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Learning_GTK4_tree/gtk/gtkdrawingarea.c

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2023-12-12 11:36:42 +01:00
/* 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 "gtkmarshalers.h"
#include "gdk/gdkmarshalers.h"
#include "gtkprivate.h"
#include "gtksnapshot.h"
#include "gtkwidgetprivate.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, };
enum {
RESIZE,
LAST_SIGNAL
};
static guint signals[LAST_SIGNAL] = { 0, };
/**
* GtkDrawingArea:
*
* `GtkDrawingArea` is a widget that allows drawing with cairo.
*
* ![An example GtkDrawingArea](drawingarea.png)
*
* It’s essentially a blank widget; you can draw on it. After
* creating a drawing area, the application may want to connect to:
*
* - The [signal@Gtk.Widget::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 [signal@Gtk.DrawingArea::resize] signal to take any necessary
* actions when the widget changes size.
*
* - Call [method@Gtk.DrawingArea.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.
*
* ## Simple GtkDrawingArea usage
*
* ```c
* static void
* draw_function (GtkDrawingArea *area,
* cairo_t *cr,
* int width,
* int height,
* gpointer data)
* {
* GdkRGBA color;
*
* cairo_arc (cr,
* width / 2.0, height / 2.0,
* MIN (width, height) / 2.0,
* 0, 2 * G_PI);
*
* gtk_widget_get_color (GTK_WIDGET (area),
* &color);
* gdk_cairo_set_source_rgba (cr, &color);
*
* cairo_fill (cr);
* }
*
* int
* main (int argc, char **argv)
* {
* gtk_init ();
*
* 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);
* return 0;
* }
* ```
*
* 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 [method@Gtk.Widget.queue_draw].
* This will cause the drawing area to call the draw function again.
*
* The available routines for drawing are documented in the
* [Cairo documentation](https://www.cairographics.org/manual/); GDK
* offers additional API to integrate with Cairo, like [func@Gdk.cairo_set_source_rgba]
* or [func@Gdk.cairo_set_source_pixbuf].
*
* To receive mouse events on a drawing area, you will need to use
* event controllers. 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.
*
* 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_size_allocate (GtkWidget *widget,
int width,
int height,
int baseline)
{
g_signal_emit (widget, signals[RESIZE], 0, width, 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;
int width, height;
if (!priv->draw_func)
return;
width = gtk_widget_get_width (widget);
height = gtk_widget_get_height (widget);
cr = gtk_snapshot_append_cairo (snapshot,
&GRAPHENE_RECT_INIT (
0, 0,
width, height
));
priv->draw_func (self,
cr,
width, height,
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->size_allocate = gtk_drawing_area_size_allocate;
widget_class->snapshot = gtk_drawing_area_snapshot;
/**
* GtkDrawingArea:content-width: (attributes org.gtk.Property.get=gtk_drawing_area_get_content_width org.gtk.Property.set=gtk_drawing_area_set_content_width)
*
* The content width.
*/
props[PROP_CONTENT_WIDTH] =
g_param_spec_int ("content-width", NULL, NULL,
0, G_MAXINT, 0,
GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);
/**
* GtkDrawingArea:content-height: (attributes org.gtk.Property.get=gtk_drawing_area_get_content_height org.gtk.Property.set=gtk_drawing_area_set_content_height)
*
* The content height.
*/
props[PROP_CONTENT_HEIGHT] =
g_param_spec_int ("content-height", NULL, NULL,
0, G_MAXINT, 0,
GTK_PARAM_READWRITE|G_PARAM_EXPLICIT_NOTIFY);
g_object_class_install_properties (gobject_class, LAST_PROP, props);
/**
* GtkDrawingArea::resize:
* @area: the `GtkDrawingArea` that emitted the signal
* @width: the width of the viewport
* @height: the height of the viewport
*
* Emitted once when the widget is realized, and then each time the widget
* is changed while realized.
*
* This is useful in order to keep state up to date with the widget size,
* like for instance a backing surface.
*/
signals[RESIZE] =
g_signal_new (I_("resize"),
G_TYPE_FROM_CLASS (class),
G_SIGNAL_RUN_LAST,
G_STRUCT_OFFSET (GtkDrawingAreaClass, resize),
NULL, NULL,
_gdk_marshal_VOID__INT_INT,
G_TYPE_NONE, 2, G_TYPE_INT, G_TYPE_INT);
g_signal_set_va_marshaller (signals[RESIZE],
G_TYPE_FROM_CLASS (class),
_gdk_marshal_VOID__INT_INTv);
}
static void
gtk_drawing_area_init (GtkDrawingArea *darea)
{
gtk_widget_set_focusable (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: (attributes org.gtk.Method.set_property=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
* [method@Gtk.Widget.set_halign] to avoid that.
*
* If the width is set to 0 (the default), the drawing area may disappear.
*/
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: (attributes org.gtk.Method.get_property=content-width)
* @self: a `GtkDrawingArea`
*
* Retrieves the content width of the `GtkDrawingArea`.
*
* Returns: The width requested for content of the drawing area
*/
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: (attributes org.gtk.Method.set_property=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
* [method@Gtk.Widget.set_valign] to avoid that.
*
* If the height is set to 0 (the default), the drawing area may disappear.
*/
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: (attributes org.gtk.Method.get_property=content-height)
* @self: a `GtkDrawingArea`
*
* Retrieves the content height of the `GtkDrawingArea`.
*
* Returns: The height requested for content of the drawing area
*/
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: (nullable): callback that lets you draw
* the drawing area's contents
* @user_data: (closure): 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.
*
* The draw function 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 [method@Gtk.Widget.queue_draw]
* on the drawing area. This will cause a redraw and will call @draw_func again.
*/
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));
}