Please see the attached screenshots to realize the problem. My code is as follows:
//Let's translate to origin of the drawing area allocation to avoid
//the cross lines to be rotated too
cairo_save(cr);
cairo_identity_matrix(cr);
cairo_translate(cr, allocation.x, allocation.y);
//This to compensate the allocation menubar height gap
//which prevents the horizontal line to be drawn at the center
//I wonder why the coordinates in the drawing area are shifted
//when the blessed menubar is hidden by the TAB key, shouldn't
//they always be 0,0 at the top left?
int menubar_height = gtk_widget_get_allocated_height(img->menubar);
if (img->textbox->draw_horizontal_line)
{
if (gtk_widget_is_visible(img->menubar))
center_y = menubar_height + center_y;
else
center_y = allocation.height / 2;
//Draw the horizontal centering line
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
cairo_set_line_width(cr, 1.0);
cairo_move_to(cr, 0, center_y - 2);
cairo_line_to(cr, allocation.width, center_y - 2);
cairo_stroke(cr);
cairo_set_source_rgb(cr, 0.8, 0.7, 0.3);
cairo_move_to(cr, 0, center_y);
cairo_line_to(cr, allocation.width, center_y);
cairo_stroke(cr);
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
cairo_move_to(cr, 0, center_y + 2);
cairo_line_to(cr, allocation.width, center_y + 2);
cairo_stroke(cr);
}
// Draw the vertical centering line
if (img->textbox->draw_vertical_line)
{
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
cairo_set_line_width(cr, 1.0);
cairo_move_to(cr, center_x - 2, 0);
cairo_line_to(cr, center_x - 2, allocation.height + menubar_height);
cairo_stroke(cr);
cairo_set_source_rgb(cr, 0.8, 0.7, 0.3);
cairo_move_to(cr, center_x, 0);
cairo_line_to(cr, center_x, allocation.height + menubar_height);
cairo_stroke(cr);
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
cairo_move_to(cr, center_x + 2, 0);
cairo_line_to(cr, center_x + 2, allocation.height + menubar_height);
cairo_stroke(cr);
}
cairo_restore(cr);
This is how I pack the drawing area instead:
/* Create the image area */
vbox = gtk_box_new(GTK_ORIENTATION_VERTICAL, 0);
g_object_set(G_OBJECT(vbox), "valign", GTK_ALIGN_CENTER);
gtk_box_pack_start (GTK_BOX (right_horizontal_box), vbox, TRUE, TRUE, 0);
img_struct->image_area = gtk_drawing_area_new();
gtk_box_pack_start(GTK_BOX(vbox), img_struct->image_area, FALSE, FALSE, 0);
gtk_widget_set_hexpand(img_struct->image_area, FALSE);
gtk_widget_set_vexpand(img_struct->image_area, FALSE);
gtk_widget_set_halign(img_struct->image_area, GTK_ALIGN_CENTER);
gtk_widget_set_valign(img_struct->image_area, GTK_ALIGN_CENTER);
gtk_widget_set_events(img_struct->image_area,
GDK_KEY_PRESS_MASK
| GDK_BUTTON_PRESS_MASK
| GDK_BUTTON_RELEASE_MASK
| GDK_POINTER_MOTION_MASK);
gtk_widget_set_can_focus(img_struct->image_area, TRUE);
gtk_widget_grab_focus(img_struct->image_area);
Can someone explain to me why the 0,0 coords are shifted in the drawing area when other widgets packed together with it are visible?
