297 lines
8.3 KiB
C
297 lines
8.3 KiB
C
/* Drawing Area
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*
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* GtkDrawingArea is a blank area where you can draw custom displays
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* of various kinds.
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*
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* This demo has two drawing areas. The checkerboard area shows
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* how you can just draw something; all you have to do is write
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* a signal handler for expose_event, as shown here.
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*
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* The "scribble" area is a bit more advanced, and shows how to handle
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* events such as button presses and mouse motion. Click the mouse
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* and drag in the scribble area to draw squiggles. Resize the window
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* to clear the area.
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*/
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#include <gtk/gtk.h>
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static GtkWidget *window = NULL;
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/* Pixmap for scribble area, to store current scribbles */
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static cairo_surface_t *surface = NULL;
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/* Create a new surface of the appropriate size to store our scribbles */
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static gboolean
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scribble_configure_event (GtkWidget *widget,
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GdkEventConfigure *event,
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gpointer data)
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{
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GtkAllocation allocation;
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cairo_t *cr;
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if (surface)
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cairo_surface_destroy (surface);
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gtk_widget_get_allocation (widget, &allocation);
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surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
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CAIRO_CONTENT_COLOR,
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allocation.width,
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allocation.height);
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/* Initialize the surface to white */
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cr = cairo_create (surface);
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cairo_set_source_rgb (cr, 1, 1, 1);
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cairo_paint (cr);
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cairo_destroy (cr);
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/* We've handled the configure event, no need for further processing. */
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return TRUE;
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}
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/* Redraw the screen from the surface */
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static gboolean
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scribble_draw (GtkWidget *widget,
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cairo_t *cr,
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gpointer data)
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{
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cairo_set_source_surface (cr, surface, 0, 0);
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cairo_paint (cr);
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return FALSE;
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}
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/* Draw a rectangle on the screen */
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static void
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draw_brush (GtkWidget *widget,
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gdouble x,
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gdouble y)
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{
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GdkRectangle update_rect;
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cairo_t *cr;
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update_rect.x = x - 3;
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update_rect.y = y - 3;
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update_rect.width = 6;
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update_rect.height = 6;
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/* Paint to the surface, where we store our state */
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cr = cairo_create (surface);
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gdk_cairo_rectangle (cr, &update_rect);
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cairo_fill (cr);
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cairo_destroy (cr);
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/* Now invalidate the affected region of the drawing area. */
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gdk_window_invalidate_rect (gtk_widget_get_window (widget),
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&update_rect,
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FALSE);
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}
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static gboolean
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scribble_button_press_event (GtkWidget *widget,
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GdkEventButton *event,
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gpointer data)
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{
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if (surface == NULL)
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return FALSE; /* paranoia check, in case we haven't gotten a configure event */
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if (event->button == GDK_BUTTON_PRIMARY)
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draw_brush (widget, event->x, event->y);
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/* We've handled the event, stop processing */
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return TRUE;
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}
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static gboolean
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scribble_motion_notify_event (GtkWidget *widget,
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GdkEventMotion *event,
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gpointer data)
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{
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int x, y;
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GdkModifierType state;
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if (surface == NULL)
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return FALSE; /* paranoia check, in case we haven't gotten a configure event */
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/* This call is very important; it requests the next motion event.
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* If you don't call gdk_window_get_pointer() you'll only get
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* a single motion event. The reason is that we specified
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* GDK_POINTER_MOTION_HINT_MASK to gtk_widget_set_events().
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* If we hadn't specified that, we could just use event->x, event->y
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* as the pointer location. But we'd also get deluged in events.
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* By requesting the next event as we handle the current one,
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* we avoid getting a huge number of events faster than we
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* can cope.
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*/
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gdk_window_get_device_position (event->window, event->device, &x, &y, &state);
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if (state & GDK_BUTTON1_MASK)
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draw_brush (widget, x, y);
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/* We've handled it, stop processing */
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return TRUE;
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}
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static gboolean
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checkerboard_draw (GtkWidget *da,
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cairo_t *cr,
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gpointer data)
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{
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gint i, j, xcount, ycount, width, height;
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#define CHECK_SIZE 10
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#define SPACING 2
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/* At the start of a draw handler, a clip region has been set on
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* the Cairo context, and the contents have been cleared to the
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* widget's background color. The docs for
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* gdk_window_begin_paint_region() give more details on how this
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* works.
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*/
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xcount = 0;
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width = gtk_widget_get_allocated_width (da);
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height = gtk_widget_get_allocated_height (da);
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i = SPACING;
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while (i < width)
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{
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j = SPACING;
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ycount = xcount % 2; /* start with even/odd depending on row */
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while (j < height)
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{
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if (ycount % 2)
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cairo_set_source_rgb (cr, 0.45777, 0, 0.45777);
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else
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cairo_set_source_rgb (cr, 1, 1, 1);
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/* If we're outside the clip, this will do nothing.
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*/
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cairo_rectangle (cr, i, j, CHECK_SIZE, CHECK_SIZE);
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cairo_fill (cr);
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j += CHECK_SIZE + SPACING;
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++ycount;
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}
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i += CHECK_SIZE + SPACING;
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++xcount;
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}
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/* return TRUE because we've handled this event, so no
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* further processing is required.
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*/
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return TRUE;
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}
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static void
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close_window (void)
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{
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window = NULL;
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if (surface)
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cairo_surface_destroy (surface);
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surface = NULL;
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}
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GtkWidget *
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do_drawingarea (GtkWidget *do_widget)
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{
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GtkWidget *frame;
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GtkWidget *vbox;
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GtkWidget *da;
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GtkWidget *label;
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if (!window)
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{
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window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
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gtk_window_set_screen (GTK_WINDOW (window),
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gtk_widget_get_screen (do_widget));
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gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");
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g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
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gtk_container_set_border_width (GTK_CONTAINER (window), 8);
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vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 8);
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gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);
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gtk_container_add (GTK_CONTAINER (window), vbox);
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/*
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* Create the checkerboard area
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*/
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label = gtk_label_new (NULL);
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gtk_label_set_markup (GTK_LABEL (label),
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"<u>Checkerboard pattern</u>");
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gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
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frame = gtk_frame_new (NULL);
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gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
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gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
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da = gtk_drawing_area_new ();
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/* set a minimum size */
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gtk_widget_set_size_request (da, 100, 100);
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gtk_container_add (GTK_CONTAINER (frame), da);
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g_signal_connect (da, "draw",
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G_CALLBACK (checkerboard_draw), NULL);
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/*
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* Create the scribble area
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*/
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label = gtk_label_new (NULL);
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gtk_label_set_markup (GTK_LABEL (label),
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"<u>Scribble area</u>");
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gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
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frame = gtk_frame_new (NULL);
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gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
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gtk_box_pack_start (GTK_BOX (vbox), frame, TRUE, TRUE, 0);
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da = gtk_drawing_area_new ();
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/* set a minimum size */
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gtk_widget_set_size_request (da, 100, 100);
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gtk_container_add (GTK_CONTAINER (frame), da);
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/* Signals used to handle backing surface */
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g_signal_connect (da, "draw",
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G_CALLBACK (scribble_draw), NULL);
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g_signal_connect (da,"configure-event",
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G_CALLBACK (scribble_configure_event), NULL);
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/* Event signals */
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g_signal_connect (da, "motion-notify-event",
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G_CALLBACK (scribble_motion_notify_event), NULL);
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g_signal_connect (da, "button-press-event",
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G_CALLBACK (scribble_button_press_event), NULL);
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/* Ask to receive events the drawing area doesn't normally
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* subscribe to
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*/
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gtk_widget_set_events (da, gtk_widget_get_events (da)
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| GDK_LEAVE_NOTIFY_MASK
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| GDK_BUTTON_PRESS_MASK
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| GDK_POINTER_MOTION_MASK
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| GDK_POINTER_MOTION_HINT_MASK);
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}
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if (!gtk_widget_get_visible (window))
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gtk_widget_show_all (window);
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else
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gtk_widget_destroy (window);
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return window;
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}
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