[gtk/matthiasc/for-master: 7/7] docs: Add GtkDrawingArea to the gallery

[Matthias Clasen <matthiasc src gnome org>]

commit e51a98d1846914137ff6aad14bf1c4435a66f3ab
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Oct 26 01:07:54 2020 -0400

    docs: Add GtkDrawingArea to the gallery

 docs/reference/gtk/images/drawingarea.png | Bin 0 -> 8303 bytes
 docs/reference/gtk/images/glarea.png      | Bin 3016 -> 4465 bytes
 docs/reference/gtk/meson.build            |   1 +
 docs/reference/gtk/visual_index.xml       |   1 +
 docs/tools/widgets.c                      | 188 +++++++++++++++++++++++++++++-
 5 files changed, 188 insertions(+), 2 deletions(-)
---
diff --git a/docs/reference/gtk/images/drawingarea.png b/docs/reference/gtk/images/drawingarea.png
new file mode 100644
index 0000000000..7ab304522b
Binary files /dev/null and b/docs/reference/gtk/images/drawingarea.png differ
diff --git a/docs/reference/gtk/images/glarea.png b/docs/reference/gtk/images/glarea.png
index 1325afcab0..50bf77c062 100644
Binary files a/docs/reference/gtk/images/glarea.png and b/docs/reference/gtk/images/glarea.png differ
diff --git a/docs/reference/gtk/meson.build b/docs/reference/gtk/meson.build
index 4e72c167da..30d7737339 100644
--- a/docs/reference/gtk/meson.build
+++ b/docs/reference/gtk/meson.build
@@ -259,6 +259,7 @@ images = [
   'images/down-start.png',
   'images/drop-down.png',
   'images/drawing.png',
+  'images/drawingarea.png',
   'images/ease-in-out.png',
   'images/ease-in.png',
   'images/ease-out.png',
diff --git a/docs/reference/gtk/visual_index.xml b/docs/reference/gtk/visual_index.xml
index 82fc571465..664d3922fe 100644
--- a/docs/reference/gtk/visual_index.xml
+++ b/docs/reference/gtk/visual_index.xml
@@ -20,6 +20,7 @@
     <link linkend="GtkScale"><inlinegraphic fileref="scales.png" format="PNG"></inlinegraphic></link>
     <link linkend="GtkCalendar"><inlinegraphic fileref="calendar.png" format="PNG"></inlinegraphic></link>
     <link linkend="GtkGLArea"><inlinegraphic fileref="glarea.png" format="PNG"></inlinegraphic></link>
+    <link linkend="GtkDrawingArea"><inlinegraphic fileref="drawingarea.png" 
format="PNG"></inlinegraphic></link>
     <link linkend="GtkVideo"><inlinegraphic fileref="video.png" format="PNG"></inlinegraphic></link>
     <link linkend="GtkMediaControls"><inlinegraphic fileref="media-controls.png" 
format="PNG"></inlinegraphic></link>
     <link linkend="GtkWindowControls"><inlinegraphic fileref="windowcontrols.png" 
format="PNG"></inlinegraphic></link>
diff --git a/docs/tools/widgets.c b/docs/tools/widgets.c
index c99cef1d06..3cb08a3410 100644
--- a/docs/tools/widgets.c
+++ b/docs/tools/widgets.c
@@ -1497,6 +1497,7 @@ create_flow_box (void)
 static WidgetInfo *
 create_gl_area (void)
 {
+  GtkWidget *vbox;
   WidgetInfo *info;
   GtkWidget *widget;
   GtkWidget *gears;
@@ -1513,12 +1514,15 @@ create_gl_area (void)
   gtk_style_context_add_provider (gtk_widget_get_style_context (gears), GTK_STYLE_PROVIDER (provider), 800);
   g_object_unref (provider);
 
+  vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 3);
   gtk_widget_set_halign (widget, GTK_ALIGN_FILL);
   gtk_widget_set_valign (widget, GTK_ALIGN_FILL);
+  gtk_box_append (GTK_BOX (vbox), widget);
+  gtk_box_append (GTK_BOX (vbox), gtk_label_new ("GL Area"));
 
-  add_margin (widget);
+  add_margin (vbox);
 
-  info = new_widget_info ("glarea", widget, MEDIUM);
+  info = new_widget_info ("glarea", vbox, MEDIUM);
 
   return info;
 }
@@ -1741,6 +1745,185 @@ create_shortcuts_window (void)
   return new_widget_info ("shortcuts-window", overlay, ASIS);
 }
 
+static void
+oval_path (cairo_t *cr,
+           double xc, double yc,
+           double xr, double yr)
+{
+  cairo_save (cr);
+
+  cairo_translate (cr, xc, yc);
+  cairo_scale (cr, 1.0, yr / xr);
+  cairo_move_to (cr, xr, 0.0);
+  cairo_arc (cr,
+             0, 0,
+             xr,
+             0, 2 * G_PI);
+  cairo_close_path (cr);
+
+  cairo_restore (cr);
+}
+
+static void
+fill_checks (cairo_t *cr,
+             int x,     int y,
+             int width, int height)
+{
+  int i, j;
+
+#define CHECK_SIZE 16
+
+  cairo_rectangle (cr, x, y, width, height);
+  cairo_set_source_rgb (cr, 0.4, 0.4, 0.4);
+  cairo_fill (cr);
+
+  /* Only works for CHECK_SIZE a power of 2 */
+  j = x & (-CHECK_SIZE);
+
+  for (; j < height; j += CHECK_SIZE)
+    {
+      i = y & (-CHECK_SIZE);
+      for (; i < width; i += CHECK_SIZE)
+        if ((i / CHECK_SIZE + j / CHECK_SIZE) % 2 == 0)
+          cairo_rectangle (cr, i, j, CHECK_SIZE, CHECK_SIZE);
+    }
+
+  cairo_set_source_rgb (cr, 0.7, 0.7, 0.7);
+  cairo_fill (cr);
+
+#undef CHECK_SIZE
+}
+
+static void
+draw_3circles (cairo_t *cr,
+               double xc, double yc,
+               double radius,
+               double alpha)
+{
+  double subradius = radius * (2 / 3. - 0.1);
+
+  cairo_set_source_rgba (cr, 1., 0., 0., alpha);
+  oval_path (cr,
+             xc + radius / 3. * cos (G_PI * (0.5)),
+             yc - radius / 3. * sin (G_PI * (0.5)),
+             subradius, subradius);
+  cairo_fill (cr);
+
+  cairo_set_source_rgba (cr, 0., 1., 0., alpha);
+  oval_path (cr,
+             xc + radius / 3. * cos (G_PI * (0.5 + 2/.3)),
+             yc - radius / 3. * sin (G_PI * (0.5 + 2/.3)),
+             subradius, subradius);
+  cairo_fill (cr);
+
+  cairo_set_source_rgba (cr, 0., 0., 1., alpha);
+  oval_path (cr,
+             xc + radius / 3. * cos (G_PI * (0.5 + 4/.3)),
+             yc - radius / 3. * sin (G_PI * (0.5 + 4/.3)),
+             subradius, subradius);
+  cairo_fill (cr);
+}
+
+static void
+groups_draw (GtkDrawingArea *darea,
+             cairo_t        *cr,
+             int             width,
+             int             height,
+             gpointer        data)
+{
+  cairo_surface_t *overlay, *punch, *circles;
+  cairo_t *overlay_cr, *punch_cr, *circles_cr;
+
+  /* Fill the background */
+  double radius = 0.5 * (width < height ? width : height) - 10;
+  double xc = width / 2.;
+  double yc = height / 2.;
+
+  overlay = cairo_surface_create_similar (cairo_get_target (cr),
+                                          CAIRO_CONTENT_COLOR_ALPHA,
+                                          width, height);
+
+  punch = cairo_surface_create_similar (cairo_get_target (cr),
+                                        CAIRO_CONTENT_ALPHA,
+                                        width, height);
+
+  circles = cairo_surface_create_similar (cairo_get_target (cr),
+                                          CAIRO_CONTENT_COLOR_ALPHA,
+                                          width, height);
+
+  fill_checks (cr, 0, 0, width, height);
+
+  /* Draw a black circle on the overlay
+   */
+  overlay_cr = cairo_create (overlay);
+  cairo_set_source_rgb (overlay_cr, 0., 0., 0.);
+  oval_path (overlay_cr, xc, yc, radius, radius);
+  cairo_fill (overlay_cr);
+
+  /* Draw 3 circles to the punch surface, then cut
+   * that out of the main circle in the overlay
+   */
+  punch_cr = cairo_create (punch);
+  draw_3circles (punch_cr, xc, yc, radius, 1.0);
+  cairo_destroy (punch_cr);
+
+  cairo_set_operator (overlay_cr, CAIRO_OPERATOR_DEST_OUT);
+  cairo_set_source_surface (overlay_cr, punch, 0, 0);
+  cairo_paint (overlay_cr);
+
+  /* Now draw the 3 circles in a subgroup again
+   * at half intensity, and use OperatorAdd to join up
+   * without seams.
+   */
+  circles_cr = cairo_create (circles);
+
+  cairo_set_operator (circles_cr, CAIRO_OPERATOR_OVER);
+  draw_3circles (circles_cr, xc, yc, radius, 0.5);
+  cairo_destroy (circles_cr);
+
+  cairo_set_operator (overlay_cr, CAIRO_OPERATOR_ADD);
+  cairo_set_source_surface (overlay_cr, circles, 0, 0);
+  cairo_paint (overlay_cr);
+
+  cairo_destroy (overlay_cr);
+
+  cairo_set_source_surface (cr, overlay, 0, 0);
+  cairo_paint (cr);
+
+  cairo_surface_destroy (overlay);
+  cairo_surface_destroy (punch);
+  cairo_surface_destroy (circles);
+}
+
+
+static WidgetInfo *
+create_drawing_area (void)
+{
+  GtkWidget *vbox;
+  WidgetInfo *info;
+  GtkWidget *widget;
+  GtkWidget *da;
+
+  widget = gtk_frame_new (NULL);
+  da = gtk_drawing_area_new ();
+  gtk_widget_set_size_request (da, 96, 96);
+  gtk_drawing_area_set_draw_func (GTK_DRAWING_AREA (da), groups_draw, NULL, NULL);
+  gtk_frame_set_child (GTK_FRAME (widget), da);
+
+  vbox = gtk_box_new (GTK_ORIENTATION_VERTICAL, 6);
+  gtk_widget_set_halign (widget, GTK_ALIGN_FILL);
+  gtk_widget_set_valign (widget, GTK_ALIGN_FILL);
+
+  gtk_box_append (GTK_BOX (vbox), widget);
+  gtk_box_append (GTK_BOX (vbox), gtk_label_new ("Drawing Area"));
+
+  add_margin (vbox);
+
+  info = new_widget_info ("drawingarea", vbox, MEDIUM);
+
+  return info;
+}
+
 GList *
 get_all_widgets (void)
 {
@@ -1814,6 +1997,7 @@ get_all_widgets (void)
   retval = g_list_prepend (retval, create_popover ());
   retval = g_list_prepend (retval, create_menu ());
   retval = g_list_prepend (retval, create_shortcuts_window ());
+  retval = g_list_prepend (retval, create_drawing_area());
 
   return retval;
 }