GTK+ 示例/樹形檢視/自定義單元格渲染器
與 Gtk+ 一起提供的單元格渲染器應該足以滿足大多數目的，但可能在某些情況下，您希望在樹形檢視中顯示無法使用提供的單元格渲染器顯示的內容，或者您希望從提供的單元格渲染器中派生以擴充套件其功能。
您可以透過編寫一個從 GtkCellRenderer 派生的新物件來實現這一點（如果您只想擴充套件現有物件，甚至可以從其他單元格渲染器中派生）。
在該過程中，您需要做三件事
- 使用型別系統註冊您的渲染器所需的一些新屬性，並編寫您自己的 set_property 和 get_property 函式來設定和獲取您的新渲染器的屬性。
- 編寫您自己的 cell_renderer_get_size 函式並覆蓋父物件的函式（通常父物件是 GtkCellRenderer 型別。請注意，您應該在這裡尊重父物件的填充和單元格對齊的標準屬性）。
- 編寫您自己的 cell_renderer_render 函式並覆蓋父物件的函式。此函式執行實際渲染。
編寫新單元格渲染器的 GObject 型別系統內容類似於我們在編寫自定義樹模型時所做的內容，在這種情況下相對簡單。複製貼上並根據您的需要修改。
在 Gtk+ 原始碼樹中，可以檢視或修改單元格渲染器程式碼的良好示例是 GtkCellRendererPixbuf 和 GtkCellRendererToggle。這兩個案例都不到 500 行程式碼，因此應該很容易理解。12.1. 工作示例：進度條單元格渲染器
在以下示例中，我們將編寫一個自定義單元格渲染器，以便將進度條渲染到樹形檢視中（程式碼“很大程度上受到” Sean Egan 在 GAIM 中的進度條單元格渲染器實現的啟發；請注意，這僅僅是為了演示目的，Gtk+ 已經有一段時間了。現在有一個進度條單元格渲染器：有關詳細資訊，請參閱 GtkCellRendererProgress API 文件）。
- custom-cell-renderer-progressbar.h
- custom-cell-renderer-progressbar.c
- main.c
標頭檔案包含通常的 GObject 型別轉換和型別檢查定義以及我們的 CustomCellRendererProgress 結構。如父型別所示，我們從 GtkCellRenderer 派生。父物件必須始終是結構中的第一個專案（還要注意，它不是指向物件的指標，而是嵌入在我們的結構中的父物件結構本身）。
我們的 CustomCellRendererProgress 結構相當平淡，只包含一個雙精度浮點變數，我們在其中儲存我們的新“百分比”屬性（它將決定進度條的長度）。
#ifndef _custom_cell_renderer_progressbar_included_
#define _custom_cell_renderer_progressbar_included_
#include <gtk/gtk.h>
/* Some boilerplate GObject type check and type cast macros. */
#define CUSTOM_TYPE_CELL_RENDERER_PROGRESS (custom_cell_renderer_progress_get_type())
G_DECLARE_DERIVABLE_TYPE(CustomCellRendererProgress, custom_cell_renderer_progress, CUSTOM, CELL_RENDERER_PROGRESS, GtkCellRenderer)
struct _CustomCellRendererProgressClass
{
GtkCellRendererClass parent_class;
};
GType custom_cell_renderer_progress_get_type (void);
GtkCellRenderer *custom_cell_renderer_progress_new (void);
#endif /* _custom_cell_renderer_progressbar_included_ */
程式碼包含上面描述的所有內容，所以讓我們直接進入程式碼
#include "custom-cell-renderer-progressbar.h"
/* This is based mainly on GtkCellRendererProgress
* in GAIM, written and (c) 2002 by Sean Egan
* (Licensed under the GPL), which in turn is
* based on Gtk's GtkCellRenderer[Text|Toggle|Pixbuf]
* implementation by Jonathan Blandford */
typedef struct _CustomCellRendererProgressPrivate CustomCellRendererProgressPrivate;
struct _CustomCellRendererProgressPrivate
{
gdouble progress;
};
G_DEFINE_TYPE_WITH_PRIVATE(CustomCellRendererProgress, custom_cell_renderer_progress, GTK_TYPE_CELL_RENDERER)
/* Some boring function declarations: GObject type system stuff */
static void custom_cell_renderer_progress_init (CustomCellRendererProgress *cellprogress);
static void custom_cell_renderer_progress_class_init (CustomCellRendererProgressClass *klass);
static void custom_cell_renderer_progress_get_property (GObject *object,
guint param_id,
GValue *value,
GParamSpec *pspec);
static void custom_cell_renderer_progress_set_property (GObject *object,
guint param_id,
const GValue *value,
GParamSpec *pspec);
static void custom_cell_renderer_progress_finalize (GObject *gobject);
/* These functions are the heart of our custom cell renderer: */
static void custom_cell_renderer_progress_get_preferred_width (
GtkCellRenderer *cell_renderer,
GtkWidget *parent_widget,
int *minimal_size,
int *natural_size);
static void custom_cell_renderer_progress_get_preferred_height (
GtkCellRenderer *cell_renderer,
GtkWidget *parent_widget,
int *minimal_size,
int *natural_size);
static void custom_cell_renderer_progress_render (
GtkCellRenderer *cell_renderer,
cairo_t *cr,
GtkWidget *widget,
const GdkRectangle *background_area,
const GdkRectangle *cell_area,
GtkCellRendererState flags);
enum
{
PROP_PERCENTAGE = 1,
};
static gpointer parent_class;
/******************************************************************
*
* CustomCellRendererProgressPrivate: shortcut function to access
* private data.
*
******************************************************************/
static inline CustomCellRendererProgressPrivate *
private (CustomCellRendererProgress *self)
{
return custom_cell_renderer_progress_get_instance_private(self);
}
/***************************************************************************
*
* custom_cell_renderer_progress_init: set some default properties of the
* parent (GtkCellRenderer).
*
***************************************************************************/
static void
custom_cell_renderer_progress_init (CustomCellRendererProgress *self)
{
/* init parent */
{
GtkCellRenderer *parent = GTK_CELL_RENDERER(self);
g_object_set (parent, "mode", GTK_CELL_RENDERER_MODE_INERT, NULL);
g_object_set (parent, "xpad", 2, NULL);
g_object_set (parent, "ypad", 2, NULL);
}
/* init private variables */
{
private (self)->progress = 0.0;
}
}
/***************************************************************************
*
* custom_cell_renderer_progress_class_init:
*
* set up our own get_property and set_property functions, and
* override the parent's functions that we need to implement.
* And make our new "percentage" property known to the type system.
* If you want cells that can be activated on their own (ie. not
* just the whole row selected) or cells that are editable, you
* will need to override 'activate' and 'start_editing' as well.
*
***************************************************************************/
static void
custom_cell_renderer_progress_class_init (CustomCellRendererProgressClass *klass)
{
GtkCellRendererClass *cell_class = GTK_CELL_RENDERER_CLASS(klass);
GObjectClass *object_class = G_OBJECT_CLASS(klass);
parent_class = g_type_class_peek_parent (klass);
object_class->finalize = custom_cell_renderer_progress_finalize;
/* Hook up functions to set and get our
* custom cell renderer properties */
object_class->get_property = custom_cell_renderer_progress_get_property;
object_class->set_property = custom_cell_renderer_progress_set_property;
/* Override the crucial functions that are the heart
* of a cell renderer in the parent class */
cell_class->get_preferred_width = custom_cell_renderer_progress_get_preferred_width;
cell_class->get_preferred_height = custom_cell_renderer_progress_get_preferred_height;
cell_class->render = custom_cell_renderer_progress_render;
/* Install our very own properties */
g_object_class_install_property (object_class,
PROP_PERCENTAGE,
g_param_spec_double ("percentage",
"Percentage",
"The fractional progress to display",
0, 1, 0,
G_PARAM_READWRITE));
}
/***************************************************************************
*
* custom_cell_renderer_progress_finalize: free any resources here
*
***************************************************************************/
static void
custom_cell_renderer_progress_finalize (GObject *object)
{
/*
CustomCellRendererProgress *cellrendererprogress = CUSTOM_CELL_RENDERER_PROGRESS(object);
*/
/* Free any dynamically allocated resources here */
(* G_OBJECT_CLASS (parent_class)->finalize) (object);
}
/***************************************************************************
*
* custom_cell_renderer_progress_get_property: as it says
*
***************************************************************************/
static void
custom_cell_renderer_progress_get_property (GObject *object,
guint param_id,
GValue *value,
GParamSpec *psec)
{
CustomCellRendererProgress *self = CUSTOM_CELL_RENDERER_PROGRESS(object);
switch (param_id)
{
case PROP_PERCENTAGE:
g_value_set_double(value, private (self)->progress);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, param_id, psec);
break;
}
}
/***************************************************************************
*
* custom_cell_renderer_progress_set_property: as it says
*
***************************************************************************/
static void
custom_cell_renderer_progress_set_property (GObject *object,
guint param_id,
const GValue *value,
GParamSpec *pspec)
{
CustomCellRendererProgress *self = CUSTOM_CELL_RENDERER_PROGRESS (object);
switch (param_id)
{
case PROP_PERCENTAGE:
private (self)->progress = g_value_get_double(value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID(object, param_id, pspec);
break;
}
}
/***************************************************************************
*
* custom_cell_renderer_progress_new: return a new cell renderer instance
*
***************************************************************************/
GtkCellRenderer *
custom_cell_renderer_progress_new (void)
{
return g_object_new(CUSTOM_TYPE_CELL_RENDERER_PROGRESS, NULL);
}
/***************************************************************************
*
* custom_cell_renderer_progress_get_preferred_width:
* crucial - calculate the size of our cell, taking into account
* padding and alignment properties of parent.
*
***************************************************************************/
#define FIXED_WIDTH 100
#define FIXED_HEIGHT 10
static void
custom_cell_renderer_progress_get_preferred_width (GtkCellRenderer *cell_renderer,
GtkWidget *parent_widget,
int *minimal_size,
int *natural_size)
{
gint calc_width;
gint xpad;
g_object_get( cell_renderer, "xpad", &xpad, NULL);
calc_width = (gint) xpad * 2 + FIXED_WIDTH;
if (minimal_size)
*minimal_size = calc_width;
if (natural_size)
*natural_size = calc_width;
}
/***************************************************************************
*
* custom_cell_renderer_progress_get_preferred_height:
* crucial - calculate the size of our cell, taking into account
* padding and alignment properties of parent.
*
***************************************************************************/
static void
custom_cell_renderer_progress_get_preferred_height (GtkCellRenderer *cell_renderer,
GtkWidget *parent_widget,
int *minimal_size,
int *natural_size)
{
gint calc_height;
gint ypad;
g_object_get( cell_renderer, "ypad", &ypad, NULL);
calc_height = (gint) ypad * 2 + FIXED_HEIGHT;
if (minimal_size)
*minimal_size = calc_height;
if (natural_size)
*natural_size = calc_height;
}
/***************************************************************************
*
* custom_cell_renderer_progress_render: crucial - do the rendering.
*
***************************************************************************/
static void
custom_cell_renderer_progress_render(GtkCellRenderer *cell_renderer,
cairo_t *cr,
GtkWidget *widget,
const GdkRectangle *background_area,
const GdkRectangle *cell_area,
GtkCellRendererState flags)
{
CustomCellRendererProgress *self = CUSTOM_CELL_RENDERER_PROGRESS (cell_renderer);
GtkStateType state;
gint width, height, x_pad, y_pad;
gint x_offset, y_offset;
custom_cell_renderer_progress_get_preferred_height (cell_renderer, widget, &height, &height);
custom_cell_renderer_progress_get_preferred_width (cell_renderer, widget, &width, &width);
if (gtk_widget_is_focus (widget))
state = GTK_STATE_ACTIVE;
else
state = GTK_STATE_NORMAL;
g_object_get (cell_renderer, "xpad", &x_pad, NULL);
width -= x_pad*2;
g_object_get (cell_renderer, "ypad", &y_pad, NULL);
height -= y_pad*2;
{
GtkStyleContext *style = gtk_widget_get_style_context(widget);
gtk_style_context_save(style);
gtk_style_context_set_state(style, state);
gint draw_width = cell_area->x + x_pad;
gint draw_height = cell_area->y + y_pad;
/* draw border */
{
gtk_render_frame (style, cr,
draw_width, draw_height,
width - 1, height - 1);
/* fallback, if gtk_render_frame is now shown (as on my system) */
gtk_render_background (style, cr,
draw_width, draw_height,
width - 1, height - 1);
}
/* draw progress indicator */
{
gint progress_width = (private (self)->progress) * (width - 1);
gtk_style_context_set_state(style, GTK_STATE_INSENSITIVE);
gtk_render_background (style, cr,
draw_width + 1, draw_height + 1,
progress_width - 2, height - 1 - 2);
}
gtk_style_context_restore(style);
}
}
這裡是一個使用我們的新 CustomCellRendererProgress 進行測試的小示例
#include "custom-cell-renderer-progressbar.h"
static GtkListStore *liststore;
static gboolean increasing = TRUE; /* direction of progress bar change */
enum
{
COL_PERCENTAGE = 0,
COL_TEXT,
NUM_COLS
};
#define STEP 0.01
gboolean
increase_progress_timeout (GtkCellRenderer *renderer)
{
GtkTreeIter iter;
gfloat perc = 0.0;
gchar buf[20];
gtk_tree_model_get_iter_first(GTK_TREE_MODEL(liststore), &iter); /* first and only row */
gtk_tree_model_get (GTK_TREE_MODEL(liststore), &iter, COL_PERCENTAGE, &perc, -1);
if ( perc > (1.0-STEP) || (perc < STEP && perc > 0.0) )
{
increasing = (!increasing);
}
if (increasing)
perc = perc + STEP;
else
perc = perc - STEP;
g_snprintf(buf, sizeof(buf), "%u %%", (guint)(perc*100));
gtk_list_store_set (liststore, &iter, COL_PERCENTAGE, perc, COL_TEXT, buf, -1);
return TRUE; /* Call again */
}
GtkWidget *
create_view_and_model (void)
{
GtkTreeViewColumn *col;
GtkCellRenderer *renderer;
GtkTreeIter iter;
GtkWidget *view;
liststore = gtk_list_store_new(NUM_COLS, G_TYPE_FLOAT, G_TYPE_STRING);
gtk_list_store_append(liststore, &iter);
gtk_list_store_set (liststore, &iter, COL_PERCENTAGE, 0.5, -1); /* start at 50% */
view = gtk_tree_view_new_with_model(GTK_TREE_MODEL(liststore));
g_object_unref(liststore); /* destroy store automatically with view */
renderer = gtk_cell_renderer_text_new();
col = gtk_tree_view_column_new();
gtk_tree_view_column_pack_start (col, renderer, TRUE);
gtk_tree_view_column_add_attribute (col, renderer, "text", COL_TEXT);
gtk_tree_view_column_set_title (col, "Progress");
gtk_tree_view_append_column(GTK_TREE_VIEW(view),col);
renderer = custom_cell_renderer_progress_new();
col = gtk_tree_view_column_new();
gtk_tree_view_column_pack_start (col, renderer, TRUE);
gtk_tree_view_column_add_attribute (col, renderer, "percentage", COL_PERCENTAGE);
gtk_tree_view_column_set_title (col, "Progress");
gtk_tree_view_append_column(GTK_TREE_VIEW(view),col);
g_timeout_add(50, (GSourceFunc) increase_progress_timeout, NULL);
return view;
}
int
main (int argc, char **argv)
{
GtkWidget *window, *view;
gtk_init(&argc,&argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_default_size (GTK_WINDOW(window), 150, 100);
g_signal_connect(window, "delete_event", gtk_main_quit, NULL);
view = create_view_and_model();
gtk_container_add(GTK_CONTAINER(window), view);
gtk_widget_show_all(window);
gtk_main();
return 0;
}
如果您不喜歡重新發明輪子，這裡列出了一些其他人編寫的自定義單元格渲染器
- 日期單元格渲染器（規劃器）（這個容易重用嗎？）
- 列表/組合單元格渲染器（規劃器）（這個容易重用嗎？）(FIXME: 由 GtkCellRendererCombo 棄用)
- 彈出視窗單元格渲染器（規劃器）（這個做什麼？）
- 您的自定義單元格渲染器在這裡？！