[gnome-todo] Introduce GtdTextWidthLayout

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 2dd7b68ca6f7ba33ccfe50566ddf1bd846e35d01
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sat May 2 00:22:04 2020 -0300

    Introduce GtdTextWidthLayout
    
    A new layout manager that allows setting minimum and maximum
    widths but based on font sizes.

 src/gnome-todo.h            |   1 +
 src/gtd-text-width-layout.c | 324 ++++++++++++++++++++++++++++++++++++++++++++
 src/gtd-text-width-layout.h |  42 ++++++
 src/meson.build             |   4 +
 4 files changed, 371 insertions(+)
---
diff --git a/src/gnome-todo.h b/src/gnome-todo.h
index 124f469..3745613 100644
--- a/src/gnome-todo.h
+++ b/src/gnome-todo.h
@@ -38,6 +38,7 @@
 #include "gtd-task.h"
 #include "gtd-task-list.h"
 #include "gtd-task-list-view.h"
+#include "gtd-text-width-layout.h"
 #include "gtd-types.h"
 #include "gtd-utils.h"
 #include "gtd-window.h"
diff --git a/src/gtd-text-width-layout.c b/src/gtd-text-width-layout.c
new file mode 100644
index 0000000..1227b59
--- /dev/null
+++ b/src/gtd-text-width-layout.c
@@ -0,0 +1,324 @@
+/* gtd-text-width-layout.c
+ *
+ * Copyright 2020 Georges Basile Stavracas Neto <georges stavracas gmail com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#include "gtd-text-width-layout.h"
+
+struct _GtdTextWidthLayout
+{
+  GtkLayoutManager    parent;
+
+  gint                max_width_chars;
+  gint                width_chars;
+};
+
+G_DEFINE_TYPE (GtdTextWidthLayout, gtd_text_width_layout, GTK_TYPE_BIN_LAYOUT)
+
+enum
+{
+  PROP_0,
+  PROP_MAX_WIDTH_CHARS,
+  PROP_WIDTH_CHARS,
+  N_PROPS
+};
+
+static GParamSpec *properties [N_PROPS];
+
+
+/*
+ * GtkLayoutManager overrides
+ */
+
+static void
+gtd_text_width_layout_measure (GtkLayoutManager *layout_manager,
+                               GtkWidget        *widget,
+                               GtkOrientation    orientation,
+                               gint              for_size,
+                               gint             *minimum,
+                               gint             *natural,
+                               gint             *minimum_baseline,
+                               gint             *natural_baseline)
+{
+  GtdTextWidthLayout *self = (GtdTextWidthLayout *)layout_manager;
+  GtkWidget *child;
+
+  for (child = gtk_widget_get_first_child (widget);
+       child != NULL;
+       child = gtk_widget_get_next_sibling (child))
+    {
+      gint child_min_baseline = -1;
+      gint child_nat_baseline = -1;
+      gint child_min = 0;
+      gint child_nat = 0;
+
+      if (!gtk_widget_should_layout (child))
+        continue;
+
+      gtk_widget_measure (child, orientation, for_size,
+                          &child_min, &child_nat,
+                          &child_min_baseline, &child_nat_baseline);
+
+      *minimum = MAX (*minimum, child_min);
+      *natural = MAX (*natural, child_nat);
+
+      if (child_min_baseline > -1)
+        *minimum_baseline = MAX (*minimum_baseline, child_min_baseline);
+      if (child_nat_baseline > -1)
+        *natural_baseline = MAX (*natural_baseline, child_nat_baseline);
+    }
+
+  if (orientation == GTK_ORIENTATION_HORIZONTAL)
+    {
+      PangoFontMetrics *metrics;
+      PangoContext *context;
+      gint max_width_chars = G_MAXINT;
+      gint width_chars = 0;
+      gint char_width;
+      gint digit_width;
+
+      context = gtk_widget_get_pango_context (widget);
+      metrics = pango_context_get_metrics (context,
+                                           pango_context_get_font_description (context),
+                                           pango_context_get_language (context));
+
+      char_width = pango_font_metrics_get_approximate_char_width (metrics);
+      digit_width = pango_font_metrics_get_approximate_digit_width (metrics);
+
+      if (self->width_chars >= 0)
+        width_chars = MAX (char_width, digit_width) * self->width_chars / PANGO_SCALE;
+
+      if (self->max_width_chars >= 0)
+        max_width_chars = MAX (char_width, digit_width) * self->max_width_chars / PANGO_SCALE;
+
+      *minimum = MAX (*minimum, width_chars);
+      *natural = MAX (*natural, max_width_chars);
+
+      pango_font_metrics_unref (metrics);
+    }
+}
+
+static void
+gtd_text_width_layout_allocate (GtkLayoutManager *layout_manager,
+                                GtkWidget        *widget,
+                                gint              width,
+                                gint              height,
+                                gint              baseline)
+{
+  GtkWidget *child;
+
+  for (child = gtk_widget_get_first_child (widget);
+       child != NULL;
+       child = gtk_widget_get_next_sibling (child))
+    {
+      if (child && gtk_widget_should_layout (child))
+        gtk_widget_allocate (child, width, height, baseline, NULL);
+    }
+}
+
+
+/*
+ * GObject overrides
+ */
+
+static void
+gtd_text_width_layout_get_property (GObject    *object,
+                                    guint       prop_id,
+                                    GValue     *value,
+                                    GParamSpec *pspec)
+{
+  GtdTextWidthLayout *self = GTD_TEXT_WIDTH_LAYOUT (object);
+
+  switch (prop_id)
+    {
+    case PROP_MAX_WIDTH_CHARS:
+      g_value_set_int (value, self->max_width_chars);
+      break;
+
+    case PROP_WIDTH_CHARS:
+      g_value_set_int (value, self->width_chars);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+gtd_text_width_layout_set_property (GObject      *object,
+                                    guint         prop_id,
+                                    const GValue *value,
+                                    GParamSpec   *pspec)
+{
+  GtdTextWidthLayout *self = GTD_TEXT_WIDTH_LAYOUT (object);
+
+  switch (prop_id)
+    {
+    case PROP_MAX_WIDTH_CHARS:
+      gtd_text_width_layout_set_max_width_chars (self, g_value_get_int (value));
+      break;
+
+    case PROP_WIDTH_CHARS:
+      gtd_text_width_layout_set_width_chars (self, g_value_get_int (value));
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+    }
+}
+
+static void
+gtd_text_width_layout_class_init (GtdTextWidthLayoutClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GtkLayoutManagerClass *layout_manager_class = GTK_LAYOUT_MANAGER_CLASS (klass);
+
+  layout_manager_class->measure = gtd_text_width_layout_measure;
+  layout_manager_class->allocate = gtd_text_width_layout_allocate;
+
+  object_class->get_property = gtd_text_width_layout_get_property;
+  object_class->set_property = gtd_text_width_layout_set_property;
+
+  /**
+   * GtdTextWidthLayout:max-width-chars:
+   *
+   * Sets the maximum size of the #GtkWidget in characters.
+   */
+  properties[PROP_MAX_WIDTH_CHARS] = g_param_spec_int ("max-width-chars",
+                                                       "Max Width Chars",
+                                                       "Max Width Chars",
+                                                       -1,
+                                                       G_MAXINT,
+                                                       -1,
+                                                       G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | 
G_PARAM_STATIC_STRINGS);
+
+  /**
+   * GtdTextWidthLayout:width-chars:
+   *
+   * Sets the size of the #GtkWidget in characters.
+   */
+  properties[PROP_WIDTH_CHARS] = g_param_spec_int ("width-chars",
+                                                   "Width Chars",
+                                                   "Width Chars",
+                                                   -1,
+                                                   G_MAXINT,
+                                                   -1,
+                                                   G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY | 
G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (object_class, N_PROPS, properties);
+}
+
+static void
+gtd_text_width_layout_init (GtdTextWidthLayout *self)
+{
+  self->max_width_chars = -1;
+  self->width_chars = -1;
+}
+
+/**
+ * gtd_text_width_layout_new:
+ *
+ * Creates a new #GtdTextWidthLayout.
+ *
+ * Returns: (transfer full): a #GtdTextWidthLayout
+ */
+GtkLayoutManager*
+gtd_text_width_layout_new (void)
+{
+  return g_object_new (GTD_TYPE_TEXT_WIDTH_LAYOUT, NULL);
+}
+
+/**
+ * gtd_text_width_layout_get_max_width_chars:
+ *
+ * Retrieves the maximum width in characters of @self.
+ *
+ * Returns: maximum width in characters
+ */
+gint
+gtd_text_width_layout_get_max_width_chars (GtdTextWidthLayout *self)
+{
+  g_return_val_if_fail (GTD_IS_TEXT_WIDTH_LAYOUT (self), -1);
+
+  return self->max_width_chars;
+}
+
+/**
+ * gtd_text_width_layout_set_max_width_chars:
+ * @self: a #GtdTextWidthLayout
+ * @with_chars: maximum width of the widget @self is attached to, in character length
+ *
+ * Sets the maximum width @self has, in characters length. It is a programming
+ * error to set a value smaller than #GtdTextWidthLayout:width-layout.
+ */
+void
+gtd_text_width_layout_set_max_width_chars (GtdTextWidthLayout *self,
+                                           gint                max_width_chars)
+{
+  g_return_if_fail (GTD_IS_TEXT_WIDTH_LAYOUT (self));
+  g_return_if_fail (max_width_chars >= -1);
+  g_return_if_fail (self->width_chars == -1 || max_width_chars >= self->width_chars);
+
+  if (self->max_width_chars == max_width_chars)
+    return;
+
+  self->max_width_chars = max_width_chars;
+  gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (self));
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_MAX_WIDTH_CHARS]);
+}
+
+/**
+ * gtd_text_width_layout_get_width_chars:
+ *
+ * Retrieves the minimum width in characters of @self.
+ *
+ * Returns: minimum width in characters
+ */
+gint
+gtd_text_width_layout_get_width_chars (GtdTextWidthLayout *self)
+{
+  g_return_val_if_fail (GTD_IS_TEXT_WIDTH_LAYOUT (self), -1);
+
+  return self->width_chars;
+}
+
+/**
+ * gtd_text_width_layout_set_width_chars:
+ * @self: a #GtdTextWidthLayout
+ * @with_chars: minimum width of the widget @self is attached to, in character length
+ *
+ * Sets the minimum width @self has, in characters length. It is a programming
+ * error to set a value bigger than #GtdTextWidthLayout:max-width-layout.
+ */
+void
+gtd_text_width_layout_set_width_chars (GtdTextWidthLayout *self,
+                                       gint                width_chars)
+{
+  g_return_if_fail (GTD_IS_TEXT_WIDTH_LAYOUT (self));
+  g_return_if_fail (width_chars >= -1);
+  g_return_if_fail (self->max_width_chars == -1 || width_chars <= self->max_width_chars);
+
+  if (self->width_chars == width_chars)
+    return;
+
+  self->width_chars = width_chars;
+  gtk_layout_manager_layout_changed (GTK_LAYOUT_MANAGER (self));
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_WIDTH_CHARS]);
+}
diff --git a/src/gtd-text-width-layout.h b/src/gtd-text-width-layout.h
new file mode 100644
index 0000000..e1ea2e7
--- /dev/null
+++ b/src/gtd-text-width-layout.h
@@ -0,0 +1,42 @@
+/* gtd-text-width-layout.h
+ *
+ * Copyright 2020 Georges Basile Stavracas Neto <georges stavracas gmail com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define GTD_TYPE_TEXT_WIDTH_LAYOUT (gtd_text_width_layout_get_type())
+G_DECLARE_FINAL_TYPE (GtdTextWidthLayout, gtd_text_width_layout, GTD, TEXT_WIDTH_LAYOUT, GtkBinLayout)
+
+GtkLayoutManager*    gtd_text_width_layout_new                   (void);
+
+gint                 gtd_text_width_layout_get_max_width_chars   (GtdTextWidthLayout *self);
+
+void                 gtd_text_width_layout_set_max_width_chars   (GtdTextWidthLayout *self,
+                                                                  gint                max_width_chars);
+
+gint                 gtd_text_width_layout_get_width_chars       (GtdTextWidthLayout *self);
+
+void                 gtd_text_width_layout_set_width_chars       (GtdTextWidthLayout *self,
+                                                                  gint                width_chars);
+
+G_END_DECLS
diff --git a/src/meson.build b/src/meson.build
index b0434f6..50b51a7 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -67,6 +67,7 @@ headers = enum_headers + files(
   'gtd-omni-area-addin.h',
   'gtd-task.h',
   'gtd-task-list.h',
+  'gtd-text-width-layout.h',
   'gtd-types.h',
   'gtd-utils.h',
   'gtd-window.h',
@@ -119,6 +120,7 @@ sources += files(
   'gtd-rows-common.c',
   'gtd-task.c',
   'gtd-task-list.c',
+  'gtd-text-width-layout.c',
   'gtd-utils.c',
   'gtd-window.c',
   'main.c'
@@ -275,6 +277,8 @@ if get_option('introspection')
     'gtd-task.h',
     'gtd-task-list.c',
     'gtd-task-list.h',
+    'gtd-text-width-layout.c',
+    'gtd-text-width-layout.h',
     'gtd-types.h',
     'gtd-window.c',
     'gtd-window.h'