[gtk/wip/otte/inscription: 3/3] gtk-demo: Add a "Read More" label demo.

[Benjamin Otte <otte src gnome org>]

commit 98e0ca7477a31fb2d40c7d6ede36acbf809efe7b
Author: Benjamin Otte <otte redhat com>
Date:   Sat Jun 11 20:27:53 2022 +0200

    gtk-demo: Add a "Read More" label demo.

 demos/gtk-demo/demo.gresource.xml |   1 +
 demos/gtk-demo/meson.build        |   1 +
 demos/gtk-demo/read_more.c        | 238 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 240 insertions(+)
---
diff --git a/demos/gtk-demo/demo.gresource.xml b/demos/gtk-demo/demo.gresource.xml
index f1caed2b8d..849ef462dc 100644
--- a/demos/gtk-demo/demo.gresource.xml
+++ b/demos/gtk-demo/demo.gresource.xml
@@ -329,6 +329,7 @@
     <file>pickers.c</file>
     <file>printing.c</file>
     <file>revealer.c</file>
+    <file>read_more.c</file>
     <file>rotated_text.c</file>
     <file>scale.c</file>
     <file>search_entry.c</file>
diff --git a/demos/gtk-demo/meson.build b/demos/gtk-demo/meson.build
index 1347baf2aa..ef89fbc7d2 100644
--- a/demos/gtk-demo/meson.build
+++ b/demos/gtk-demo/meson.build
@@ -73,6 +73,7 @@ demos = files([
   'peg_solitaire.c',
   'pickers.c',
   'printing.c',
+  'read_more.c',
   'revealer.c',
   'rotated_text.c',
   'scale.c',
diff --git a/demos/gtk-demo/read_more.c b/demos/gtk-demo/read_more.c
new file mode 100644
index 0000000000..3d772068eb
--- /dev/null
+++ b/demos/gtk-demo/read_more.c
@@ -0,0 +1,238 @@
+/* Read More
+ *
+ * A simple implementation of a widget that can either
+ * display a lot of text or just the first few lines with a
+ * "Read More" button.
+ */
+
+#include <gtk/gtk.h>
+
+#define READ_TYPE_MORE (read_more_get_type ())
+G_DECLARE_FINAL_TYPE(ReadMore, read_more, READ, MORE, GtkWidget)
+
+struct _ReadMore {
+  GtkWidget parent_instance;
+ 
+  GtkWidget *label;
+  GtkWidget *inscription;
+  GtkWidget *box;
+  gboolean show_more;
+};
+
+G_DEFINE_TYPE (ReadMore, read_more, GTK_TYPE_WIDGET)
+
+static GtkSizeRequestMode
+read_more_get_request_mode (GtkWidget *widget)
+{
+  return GTK_SIZE_REQUEST_HEIGHT_FOR_WIDTH;
+}
+
+static void
+read_more_measure (GtkWidget      *widget,
+                   GtkOrientation  orientation,
+                   int             for_size,
+                   int            *minimum,
+                   int            *natural,
+                   int            *minimum_baseline,
+                   int            *natural_baseline)
+{
+  ReadMore *self = READ_MORE (widget);
+  int label_min, label_nat, label_min_baseline, label_nat_baseline;
+  int box_min, box_nat, box_min_baseline, box_nat_baseline;
+  int min_check;
+
+  if (self->show_more)
+    min_check = G_MAXINT;
+  else if (for_size >= 0)
+    gtk_widget_measure (self->box, 1 - orientation, -1, &min_check, NULL, NULL, NULL);
+  else
+    min_check = -1;
+
+  if (min_check > for_size)
+    {
+      gtk_widget_measure (self->label,
+                          orientation,
+                          for_size,
+                          minimum, natural,
+                          minimum_baseline, natural_baseline);
+      return;
+    }
+
+  else if (for_size >= 0)
+    gtk_widget_measure (self->label, 1 - orientation, -1, &min_check, NULL, NULL, NULL);
+  else
+    min_check = -1;
+
+  if (min_check > for_size)
+    {
+      gtk_widget_measure (self->box,
+                          orientation,
+                          for_size,
+                          minimum, natural,
+                          minimum_baseline, natural_baseline);
+      return;
+    }
+
+  gtk_widget_measure (self->label,
+                      orientation,
+                      for_size,
+                      &label_min, &label_nat,
+                      &label_min_baseline, &label_nat_baseline);
+  gtk_widget_measure (self->box,
+                      orientation,
+                      for_size,
+                      &box_min, &box_nat,
+                      &box_min_baseline, &box_nat_baseline);
+
+  *minimum = MIN (label_min, box_min);
+  *natural = MIN (label_nat, box_nat);
+
+  /* FIXME: Figure out baselines! */
+}
+
+static void
+read_more_allocate (GtkWidget *widget,
+                    int        width,
+                    int        height,
+                    int        baseline)
+{
+  ReadMore *self = READ_MORE (widget);
+  gboolean show_more;
+
+  if (self->show_more)
+    {
+      show_more = TRUE;
+    }
+  else
+    {
+      int needed;
+
+      /* check to see if we have enough space to show all text */
+      gtk_widget_measure (self->label,
+                          GTK_ORIENTATION_VERTICAL,
+                          width,
+                          &needed, NULL, NULL, NULL);
+
+      show_more = needed <= height;
+    }
+
+  gtk_widget_set_child_visible (self->label, show_more);
+  gtk_widget_set_child_visible (self->box, !show_more);
+
+  if (show_more)
+    gtk_widget_size_allocate (self->label, &(GtkAllocation) { 0, 0, width, height }, baseline);
+  else
+    gtk_widget_size_allocate (self->box, &(GtkAllocation) { 0, 0, width, height }, baseline);
+}
+
+static void
+read_more_dispose (GObject *object)
+{
+  ReadMore *self = READ_MORE (object);
+
+  g_clear_pointer (&self->label, gtk_widget_unparent);
+  g_clear_pointer (&self->box, gtk_widget_unparent);
+
+  G_OBJECT_CLASS (read_more_parent_class)->dispose (object);
+}
+
+static void
+read_more_class_init (ReadMoreClass *klass)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  widget_class->get_request_mode = read_more_get_request_mode;
+  widget_class->measure = read_more_measure;
+  widget_class->size_allocate = read_more_allocate;
+
+  object_class->dispose = read_more_dispose;
+}
+
+static void
+read_more_clicked (GtkButton *button,
+                   ReadMore  *self)
+{
+  self->show_more = TRUE;
+  gtk_widget_queue_resize (GTK_WIDGET (self));
+}
+
+static void
+read_more_init (ReadMore *self)
+{
+  GtkWidget *button;
+
+  self->label = gtk_label_new (NULL);
+  gtk_label_set_xalign (GTK_LABEL (self->label), 0.0);
+  gtk_label_set_yalign (GTK_LABEL (self->label), 0.0);
+  gtk_label_set_wrap (GTK_LABEL (self->label), TRUE);
+  gtk_label_set_width_chars (GTK_LABEL (self->label), 3);
+  gtk_label_set_max_width_chars (GTK_LABEL (self->label), 30);
+  gtk_widget_set_parent (self->label, GTK_WIDGET (self));
+
+  self->box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 0);
+  gtk_widget_set_vexpand (self->box, FALSE);
+  gtk_widget_set_parent (self->box, GTK_WIDGET (self));
+
+  self->inscription = gtk_inscription_new (NULL);
+  gtk_inscription_set_xalign (GTK_INSCRIPTION (self->inscription), 0.0);
+  gtk_inscription_set_yalign (GTK_INSCRIPTION (self->inscription), 0.0);
+  gtk_inscription_set_min_lines (GTK_INSCRIPTION (self->inscription), 3);
+  gtk_inscription_set_nat_chars (GTK_INSCRIPTION (self->inscription), 30);
+  gtk_widget_set_vexpand (self->inscription, TRUE);
+  gtk_box_append (GTK_BOX (self->box), self->inscription);
+  
+  button = gtk_button_new_with_label ("Read More");
+  g_signal_connect (button, "clicked", G_CALLBACK (read_more_clicked), self);
+  gtk_box_append (GTK_BOX (self->box), button);
+}
+
+static void
+read_more_set_text (ReadMore   *self,
+                    const char *text)
+{
+  gtk_label_set_label (GTK_LABEL (self->label), text);
+  gtk_inscription_set_text (GTK_INSCRIPTION (self->inscription), text);
+}
+
+static GtkWidget *
+read_more_new (const char *text)
+{
+  ReadMore *self = g_object_new (READ_TYPE_MORE, NULL);
+
+  read_more_set_text (self, text);
+
+  return GTK_WIDGET (self);
+}
+
+GtkWidget *
+do_read_more (GtkWidget *do_widget)
+{
+  static GtkWidget *window = NULL;
+
+  if (!window)
+    {
+      GtkWidget *readmore;
+
+      window = gtk_window_new ();
+      gtk_window_set_display (GTK_WINDOW (window),
+                              gtk_widget_get_display (do_widget));
+      gtk_window_set_title (GTK_WINDOW (window), "Read More");
+      g_object_add_weak_pointer (G_OBJECT (window), (gpointer *)&window);
+
+      readmore = read_more_new (
+"I'd just like to interject for a moment. What you're referring to as Linux, is in fact, GNU/Linux, or as 
I've recently taken to calling it, GNU plus Linux. Linux is not an operating system unto itself, but rather 
another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities and 
vital system components comprising a full OS as defined by POSIX.\n"
+"\n"
+"Many computer users run a modified version of the GNU system every day, without realizing it. Through a 
peculiar turn of events, the version of GNU which is widely used today is often called \"Linux\", and many of 
its users are not aware that it is basically the GNU system, developed by the GNU Project.\n"
+"\n"
+"There really is a Linux, and these people are using it, but it is just a part of the system they use. Linux 
is the kernel: the program in the system that allocates the machine's resources to the other programs that 
you run. The kernel is an essential part of an operating system, but useless by itself; it can only function 
in the context of a complete operating system. Linux is normally used in combination with the GNU operating 
system: the whole system is basically GNU with Linux added, or GNU/Linux. All the so-called \"Linux\" 
distributions are really distributions of GNU/Linux.");
+      gtk_window_set_child (GTK_WINDOW (window), readmore);
+    }
+
+  if (!gtk_widget_get_visible (window))
+    gtk_widget_show (window);
+  else
+    gtk_window_destroy (GTK_WINDOW (window));
+
+  return window;
+}