[libhandy] Add HdyFadingLabel

[Adrien Plazas <aplazas src gnome org>]

commit 19be2f98573ac608f27ab9a57385481d207be8e3
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Jan 26 21:00:05 2021 +0500

    Add HdyFadingLabel
    
    Add a helper widget for showing fading ellipsized titles in tabs.

 doc/meson.build                |   1 +
 src/hdy-fading-label-private.h |  31 ++++
 src/hdy-fading-label.c         | 328 +++++++++++++++++++++++++++++++++++++++++
 src/meson.build                |   1 +
 4 files changed, 361 insertions(+)
---
diff --git a/doc/meson.build b/doc/meson.build
index dd18fca6..622784b1 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -12,6 +12,7 @@ private_headers = [
     'hdy-css-private.h',
     'hdy-enums.h',
     'hdy-enums-private.h',
+    'hdy-fading-label-private.h',
     'hdy-main-private.h',
     'hdy-nothing-private.h',
     'hdy-keypad-button-private.h',
diff --git a/src/hdy-fading-label-private.h b/src/hdy-fading-label-private.h
new file mode 100644
index 00000000..2ef5d928
--- /dev/null
+++ b/src/hdy-fading-label-private.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2021 Purism SPC
+ *
+ * SPDX-License-Identifier: LGPL-2.1+
+ *
+ * Author: Alexander Mikhaylenko <alexander mikhaylenko puri sm>
+ */
+
+#pragma once
+
+#if !defined(_HANDY_INSIDE) && !defined(HANDY_COMPILATION)
+#error "Only <handy.h> can be included directly."
+#endif
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define HDY_TYPE_FADING_LABEL (hdy_fading_label_get_type())
+
+G_DECLARE_FINAL_TYPE (HdyFadingLabel, hdy_fading_label, HDY, FADING_LABEL, GtkBin)
+
+const gchar *hdy_fading_label_get_label (HdyFadingLabel *self);
+void         hdy_fading_label_set_label (HdyFadingLabel *self,
+                                         const gchar    *label);
+
+float        hdy_fading_label_get_align (HdyFadingLabel *self);
+void         hdy_fading_label_set_align (HdyFadingLabel *self,
+                                         gfloat          align);
+
+G_END_DECLS
diff --git a/src/hdy-fading-label.c b/src/hdy-fading-label.c
new file mode 100644
index 00000000..3d1f014b
--- /dev/null
+++ b/src/hdy-fading-label.c
@@ -0,0 +1,328 @@
+/*
+ * Copyright (C) 2021 Purism SPC
+ *
+ * SPDX-License-Identifier: LGPL-2.1+
+ *
+ * Author: Alexander Mikhaylenko <alexander mikhaylenko puri sm>
+ */
+
+#include "config.h"
+#include "hdy-fading-label-private.h"
+
+#include <glib/gi18n-lib.h>
+#include "hdy-bidi-private.h"
+
+/**
+ * PRIVATE:hdy-fading-label
+ * @short_description: A helper object for #HdyTab
+ * @title: HdyFadingLabel
+ * @stability: Private
+ *
+ * The HdyFadingLabel widget allows to ellipsize a label with a fading effect.
+ *
+ * Since: 1.1
+ */
+
+#define FADE_WIDTH 18
+
+struct _HdyFadingLabel
+{
+  GtkBin parent_instance;
+
+  GtkWidget *label;
+  gfloat align;
+  cairo_pattern_t *gradient;
+};
+
+G_DEFINE_TYPE (HdyFadingLabel, hdy_fading_label, GTK_TYPE_BIN)
+
+enum {
+  PROP_0,
+  PROP_LABEL,
+  PROP_ALIGN,
+  LAST_PROP
+};
+
+static GParamSpec *props[LAST_PROP];
+
+static gboolean
+is_rtl (HdyFadingLabel *self)
+{
+  PangoDirection pango_direction = PANGO_DIRECTION_NEUTRAL;
+  const gchar *label = hdy_fading_label_get_label (self);
+
+  if (label)
+    pango_direction = hdy_find_base_dir (label, -1);
+
+  if (pango_direction == PANGO_DIRECTION_RTL)
+    return TRUE;
+
+  if (pango_direction == PANGO_DIRECTION_LTR)
+    return FALSE;
+
+  return gtk_widget_get_direction (GTK_WIDGET (self)) == GTK_TEXT_DIR_RTL;
+}
+
+static void
+ensure_gradient (HdyFadingLabel *self)
+{
+  if (self->gradient)
+    return;
+
+  self->gradient = cairo_pattern_create_linear (0, 0, 1, 0);
+  cairo_pattern_add_color_stop_rgba (self->gradient, 0, 1, 1, 1, 0);
+  cairo_pattern_add_color_stop_rgba (self->gradient, 1, 1, 1, 1, 1);
+}
+
+static void
+hdy_fading_label_get_preferred_width (GtkWidget *widget,
+                                      gint      *min,
+                                      gint      *nat)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (widget);
+
+  gtk_widget_get_preferred_width (self->label, min, nat);
+
+  if (min)
+    *min = 0;
+}
+
+static void
+hdy_fading_label_get_preferred_width_for_height (GtkWidget *widget,
+                                                 gint       for_height,
+                                                 gint      *min,
+                                                 gint      *nat)
+{
+  hdy_fading_label_get_preferred_width (widget, min, nat);
+}
+
+static void
+hdy_fading_label_size_allocate (GtkWidget     *widget,
+                                GtkAllocation *allocation)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (widget);
+  gfloat align = is_rtl (self) ? 1 - self->align : self->align;
+  GtkAllocation child_allocation;
+  gint child_width;
+
+  gtk_widget_set_allocation (widget, allocation);
+
+  hdy_fading_label_get_preferred_width (widget, NULL, &child_width);
+
+  child_allocation.x = allocation->x + (gint) ((allocation->width - child_width) * align);
+  child_allocation.y = allocation->y;
+  child_allocation.width = child_width;
+  child_allocation.height = allocation->height;
+
+  gtk_widget_size_allocate (self->label, &child_allocation);
+
+  gtk_widget_get_clip (self->label, &child_allocation);
+  child_allocation.x = allocation->x;
+  child_allocation.width = allocation->width;
+  gtk_widget_set_clip (self->label, &child_allocation);
+}
+
+static gboolean
+hdy_fading_label_draw (GtkWidget *widget,
+                       cairo_t   *cr)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (widget);
+  gfloat align = is_rtl (self) ? 1 - self->align : self->align;
+  GtkAllocation clip, alloc;
+  int child_width = gtk_widget_get_allocated_width (self->label);
+
+  gtk_widget_get_allocation (widget, &alloc);
+
+  if (child_width <= alloc.width) {
+      gtk_container_propagate_draw (GTK_CONTAINER (widget), self->label, cr);
+
+      return GDK_EVENT_PROPAGATE;
+  }
+
+  ensure_gradient (self);
+
+  gtk_widget_get_clip (self->label, &clip);
+  clip.x = 0;
+  clip.y -= alloc.y;
+  clip.width = alloc.width;
+
+  cairo_save (cr);
+  cairo_rectangle (cr, clip.x, clip.y, clip.width, clip.height);
+  cairo_clip (cr);
+
+  cairo_push_group (cr);
+  gtk_container_propagate_draw (GTK_CONTAINER (widget), self->label, cr);
+
+  if (align > 0) {
+      cairo_save (cr);
+      cairo_translate (cr, clip.x + FADE_WIDTH, clip.y);
+      cairo_scale (cr, -FADE_WIDTH, clip.height);
+      cairo_set_source (cr, self->gradient);
+      cairo_rectangle (cr, 0, 0, 1, 1);
+      cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OUT);
+      cairo_fill (cr);
+      cairo_restore (cr);
+  }
+
+  if (align < 1) {
+      cairo_translate (cr, clip.x + clip.width - FADE_WIDTH, clip.y);
+      cairo_scale (cr, FADE_WIDTH, clip.height);
+      cairo_set_source (cr, self->gradient);
+      cairo_rectangle (cr, 0, 0, 1, 1);
+      cairo_set_operator (cr, CAIRO_OPERATOR_DEST_OUT);
+      cairo_fill (cr);
+  }
+
+  cairo_pop_group_to_source (cr);
+  cairo_paint (cr);
+
+  cairo_restore (cr);
+
+  return GDK_EVENT_PROPAGATE;
+}
+
+static void
+hdy_fading_label_get_property (GObject    *object,
+                               guint       prop_id,
+                               GValue     *value,
+                               GParamSpec *pspec)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (object);
+
+  switch (prop_id) {
+  case PROP_LABEL:
+    g_value_set_string (value, hdy_fading_label_get_label (self));
+    break;
+
+  case PROP_ALIGN:
+    g_value_set_float (value, hdy_fading_label_get_align (self));
+    break;
+
+    default:
+    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+  }
+}
+
+static void
+hdy_fading_label_set_property (GObject      *object,
+                               guint         prop_id,
+                               const GValue *value,
+                               GParamSpec   *pspec)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (object);
+
+  switch (prop_id) {
+  case PROP_LABEL:
+    hdy_fading_label_set_label (self, g_value_get_string (value));
+    break;
+
+  case PROP_ALIGN:
+    hdy_fading_label_set_align (self, g_value_get_float (value));
+    break;
+
+  default:
+    G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+  }
+}
+
+static void
+hdy_fading_label_finalize (GObject *object)
+{
+  HdyFadingLabel *self = HDY_FADING_LABEL (object);
+
+  g_clear_pointer (&self->gradient, cairo_pattern_destroy);
+
+  G_OBJECT_CLASS (hdy_fading_label_parent_class)->finalize (object);
+}
+
+static void
+hdy_fading_label_class_init (HdyFadingLabelClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  object_class->get_property = hdy_fading_label_get_property;
+  object_class->set_property = hdy_fading_label_set_property;
+  object_class->finalize = hdy_fading_label_finalize;
+
+  widget_class->get_preferred_width = hdy_fading_label_get_preferred_width;
+  widget_class->get_preferred_width_for_height = hdy_fading_label_get_preferred_width_for_height;
+  widget_class->size_allocate = hdy_fading_label_size_allocate;
+  widget_class->draw = hdy_fading_label_draw;
+
+  props[PROP_LABEL] =
+    g_param_spec_string ("label",
+                         _("Label"),
+                         _("Label"),
+                         NULL,
+                         G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  props[PROP_ALIGN] =
+    g_param_spec_float ("align",
+                        _("Align"),
+                        _("Align"),
+                        0.0, 1.0, 0.0,
+                        G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  g_object_class_install_properties (object_class, LAST_PROP, props);
+}
+
+static void
+hdy_fading_label_init (HdyFadingLabel *self)
+{
+  gtk_widget_set_has_window (GTK_WIDGET (self), FALSE);
+
+  self->label = gtk_label_new (NULL);
+  gtk_widget_show (self->label);
+  gtk_label_set_single_line_mode (GTK_LABEL (self->label), TRUE);
+
+  gtk_container_add (GTK_CONTAINER (self), self->label);
+}
+
+const gchar *
+hdy_fading_label_get_label (HdyFadingLabel *self)
+{
+  g_return_val_if_fail (HDY_IS_FADING_LABEL (self), NULL);
+
+  return gtk_label_get_label (GTK_LABEL (self->label));
+}
+
+void
+hdy_fading_label_set_label (HdyFadingLabel *self,
+                            const gchar    *label)
+{
+  g_return_if_fail (HDY_IS_FADING_LABEL (self));
+
+  if (!g_strcmp0 (label, hdy_fading_label_get_label (self)))
+    return;
+
+  gtk_label_set_label (GTK_LABEL (self->label), label);
+
+  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_LABEL]);
+}
+
+float
+hdy_fading_label_get_align (HdyFadingLabel *self)
+{
+  g_return_val_if_fail (HDY_IS_FADING_LABEL (self), 0.0f);
+
+  return self->align;
+}
+
+void
+hdy_fading_label_set_align (HdyFadingLabel *self,
+                            gfloat          align)
+{
+  g_return_if_fail (HDY_IS_FADING_LABEL (self));
+
+  align = CLAMP (align, 0.0, 1.0);
+
+  if (self->align == align)
+    return;
+
+  self->align = align;
+
+  gtk_widget_queue_allocate (GTK_WIDGET (self));
+
+  g_object_notify_by_pspec (G_OBJECT (self), props[PROP_ALIGN]);
+}
diff --git a/src/meson.build b/src/meson.build
index 7992f72c..f9411a76 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -133,6 +133,7 @@ src_sources = [
   'hdy-deck.c',
   'hdy-enum-value-object.c',
   'hdy-expander-row.c',
+  'hdy-fading-label.c',
   'hdy-flap.c',
   'hdy-header-bar.c',
   'hdy-header-group.c',