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struct | GdkPangoRenderer |
struct | GdkPangoRendererClass |
struct | GdkPangoAttrEmbossed |
struct | GdkPangoAttrEmbossColor |
struct | GdkPangoAttrStipple |
Pango is the text layout system used by GDK and GTK+. The functions and types in this section are used to render Pango objects to GDK. drawables, and also extend the set of Pango attributes to include stippling and embossing.
Creating a PangoLayout object is the first step in rendering text,
and requires getting a handle to a PangoContext. For GTK+ programs,
you'll usually want to use gtk_widget_get_pango_context()
, or
gtk_widget_create_pango_layout()
, rather than using the lowlevel
gdk_pango_context_get_for_screen()
. Once you have a PangoLayout, you
can set the text and attributes of it with Pango functions like
pango_layout_set_text()
and get its size with pango_layout_get_size()
.
(Note that Pango uses a fixed point system internally, so converting
between Pango units and pixels using PANGO_SCALE or the PANGO_PIXELS()
macro.)
Rendering a Pango layout is done most simply with gdk_draw_layout()
;
you can also draw pieces of the layout with gdk_draw_layout()
or
gdk_draw_glyphs()
. GdkPangoRenderer is a subclass of PangoRenderer
that is used internally to implement these functions. Using it
directly or subclassing it can be useful in some cases. See the
GdkPangoRenderer documentation for details.
Example 8. Using GdkPangoRenderer to draw transformed text
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#define RADIUS 100 #define N_WORDS 10 #define FONT "Sans Bold 18" GdkScreen *screen = gdk_drawable_get_screen (drawable); PangoRenderer *renderer; GdkGC *gc; PangoMatrix matrix = PANGO_MATRIX_INIT; PangoContext *context; PangoLayout *layout; PangoFontDescription *desc; double device_radius; int width, height; int i; /* Get the default renderer for the screen, and set it up for drawing */ renderer = gdk_pango_renderer_get_default (screen); gdk_pango_renderer_set_drawable (GDK_PANGO_RENDERER (renderer), drawable); gc = gdk_gc_new (drawable); gdk_pango_renderer_set_gc (GDK_PANGO_RENDERER (renderer), gc); /* Set up a transformation matrix so that the user space coordinates for * where we are drawing are [-RADIUS, RADIUS], [-RADIUS, RADIUS] * We first center, then change the scale */ gdk_drawable_get_size (drawable, &width, &height); device_radius = MIN (width, height) / 2.; pango_matrix_translate (&matrix, device_radius + (width - 2 * device_radius) / 2, device_radius + (height - 2 * device_radius) / 2); pango_matrix_scale (&matrix, device_radius / RADIUS, device_radius / RADIUS); /* Create a PangoLayout, set the font and text */ context = gdk_pango_context_get_for_screen (screen); layout = pango_layout_new (context); pango_layout_set_text (layout, "Text", -1); desc = pango_font_description_from_string (FONT); pango_layout_set_font_description (layout, desc); pango_font_description_free (desc); /* Draw the layout N_WORDS times in a circle */ for (i = 0; i < N_WORDS; i++) { GdkColor color; PangoMatrix rotated_matrix = matrix; int width, height; double angle = (360. * i) / N_WORDS; /* Gradient from red at angle == 60 to blue at angle == 300 */ color.red = 65535 * (1 + cos ((angle - 60) * M_PI / 180.)) / 2; color.green = 0; color.blue = 65535 - color.red; gdk_pango_renderer_set_override_color (GDK_PANGO_RENDERER (renderer), PANGO_RENDER_PART_FOREGROUND, &color); pango_matrix_rotate (&rotated_matrix, angle); pango_context_set_matrix (context, &rotated_matrix); /* Inform Pango to re-layout the text with the new transformation matrix */ pango_layout_context_changed (layout); pango_layout_get_size (layout, &width, &height); pango_renderer_draw_layout (renderer, layout, - width / 2, - RADIUS * PANGO_SCALE); } /* Clean up default renderer, since it is shared */ gdk_pango_renderer_set_override_color (GDK_PANGO_RENDERER (renderer), PANGO_RENDER_PART_FOREGROUND, NULL); gdk_pango_renderer_set_drawable (GDK_PANGO_RENDERER (renderer), NULL); gdk_pango_renderer_set_gc (GDK_PANGO_RENDERER (renderer), NULL); /* free the objects we created */ g_object_unref (layout); g_object_unref (context); g_object_unref (gc); |
PangoRenderer *
gdk_pango_renderer_new (GdkScreen *screen
);
Creates a new PangoRenderer for screen
. Normally you can use the
results of gdk_pango_renderer_get_default()
rather than creating a new
renderer.
Since 2.6
PangoRenderer *
gdk_pango_renderer_get_default (GdkScreen *screen
);
Gets the default PangoRenderer for a screen. This default renderer
is shared by all users of the display, so properties such as the color
or transformation matrix set for the renderer may be overwritten
by functions such as gdk_draw_layout()
.
Before using the renderer, you need to call gdk_pango_renderer_set_drawable()
and gdk_pango_renderer_set_gc()
to set the drawable and graphics context
to use for drawing.
the default PangoRenderer for screen
. The
renderer is owned by GTK+ and will be kept around until the
screen is closed.
Since 2.6
void gdk_pango_renderer_set_drawable (GdkPangoRenderer *gdk_renderer
,GdkDrawable *drawable
);
Sets the drawable the renderer draws to.
Since 2.6
void gdk_pango_renderer_set_gc (GdkPangoRenderer *gdk_renderer
,GdkGC *gc
);
Sets the GC the renderer draws with. Note that the GC must not be
modified until it is unset by calling the function again with
NULL
for the gc
parameter, since GDK may make internal copies
of the GC which won't be updated to follow changes to the
original GC.
Since 2.6
void gdk_pango_renderer_set_stipple (GdkPangoRenderer *gdk_renderer
,PangoRenderPart part
,GdkBitmap *stipple
);
Sets the stipple for one render part (foreground, background, underline,
etc.) Note that this is overwritten when iterating through the individual
styled runs of a PangoLayout or PangoLayoutLine. This function is thus
only useful when you call low level functions like pango_renderer_draw_glyphs()
directly, or in the 'prepare_run' virtual function of a subclass of
GdkPangoRenderer.
Since 2.6
void gdk_pango_renderer_set_override_color (GdkPangoRenderer *gdk_renderer
,PangoRenderPart part
,const GdkColor *color
);
Sets the color for a particular render part (foreground, background, underline, etc.), overriding any attributes on the layouts renderered with this renderer.
gdk_renderer |
||
part |
the part to render to set the color of |
|
color |
the color to use, or |
[allow-none] |
Since 2.6
PangoContext *
gdk_pango_context_get (void
);
Creates a PangoContext for the default GDK screen.
The context must be freed when you're finished with it.
When using GTK+, normally you should use gtk_widget_get_pango_context()
instead of this function, to get the appropriate context for
the widget you intend to render text onto.
The newly created context will have the default font options (see
cairo_font_options_t) for the default screen; if these options
change it will not be updated. Using gtk_widget_get_pango_context()
is more convenient if you want to keep a context around and track
changes to the screen's font rendering settings.
PangoContext *
gdk_pango_context_get_for_screen (GdkScreen *screen
);
Creates a PangoContext for screen
.
The context must be freed when you're finished with it.
When using GTK+, normally you should use gtk_widget_get_pango_context()
instead of this function, to get the appropriate context for
the widget you intend to render text onto.
The newly created context will have the default font options
(see cairo_font_options_t) for the screen; if these options
change it will not be updated. Using gtk_widget_get_pango_context()
is more convenient if you want to keep a context around and track
changes to the screen's font rendering settings.
Since 2.2
void gdk_pango_context_set_colormap (PangoContext *context
,GdkColormap *colormap
);
gdk_pango_context_set_colormap
is deprecated and should not be used in newly-written code.
This function used to set the colormap to be used for drawing with
context
. The colormap is now always derived from the graphics
context used for drawing, so calling this function is no longer
necessary.
PangoAttribute *
gdk_pango_attr_emboss_color_new (const GdkColor *color
);
Creates a new attribute specifying the color to emboss text with.
Since 2.12
PangoAttribute *
gdk_pango_attr_embossed_new (gboolean embossed
);
Creates a new attribute flagging a region as embossed or not.
PangoAttribute *
gdk_pango_attr_stipple_new (GdkBitmap *stipple
);
Creates a new attribute containing a stipple bitmap to be used when rendering the text.
GdkRegion * gdk_pango_layout_get_clip_region (PangoLayout *layout
,gint x_origin
,gint y_origin
,const gint *index_ranges
,gint n_ranges
);
Obtains a clip region which contains the areas where the given ranges
of text would be drawn. x_origin
and y_origin
are the same position
you would pass to gdk_draw_layout_line()
. index_ranges
should contain
ranges of bytes in the layout's text.
Note that the regions returned correspond to logical extents of the text ranges, not ink extents. So the drawn layout may in fact touch areas out of the clip region. The clip region is mainly useful for highlightling parts of text, such as when text is selected.
layout |
||
x_origin |
X pixel where you intend to draw the layout with this clip |
|
y_origin |
Y pixel where you intend to draw the layout with this clip |
|
index_ranges |
array of byte indexes into the layout, where even members of array are start indexes and odd elements are end indexes |
|
n_ranges |
number of ranges in |
GdkRegion * gdk_pango_layout_line_get_clip_region (PangoLayoutLine *line
,gint x_origin
,gint y_origin
,const gint *index_ranges
,gint n_ranges
);
Obtains a clip region which contains the areas where the given
ranges of text would be drawn. x_origin
and y_origin
are the same
position you would pass to gdk_draw_layout_line()
. index_ranges
should contain ranges of bytes in the layout's text. The clip
region will include space to the left or right of the line (to the
layout bounding box) if you have indexes above or below the indexes
contained inside the line. This is to draw the selection all the way
to the side of the layout. However, the clip region is in line coordinates,
not layout coordinates.
Note that the regions returned correspond to logical extents of the text ranges, not ink extents. So the drawn line may in fact touch areas out of the clip region. The clip region is mainly useful for highlightling parts of text, such as when text is selected.
line |
||
x_origin |
X pixel where you intend to draw the layout line with this clip |
|
y_origin |
baseline pixel where you intend to draw the layout line with this clip |
|
index_ranges |
array of byte indexes into the layout, where even members of array are start indexes and odd elements are end indexes |
|
n_ranges |
number of ranges in |
struct GdkPangoRenderer;
GdkPangoRenderer is a subclass of PangoRenderer used for rendering
Pango objects into GDK drawables. The default renderer for a particular
screen is obtained with gdk_pango_renderer_get_default()
; Pango
functions like pango_renderer_draw_layout()
and
pango_renderer_draw_layout_line()
are then used to draw objects with
the renderer.
In most simple cases, applications can just use gdk_draw_layout()
, and
don't need to directly use GdkPangoRenderer at all. Using the
GdkPangoRenderer directly is most useful when working with a
transformation such as a rotation, because the Pango drawing functions
take user space coordinates (coordinates before the transformation)
instead of device coordinates.
In certain cases it can be useful to subclass GdkPangoRenderer. Examples of reasons to do this are to add handling of custom attributes by overriding 'prepare_run' or to do custom drawing of embedded objects by overriding 'draw_shape'.
Since 2.6
struct GdkPangoRendererClass { };
GdkPangoRenderer is the class structure for GdkPangoRenderer.
Since 2.6
struct GdkPangoAttrEmbossed { PangoAttribute attr; gboolean embossed; };
A Pango text attribute containing a embossed bitmap to be used when rendering the text.
struct GdkPangoAttrEmbossColor { PangoAttribute attr; PangoColor color; };
A Pango text attribute specifying the color to emboss text with.
“screen”
property“screen” GdkScreen *
the GdkScreen for the renderer.
Flags: Read / Write / Construct Only