GTK实现绘图功能（draw.c）

/* 绘图软件 draw.c */
#include <gtk/gtk.h>
static GtkWidget *window = NULL;
static GdkPixmap *pixmap = NULL;
static gboolean
scribble_configure_event (GtkWidget *widget,GdkEventConfigure *event,gpointer data)
{if (pixmap)g_object_unref (G_OBJECT (pixmap));pixmap = gdk_pixmap_new (widget->window,widget->allocation.width,widget->allocation.height,-1);gdk_draw_rectangle (pixmap,widget->style->white_gc,TRUE,0,0,widget->allocation.width,widget->allocation.height);return TRUE;
}
static gboolean scribble_expose_event (GtkWidget *widget,GdkEventExpose *event,gpointer data)
{gdk_draw_drawable (widget->window,widget->style->fg_gc[GTK_WIDGET_STATE (widget)],pixmap,event->area.x, event->area.y,event->area.x, event->area.y,event->area.width, event->area.height);return FALSE;
}
static void draw_brush (GtkWidget *widget, gdouble x, gdouble y)
{GdkRectangle update_rect;update_rect.x = x - 3;update_rect.y = y - 3;update_rect.width = 6;update_rect.height = 6;gdk_draw_rectangle (pixmap,widget->style->black_gc,TRUE,update_rect.x, update_rect.y,update_rect.width, update_rect.height);gdk_window_invalidate_rect (widget->window,&update_rect,FALSE);
}
static gboolean scribble_button_press_event (GtkWidget *widget,GdkEventButton *event,gpointer data)
{if (pixmap == NULL)return FALSE;if (event->button == 1)draw_brush (widget, event->x, event->y);return TRUE;
}
static gboolean scribble_motion_notify_event (GtkWidget *widget,GdkEventMotion *event,gpointer data)
{int x, y;GdkModifierType state;if (pixmap == NULL)return FALSE;gdk_window_get_pointer (event->window, &x, &y, &state);if (state & GDK_BUTTON1_MASK)draw_brush (widget, x, y);return TRUE;
}
static gboolean checkerboard_expose (GtkWidget *da, GdkEventExpose *event,gpointer data)
{gint i, j, xcount, ycount;GdkGC *gc1, *gc2;GdkColor color;
#define CHECK_SIZE 10
#define SPACING 2gc1 = gdk_gc_new (da->window);color.red = 30000;color.green = 0;color.blue = 30000;gdk_gc_set_rgb_fg_color (gc1, &color);gc2 = gdk_gc_new (da->window);color.red = 65535;color.green = 65535;color.blue = 65535;gdk_gc_set_rgb_fg_color (gc2, &color);xcount = 0;i = SPACING;while (i < da->allocation.width){j = SPACING;ycount = xcount % 2;while (j < da->allocation.height){GdkGC *gc;if (ycount % 2)gc = gc1;elsegc = gc2;gdk_draw_rectangle (da->window, gc, TRUE,i, j, CHECK_SIZE, CHECK_SIZE);j += CHECK_SIZE + SPACING;++ycount;}i += CHECK_SIZE + SPACING;++xcount;}g_object_unref (G_OBJECT (gc1));g_object_unref (G_OBJECT (gc2));return TRUE;
}
int main (int argc,char* argv[])
{GtkWidget *frame;GtkWidget *vbox;GtkWidget *da;GtkWidget *label;gtk_init(&argc,&argv);window = gtk_window_new (GTK_WINDOW_TOPLEVEL);gtk_window_set_title (GTK_WINDOW (window), "绘图软件");g_signal_connect (G_OBJECT(window), "delete_event",G_CALLBACK (gtk_main_quit), NULL);gtk_container_set_border_width (GTK_CONTAINER (window), 10);vbox = gtk_vbox_new (FALSE, 8);gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);gtk_container_add (GTK_CONTAINER (window), vbox);label = gtk_label_new (NULL);gtk_label_set_markup (GTK_LABEL (label),"<u>绘图区域</u>");gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);frame = gtk_frame_new (NULL);gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);da = gtk_drawing_area_new ();gtk_widget_set_size_request (da, 100, 100);gtk_container_add (GTK_CONTAINER (frame), da);g_signal_connect (da, "expose_event",G_CALLBACK (scribble_expose_event), NULL);g_signal_connect (da, "configure_event",G_CALLBACK (scribble_configure_event), NULL);g_signal_connect (da, "motion_notify_event",G_CALLBACK (scribble_motion_notify_event), NULL);g_signal_connect (da, "button_press_event",G_CALLBACK (scribble_button_press_event), NULL);gtk_widget_set_events (da, gtk_widget_get_events (da)| GDK_LEAVE_NOTIFY_MASK| GDK_BUTTON_PRESS_MASK| GDK_POINTER_MOTION_MASK| GDK_POINTER_MOTION_HINT_MASK);gtk_widget_show_all (window);gtk_main();return FALSE;
}

编译与运行：

-bash-4.1$ gcc -o a draw.c `pkg-config --cflags --libs gtk+-2.0`
-bash-4.1$ ./a

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