PangoRenderer

PangoRenderer — Rendering driver base class

Synopsis




            PangoRenderer;
enum        PangoRenderPart;
#define     PANGO_TYPE_RENDER_PART
            PangoRendererClass;
void        pango_renderer_draw_layout      (PangoRenderer *renderer,
                                             PangoLayout *layout,
                                             int x,
                                             int y);
void        pango_renderer_draw_layout_line (PangoRenderer *renderer,
                                             PangoLayoutLine *line,
                                             int x,
                                             int y);
void        pango_renderer_draw_glyphs      (PangoRenderer *renderer,
                                             PangoFont *font,
                                             PangoGlyphString *glyphs,
                                             int x,
                                             int y);
void        pango_renderer_draw_rectangle   (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             int x,
                                             int y,
                                             int width,
                                             int height);
void        pango_renderer_draw_error_underline
                                            (PangoRenderer *renderer,
                                             int x,
                                             int y,
                                             int width,
                                             int height);
void        pango_renderer_draw_trapezoid   (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             double y1_,
                                             double x11,
                                             double x21,
                                             double y2,
                                             double x12,
                                             double x22);
void        pango_renderer_draw_glyph       (PangoRenderer *renderer,
                                             PangoFont *font,
                                             PangoGlyph glyph,
                                             double x,
                                             double y);
void        pango_renderer_activate         (PangoRenderer *renderer);
void        pango_renderer_deactivate       (PangoRenderer *renderer);
void        pango_renderer_part_changed     (PangoRenderer *renderer,
                                             PangoRenderPart part);
void        pango_renderer_set_color        (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             const PangoColor *color);
PangoColor* pango_renderer_get_color        (PangoRenderer *renderer,
                                             PangoRenderPart part);
void        pango_renderer_set_matrix       (PangoRenderer *renderer,
                                             const PangoMatrix *matrix);
const PangoMatrix* pango_renderer_get_matrix
                                            (PangoRenderer *renderer);


Description

PangoRenderer is a base class that contains the necessary logic for rendering a PangoLayout or PangoLayoutLine. By subclassing PangoRenderer and overriding operations such as draw_glyphs and draw_rectangle, renderers for particular font backends and destinations can be created.

Details

PangoRenderer

typedef struct {
  PangoMatrix *matrix;		/* May be NULL */
} PangoRenderer;

PangoRenderer is a base class for objects that are used to render Pango objects such as PangoGlyphString and PangoLayout.

PangoMatrix *matrix; the current transformation matrix for the Renderer; may be NULL, which should be treated the same as the identity matrix.

Since 1.8


enum PangoRenderPart

typedef enum
{
  PANGO_RENDER_PART_FOREGROUND,
  PANGO_RENDER_PART_BACKGROUND,
  PANGO_RENDER_PART_UNDERLINE,
  PANGO_RENDER_PART_STRIKETHROUGH
} PangoRenderPart;

PangoRenderPart defines different items to render for such purposes as setting colors.

PANGO_RENDER_PART_FOREGROUND the text itself
PANGO_RENDER_PART_BACKGROUND the area behind the text
PANGO_RENDER_PART_UNDERLINE underlines
PANGO_RENDER_PART_STRIKETHROUGH strikethrough lines

Since 1.8


PANGO_TYPE_RENDER_PART

#define PANGO_TYPE_RENDER_PART (pango_render_part_get_type())

The GObject type for PangoRenderPart.


PangoRendererClass

typedef struct {
  /* All of the following have default implementations
   * and take as coordinates user coordinates in Pango units
   */
  void (*draw_glyphs) (PangoRenderer     *renderer,
		       PangoFont         *font,
		       PangoGlyphString  *glyphs,
		       int                x,
		       int                y);
  void (*draw_rectangle) (PangoRenderer     *renderer,
			  PangoRenderPart    part,
			  int                x,
			  int                y,
			  int                width,
			  int                height);
  void (*draw_error_underline) (PangoRenderer     *renderer,
				int                x,
				int                y,
				int                width,
				int                height);

  /* Nothing is drawn for shaped glyphs unless this is implemented */
  void (*draw_shape) (PangoRenderer  *renderer,
		      PangoAttrShape *attr,
		      int             x,
		      int             y);

  /* These two must be implemented and take coordinates in
   * device space as doubles.
   */
  void (*draw_trapezoid) (PangoRenderer  *renderer,
			  PangoRenderPart part,
			  double          y1_,
			  double          x11,
			  double          x21,
			  double          y2,
			  double          x12,
			  double          x22);
  void (*draw_glyph) (PangoRenderer *renderer,
		      PangoFont     *font,
		      PangoGlyph     glyph,
		      double         x,
		      double         y);

  /* Notification of change in rendering attributes
   */
  void (*part_changed) (PangoRenderer   *renderer,
			PangoRenderPart  part);

  /* Paired around drawing operations
   */
  void (*begin) (PangoRenderer *renderer);
  void (*end)   (PangoRenderer *renderer);

  /* Hooks into the details of layout rendering
   */
  void (*prepare_run) (PangoRenderer  *renderer,
		       PangoLayoutRun *run);
} PangoRendererClass;

Class structure for PangoRenderer.

draw_glyphs () draws a PangoGlyphString
draw_rectangle () draws a rectangle
draw_error_underline () draws a squiggly line that approximately covers the given rectangle in the style of an underline used to indicate a spelling error.
draw_shape () draw content for a glyph shaped with PangoAttrShape. x, y are the coordinates of the left edge of the baseline, in user coordinates.
draw_trapezoid () draws a trapezoidal filled area
draw_glyph () draws a single glyph
part_changed () do renderer specific processing when rendering attributes change
begin () Do renderer-specific initialization before drawing
end () Do renderer-specific cleanup after drawing
prepare_run () updates the renderer for a new run

Since 1.8


pango_renderer_draw_layout ()

void        pango_renderer_draw_layout      (PangoRenderer *renderer,
                                             PangoLayout *layout,
                                             int x,
                                             int y);

Draws layout with the specified PangoRenderer.

renderer : a PangoRenderer
layout : a PangoLayout
x : X position of left edge of baseline, in user space coordinates in Pango units.
y : Y position of left edge of baseline, in user space coordinates in Pango units.

Since 1.8


pango_renderer_draw_layout_line ()

void        pango_renderer_draw_layout_line (PangoRenderer *renderer,
                                             PangoLayoutLine *line,
                                             int x,
                                             int y);

Draws line with the specified PangoRenderer.

renderer : a PangoRenderer
line : a PangoLayoutLine
x : X position of left edge of baseline, in user space coordinates in Pango units.
y : Y position of left edge of baseline, in user space coordinates in Pango units.

Since 1.8


pango_renderer_draw_glyphs ()

void        pango_renderer_draw_glyphs      (PangoRenderer *renderer,
                                             PangoFont *font,
                                             PangoGlyphString *glyphs,
                                             int x,
                                             int y);

Draws the glyphs in glyphs with the specified PangoRenderer.

renderer : a PangoRenderer
font : a PangoFont
glyphs : a PangoGlyphString
x : X position of left edge of baseline, in user space coordinates in Pango units.
y : Y position of left edge of baseline, in user space coordinates in Pango units.

Since 1.8


pango_renderer_draw_rectangle ()

void        pango_renderer_draw_rectangle   (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             int x,
                                             int y,
                                             int width,
                                             int height);

Draws an axis-aligned rectangle in user space coordinates with the specified PangoRenderer.

This should be called while renderer is already active. Use pango_renderer_activate() to activate a renderer.

renderer : a PangoRenderer
part : type of object this rectangle is part of
x : X position at which to draw rectangle, in user space coordinates in Pango units
y : Y position at which to draw rectangle, in user space coordinates in Pango units
width : width of rectangle in Pango units in user space coordinates
height : height of rectangle in Pango units in user space coordinates

Since 1.8


pango_renderer_draw_error_underline ()

void        pango_renderer_draw_error_underline
                                            (PangoRenderer *renderer,
                                             int x,
                                             int y,
                                             int width,
                                             int height);

Draw a squiggly line that approximately covers the given rectangle in the style of an underline used to indicate a spelling error. (The width of the underline is rounded to an integer number of up/down segments and the resulting rectangle is centered in the original rectangle)

This should be called while renderer is already active. Use pango_renderer_activate() to activate a renderer.

renderer : a PangoRenderer
x : X coordinate of underline, in Pango units in user coordinate system
y : Y coordinate of underline, in Pango units in user coordinate system
width : width of underline, in Pango units in user coordinate system
height : height of underline, in Pango units in user coordinate system

Since 1.8


pango_renderer_draw_trapezoid ()

void        pango_renderer_draw_trapezoid   (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             double y1_,
                                             double x11,
                                             double x21,
                                             double y2,
                                             double x12,
                                             double x22);

Draws a trapezoid with the parallel sides aligned with the X axis using the given PangoRenderer; coordinates are in device space.

renderer : a PangoRenderer
part : type of object this trapezoid is part of
y1_ : Y coordinate of top of trapezoid
x11 : X coordinate of left end of top of trapezoid
x21 : X coordinate of right end of top of trapezoid
y2 : Y coordinate of bottom of trapezoid
x12 : X coordinate of left end of bottom of trapezoid
x22 : X coordinate of right end of bottom of trapezoid

Since 1.8


pango_renderer_draw_glyph ()

void        pango_renderer_draw_glyph       (PangoRenderer *renderer,
                                             PangoFont *font,
                                             PangoGlyph glyph,
                                             double x,
                                             double y);

Draws a single glyph with coordinates in device space.

renderer : a PangoRenderer
font : a PangoFont
glyph : the glyph index of a single glyph
x : X coordinate of left edge of baseline of glyph
y : Y coordinate of left edge of baseline of glyph

Since 1.8


pango_renderer_activate ()

void        pango_renderer_activate         (PangoRenderer *renderer);

Does initial setup before rendering operations on renderer. pango_renderer_deactivate() should be called when done drawing. Calls such as pango_renderer_draw_layout() automatically activate the layout before drawing on it. Calls to pango_renderer_activate() and pango_renderer_deactivate() can be nested and the renderer will only be initialized and deinitialized once.

renderer : a PangoRenderer

Since 1.8


pango_renderer_deactivate ()

void        pango_renderer_deactivate       (PangoRenderer *renderer);

Cleans up after rendering operations on renderer. See docs for pango_renderer_activate().

renderer : a PangoRenderer

Since 1.8


pango_renderer_part_changed ()

void        pango_renderer_part_changed     (PangoRenderer *renderer,
                                             PangoRenderPart part);

Informs Pango that the way that the rendering is done for part has changed in a way that would prevent multiple pieces being joined together into one drawing call. For instance, if a subclass of PangoRenderer was to add a stipple option for drawing underlines, it needs to call

pango_renderer_part_changed (render, PANGO_RENDER_PART_UNDERLINE);

When the stipple changes or underlines with different stipples might be joined together. Pango automatically calls this for changes to colors. (See pango_renderer_set_color())

renderer : a PangoRenderer
part : the part for which rendering has changed.

Since 1.8


pango_renderer_set_color ()

void        pango_renderer_set_color        (PangoRenderer *renderer,
                                             PangoRenderPart part,
                                             const PangoColor *color);

Sets the color for part of the rendering.

renderer : a PangoRenderer
part : the part to change the color of
color : the new color or NULL to unset the current color

Since 1.8


pango_renderer_get_color ()

PangoColor* pango_renderer_get_color        (PangoRenderer *renderer,
                                             PangoRenderPart part);

Gets the current rendering color for the specified part.

renderer : a PangoRenderer
part : the part to get the color for
Returns : the color for the specified part, or NULL if it hasn't been set and should be inherited from the environment.

Since 1.8


pango_renderer_set_matrix ()

void        pango_renderer_set_matrix       (PangoRenderer *renderer,
                                             const PangoMatrix *matrix);

Sets the transformation matrix that will be applied when rendering.

renderer : a PangoRenderer
matrix : a PangoMatrix, or NULL to unset any existing matrix. (No matrix set is the same as setting the identity matrix.)

Since 1.8


pango_renderer_get_matrix ()

const PangoMatrix* pango_renderer_get_matrix
                                            (PangoRenderer *renderer);

Gets the transformation matrix that will be applied when rendering. See pango_renderer_set_matrix().

renderer : a PangoRenderer
Returns : the matrix, or NULL if no matrix has been set (which is the same as the identity matrix). The returned matrix is owned by Pango and must not be modified or freed.

Since 1.8