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gtk/demos/gtk-demo/drawingarea.c

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/* Drawing Area
*
* GtkDrawingArea is a blank area where you can draw custom displays
* of various kinds.
*
* This demo has two drawing areas. The checkerboard area shows
* how you can just draw something; all you have to do is write
* a signal handler for expose_event, as shown here.
*
* The "scribble" area is a bit more advanced, and shows how to handle
* events such as button presses and mouse motion. Click the mouse
* and drag in the scribble area to draw squiggles. Resize the window
* to clear the area.
*/
#include <gtk/gtk.h>
static GtkWidget *window = NULL;
/* Pixmap for scribble area, to store current scribbles */
static GdkPixmap *pixmap = NULL;
/* Create a new pixmap of the appropriate size to store our scribbles */
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);
/* Initialize the pixmap to white */
gdk_draw_rectangle (pixmap,
widget->style->white_gc,
TRUE,
0, 0,
widget->allocation.width,
widget->allocation.height);
/* We've handled the configure event, no need for further processing. */
return TRUE;
}
/* Redraw the screen from the pixmap */
static gboolean
scribble_expose_event (GtkWidget *widget,
GdkEventExpose *event,
gpointer data)
{
/* We use the "foreground GC" for the widget since it already exists,
* but honestly any GC would work. The only thing to worry about
* is whether the GC has an inappropriate clip region set.
*/
gdk_draw_drawable (widget->window,
widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
pixmap,
/* Only copy the area that was exposed. */
event->area.x, event->area.y,
event->area.x, event->area.y,
event->area.width, event->area.height);
return FALSE;
}
/* Draw a rectangle on the screen */
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;
/* Paint to the pixmap, where we store our state */
gdk_draw_rectangle (pixmap,
widget->style->black_gc,
TRUE,
update_rect.x, update_rect.y,
update_rect.width, update_rect.height);
/* Now invalidate the affected region of the drawing area. */
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; /* paranoia check, in case we haven't gotten a configure event */
if (event->button == 1)
draw_brush (widget, event->x, event->y);
/* We've handled the event, stop processing */
return TRUE;
}
static gboolean
scribble_motion_notify_event (GtkWidget *widget,
GdkEventMotion *event,
gpointer data)
{
int x, y;
GdkModifierType state;
if (pixmap == NULL)
return FALSE; /* paranoia check, in case we haven't gotten a configure event */
/* This call is very important; it requests the next motion event.
* If you don't call gdk_window_get_pointer() you'll only get
* a single motion event. The reason is that we specified
* GDK_POINTER_MOTION_HINT_MASK to gtk_widget_set_events().
* If we hadn't specified that, we could just use event->x, event->y
* as the pointer location. But we'd also get deluged in events.
* By requesting the next event as we handle the current one,
* we avoid getting a huge number of events faster than we
* can cope.
*/
gdk_window_get_pointer (event->window, &x, &y, &state);
if (state & GDK_BUTTON1_MASK)
draw_brush (widget, x, y);
/* We've handled it, stop processing */
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 2
/* At the start of an expose handler, a clip region of event->area
* is set on the window, and event->area has been cleared to the
* widget's background color. The docs for
* gdk_window_begin_paint_region() give more details on how this
* works.
*/
/* It would be a bit more efficient to keep these
* GC's around instead of recreating on each expose, but
* this is the lazy/slow way.
*/
gc1 = 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; /* start with even/odd depending on row */
while (j < da->allocation.height)
{
GdkGC *gc;
if (ycount % 2)
gc = gc1;
else
gc = gc2;
/* If we're outside event->area, this will do nothing.
* It might be mildly more efficient if we handled
* the clipping ourselves, but again we're feeling lazy.
*/
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 because we've handled this event, so no
* further processing is required.
*/
return TRUE;
}
GtkWidget *
do_drawingarea (void)
{
GtkWidget *frame;
GtkWidget *vbox;
GtkWidget *da;
GtkWidget *label;
if (!window)
{
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
gtk_signal_connect (GTK_OBJECT (window), "destroy", GTK_SIGNAL_FUNC (gtk_widget_destroyed), &window);
gtk_container_set_border_width (GTK_CONTAINER (window), 8);
vbox = gtk_vbox_new (FALSE, 8);
gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);
gtk_container_add (GTK_CONTAINER (window), vbox);
/*
* Create the checkerboard area
*/
label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label),
"<u>Checkerboard pattern</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 ();
/* set a minimum size */
gtk_widget_set_size_request (da, 100, 100);
gtk_container_add (GTK_CONTAINER (frame), da);
gtk_signal_connect (GTK_OBJECT (da),
"expose_event",
GTK_SIGNAL_FUNC (checkerboard_expose),
NULL);
/*
* Create the scribble area
*/
label = gtk_label_new (NULL);
gtk_label_set_markup (GTK_LABEL (label),
"<u>Scribble area</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 ();
/* set a minimum size */
gtk_widget_set_size_request (da, 100, 100);
gtk_container_add (GTK_CONTAINER (frame), da);
/* Signals used to handle backing pixmap */
gtk_signal_connect (GTK_OBJECT (da), "expose_event",
GTK_SIGNAL_FUNC (scribble_expose_event), NULL);
gtk_signal_connect (GTK_OBJECT (da),"configure_event",
GTK_SIGNAL_FUNC (scribble_configure_event), NULL);
/* Event signals */
gtk_signal_connect (GTK_OBJECT (da), "motion_notify_event",
GTK_SIGNAL_FUNC (scribble_motion_notify_event), NULL);
gtk_signal_connect (GTK_OBJECT (da), "button_press_event",
GTK_SIGNAL_FUNC (scribble_button_press_event), NULL);
/* Ask to receive events the drawing area doesn't normally
* subscribe to
*/
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);
}
if (!GTK_WIDGET_VISIBLE (window))
{
gtk_widget_show_all (window);
}
else
{
gtk_widget_destroy (window);
window = NULL;
}
return window;
}
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