Also check pango/examples/cairotwisted.c for some interesting stuff you
can do with pangocairo.
behdad
On Sat, 2007-02-03 at 21:48 +0200, Dov Grobgeld wrote:
> I'm trying to understand how to get the baseline information from a
> single line PangoLayout or equivalently a PangoLayoutLine.
>
> More concretely I would like to translate the following postscript
> program into Pango/Cairo:
>
> %!
> 1.0 0 0 setrgbcolor
> 100 100 moveto
> 150 0 rlineto stroke
> 100 100 moveto
> /Helvetica findfont 36 scalefont setfont
> 0 setgray
> (yd) show
> showpage
>
> This programs draws a red line at position 100 100 from the lower
> corner left of the page and then writes "yd" on it. Note that the
> descender of the y descends below the y=100 line.
>
> In pango_cairo_show_layout() on the other hand, the layout logical
> upper left corner is aligned at the current cairo point when drawing,
> and I could not find any PangoLayout call that gets the distance from
> the top of the logical rectangle to the baseline position. Is this a
> bug, or did I miss something?
>
> Here is some pangocairo code that shows this alignment. So the
> question is how can I get the distance from the top of the PangoLayout
> to the baseline?
>
> Regards,
> Dov
>
> //======================================================================
> // Example that shows the relation between cairo coordinates and
> // Pango coordinates.
> //
> // Dov Grobgeld <dov.grobgeld@xxxxxxxxx>
> // Sat 2007-02-03 21:43
> //
> // This program is in the public domain
> //
> // Compile with:
> //
> // gcc `pkg-config --cflags --libs pangocairo` -o pango-bbox pango-bbox.c
> //----------------------------------------------------------------------
> #include <math.h>
> #include <pango/pangocairo.h>
>
> #define WIDTH 800
> #define HEIGHT 300
>
> static void
> draw_text (cairo_t *cr,
> const char *text)
> {
> PangoLayout *layout;
> PangoFontDescription *desc;
> PangoRectangle ink_rect, logical_rect;
> int width, height;
> double x, y;
>
> // Center coordinates on the middle of the region we are drawing
> cairo_translate (cr, WIDTH/2, HEIGHT/2);
>
> // Create a PangoLayout, set the font and text
> layout = pango_cairo_create_layout (cr);
>
> pango_layout_set_markup (layout, text, -1);
> desc = pango_font_description_from_string ("Serif 70");
> pango_layout_set_font_description (layout, desc);
> pango_font_description_free (desc);
>
> pango_layout_get_extents(layout,
> &ink_rect,
> &logical_rect);
> x = -((double)logical_rect.width / PANGO_SCALE) / 2;
> y = -((double)logical_rect.height / PANGO_SCALE) / 2;
>
> // Draw a green point at the current x,y position
> cairo_set_source_rgba (cr, 0.0, 1.0, 0.0, 0.5); // green
> cairo_arc(cr,
> x, y,
> 5, 0, 2*M_PI);
> cairo_fill(cr);
>
> // Draw the logical rectangle
> cairo_set_source_rgba (cr, 0.0, 0.0, 1.0, 0.5); // blue
> cairo_rectangle(cr,
> x+logical_rect.x/PANGO_SCALE,
> y+logical_rect.y/PANGO_SCALE,
> logical_rect.width/PANGO_SCALE,
> logical_rect.height/PANGO_SCALE);
> cairo_stroke(cr);
>
> // Draw the text
> cairo_move_to (cr, x, y);
> cairo_set_source_rgb (cr, 0.0, 0.0, 0.0); // black
> pango_cairo_show_layout (cr, layout);
>
> // Question: How can I draw a line at the baseline position?
>
> // free the layout object
> g_object_unref (layout);
> }
>
> int main (int argc, char **argv)
> {
> cairo_t *cr;
> const char *filename = "pango-bbox.png";
> cairo_surface_t *surface;
>
> surface = cairo_image_surface_create (CAIRO_FORMAT_RGB24, WIDTH, HEIGHT);
>
> cr = cairo_create (surface);
>
> cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
> cairo_paint (cr);
> draw_text (cr,
> "yd"
> );
> cairo_show_page (cr);
> cairo_destroy (cr);
>
> cairo_surface_write_to_png(surface, filename);
>
> cairo_surface_destroy (surface);
>
> return 0;
> }
--
behdad
http://behdad.org/
"Those who would give up Essential Liberty to purchase a little
Temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin, 1759
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