C：使用 GTk+ 跟踪鼠标移动
C: Tracking mouse movement with GTk+
考虑以下代码：
#include<gtk/gtk.h>
#include<stdio.h>
static void destroy(GtkWidget*, gpointer);
static gboolean mouse_moved(GtkWidget *widget,GdkEvent *event,gpointer user_data);
int main(int argc, char* argv[]) {
GtkWidget *main_window;
// initializing
gtk_init(&argc, &argv);
main_window=gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(main_window),"Test");
gtk_widget_set_size_request (main_window, 500, 300);
// connect the window with signals
g_signal_connect (G_OBJECT (main_window), "destroy",G_CALLBACK (destroy), NULL);
g_signal_connect (G_OBJECT (main_window), "motion-notify-event",G_CALLBACK (mouse_moved), NULL);
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_MASK);
// show window
gtk_widget_show_all (main_window);
gtk_main();
return 0;
}
static void destroy(GtkWidget *window,gpointer data) {
gtk_main_quit ();
}
static gboolean mouse_moved(GtkWidget *widget,GdkEvent *event, gpointer user_data) {
if (event->type==GDK_MOTION_NOTIFY) {
GdkEventMotion* e=(GdkEventMotion*)event;
printf("Coordinates: (%u,%u)\n", (guint)e->x,(guint)e->y);
}
}
当我从终端 运行 这段代码时，它会打开一个空的 window，并且每次都打印出鼠标坐标。
这是上次执行的（部分）输出：
Coordinates: (390,17)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,19)
Coordinates: (390,19)
Coordinates: (390,19)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,23)
Coordinates: (391,23)
Coordinates: (391,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,29)
Coordinates: (390,29)
Coordinates: (390,29)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,31)
Coordinates: (390,31)
Coordinates: (390,32)
Coordinates: (390,32)
Coordinates: (390,32)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,34)
Coordinates: (390,34)
Coordinates: (390,34)
Coordinates: (389,34)
Coordinates: (389,35)
Coordinates: (389,36)
Coordinates: (389,36)
Coordinates: (389,36)
Coordinates: (389,37)
Coordinates: (389,36)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,38)
Coordinates: (389,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (381,43)
Coordinates: (381,43)
Coordinates: (381,43)
Coordinates: (380,43)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (379,44)
Coordinates: (378,44)
Coordinates: (378,44)
Coordinates: (377,44)
Coordinates: (377,44)
等等...
让我困惑的是：怎么会有两个连续的事件持有相同的坐标？例如，采用这两行：
Coordinates: (380,44)
Coordinates: (380,44)
这基本上是说鼠标没有移动（它从 (380,44) 移动到 (380,44)），所以怎么可能有一个移动事件来启动第二行的处理程序输入的？
另一个不太重要且（可能）不相关的问题：
为什么需要这条线？
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_MASK);
在 Gtk+ 开发基础一书中说：
Next, you need to add an event mask to the event box so that it knows
what type of events the widget will receive. Values for the
GdkEventMask enumeration that specify event masks are shown in Table
3-3. A bitwise list of GdkEventMask values can be passed to
gtk_widget_set_events() if you need to set more than one.
但是鉴于我们已经有了 g_signal_connect()，这个调用不是多余的吗？也就是说，根据文档：
Connects a GCallback function to a signal for a particular object.
The handler will be called before the default handler of the signal.
为什么我需要注册两次信号？
一次是 gtk_widget_set_events()，第二次是 g_signal_connect()?
我尝试直接使用 xev 监视 X 服务器中的鼠标移动，xorg 似乎报告了具有相同坐标但时间戳不同的多个鼠标事件。然而，当使用键盘上的指点杆时，它并没有这样做，只能使用触控板或外接鼠标。
我的猜测是精度实际上更高，但事件是针对屏幕上的一个像素报告的。这可能会导致驱动程序报告比需要更多的鼠标事件。
Why is this line necessary?
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_掩码);
But isn't this call redundant, given that we already have g_signal_connect()? which is, according to the documentation:
以 GtkButton like this one 为例。
如果您单击 Signals Link，您会注意到有 6 个信号可用：
Signals
void activate Action
void clicked Action
void enter Run First
void leave Run First
void pressed Run First
void released Run First
None 其中 scroll_event 来自 GdkEventScroll ，这意味着下面的程序不能像（可能）预期的那样工作：
#include <gtk/gtk.h>
gboolean scroll_callback ( GtkWidget *widget, GdkEvent *event, gpointer user_data );
int main ( void )
{
GtkWidget *window;
GtkWidget *button;
gtk_init( NULL, NULL );
/// ***
window = gtk_window_new( GTK_WINDOW_TOPLEVEL );
gtk_window_set_default_size( GTK_WINDOW( window ), 300, 250 );
g_signal_connect( window, "destroy", gtk_main_quit, NULL );
gtk_container_set_border_width( GTK_CONTAINER( window ), 25 );
/// ***
button = gtk_button_new_with_mnemonic( "_Click me" );
g_signal_connect( button, "clicked", gtk_main_quit, NULL );
gtk_container_add( GTK_CONTAINER( window ), button );
/// ***
g_signal_connect( button, "scroll_event", G_CALLBACK( scroll_callback ), window );
/// ***
gtk_widget_show_all( window );
gtk_main();
}
gboolean scroll_callback ( GtkWidget *widget, GdkEvent *event, gpointer data )
{
(void)widget;
if ( event->type == GDK_SCROLL ) /// Scroll the was Catched
{
if ( event->scroll.direction == GDK_SCROLL_DOWN )
{
g_print( "Scroll-Down Detected\n" );
gtk_window_set_title( GTK_WINDOW( data ), "Scroll-Down Detected" );
}
if ( event->scroll.direction == GDK_SCROLL_UP )
{
g_print( "Scroll-UP Detected\n" );
gtk_window_set_title( GTK_WINDOW( data ), "Scroll-UP Detected" );
}
return FALSE;
}
return TRUE;
}
这里我们尝试捕获scroll_event信号事件，但是它自己的widget（按钮）没有这种信号。
为了修复它，我们 set/add 在创建按钮后立即向按钮发送事件：
button = gtk_button_new_with_mnemonic( "_Click me" );
gtk_widget_set_events( button, GDK_SCROLL_MASK );
程序运行良好：
Scroll-Down Detected
Scroll-Down Detected
Scroll-Down Detected
Scroll-UP Detected
Scroll-UP Detected
Scroll-UP Detected
考虑以下代码：
#include<gtk/gtk.h>
#include<stdio.h>
static void destroy(GtkWidget*, gpointer);
static gboolean mouse_moved(GtkWidget *widget,GdkEvent *event,gpointer user_data);
int main(int argc, char* argv[]) {
GtkWidget *main_window;
// initializing
gtk_init(&argc, &argv);
main_window=gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(main_window),"Test");
gtk_widget_set_size_request (main_window, 500, 300);
// connect the window with signals
g_signal_connect (G_OBJECT (main_window), "destroy",G_CALLBACK (destroy), NULL);
g_signal_connect (G_OBJECT (main_window), "motion-notify-event",G_CALLBACK (mouse_moved), NULL);
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_MASK);
// show window
gtk_widget_show_all (main_window);
gtk_main();
return 0;
}
static void destroy(GtkWidget *window,gpointer data) {
gtk_main_quit ();
}
static gboolean mouse_moved(GtkWidget *widget,GdkEvent *event, gpointer user_data) {
if (event->type==GDK_MOTION_NOTIFY) {
GdkEventMotion* e=(GdkEventMotion*)event;
printf("Coordinates: (%u,%u)\n", (guint)e->x,(guint)e->y);
}
}
当我从终端 运行 这段代码时，它会打开一个空的 window，并且每次都打印出鼠标坐标。
这是上次执行的（部分）输出：
Coordinates: (390,17)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,18)
Coordinates: (390,19)
Coordinates: (390,19)
Coordinates: (390,19)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,22)
Coordinates: (391,23)
Coordinates: (391,23)
Coordinates: (391,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,23)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,24)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,25)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,26)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,27)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,28)
Coordinates: (390,29)
Coordinates: (390,29)
Coordinates: (390,29)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,30)
Coordinates: (390,31)
Coordinates: (390,31)
Coordinates: (390,32)
Coordinates: (390,32)
Coordinates: (390,32)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,33)
Coordinates: (390,34)
Coordinates: (390,34)
Coordinates: (390,34)
Coordinates: (389,34)
Coordinates: (389,35)
Coordinates: (389,36)
Coordinates: (389,36)
Coordinates: (389,36)
Coordinates: (389,37)
Coordinates: (389,36)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,37)
Coordinates: (389,38)
Coordinates: (389,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,38)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,39)
Coordinates: (388,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (387,40)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (386,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (385,41)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (384,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,42)
Coordinates: (383,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (382,43)
Coordinates: (381,43)
Coordinates: (381,43)
Coordinates: (381,43)
Coordinates: (380,43)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (380,44)
Coordinates: (379,44)
Coordinates: (378,44)
Coordinates: (378,44)
Coordinates: (377,44)
Coordinates: (377,44)
等等...
让我困惑的是：怎么会有两个连续的事件持有相同的坐标？例如，采用这两行：
Coordinates: (380,44)
Coordinates: (380,44)
这基本上是说鼠标没有移动（它从 (380,44) 移动到 (380,44)），所以怎么可能有一个移动事件来启动第二行的处理程序输入的？
另一个不太重要且（可能）不相关的问题：
为什么需要这条线？
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_MASK);
在 Gtk+ 开发基础一书中说：
Next, you need to add an event mask to the event box so that it knows what type of events the widget will receive. Values for the GdkEventMask enumeration that specify event masks are shown in Table 3-3. A bitwise list of GdkEventMask values can be passed to gtk_widget_set_events() if you need to set more than one.
但是鉴于我们已经有了 g_signal_connect()，这个调用不是多余的吗？也就是说，根据文档：
Connects a GCallback function to a signal for a particular object.
The handler will be called before the default handler of the signal.
为什么我需要注册两次信号？
一次是 gtk_widget_set_events()，第二次是 g_signal_connect()?
我尝试直接使用 xev 监视 X 服务器中的鼠标移动，xorg 似乎报告了具有相同坐标但时间戳不同的多个鼠标事件。然而，当使用键盘上的指点杆时，它并没有这样做，只能使用触控板或外接鼠标。
我的猜测是精度实际上更高，但事件是针对屏幕上的一个像素报告的。这可能会导致驱动程序报告比需要更多的鼠标事件。
Why is this line necessary?
gtk_widget_set_events(main_window, GDK_POINTER_MOTION_掩码);
But isn't this call redundant, given that we already have g_signal_connect()? which is, according to the documentation:
以 GtkButton like this one 为例。 如果您单击 Signals Link，您会注意到有 6 个信号可用：
Signals
void activate Action
void clicked Action
void enter Run First
void leave Run First
void pressed Run First
void released Run First
None 其中 scroll_event 来自 GdkEventScroll ，这意味着下面的程序不能像（可能）预期的那样工作：
#include <gtk/gtk.h>
gboolean scroll_callback ( GtkWidget *widget, GdkEvent *event, gpointer user_data );
int main ( void )
{
GtkWidget *window;
GtkWidget *button;
gtk_init( NULL, NULL );
/// ***
window = gtk_window_new( GTK_WINDOW_TOPLEVEL );
gtk_window_set_default_size( GTK_WINDOW( window ), 300, 250 );
g_signal_connect( window, "destroy", gtk_main_quit, NULL );
gtk_container_set_border_width( GTK_CONTAINER( window ), 25 );
/// ***
button = gtk_button_new_with_mnemonic( "_Click me" );
g_signal_connect( button, "clicked", gtk_main_quit, NULL );
gtk_container_add( GTK_CONTAINER( window ), button );
/// ***
g_signal_connect( button, "scroll_event", G_CALLBACK( scroll_callback ), window );
/// ***
gtk_widget_show_all( window );
gtk_main();
}
gboolean scroll_callback ( GtkWidget *widget, GdkEvent *event, gpointer data )
{
(void)widget;
if ( event->type == GDK_SCROLL ) /// Scroll the was Catched
{
if ( event->scroll.direction == GDK_SCROLL_DOWN )
{
g_print( "Scroll-Down Detected\n" );
gtk_window_set_title( GTK_WINDOW( data ), "Scroll-Down Detected" );
}
if ( event->scroll.direction == GDK_SCROLL_UP )
{
g_print( "Scroll-UP Detected\n" );
gtk_window_set_title( GTK_WINDOW( data ), "Scroll-UP Detected" );
}
return FALSE;
}
return TRUE;
}
这里我们尝试捕获scroll_event信号事件，但是它自己的widget（按钮）没有这种信号。
为了修复它，我们 set/add 在创建按钮后立即向按钮发送事件：
button = gtk_button_new_with_mnemonic( "_Click me" );
gtk_widget_set_events( button, GDK_SCROLL_MASK );
程序运行良好：
Scroll-Down Detected
Scroll-Down Detected
Scroll-Down Detected
Scroll-UP Detected
Scroll-UP Detected
Scroll-UP Detected