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298 lines
10 KiB
C
298 lines
10 KiB
C
/* GDK - The GIMP Drawing Kit
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* Copyright (C) 2000 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "config.h"
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#include "gdkpango.h"
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#include "gdkintl.h"
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#include <math.h>
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#include <pango/pangocairo.h>
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/**
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* SECTION:pango_interaction
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* @Short_description: Using Pango in GDK
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* @Title: Pango Interaction
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*
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* Pango is the text layout system used by GDK and GTK+. The functions
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* and types in this section are used to obtain clip regions for
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* #PangoLayouts, and to get #PangoContexts that can be used with
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* GDK.
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*
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* Creating a #PangoLayout object is the first step in rendering text,
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* and requires getting a handle to a #PangoContext. For GTK+ programs,
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* you’ll usually want to use gtk_widget_get_pango_context(), or
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* gtk_widget_create_pango_layout(). Once you have a #PangoLayout,
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* you can set the text and attributes of it with Pango functions like
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* pango_layout_set_text() and get its size with pango_layout_get_size().
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* (Note that Pango uses a fixed point system internally, so converting
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* between Pango units and pixels using [PANGO_SCALE][PANGO-SCALE-CAPS]
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* or the PANGO_PIXELS() macro.)
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*
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* Rendering a Pango layout is done most simply with pango_cairo_show_layout();
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* you can also draw pieces of the layout with pango_cairo_show_layout_line().
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*
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* ## Draw transformed text with Pango and cairo ## {#rotated-example}
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*
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* |[<!-- language="C" -->
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* #define RADIUS 100
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* #define N_WORDS 10
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* #define FONT "Sans Bold 18"
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*
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* PangoContext *context;
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* PangoLayout *layout;
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* PangoFontDescription *desc;
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*
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* double radius;
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* int width, height;
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* int i;
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*
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* // Set up a transformation matrix so that the user space coordinates for
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* // where we are drawing are [-RADIUS, RADIUS], [-RADIUS, RADIUS]
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* // We first center, then change the scale
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*
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* width = gdk_window_get_width (window);
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* height = gdk_window_get_height (window);
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* radius = MIN (width, height) / 2.;
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*
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* cairo_translate (cr,
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* radius + (width - 2 * radius) / 2,
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* radius + (height - 2 * radius) / 2);
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* cairo_scale (cr, radius / RADIUS, radius / RADIUS);
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*
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* // Create a PangoLayout, set the font and text
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* context = gdk_pango_context_get_for_display (display);
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* layout = pango_layout_new (context);
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* pango_layout_set_text (layout, "Text", -1);
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* desc = pango_font_description_from_string (FONT);
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* pango_layout_set_font_description (layout, desc);
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* pango_font_description_free (desc);
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*
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* // Draw the layout N_WORDS times in a circle
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* for (i = 0; i < N_WORDS; i++)
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* {
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* double red, green, blue;
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* double angle = 2 * G_PI * i / n_words;
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*
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* cairo_save (cr);
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*
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* // Gradient from red at angle == 60 to blue at angle == 300
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* red = (1 + cos (angle - 60)) / 2;
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* green = 0;
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* blue = 1 - red;
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*
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* cairo_set_source_rgb (cr, red, green, blue);
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* cairo_rotate (cr, angle);
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*
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* // Inform Pango to re-layout the text with the new transformation matrix
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* pango_cairo_update_layout (cr, layout);
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*
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* pango_layout_get_size (layout, &width, &height);
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*
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* cairo_move_to (cr, - width / 2 / PANGO_SCALE, - DEFAULT_TEXT_RADIUS);
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* pango_cairo_show_layout (cr, layout);
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*
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* cairo_restore (cr);
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* }
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*
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* g_object_unref (layout);
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* g_object_unref (context);
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* ]|
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*
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* ## Output of the [example][rotated-example] above.
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*
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* 
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*/
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/* Get a clip region to draw only part of a layout. index_ranges
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* contains alternating range starts/stops. The region is the
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* region which contains the given ranges, i.e. if you draw with the
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* region as clip, only the given ranges are drawn.
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*/
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static cairo_region_t*
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layout_iter_get_line_clip_region (PangoLayoutIter *iter,
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gint x_origin,
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gint y_origin,
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const gint *index_ranges,
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gint n_ranges)
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{
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PangoLayoutLine *line;
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cairo_region_t *clip_region;
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PangoRectangle logical_rect;
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gint baseline;
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gint i;
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line = pango_layout_iter_get_line_readonly (iter);
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clip_region = cairo_region_create ();
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pango_layout_iter_get_line_extents (iter, NULL, &logical_rect);
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baseline = pango_layout_iter_get_baseline (iter);
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i = 0;
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while (i < n_ranges)
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{
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gint *pixel_ranges = NULL;
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gint n_pixel_ranges = 0;
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gint j;
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/* Note that get_x_ranges returns layout coordinates
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*/
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if (index_ranges[i*2+1] >= line->start_index &&
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index_ranges[i*2] < line->start_index + line->length)
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pango_layout_line_get_x_ranges (line,
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index_ranges[i*2],
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index_ranges[i*2+1],
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&pixel_ranges, &n_pixel_ranges);
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for (j = 0; j < n_pixel_ranges; j++)
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{
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GdkRectangle rect;
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int x_off, y_off;
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x_off = PANGO_PIXELS (pixel_ranges[2*j] - logical_rect.x);
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y_off = PANGO_PIXELS (baseline - logical_rect.y);
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rect.x = x_origin + x_off;
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rect.y = y_origin - y_off;
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rect.width = PANGO_PIXELS (pixel_ranges[2*j + 1] - logical_rect.x) - x_off;
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rect.height = PANGO_PIXELS (baseline - logical_rect.y + logical_rect.height) - y_off;
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cairo_region_union_rectangle (clip_region, &rect);
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}
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g_free (pixel_ranges);
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++i;
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}
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return clip_region;
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}
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/**
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* gdk_pango_layout_line_get_clip_region: (skip)
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* @line: a #PangoLayoutLine
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* @x_origin: X pixel where you intend to draw the layout line with this clip
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* @y_origin: baseline pixel where you intend to draw the layout line with this clip
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* @index_ranges: (array): array of byte indexes into the layout,
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* where even members of array are start indexes and odd elements
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* are end indexes
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* @n_ranges: number of ranges in @index_ranges, i.e. half the size of @index_ranges
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*
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* Obtains a clip region which contains the areas where the given
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* ranges of text would be drawn. @x_origin and @y_origin are the top left
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* position of the layout. @index_ranges
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* should contain ranges of bytes in the layout’s text. The clip
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* region will include space to the left or right of the line (to the
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* layout bounding box) if you have indexes above or below the indexes
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* contained inside the line. This is to draw the selection all the way
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* to the side of the layout. However, the clip region is in line coordinates,
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* not layout coordinates.
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*
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* Note that the regions returned correspond to logical extents of the text
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* ranges, not ink extents. So the drawn line may in fact touch areas out of
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* the clip region. The clip region is mainly useful for highlightling parts
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* of text, such as when text is selected.
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*
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* Returns: a clip region containing the given ranges
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**/
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cairo_region_t*
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gdk_pango_layout_line_get_clip_region (PangoLayoutLine *line,
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gint x_origin,
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gint y_origin,
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const gint *index_ranges,
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gint n_ranges)
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{
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cairo_region_t *clip_region;
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PangoLayoutIter *iter;
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g_return_val_if_fail (line != NULL, NULL);
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g_return_val_if_fail (index_ranges != NULL, NULL);
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iter = pango_layout_get_iter (line->layout);
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while (pango_layout_iter_get_line_readonly (iter) != line)
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pango_layout_iter_next_line (iter);
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clip_region = layout_iter_get_line_clip_region(iter, x_origin, y_origin, index_ranges, n_ranges);
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pango_layout_iter_free (iter);
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return clip_region;
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}
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/**
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* gdk_pango_layout_get_clip_region: (skip)
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* @layout: a #PangoLayout
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* @x_origin: X pixel where you intend to draw the layout with this clip
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* @y_origin: Y pixel where you intend to draw the layout with this clip
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* @index_ranges: array of byte indexes into the layout, where even members of array are start indexes and odd elements are end indexes
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* @n_ranges: number of ranges in @index_ranges, i.e. half the size of @index_ranges
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*
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* Obtains a clip region which contains the areas where the given ranges
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* of text would be drawn. @x_origin and @y_origin are the top left point
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* to center the layout. @index_ranges should contain
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* ranges of bytes in the layout’s text.
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*
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* Note that the regions returned correspond to logical extents of the text
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* ranges, not ink extents. So the drawn layout may in fact touch areas out of
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* the clip region. The clip region is mainly useful for highlightling parts
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* of text, such as when text is selected.
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*
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* Returns: a clip region containing the given ranges
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**/
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cairo_region_t*
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gdk_pango_layout_get_clip_region (PangoLayout *layout,
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gint x_origin,
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gint y_origin,
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const gint *index_ranges,
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gint n_ranges)
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{
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PangoLayoutIter *iter;
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cairo_region_t *clip_region;
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g_return_val_if_fail (PANGO_IS_LAYOUT (layout), NULL);
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g_return_val_if_fail (index_ranges != NULL, NULL);
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clip_region = cairo_region_create ();
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iter = pango_layout_get_iter (layout);
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do
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{
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PangoRectangle logical_rect;
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cairo_region_t *line_region;
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gint baseline;
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pango_layout_iter_get_line_extents (iter, NULL, &logical_rect);
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baseline = pango_layout_iter_get_baseline (iter);
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line_region = layout_iter_get_line_clip_region(iter,
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x_origin + PANGO_PIXELS (logical_rect.x),
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y_origin + PANGO_PIXELS (baseline),
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index_ranges,
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n_ranges);
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cairo_region_union (clip_region, line_region);
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cairo_region_destroy (line_region);
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}
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while (pango_layout_iter_next_line (iter));
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pango_layout_iter_free (iter);
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return clip_region;
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}
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