在gtk中绘制背景图像 - 我的尝试都没有

Question

即使在尝试了4种不同的方法之后,我一直试图在gtk小部件上设置背景图像但没有成功.

以下程序包含3种方法(第4种方法不涉及代码).我使用MinGW(g ++ 4.5.0)和gtkmm 2.4编译它.所述APPROACH宏可以选择编译哪种方法被设置为1,2或3.我还在评论中添加了参考文献,因此您可以找到我从哪里获得的想法.

#include <iostream>
#include <gtkmm/main.h>
#include <gtkmm/alignment.h>
#include <gtkmm/box.h>
#include <gtkmm/entry.h>
#include <gtkmm/eventbox.h>
#include <gtkmm/frame.h>
#include <gtkmm/image.h>
#include <gtkmm/label.h>
#include <gtkmm/table.h>
#include <gtkmm/window.h>

// Set this to 1, 2 or 3 to try different ways of drawing the background
// Set to 0 to load no background at all
#define APPROACH (0)

// Making this alignment global in order to modify it from drawBackground
Gtk::Alignment* alignment;

bool drawBackground(GdkEventExpose* event) {
    std::cout << "Draw background" << std::endl;

    // Load background image
    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Gdk::Pixbuf::create_from_file("background.jpg");
    Glib::RefPtr<Gdk::Pixmap> pixmap;
    Glib::RefPtr<Gdk::Bitmap> mask;
    pixbuf->render_pixmap_and_mask(pixmap, mask,0);

    {
        // Test that pixbuf was created correctly
        Glib::RefPtr<Gdk::Pixbuf> back_to_pixbuf = Gdk::Pixbuf::create((Glib::RefPtr<Gdk::Drawable>)pixmap, 0, 0, pixbuf->get_width(), pixbuf->get_height());
        back_to_pixbuf->save("back_to_pixbuf.png", "png");
    }

#if APPROACH == 1
    // Approach 1: draw_pixbuf
    // Ref: http://islascruz.org/html/index.php/blog/show/Image-as-background-in-a-Gtk-Application..html
    Glib::RefPtr<Gtk::Style> style = alignment->get_style();
    alignment->get_window()->draw_pixbuf(style->get_bg_gc(Gtk::STATE_NORMAL), pixbuf, 0, 0, 0, 200, pixbuf->get_width(), pixbuf->get_height(), Gdk::RGB_DITHER_NONE, 0, 0);
#endif

#if APPROACH == 2
    // Approach 2: set_back_pixmap
    // Ref: http://www.gtkforums.com/viewtopic.php?t=446
    //      http://stackoverflow.com/questions/3150706/gtk-drawing-set-background-image
    alignment->get_window()->set_back_pixmap(pixmap);
#endif
}

int main (int argc, char *argv[])
{
    Gtk::Main kit(argc, argv);

    Gtk::Window w;
    Gtk::VBox mainBox;

    // Top image
    Gtk::Image topImage("header.jpg");
    mainBox.pack_start(topImage,false,false,0);

    // Middle alignment
    alignment = Gtk::manage(new Gtk::Alignment);
    mainBox.pack_start(*alignment,true,true,0);

    // Create widget
    Gtk::Alignment mywidget(0.5, 0.5, 0.1, 0.9);
    Gtk::Table table;
    Gtk::Label label1("Username"); table.attach(label1,0,1,0,1);
    Gtk::Label label2("Password"); table.attach(label2,0,1,1,2);
    Gtk::Entry entry1;             table.attach(entry1,1,2,0,1);
    Gtk::Entry entry2;             table.attach(entry2,1,2,1,2);
    Gtk::Button button("Login");   table.attach(button,1,2,2,3);
    mywidget.add(table);

    // Put widget in middle alignment
    alignment->add(mywidget);

    // Try to change the background
#if APPROACH == 1 || APPROACH == 2
    alignment->signal_expose_event().connect(sigc::ptr_fun(&drawBackground), true);
#endif

#if APPROACH == 3
    // Approach 3: modify the style using code
    // Ref: http://www.gtkforums.com/viewtopic.php?t=446
    // Load background image
    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Gdk::Pixbuf::create_from_file("background.jpg");
    Glib::RefPtr<Gdk::Pixmap> pixmap;
    Glib::RefPtr<Gdk::Bitmap> mask;
    pixbuf->render_pixmap_and_mask(pixmap, mask,0);
    Glib::RefPtr<Gtk::Style> style = alignment->get_style()->copy();
    style->set_bg_pixmap(Gtk::STATE_NORMAL,pixmap);
    style->set_bg_pixmap(Gtk::STATE_ACTIVE,pixmap);
    style->set_bg_pixmap(Gtk::STATE_PRELIGHT,pixmap);
    style->set_bg_pixmap(Gtk::STATE_SELECTED,pixmap);
    style->set_bg_pixmap(Gtk::STATE_INSENSITIVE,pixmap);
    alignment->set_style(style);
#endif

    // Approach 4: modify share\themes\MS-Windows\gtk-2.0
    // adding the following line
    // bg_pixmap[NORMAL] = "D:\\path\\to\\file\\background.jpg"
    // in the style "msw-default" section
    // Ref: http://lists.ximian.com/pipermail/gtk-sharp-list/2005-August/006324.html

    // Show the window
    w.add(mainBox);
    w.show_all();
    kit.run(w);
    return 0;
}

我使用的图像的链接:header.jpg background.jpg

布局模仿我的实际程序.主窗口包含一个Gtk :: VBox,顶部有一个标题图像,底部有一个Gtk :: Alignment.此对齐的内容将随着时间的推移而改变,但我希望它始终可见背景图像.

当根本不加载背景时,标题图像正确加载,窗口如下所示:

方法1是更接近工作的方法,虽然它隐藏了标签和按钮:

方法2和3看起来与加载无背景相同.此外,方法2给我以下错误信息:

(test-img-fondo.exe:1752): Gdk-CRITICAL **: gdk_window_set_back_pixmap: assertion `pixmap == NULL || !parent_relative' failed

最后,在方法4中,我尝试通过添加以下行来修改share\themes\MS-Windows\gtk-2.0

bg_pixmap[NORMAL] = "D:\\path\\to\\file\\background.jpg"

在"msw-default"部分中.它也不起作用.

那么,是否有人在Gtk小部件上成功绘制了背景图像？这有可能吗？我的代码中的任何更改都会使其工作？任何解决方法？

非常感谢所有帮助.

Answer 1

我想我自己已经解决了.使用方法1但更改此行

alignment->signal_expose_event().connect(sigc::ptr_fun(&drawBackground), true);

为了这:

alignment->signal_expose_event().connect(sigc::ptr_fun(&drawBackground), false);

这样,在gtk调用自己的处理程序之前,就会调用drawBackground.

我还应该指出,在一个真实的程序中,图像应该在外面加载一次drawBackground.