Desenhando texto
- 17.5.1. Desenhando texto com pango
- 17.5.2. Exemplo
17.5.1. Desenhando texto com pango
Text is drawn via Pango Layouts. The easiest way to create a Pango::Layout is to use Gtk::Widget::create_pango_layout(). Once created, the layout can be manipulated in various ways, including changing the text, font, etc. Finally, the layout can be rendered using the Pango::Layout::show_in_cairo_context() method.
17.5.2. Exemplo
Here is an example of a program that draws some text, some of it upside-down. The Printing chapter contains another example of drawing text.
File: myarea.h (For use with gtkmm 3, not gtkmm 2)
#ifndef GTKMM_EXAMPLE_MYAREA_H #define GTKMM_EXAMPLE_MYAREA_H #include <gtkmm/drawingarea.h> class MyArea : public Gtk::DrawingArea { public: MyArea(); virtual ~MyArea(); protected: //Override default signal handler: virtual bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr); private: void draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height); void draw_text(const Cairo::RefPtr<Cairo::Context>& cr, int rectangle_width, int rectangle_height); }; #endif // GTKMM_EXAMPLE_MYAREA_H
File: myarea.cc (For use with gtkmm 3, not gtkmm 2)
#include "myarea.h" MyArea::MyArea() { } MyArea::~MyArea() { } bool MyArea::on_draw(const Cairo::RefPtr<Cairo::Context>& cr) { Gtk::Allocation allocation = get_allocation(); const int width = allocation.get_width(); const int height = allocation.get_height(); const int rectangle_width = width; const int rectangle_height = height / 2; // Draw a black rectangle cr->set_source_rgb(0.0, 0.0, 0.0); draw_rectangle(cr, rectangle_width, rectangle_height); // and some white text cr->set_source_rgb(1.0, 1.0, 1.0); draw_text(cr, rectangle_width, rectangle_height); // flip the image vertically // see http://www.cairographics.org/documentation/cairomm/reference/classCairo_1_1Matrix.html // the -1 corresponds to the yy part (the flipping part) // the height part is a translation (we could have just called cr->translate(0, height) instead) // it's height and not height / 2, since we want this to be on the second part of our drawing // (otherwise, it would draw over the previous part) Cairo::Matrix matrix(1.0, 0.0, 0.0, -1.0, 0.0, height); // apply the matrix cr->transform(matrix); // white rectangle cr->set_source_rgb(1.0, 1.0, 1.0); draw_rectangle(cr, rectangle_width, rectangle_height); // black text cr->set_source_rgb(0.0, 0.0, 0.0); draw_text(cr, rectangle_width, rectangle_height); return true; } void MyArea::draw_rectangle(const Cairo::RefPtr<Cairo::Context>& cr, int width, int height) { cr->rectangle(0, 0, width, height); cr->fill(); } void MyArea::draw_text(const Cairo::RefPtr<Cairo::Context>& cr, int rectangle_width, int rectangle_height) { // http://developer.gnome.org/pangomm/unstable/classPango_1_1FontDescription.html Pango::FontDescription font; font.set_family("Monospace"); font.set_weight(Pango::WEIGHT_BOLD); // http://developer.gnome.org/pangomm/unstable/classPango_1_1Layout.html Glib::RefPtr<Pango::Layout> layout = create_pango_layout("Hi there!"); layout->set_font_description(font); int text_width; int text_height; //get the text dimensions (it updates the variables -- by reference) layout->get_pixel_size(text_width, text_height); // Position the text in the middle cr->move_to((rectangle_width-text_width)/2, (rectangle_height-text_height)/2); layout->show_in_cairo_context(cr); }
File: main.cc (For use with gtkmm 3, not gtkmm 2)
#include "myarea.h" #include <gtkmm/application.h> #include <gtkmm/window.h> int main(int argc, char* argv[]) { Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "org.gtkmm.example"); Gtk::Window window; window.set_title("Drawing text example"); MyArea area; window.add(area); area.show(); return app->run(window); }