gtkdrawingarea.c 7.63 KB
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/* GTK - The GIMP Toolkit
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 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
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 */
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/*
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 * Modified by the GTK+ Team and others 1997-2000.  See the AUTHORS
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 * file for a list of people on the GTK+ Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
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 * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
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 */

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#include "config.h"
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#include "gtkdrawingarea.h"
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#include "gtkintl.h"
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#include "gtkstylecontext.h"
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/**
 * SECTION:gtkdrawingarea
 * @Short_description: A widget for custom user interface elements
 * @Title: GtkDrawingArea
 * @See_also: #GtkImage
 *
 * The #GtkDrawingArea widget is used for creating custom user interface
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 * elements. It’s essentially a blank widget; you can draw on it. After
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 * creating a drawing area, the application may want to connect to:
 *
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 * - Mouse and button press signals to respond to input from
 *   the user. (Use gtk_widget_add_events() to enable events
 *   you wish to receive.)
 *
 * - The #GtkWidget::realize signal to take any necessary actions
 *   when the widget is instantiated on a particular display.
 *   (Create GDK resources in response to this signal.)
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 *
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 * - The #GtkWidget::configure-event signal to take any necessary
 *   actions when the widget changes size.
 *
 * - The #GtkWidget::draw signal to handle redrawing the
 *   contents of the widget.
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 *
 * The following code portion demonstrates using a drawing
 * area to display a circle in the normal widget foreground
 * color.
 *
 * Note that GDK automatically clears the exposed area to the
 * background color before sending the expose event, and that
 * drawing is implicitly clipped to the exposed area.
 *
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 * ## Simple GtkDrawingArea usage
 *
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 * |[<!-- language="C" -->
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 * gboolean
 * draw_callback (GtkWidget *widget, cairo_t *cr, gpointer data)
 * {
 *   guint width, height;
 *   GdkRGBA color;
 *
 *   width = gtk_widget_get_allocated_width (widget);
 *   height = gtk_widget_get_allocated_height (widget);
 *   cairo_arc (cr,
 *              width / 2.0, height / 2.0,
 *              MIN (width, height) / 2.0,
 *              0, 2 * G_PI);
 *
 *   gtk_style_context_get_color (gtk_widget_get_style_context (widget),
 *                                0,
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 *                                &color);
 *   gdk_cairo_set_source_rgba (cr, &color);
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 *
 *   cairo_fill (cr);
 *
 *  return FALSE;
 * }
 * [...]
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 *   GtkWidget *drawing_area = gtk_drawing_area_new ();
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 *   gtk_widget_set_size_request (drawing_area, 100, 100);
 *   g_signal_connect (G_OBJECT (drawing_area), "draw",
 *                     G_CALLBACK (draw_callback), NULL);
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 * ]|
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 *
 * Draw signals are normally delivered when a drawing area first comes
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 * onscreen, or when it’s covered by another window and then uncovered.
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 * You can also force an expose event by adding to the “damage region”
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 * of the drawing area’s window; gtk_widget_queue_draw_area() and
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 * gdk_window_invalidate_rect() are equally good ways to do this.
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 * You’ll then get a draw signal for the invalid region.
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 *
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 * The available routines for drawing are documented on the
 * [GDK Drawing Primitives][gdk3-Cairo-Interaction] page
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 * and the cairo documentation.
 *
 * To receive mouse events on a drawing area, you will need to enable
 * them with gtk_widget_add_events(). To receive keyboard events, you
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 * will need to set the “can-focus” property on the drawing area, and you
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 * should probably draw some user-visible indication that the drawing
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 * area is focused. Use gtk_widget_has_focus() in your expose event
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 * handler to decide whether to draw the focus indicator. See
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 * gtk_render_focus() for one way to draw focus.
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 */

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static void gtk_drawing_area_realize       (GtkWidget           *widget);
static void gtk_drawing_area_size_allocate (GtkWidget           *widget,
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                                            GtkAllocation       *allocation);
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static void gtk_drawing_area_send_configure (GtkDrawingArea     *darea);
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G_DEFINE_TYPE (GtkDrawingArea, gtk_drawing_area, GTK_TYPE_WIDGET)
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static void
gtk_drawing_area_class_init (GtkDrawingAreaClass *class)
{
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  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
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  widget_class->realize = gtk_drawing_area_realize;
  widget_class->size_allocate = gtk_drawing_area_size_allocate;
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  gtk_widget_class_set_accessible_role (widget_class, ATK_ROLE_DRAWING_AREA);
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}

static void
gtk_drawing_area_init (GtkDrawingArea *darea)
{
}

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/**
 * gtk_drawing_area_new:
 *
 * Creates a new drawing area.
 *
 * Returns: a new #GtkDrawingArea
 */
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GtkWidget*
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gtk_drawing_area_new (void)
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{
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  return g_object_new (GTK_TYPE_DRAWING_AREA, NULL);
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}

static void
gtk_drawing_area_realize (GtkWidget *widget)
{
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  GtkAllocation allocation;
  GdkWindow *window;
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  GdkWindowAttr attributes;
  gint attributes_mask;

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  if (!gtk_widget_get_has_window (widget))
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    {
      GTK_WIDGET_CLASS (gtk_drawing_area_parent_class)->realize (widget);
    }
  else
    {
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      gtk_widget_set_realized (widget, TRUE);
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      gtk_widget_get_allocation (widget, &allocation);

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      attributes.window_type = GDK_WINDOW_CHILD;
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      attributes.x = allocation.x;
      attributes.y = allocation.y;
      attributes.width = allocation.width;
      attributes.height = allocation.height;
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      attributes.wclass = GDK_INPUT_OUTPUT;
      attributes.visual = gtk_widget_get_visual (widget);
      attributes.event_mask = gtk_widget_get_events (widget) | GDK_EXPOSURE_MASK;

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      attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL;
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      window = gdk_window_new (gtk_widget_get_parent_window (widget),
                               &attributes, attributes_mask);
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      gtk_widget_register_window (widget, window);
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      gtk_widget_set_window (widget, window);
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      gtk_style_context_set_background (gtk_widget_get_style_context (widget),
                                        window);
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    }
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  gtk_drawing_area_send_configure (GTK_DRAWING_AREA (widget));
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}

static void
gtk_drawing_area_size_allocate (GtkWidget     *widget,
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                                GtkAllocation *allocation)
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{
  g_return_if_fail (GTK_IS_DRAWING_AREA (widget));
  g_return_if_fail (allocation != NULL);

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  gtk_widget_set_allocation (widget, allocation);
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  if (gtk_widget_get_realized (widget))
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    {
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      if (gtk_widget_get_has_window (widget))
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        gdk_window_move_resize (gtk_widget_get_window (widget),
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                                allocation->x, allocation->y,
                                allocation->width, allocation->height);
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      gtk_drawing_area_send_configure (GTK_DRAWING_AREA (widget));
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    }
}
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static void
gtk_drawing_area_send_configure (GtkDrawingArea *darea)
{
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  GtkAllocation allocation;
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  GtkWidget *widget;
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  GdkEvent *event = gdk_event_new (GDK_CONFIGURE);
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  widget = GTK_WIDGET (darea);
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  gtk_widget_get_allocation (widget, &allocation);
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  event->configure.window = g_object_ref (gtk_widget_get_window (widget));
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  event->configure.send_event = TRUE;
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  event->configure.x = allocation.x;
  event->configure.y = allocation.y;
  event->configure.width = allocation.width;
  event->configure.height = allocation.height;
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  gtk_widget_event (widget, event);
  gdk_event_free (event);
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}