gtk2/gtk/gtkdrawingarea.c

/* GTK - The GIMP Toolkit
 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * Modified by the GTK+ Team and others 1997-2000.  See the AUTHORS
 * file for a list of people on the GTK+ Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
 */

#include "config.h"
#include "gtkdrawingarea.h"
#include "gtkintl.h"
#include "gtkprivate.h"
#include "gtksnapshot.h"
#include "gtkstylecontext.h"

typedef struct _GtkDrawingAreaPrivate GtkDrawingAreaPrivate;

struct _GtkDrawingAreaPrivate {
  int content_width;
  int content_height;

  GtkDrawingAreaDrawFunc draw_func;
  gpointer draw_func_target;
  GDestroyNotify draw_func_target_destroy_notify;
};

enum {
  PROP_0,
  PROP_CONTENT_WIDTH,
  PROP_CONTENT_HEIGHT,
  LAST_PROP
};

static GParamSpec *props[LAST_PROP] = { NULL, };

/**
 * SECTION:gtkdrawingarea
 * @Short_description: A simple widget for custom user interface elements
 * @Title: GtkDrawingArea
 * @See_also: #GtkImage
 *
 * The #GtkDrawingArea widget is used for creating custom user interface
 * elements. It’s essentially a blank widget; you can draw on it. After
 * creating a drawing area, the application may want to connect to:
 *
 * - 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.)
 *
 * - The #GtkWidget::size-allocate signal to take any necessary
 *   actions when the widget changes size.
 *
 * - Call gtk_drawing_area_set_draw_func() to handle redrawing the
 *   contents of the widget.
 *
 * 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 before causing a
 * redraw, and that drawing is implicitly clipped to the exposed
 * area. If you want to have a theme-provided background, you need
 * to call gtk_render_background() in your ::draw method.
 *
 * ## Simple GtkDrawingArea usage
 *
 * |[<!-- language="C" -->
 * void
 * draw_function (GtkDrawingArea *area, cairo_t *cr,
 *                int width, int height,
 *                gpointer data)
 * {
 *   GdkRGBA color;
 *   GtkStyleContext *context;
 *
 *   context = gtk_widget_get_style_context (GTK_WIDGET (area));
 *
 *   gtk_render_background (context, cr, 0, 0, width, height);
 *
 *   cairo_arc (cr,
 *              width / 2.0, height / 2.0,
 *              MIN (width, height) / 2.0,
 *              0, 2 * G_PI);
 *
 *   gtk_style_context_get_color (context,
 *                                gtk_style_context_get_state (context),
 *                                &color);
 *   gdk_cairo_set_source_rgba (cr, &color);
 *
 *   cairo_fill (cr);
 * }
 * [...]
 *   GtkWidget *area = gtk_drawing_area_new ();
 *   gtk_drawing_area_set_content_width (GTK_DRAWING_AREA (area), 100);
 *   gtk_drawing_area_set_content_height (GTK_DRAWING_AREA (area), 100);
 *   gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (area),
 *                                   draw_function,
 *                                   NULL, NULL);
 * ]|
 *
 * The draw function is normally called when a drawing area first comes
 * onscreen, or when it’s covered by another window and then uncovered.
 * You can also force a redraw by adding to the “damage region” of the
 * drawing area’s window using gtk_widget_queue_draw_region(),
 * gtk_widget_queue_draw_area() or gtk_widget_queue_draw().
 * This will cause the drawing area to call the draw function again.
 *
 * The available routines for drawing are documented on the
 * [GDK Drawing Primitives][gdk3-Cairo-Interaction] page
 * 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
 * will need to set the “can-focus” property on the drawing area, and you
 * should probably draw some user-visible indication that the drawing
 * area is focused. Use gtk_widget_has_focus() in your expose event
 * handler to decide whether to draw the focus indicator. See
 * gtk_render_focus() for one way to draw focus.
 *
 * If you need more complex control over your widget, you should consider
 * creating your own #GtkWidget subclass.
 */

G_DEFINE_TYPE_WITH_PRIVATE (GtkDrawingArea, gtk_drawing_area, GTK_TYPE_WIDGET)

static void
gtk_drawing_area_set_property (GObject      *gobject,
                               guint         prop_id,
                               const GValue *value,
                               GParamSpec   *pspec)
{
  GtkDrawingArea *self = GTK_DRAWING_AREA (gobject);

  switch (prop_id)
    {
    case PROP_CONTENT_WIDTH:
      gtk_drawing_area_set_content_width (self, g_value_get_int (value));
      break;

    case PROP_CONTENT_HEIGHT:
      gtk_drawing_area_set_content_height (self, g_value_get_int (value));
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
    }
}

static void
gtk_drawing_area_get_property (GObject    *gobject,
                               guint       prop_id,
                               GValue     *value,
                               GParamSpec *pspec)
{
  GtkDrawingArea *self = GTK_DRAWING_AREA (gobject);
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  switch (prop_id)
    {
    case PROP_CONTENT_WIDTH:
      g_value_set_int (value, priv->content_width);
      break;

    case PROP_CONTENT_HEIGHT:
      g_value_set_int (value, priv->content_height);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (gobject, prop_id, pspec);
    }
}

static void
gtk_drawing_area_dispose (GObject *object)
{
  GtkDrawingArea *self = GTK_DRAWING_AREA (object);
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  if (priv->draw_func_target_destroy_notify != NULL)
    priv->draw_func_target_destroy_notify (priv->draw_func_target);

  priv->draw_func = NULL;
  priv->draw_func_target = NULL;
  priv->draw_func_target_destroy_notify = NULL;

  G_OBJECT_CLASS (gtk_drawing_area_parent_class)->dispose (object);
}

static void
gtk_drawing_area_measure (GtkWidget      *widget,
                          GtkOrientation  orientation,
                          int             for_size,
                          int            *minimum,
                          int            *natural,
                          int            *minimum_baseline,
                          int            *natural_baseline)
{
  GtkDrawingArea *self = GTK_DRAWING_AREA (widget);
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  if (orientation == GTK_ORIENTATION_HORIZONTAL)
    {
      *minimum = *natural = priv->content_width;
    }
  else
    {
      *minimum = *natural = priv->content_height;
    }
}

static void
gtk_drawing_area_snapshot (GtkWidget   *widget,
                           GtkSnapshot *snapshot)
{
  GtkDrawingArea *self = GTK_DRAWING_AREA (widget);
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);
  cairo_t *cr;

  if (!priv->draw_func)
    return;

  cr = gtk_snapshot_append_cairo_node (snapshot,
                                       &GRAPHENE_RECT_INIT (0, 0,
                                         gtk_widget_get_allocated_width (widget),
                                         gtk_widget_get_allocated_height (widget)),
                                       "DrawingAreaContents");
  priv->draw_func (self,
                   cr,
                   gtk_widget_get_allocated_width (widget),
                   gtk_widget_get_allocated_height (widget),
                   priv->draw_func_target);
  cairo_destroy (cr);
}

static void
gtk_drawing_area_class_init (GtkDrawingAreaClass *class)
{
  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
  GObjectClass *gobject_class = G_OBJECT_CLASS (class);

  gobject_class->set_property = gtk_drawing_area_set_property;
  gobject_class->get_property = gtk_drawing_area_get_property;
  gobject_class->dispose = gtk_drawing_area_dispose;

  widget_class->measure = gtk_drawing_area_measure;
  widget_class->snapshot = gtk_drawing_area_snapshot;

  /**
   * GtkDrawingArea:content-width
   *
   * The content width. See gtk_drawing_area_set_content_width() for details.
   *
   * Since: 3.90
   */
  props[PROP_CONTENT_WIDTH] =
    g_param_spec_int ("content-width",
                      P_("Content Width"),
                      P_("Desired width for displayed content"),
                      0, G_MAXINT, 0,
                      GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);

  /**
   * GtkDrawingArea:content-height
   *
   * The content height. See gtk_drawing_area_set_content_height() for details.
   *
   * Since: 3.90
   */
  props[PROP_CONTENT_HEIGHT] =
    g_param_spec_int ("content-height",
                      P_("Content Height"),
                      P_("Desired height for displayed content"),
                      0, G_MAXINT, 0,
                      GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);

  g_object_class_install_properties (gobject_class, LAST_PROP, props);

  gtk_widget_class_set_accessible_role (widget_class, ATK_ROLE_DRAWING_AREA);
}

static void
gtk_drawing_area_init (GtkDrawingArea *darea)
{
  gtk_widget_set_has_window (GTK_WIDGET (darea), FALSE);
}

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

/**
 * gtk_drawing_area_set_content_width:
 * @self: a #GtkDrawingArea
 * @width: the width of contents
 *
 * Sets the desired width of the contents of the drawing area. Note that
 * because widgets may be allocated larger sizes than they requested, it is
 * possible that the actual width passed to your draw function is larger
 * than the width set here. You can use gtk_widget_set_halign() to avoid
 * that.
 *
 * If the width is set to 0 (the default), the drawing area may disappear.
 *
 * Since: 3.90
 **/
void
gtk_drawing_area_set_content_width (GtkDrawingArea *self,
                                    int             width)
{
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  g_return_if_fail (GTK_IS_DRAWING_AREA (self));
  g_return_if_fail (width >= 0);

  if (priv->content_width == width)
    return;

  priv->content_width = width;

  gtk_widget_queue_resize (GTK_WIDGET (self));
  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_CONTENT_WIDTH]);
}

/**
 * gtk_drawing_area_get_content_width:
 * @self: a #GtkDrawingArea
 *
 * Retrieves the value previously set via gtk_drawing_area_set_content_width().
 *
 * Returns: The width requested for content of the drawing area
 *
 * Since: 3.90
 **/
int
gtk_drawing_area_get_content_width (GtkDrawingArea *self)
{
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  g_return_val_if_fail (GTK_IS_DRAWING_AREA (self), 0);

  return priv->content_width;
}

/**
 * gtk_drawing_area_set_content_height:
 * @self: a #GtkDrawingArea
 * @height: the height of contents
 *
 * Sets the desired height of the contents of the drawing area. Note that
 * because widgets may be allocated larger sizes than they requested, it is
 * possible that the actual height passed to your draw function is larger
 * than the height set here. You can use gtk_widget_set_valign() to avoid
 * that.
 *
 * If the height is set to 0 (the default), the drawing area may disappear.
 *
 * Since: 3.90
 **/
void
gtk_drawing_area_set_content_height (GtkDrawingArea *self,
                                     int             height)
{
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  g_return_if_fail (GTK_IS_DRAWING_AREA (self));
  g_return_if_fail (height >= 0);

  if (priv->content_height == height)
    return;

  priv->content_height = height;

  gtk_widget_queue_resize (GTK_WIDGET (self));
  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_CONTENT_HEIGHT]);
}

/**
 * gtk_drawing_area_get_content_height:
 * @self: a #GtkDrawingArea
 *
 * Retrieves the value previously set via gtk_drawing_area_set_content_height().
 *
 * Returns: The height requested for content of the drawing area
 *
 * Since: 3.90
 **/
int
gtk_drawing_area_get_content_height (GtkDrawingArea *self)
{
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  g_return_val_if_fail (GTK_IS_DRAWING_AREA (self), 0);

  return priv->content_height;
}

/**
 * gtk_drawing_area_set_draw_func:
 * @self: a #GtkDrawingArea
 * @draw_func: (closure user_data) (allow-none): callback that lets you draw
 *     the drawing area's contents
 * @user_data: user data passed to @draw_func
 * @destroy: destroy notifier for @user_data
 *
 * Setting a draw function is the main thing you want to do when using a drawing
 * area. It is called whenever GTK needs to draw the contents of the drawing area 
 * to the screen.
 *
 * The draw function will be called during the drawing stage of GTK. In the
 * drawing stage it is not allowed to change properties of any GTK widgets or call
 * any functions that would cause any properties to be changed.
 * You should restrict yourself exclusively to drawing your contents in the draw
 * function.
 *
 * If what you are drawing does change, call gtk_widget_queue_draw() on the
 * drawing area. This will call a redraw and will call @draw_func again.
 *
 * Since: 3.90
 */
void
gtk_drawing_area_set_draw_func (GtkDrawingArea         *self,
                                GtkDrawingAreaDrawFunc  draw_func,
                                gpointer                user_data,
                                GDestroyNotify          destroy)
{
  GtkDrawingAreaPrivate *priv = gtk_drawing_area_get_instance_private (self);

  g_return_if_fail (GTK_IS_DRAWING_AREA (self));

  if (priv->draw_func_target_destroy_notify != NULL)
    priv->draw_func_target_destroy_notify (priv->draw_func_target);

  priv->draw_func = draw_func;
  priv->draw_func_target = user_data;
  priv->draw_func_target_destroy_notify = destroy;

  gtk_widget_queue_draw (GTK_WIDGET (self));
}