 ) is assumed. UNICODE boolean flag is responsible of representation of characters in 127-255 range. If 0, the default, encoding-dependent characters are assumed. If 1, the U007F-U00FF glyphs from Latin-1 set are used.

    The result is an integer array reference, where every character glyph is referred by three integers, each triplet containing A, B and C values.

    For detailed explanation of ABC meaning, see "Font ABC metrics";

    Context used: font

get_nearest_color COLOR
    Returns a nearest possible solid color in representation of object-bound graphic device. Always returns same color if the device bit depth is equals or greater than 24.

get_paint_state
    Returns paint state value - 0 if the object is in the disabled state, 1 for the enabled state, 2 for the information state.

get_physical_palette
    Returns an anonymous array of integers, in (R,G,B) format, every color entry described by three values, in range 0 - 255.

    The physical palette array is non-empty only on paletted graphic devices, the true color devices return an empty array.

    The physical palette reflects the solid colors currently available to all programs in the system. The information is volatile if the system palette can change colors, since any other application may change the system colors at any moment.

get_text_width TEXT, ADD_OVERHANG = 0
    Returns TEXT string width if it would be drawn using currently selected font.

    If ADD_OVERHANG is 1, the first character's absolute A value and the last character's absolute C value are added to the string if they are negative.

    See more on ABC values at "Font ABC metrics".

    Context used: font

get_text_box TEXT
    Returns TEXT string extensions if it would be drawn using currently selected font.

    The result is an anonymous array of 5 points ( 5 integer pairs in (X,Y) format). These 5 points are offsets for the following string extents, given the string is plotted at (0,0):

    1: start of string at ascent line ( top left )

    2: start of string at descent line ( bottom left )

    3: end of string at ascent line ( top right )

    4: end of string at descent line ( bottom right )

    5: concatenation point

    The concatenation point coordinates (XC,YC) are coordinated passed to consequent text_out() call so the conjoint string would plot as if it was a part of TEXT. Depending on the value of the "textOutBaseline" property, the concatenation point is located either on the baseline or on the descent line.

    Context used: font, textOutBaseline

          1      3         3         4
             **               ****
               *               *  *
             ***               ***
            *  *               *
             ****               **
          2       4         1        2

render_spline VERTICES, [ PRECISION ]
    Renders cubic spline from set of VERTICES to a polyline with given precision. The method can be called as static, i.e. with no object initialized. PRECISION integer, if not given, is read from "splinePrecision" property if the method was called on an alive object; in case of static call, default value 24 is used.

    The method is internally used by "spline" and "fill_spline", and is provided for cases when these are insufficient.

text_wrap TEXT, WIDTH, OPTIONS, TAB_INDENT = 8
    Breaks TEXT string in chunks that would fit into WIDTH pixels wide box.

    The break algorithm and its result are governed by OPTIONS integer value which is a combination of "tw::" constants:

    tw::CalcMnemonic
        Use 'hot key' semantics, when a character preceded by ~ has special meaning - it gets underlined. If this bit is set, the first tilde character used as an escapement is not calculated, and never appeared in the result apart from the escaped character.

    tw::CollapseTilde
        In addition to tw::CalcMnemonic, removes '~' character from the resulting chunks.

    tw::CalcTabs
        If set, calculates a tab ('\t') character as TAB_INDENT times space characters.

    tw::ExpandTabs
        If set, expands tab ('\t') character as TAB_INDENT times space characters.

    tw::BreakSingle
        Defines procedure behavior when the text cannot be fit in WIDTH, does not affect anything otherwise.

        If set, returns an empty array. If unset, returns a text broken by minimum number of characters per chunk. In the latter case, the width of the resulting text blocks will exceed WIDTH.

    tw::NewLineBreak
        Forces new chunk after a newline character ('\n') is met. If UTF8 text is passed, unicode line break characters 0x2028 and 0x2029 produce same effect as the newline character.

    tw::SpaceBreak
        Forces new chunk after a space character (' ') or a tab character ('\t') are met.

    tw::ReturnChunks
        Defines the result of text_wrap() function.

        If set, the array consists of integer pairs, each consists of a text offset within TEXT and a its length.

        If unset, the resulting array consists from text chunks.

    tw::ReturnLines
        Equals to 0, is a mnemonic to an unset tw::ReturnChunks.

    tw::WordBreak
        If unset, the TEXT breaks as soon as the chunk width exceeds WIDTH. If set, tries to keep words in TEXT so they do not appear in two chunks, e.g. breaks TEXT by words, not by characters.

    tw::ReturnFirstLineLength
        If set, "text_wrap" proceeds until the first line is wrapped, either by width or ( if specified ) by break characters. Returns length of the resulting line. Used for efficiency when the reverse function to "get_text_width" is needed.

    If OPTIONS has tw::CalcMnemonic or tw::CollapseTilde bits set, then the last scalar in the array result is a special hash reference. The hash contains extra information regarding the 'hot key' underline position - it is assumed that '~' - escapement denotes an underlined character. The hash contains the following keys:

    tildeLine
        Chunk index that contains the escaped character. Set to undef if no ~ - escapement was found. The other hash information is not relevant in this case.

    tildeStart
        Horizontal offset of a beginning of the line that underlines the escaped character.

    tildeEnd
        Horizontal offset of an end of the line that underlines the escaped character.

    tildeChar
        The escaped character.

    Context used: font

AUTHOR
Dmitry Karasik, <dmitry@karasik.eu.org>.

SEE ALSO
Prima, Prima::Object, Prima::Image