[gnome-control-center/wip/benzea/display-settings-widget] display: Add simple display scaling preview widget

[Benjamin Berg <bberg src gnome org>]

commit d9e2dfe3f6a69b9360a6afbf50c5a200247600a8
Author: Benjamin Berg <bberg redhat com>
Date:   Tue Jan 22 16:52:37 2019 +0100

    display: Add simple display scaling preview widget

 panels/display/cc-display-scaling-preview.c | 175 ++++++++++++++++++++++++++++
 panels/display/cc-display-scaling-preview.h |  42 +++++++
 panels/display/meson.build                  |   1 +
 3 files changed, 218 insertions(+)
---
diff --git a/panels/display/cc-display-scaling-preview.c b/panels/display/cc-display-scaling-preview.c
new file mode 100644
index 000000000..4410a3a4c
--- /dev/null
+++ b/panels/display/cc-display-scaling-preview.c
@@ -0,0 +1,175 @@
+/* cc-display-scaling-preview.c
+ *
+ * Copyright (C) 2019  Red Hat, Inc.
+ *
+ * Written by: Benjamin Berg <bberg redhat 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 2, 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/>.
+ */
+
+#include <glib/gi18n.h>
+#include "cc-display-scaling-preview.h"
+
+struct _CcDisplayScalingPreview
+{
+  GtkDrawingArea parent_instance;
+
+  gboolean selected;
+  gdouble scaling;
+  gdouble active_scaling;
+};
+
+G_DEFINE_TYPE (CcDisplayScalingPreview, cc_display_scaling_preview, GTK_TYPE_DRAWING_AREA)
+
+CcDisplayScalingPreview *
+cc_display_scaling_preview_new (void)
+{
+  return g_object_new (CC_TYPE_DISPLAY_SCALING_PREVIEW, NULL);
+}
+
+static gboolean
+cc_display_scaling_preview_draw (GtkWidget *widget,
+                                 cairo_t   *cr)
+{
+  CcDisplayScalingPreview *self = CC_DISPLAY_SCALING_PREVIEW (widget);
+  GtkStyleContext *context = gtk_widget_get_style_context (widget);
+  GtkBorder margin, border, padding;
+  GtkStateFlags state = GTK_STATE_FLAG_NORMAL;
+  GtkAllocation alloc;
+  PangoLayout *layout;
+  PangoFontDescription *font = NULL;
+  PangoAttrList *attrs;
+  GdkRGBA color;
+  gint w, h;
+
+  cairo_save (cr);
+  gtk_widget_get_allocation (GTK_WIDGET (self), &alloc);
+
+  w = alloc.width;
+  h = alloc.height;
+
+  gtk_style_context_save (context);
+
+  if (self->selected)
+    state = GTK_STATE_FLAG_SELECTED;
+
+  gtk_style_context_set_state (context, state);
+
+  gtk_style_context_get_margin (context, state, &margin);
+
+  w -= margin.left + margin.right;
+  h -= margin.top + margin.bottom;
+  cairo_translate (cr, margin.left, margin.top);
+
+  gtk_render_background (context, cr, 0, 0, w, h);
+  gtk_render_frame (context, cr, 0, 0, w, h);
+
+  gtk_style_context_get_border (context, state, &border);
+  gtk_style_context_get_padding (context, state, &padding);
+
+  w -= border.left + border.right;
+  h -= border.top + border.bottom;
+  cairo_translate (cr, border.left, border.top);
+  cairo_rectangle (cr, 0, 0, w, h);
+  cairo_clip (cr);
+
+  w -= padding.left + padding.right;
+  h -= padding.top + padding.bottom;
+  cairo_translate (cr, padding.left, padding.top);
+
+  /* And draw a layout with a preview string */
+  gtk_style_context_get (context, state, "font", &font, NULL);
+  /* TRANSLATORS: This is used to preview display scaling. The only
+   * purpose is to show how the text size changes with the scale. */
+  layout = gtk_widget_create_pango_layout (GTK_WIDGET (self), _("This is a sample of what text would look 
like. This is a sample of what text would look like."));
+  pango_layout_set_font_description (layout, font);
+  pango_layout_set_width (layout, w * PANGO_SCALE);
+  pango_layout_set_wrap (layout, PANGO_WRAP_WORD);
+  attrs = pango_attr_list_new ();
+  pango_attr_list_insert (attrs, pango_attr_scale_new (self->scaling / self->active_scaling));
+  pango_layout_set_attributes (layout, attrs);
+  g_clear_pointer (&attrs, pango_attr_list_unref);
+
+  gtk_style_context_get_color (context, state, &color);
+  gdk_cairo_set_source_rgba (cr, &color);
+
+  gtk_render_layout (context, cr, 0, 0, layout);
+  g_object_unref (layout);
+
+  gtk_style_context_restore (context);
+  cairo_restore (cr);
+
+  return TRUE;
+}
+
+static void
+cc_display_scaling_preview_class_init (CcDisplayScalingPreviewClass *klass)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (klass);
+
+  widget_class->draw = cc_display_scaling_preview_draw;
+}
+
+static void
+cc_display_scaling_preview_init (CcDisplayScalingPreview *self)
+{
+  GtkStyleContext *context = gtk_widget_get_style_context (GTK_WIDGET (self));
+
+  self->scaling = 1.0;
+  self->active_scaling = 1.0;
+
+  gtk_style_context_add_class (context, "frame");
+  gtk_style_context_add_class (context, "view");
+  gtk_style_context_add_class (context, "display-scaling-preview");
+}
+
+void
+cc_display_scaling_preview_set_scaling (CcDisplayScalingPreview *preview,
+                                        gdouble                  scaling,
+                                        gdouble                  active_scaling)
+{
+  g_return_if_fail (CC_IS_DISPLAY_SCALING_PREVIEW (preview));
+
+  preview->scaling = scaling;
+  preview->active_scaling = active_scaling;
+
+  gtk_widget_queue_draw (GTK_WIDGET (preview));
+}
+
+void
+cc_display_scaling_preview_get_scaling (CcDisplayScalingPreview *preview,
+                                        gdouble                 *scaling,
+                                        gdouble                 *active_scaling)
+{
+  g_return_if_fail (CC_IS_DISPLAY_SCALING_PREVIEW (preview));
+
+  if (scaling)
+    *scaling = preview->scaling;
+  if (active_scaling)
+    *active_scaling = preview->active_scaling;
+}
+
+void
+cc_display_scaling_preview_set_selected (CcDisplayScalingPreview *preview,
+                                         gboolean                 selected)
+{
+  g_return_if_fail (CC_IS_DISPLAY_SCALING_PREVIEW (preview));
+
+  if (preview->selected == selected)
+    return;
+
+  preview->selected = selected;
+  gtk_widget_queue_draw (GTK_WIDGET (preview));
+}
+
diff --git a/panels/display/cc-display-scaling-preview.h b/panels/display/cc-display-scaling-preview.h
new file mode 100644
index 000000000..1395b8927
--- /dev/null
+++ b/panels/display/cc-display-scaling-preview.h
@@ -0,0 +1,42 @@
+/* cc-display-scaling-preview.h
+ *
+ * Copyright (C) 2019  Red Hat, Inc.
+ *
+ * Written by: Benjamin Berg <bberg redhat 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 2, 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/>.
+ */
+
+#pragma once
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define CC_TYPE_DISPLAY_SCALING_PREVIEW (cc_display_scaling_preview_get_type())
+
+G_DECLARE_FINAL_TYPE (CcDisplayScalingPreview, cc_display_scaling_preview, CC, DISPLAY_SCALING_PREVIEW, 
GtkDrawingArea)
+
+CcDisplayScalingPreview *cc_display_scaling_preview_new (void);
+
+void                     cc_display_scaling_preview_set_scaling  (CcDisplayScalingPreview *preview,
+                                                                  gdouble                  scaling,
+                                                                  gdouble                  active_scaling);
+void                     cc_display_scaling_preview_get_scaling  (CcDisplayScalingPreview *preview,
+                                                                  gdouble                 *scaling,
+                                                                  gdouble                 *active_scaling);
+void                     cc_display_scaling_preview_set_selected (CcDisplayScalingPreview *preview,
+                                                                  gboolean                 selected);
+
+G_END_DECLS
diff --git a/panels/display/meson.build b/panels/display/meson.build
index 40de7bae4..bd165a436 100644
--- a/panels/display/meson.build
+++ b/panels/display/meson.build
@@ -24,6 +24,7 @@ sources = files(
   'cc-display-config-dbus.c',
   'cc-display-config-manager-dbus.c',
   'cc-display-config-manager.c',
+  'cc-display-scaling-preview.c',
   'cc-display-settings.c',
   'cc-night-light-dialog.c',
   'cc-value-object.c',