The m17n Library: Drawing

# Drawing
[GUI API]

Drawing M-texts on a window. More...

## Data Structures
struct | MDrawControl
| Type of a text drawing control. More...
struct | MDrawMetric
| Type of metric for glyphs and texts. More...
struct | MDrawGlyphInfo
| Type of information about a glyph. More...
struct | MDrawGlyph
| Type of information about a glyph metric and font. More...
## Typedefs
typedef void * | MDrawWindow
| Window system dependent type for a window.
typedef void * | MDrawRegion
| Window system dependent type for a region.
## Functions
int | mdraw_text (MFrame *frame, MDrawWindow win, int x, int y, MText *mt, int from, int to)
| Draw an M-text on a window.
int | mdraw_image_text (MFrame *frame, MDrawWindow win, int x, int y, MText *mt, int from, int to)
| Draw an M-text on a window as an image.
int | mdraw_text_with_control (MFrame *frame, MDrawWindow win, int x, int y, MText *mt, int from, int to, MDrawControl *control)
| Draw an M-text on a window with fine control.
int | mdraw_text_extents (MFrame *frame, MText *mt, int from, int to, MDrawControl *control, MDrawMetric *overall_ink_return, MDrawMetric *overall_logical_return, MDrawMetric *overall_line_return)
| Compute text pixel width.
int | mdraw_text_per_char_extents (MFrame *frame, MText *mt, int from, int to, MDrawControl *control, MDrawMetric *ink_array_return, MDrawMetric *logical_array_return, int array_size, int *num_chars_return, MDrawMetric *overall_ink_return, MDrawMetric *overall_logical_return)
| Compute the text dimensions of each character of M-text.
int | mdraw_coordinates_position (MFrame *frame, MText *mt, int from, int to, int x_offset, int y_offset, MDrawControl *control)
| Return the character position nearest to the coordinates.
int | mdraw_glyph_info (MFrame *frame, MText *mt, int from, int pos, MDrawControl *control, MDrawGlyphInfo *info)
| Compute information about a glyph.
int | mdraw_glyph_list (MFrame *frame, MText *mt, int from, int to, MDrawControl *control, MDrawGlyph *glyphs, int array_size, int *num_glyphs_return)
| Compute information about glyph sequence.
void | mdraw_text_items (MFrame *frame, MDrawWindow win, int x, int y, MDrawTextItem *items, int nitems)
| Draw one or more textitems.
int | mdraw_default_line_break (MText *mt, int pos, int from, int to, int line, int y)
| Calculate a line breaking position.
void | mdraw_per_char_extents (MFrame *frame, MText *mt, MDrawMetric *array_return, MDrawMetric *overall_return)
| Obtain per character dimension information.
void | mdraw_clear_cache (MText *mt)
| clear cached information.
## Variables
int | mdraw_line_break_option
| Option of line breaking for drawing text.

## Detailed Description

Drawing M-texts on a window.

The m17n GUI API provides functions to draw M-texts.

The fonts used for drawing are selected automatically based on the fontset and the properties of a face. A face also specifies the appearance of M-texts, i.e. font size, color, underline, etc.

The drawing format of M-texts can be controlled in a variety of ways, which provides powerful 2-dimensional layout facility.

## Typedef Documentation

typedef void* MDrawWindow

Window system dependent type for a window.

The type MDrawWindow is for a window; a rectangular area that works in several ways like a miniature screen.

What it actually points depends on a window system. A program that uses the m17n-X library must coerce the type `Drawable` to this type.

typedef void* MDrawRegion

Window system dependent type for a region.

The type MDrawRegion is for a region; an arbitrary set of pixels on the screen (typically a rectangular area).

What it actually points depends on a window system. A program that uses the m17n-X library must coerce the type `Region` to this type.

## Function Documentation

int mdraw_text | ( | MFrame * | frame,
|  | MDrawWindow | win,
|  | int | x,
|  | int | y,
|  | MText * | mt,
|  | int | from,
|  | int | to |
| ) |  |  |

Draw an M-text on a window.

The mdraw_text() function draws the text between from and to of M-text mt on window win of frame frame at coordinate (x, y).

The appearance of the text (size, style, color, etc) is specified by the value of the text property whose key is `Mface`. If the M-text or a part of the M-text does not have such a text property, the default face of frame is used.

The font used to draw a character in the M-text is selected from the value of the fontset property of a face by the following algorithm:

1. Search the text properties given to the character for the one whose key is `Mcharset`; its value should be either a symbol specifying a charset or Mnil. If the value is Mnil, proceed to the next step.

   Otherwise, search the mapping table of the fontset for the charset. If no entry is found proceed to the next step.

   If an entry is found, use one of the fonts in the entry that has a glyph for the character and that matches best with the face properties. If no such font exists, proceed to the next step.

2. Get the character property "script" of the character. If it is inherited, get the script property from the previous characters. If there is no previous character, or none of them has the script property other than inherited, proceed to the next step.

   Search the text properties given to the character for the one whose key is `Mlanguage`; its value should be either a symbol specifying a language or `Mnil`.

   Search the mapping table of the fontset for the combination of the script and language. If no entry is found, proceed to the next step.

   If an entry is found, use one of the fonts in the entry that has a glyph for the character and that matches best with the face properties. If no such font exists, proceed to the next step.

3. Search the fall-back table of the fontset for a font that has a glyph of the character. If such a font is found, use that font.

If no font is found by the algorithm above, this function draws an empty box for the character.

This function draws only the glyph foreground. To specify the background color, use mdraw_image_text() or mdraw_text_with_control().

This function is the counterpart of `XDrawString()`, `XmbDrawString()`, and `XwcDrawString()` functions in the X Window System.

Return value:
  If the operation was successful, mdraw_text() returns 0. If an error is detected, it returns -1 and assigns an error code to the external variable merror_code.

Errors:
  `MERROR_RANGE`

See Also:
  mdraw_image_text()

int mdraw_image_text | ( | MFrame * | frame,
|  | MDrawWindow | win,
|  | int | x,
|  | int | y,
|  | MText * | mt,
|  | int | from,
|  | int | to |
| ) |  |  |

Draw an M-text on a window as an image.

The mdraw_image_text() function draws the text between from and to of M-text mt as image on window win of frame frame at coordinate (x, y).

The way to draw a text is the same as in mdraw_text() except that this function also draws the background with the color specified by faces.

This function is the counterpart of `XDrawImageString()`, `XmbDrawImageString()`, and `XwcDrawImageString()` functions in the X Window System.

Return value:
  If the operation was successful, mdraw_image_text() returns 0. If an error is detected, it returns -1 and assigns an error code to the external variable merror_code.

Errors:
  `MERROR_RANGE`

See Also:
  mdraw_text()

int mdraw_text_with_control | ( | MFrame * | frame,
|  | MDrawWindow | win,
|  | int | x,
|  | int | y,
|  | MText * | mt,
|  | int | from,
|  | int | to,
|  | MDrawControl * | control |
| ) |  |  |

Draw an M-text on a window with fine control.

The mdraw_text_with_control() function draws the text between from and to of M-text mt on windows win of frame frame at coordinate (x, y).

The way to draw a text is the same as in mdraw_text() except that this function also follows what specified in the drawing control object control.

For instance, if <two_dimensional> of control is nonzero, this function draw an M-text 2-dimensionally, i.e., newlines in M-text breaks lines and the following characters are drawn in the next line. See the documentation of the structure @ MDrawControl for more detail.

int mdraw_text_extents | ( | MFrame * | frame,
|  | MText * | mt,
|  | int | from,
|  | int | to,
|  | MDrawControl * | control,
|  | MDrawMetric * | overall_ink_return,
|  | MDrawMetric * | overall_logical_return,
|  | MDrawMetric * | overall_line_return |
| ) |  |  |

Compute text pixel width.

The mdraw_text_extents() function computes the width of text between from and to of M-text mt when it is drawn on a window of frame frame using the mdraw_text_with_control() function with the drawing control object control.

If overall_ink_return is not `NULL`, this function also computes the bounding box of character ink of the M-text, and stores the results in the members of the structure pointed to by overall_ink_return. If the M-text has a face specifying a surrounding box, the box is included in the bounding box.

If overall_logical_return is not `NULL`, this function also computes the bounding box that provides minimum spacing to other graphical features (such as surrounding box) for the M-text, and stores the results in the members of the structure pointed to by overall_logical_return.

If overall_line_return is not `NULL`, this function also computes the bounding box that provides minimum spacing to the other M-text drawn, and stores the results in the members of the structure pointed to by overall_line_return. This is a union of overall_ink_return and overall_logical_return if the members min_line_ascent, min_line_descent, max_line_ascent, and max_line_descent of control are all zero.

Return value:
  This function returns the width of the text to be drawn in the unit of pixels. If control->two_dimensional is nonzero and the text is drawn in multiple physical lines, it returns the width of the widest line. If an error occurs, it returns -1 and assigns an error code to the external variable merror_code.

Errors:
  `MERROR_RANGE`

int mdraw_text_per_char_extents | ( | MFrame * | frame,
|  | MText * | mt,
|  | int | from,
|  | int | to,
|  | MDrawControl * | control,
|  | MDrawMetric * | ink_array_return,
|  | MDrawMetric * | logical_array_return,
|  | int | array_size,
|  | int * | num_chars_return,
|  | MDrawMetric * | overall_ink_return,
|  | MDrawMetric * | overall_logical_return |
| ) |  |  |

Compute the text dimensions of each character of M-text.

The mdraw_text_per_char_extents() function computes the drawn metric of each character between from and to of M-text mt assuming that they are drawn on a window of frame frame using the mdraw_text_with_control() function with the drawing control object control.

array_size specifies the size of ink_array_return and logical_array_return. Each successive element of ink_array_return and logical_array_return are set to the drawn ink and logical metrics of successive characters respectively, relative to the drawing origin of the M-text. The number of elements of ink_array_return and logical_array_return that have been set is returned to num_chars_return.

If array_size is too small to return all metrics, the function returns -1 and store the requested size in num_chars_return. Otherwise, it returns zero.

If pointer overall_ink_return and overall_logical_return are not `NULL`, this function also computes the metrics of the overall text and stores the results in the members of the structure pointed to by overall_ink_return and overall_logical_return.

If control->two_dimensional is nonzero, this function computes only the metrics of characters in the first line.

int mdraw_coordinates_position | ( | MFrame * | frame,
|  | MText * | mt,
|  | int | from,
|  | int | to,
|  | int | x_offset,
|  | int | y_offset,
|  | MDrawControl * | control |
| ) |  |  |

Return the character position nearest to the coordinates.

The mdraw_coordinates_position() function checks which character is to be drawn at coordinate (x, y) when the text between from and to of M-text mt is drawn at the coordinate (0, 0) using the mdraw_text_with_control() function with the drawing control object control. Here, the character position means the number of characters that precede the character in question in mt, that is, the character position of the first character is 0.

frame is used only to get the default face information.

Return value:
  If the glyph image of a character covers coordinate (x, y), mdraw_coordinates_position() returns the character position of that character.
  If y is less than the minimum Y-coordinate of the drawn area, it returns from.
  If y is greater than the maximum Y-coordinate of the drawn area, it returns to.
  If y fits in with the drawn area but x is less than the minimum X-coordinate, it returns the character position of the first character drawn on the line y.
  If y fits in with the drawn area but x is greater than the maximum X-coordinate, it returns the character position of the last character drawn on the line y.

int mdraw_glyph_info | ( | MFrame * | frame,
|  | MText * | mt,
|  | int | from,
|  | int | pos,
|  | MDrawControl * | control,
|  | MDrawGlyphInfo * | info |
| ) |  |  |

Compute information about a glyph.

The mdraw_glyph_info() function computes information about a glyph that covers a character at position pos of the M-text mt assuming that the text is drawn from the character at from of mt on a window of frame frame using the mdraw_text_with_control() function with the drawing control object control.

The information is stored in the members of info.

See Also:
  MDrawGlyphInfo

int mdraw_glyph_list | ( | MFrame * | frame,
|  | MText * | mt,
|  | int | from,
|  | int | to,
|  | MDrawControl * | control,
|  | MDrawGlyph * | glyphs,
|  | int | array_size,
|  | int * | num_glyphs_return |
| ) |  |  |

Compute information about glyph sequence.

The mdraw_glyph_list() function computes information about glyphs corresponding to the text between from and to of M-text mt when it is drawn on a window of frame frame using the mdraw_text_with_control() function with the drawing control object control. glyphs is an array of objects to store the information, and array_size is the array size.

If array_size is large enough to cover all glyphs, it stores the number of actually filled elements in the place pointed by num_glyphs_return, and returns 0.

Otherwise, it stores the required array size in the place pointed by num_glyphs_return, and returns -1.

See Also:
  MDrawGlyph

void mdraw_text_items | ( | MFrame * | frame,
|  | MDrawWindow | win,
|  | int | x,
|  | int | y,
|  | MDrawTextItem * | items,
|  | int | nitems |
| ) |  |  |

Draw one or more textitems.

The mdraw_text_items() function draws one or more M-texts on window win of frame frame at coordinate (x, y). items is an array of the textitems to be drawn and nitems is the number of textitems in the array.

See Also:
  MTextItem, mdraw_text().

int mdraw_default_line_break | ( | MText * | mt,
|  | int | pos,
|  | int | from,
|  | int | to,
|  | int | line,
|  | int | y |
| ) |  |  |

Calculate a line breaking position.

The function mdraw_default_line_break() calculates a line breaking position based on the line number line and the coordinate y, when a line is too long to fit within the width limit. pos is the position of the character next to the last one that fits within the limit. from is the position of the first character of the line, and to is the position of the last character displayed on the line if there were not width limit. line and y are reset to 0 when a line is broken by a newline character, and incremented each time when a long line is broken because of the width limit.

Return value:
  This function returns a character position to break the line.

void mdraw_per_char_extents | ( | MFrame * | frame,
|  | MText * | mt,
|  | MDrawMetric * | array_return,
|  | MDrawMetric * | overall_return |
| ) |  |  |

Obtain per character dimension information.

The mdraw_per_char_extents() function computes the text dimension of each character in M-text mt. The faces given as text properties in mt and the default face of frame frame determine the fonts to draw the text. Each successive element in array_return is set to the drawn metrics of successive characters, which is relative to the origin of the drawing, and a rectangle for each character in mt. The number of elements of array_return must be equal to or greater than the number of characters in mt.

If pointer overall_return is not `NULL`, this function also computes the extents of the overall text and stores the results in the members of the structure pointed to by overall_return.

void mdraw_clear_cache | ( | MText * | mt | ) |

clear cached information.

The mdraw_clear_cache() function clear cached information on M-text mt that was attached by any of the drawing functions. When the behavior of `format' or `line_break' member functions of MDrawControl is changed, the cache must be cleared.

See Also:
  MDrawControl

## Variable Documentation

int mdraw_line_break_option

Option of line breaking for drawing text.

The variable mdraw_line_break_option specifies line breaking options by logical-or of the members of MTextLineBreakOption. It controls the line breaking algorithm of the function mdraw_default_line_break().