Translate/rotate 1 single pango cairo layout

[jkraehemann (Joël Krähemann)]

Hi,

I have got a GtkDrawingArea, I am drawing with cairo and pango.

  GtkSettings *settings;

  PangoLayout *layout;
  PangoFontDescription *desc;

  PangoRectangle ink_rect, logical_rect;

  gchar *font_name;
  gchar *note_str;

  const gchar* note_strv[] = {
    "𝅝",
    "𝅗𝅥",
    "𝅘𝅥",
    "𝅘𝅥𝅮",
    "𝅘𝅥𝅯",
    NULL,
  };

  const gdouble font_size = 12.5;
  const gdouble key_font_size = 12.5;
  const gdouble x0 = 0.0;
  const gdouble y0 = 0.0;

  settings = gtk_settings_get_default();

  font_name = NULL;

  g_object_get(settings,
	       "gtk-font-name", &font_name,
               NULL);

  note_str = note_strv[2];

  if(note_str != NULL){
    layout = pango_cairo_create_layout(cr);
    pango_layout_set_text(layout,
                          note_str,
                          -1);
    desc = pango_font_description_from_string(font_name);
    pango_font_description_set_size(desc,
                                    key_font_size * PANGO_SCALE);
    pango_layout_set_font_description(layout,
                                      desc);
    pango_font_description_free(desc);

    pango_layout_get_extents(layout,
                             &ink_rect,
                             &logical_rect);

    cairo_move_to(cr,
                  x0,
                  y0);

    pango_cairo_show_layout(cr,
                            layout);

    g_object_unref(layout);
  }

If I call cairo_scale() then it scales additional layouts it shouldn’t. Howto prevent this?

I tried cairo_push_group() but this didn’t work as expected.

Just for reference my complete code:

https://git.savannah.nongnu.org/cgit/gsequencer.git/tree/ags/app/editor/ags_sheet_edit.c?h=4.4.x&id=bd0fb08a7ded5bad298d1915091652375b4cbd1d#n1406

best regards,
Joël

[jkraehemann (Joël Krähemann)]

Just figured out the solution. So what was missing:

• call cairo_translate() respecting string width and height
• call cairo_rotate() with radians
• call cairo_move_to() with additional quirks

cheers, Joël

[StefanSalewski]

There was a cairo example, drawing some rotated text, and saving to a PNG file. That was how I learned this stuff maybe 12 years ago. But I cant find it again. For scaling and rotating, it is necessary to first do a translation to the point that should stay unchanged, then rotate or scale, and then maybe translate back. Fine that you found the solution yourself.