Introduce PhoshArrow

An animated arrow. This will be used for home/overview transition.

src/arrow.c

+/*
+ * Copyright © 2019 Alexander Mikhaylenko <exalm7659@gmail.com>
+ *
+ * SPDX-License-Identifier: GPL-3.0+
+ */
+
+#include "arrow.h"
+
+#include <math.h>
+
+#define WIDTH 32
+#define HEIGHT 16
+#define LENGTH 11
+
+struct _PhoshArrow
+{
+  GtkDrawingArea parent_instance;
+
+  double progress;
+};
+
+G_DEFINE_TYPE (PhoshArrow, phosh_arrow, GTK_TYPE_DRAWING_AREA)
+
+enum {
+  PROP_0,
+  PROP_PROGRESS,
+  N_PROPS
+};
+
+static GParamSpec *properties [N_PROPS];
+
+static double
+interpolate_progress (double t)
+{
+  if (t < 1.0 / 3.0)
+    return sin (t * 1.5 * M_PI) / 2.0;
+
+  if (t > 2.0 / 3.0)
+    return cos (t * 1.5 * M_PI) / 2.0 + 1;
+
+  return 0.5;
+}
+
+// GtkWidget
+
+static gboolean
+phosh_arrow_draw (GtkWidget *widget,
+                  cairo_t   *cr)
+{
+  PhoshArrow *self = PHOSH_ARROW (widget);
+  double progress, angle, center_x, center_y;
+  GtkStyleContext *context;
+  GtkStateFlags flags;
+  GdkRGBA rgba;
+
+  progress = interpolate_progress (self->progress);
+
+  angle = (0.5 - progress) * M_PI / 2.5;
+
+  center_x = gtk_widget_get_allocated_width (widget) / 2.0;
+  center_y = (gtk_widget_get_allocated_height (widget) / 2.0 - 0.5) * (0.5 + progress);
+
+  context = gtk_widget_get_style_context (widget);
+  flags = gtk_widget_get_state_flags (widget);
+  gtk_style_context_get_color (context, flags, &rgba);
+
+  cairo_set_line_width (cr, 3);
+  cairo_set_line_cap (cr, CAIRO_LINE_CAP_ROUND);
+  cairo_set_source_rgba (cr, rgba.red, rgba.green, rgba.blue, rgba.alpha);
+
+  cairo_move_to (cr, center_x, center_y);
+  cairo_line_to (cr, center_x + LENGTH * cos (angle), center_y + LENGTH * sin (angle));
+  cairo_stroke (cr);
+
+  cairo_move_to (cr, center_x, center_y);
+  cairo_line_to (cr, center_x - LENGTH * cos (angle), center_y + LENGTH * sin (angle));
+  cairo_stroke (cr);
+
+  return GDK_EVENT_PROPAGATE;
+}
+
+static void
+phosh_arrow_get_property (GObject    *object,
+                          guint       prop_id,
+                          GValue     *value,
+                          GParamSpec *pspec)
+{
+  PhoshArrow *self = PHOSH_ARROW (object);
+
+  switch (prop_id) {
+    case PROP_PROGRESS:
+      g_value_set_double (value, phosh_arrow_get_progress (self));
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+  }
+}
+
+static void
+phosh_arrow_set_property (GObject      *object,
+                          guint         prop_id,
+                          const GValue *value,
+                          GParamSpec   *pspec)
+{
+  PhoshArrow *self = PHOSH_ARROW (object);
+
+  switch (prop_id) {
+    case PROP_PROGRESS:
+      phosh_arrow_set_progress (self, g_value_get_double (value));
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+  }
+}
+
+static void
+phosh_arrow_class_init (PhoshArrowClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  object_class->get_property = phosh_arrow_get_property;
+  object_class->set_property = phosh_arrow_set_property;
+  widget_class->draw = phosh_arrow_draw;
+
+  properties [PROP_PROGRESS] =
+    g_param_spec_double ("progress",
+                         "Progress",
+                         "Progress",
+                         0, 1, 0,
+                         G_PARAM_READWRITE | G_PARAM_EXPLICIT_NOTIFY);
+
+  g_object_class_install_properties(object_class, N_PROPS, properties);
+}
+
+static void
+phosh_arrow_init (PhoshArrow *self)
+{
+  self->progress = 0;
+  g_object_set (self,
+                "width-request", WIDTH,
+                "height-request", HEIGHT,
+                NULL);
+}
+
+PhoshArrow *
+phosh_arrow_new (void)
+{
+  return g_object_new (PHOSH_TYPE_ARROW, NULL);
+}
+
+double
+phosh_arrow_get_progress (PhoshArrow *self)
+{
+  g_return_val_if_fail (PHOSH_IS_ARROW (self), 0);
+
+  return self->progress;
+}
+
+void
+phosh_arrow_set_progress (PhoshArrow *self,
+                          double      progress)
+{
+  g_return_if_fail (PHOSH_IS_ARROW (self));
+
+  self->progress = progress;
+  gtk_widget_queue_draw (GTK_WIDGET (self));
+
+  g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_PROGRESS]);
+}

src/arrow.h

+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define PHOSH_TYPE_ARROW (phosh_arrow_get_type())
+
+G_DECLARE_FINAL_TYPE (PhoshArrow, phosh_arrow, PHOSH, ARROW, GtkDrawingArea)
+
+PhoshArrow *phosh_arrow_new (void);
+
+double      phosh_arrow_get_progress (PhoshArrow *self);
+void        phosh_arrow_set_progress (PhoshArrow *self,
+                                      double      progress);
+
+G_END_DECLS

src/meson.build

@@ -47,6 +47,8 @@ libphosh_sources = [
 ]
 
 phosh_sources = [
+  'arrow.c',
+  'arrow.h',
   'auth.c',
   'auth.h',
   'polkit-auth-agent.c',