GtkDemo: Add a CssBasics demo to demonstrate CSS theming

The main difference with the C demo is that we can't use GResource, as
it's only in gio 2.32 and later, so '@import url("resource://...' won't
work. Instead, we use a separate CssProvider to apply reset.css.

sample/GtkDemo/DemoCssBasics.cs

@@ -0,0 +1,99 @@
+/* CSS Theming/CSS Basics
+ *
+ * Gtk themes are written using CSS. Every widget is build of multiple items
+ * that you can style very similarly to a regular website.
+ *
+ */
+
+using System;
+using System.IO;
+using System.Reflection;
+using Gtk;
+
+namespace GtkDemo
+{
+	[Demo ("CSS Basics", "DemoCssBasics.cs", "CSS Theming")]
+	public class DemoCssBasics : Window
+	{
+		TextBuffer buffer;
+		CssProvider provider;
+		CssProvider provider_reset;
+
+		public DemoCssBasics () : base ("CSS Basics")
+		{
+			SetDefaultSize (600, 500);
+
+			buffer = new TextBuffer (null);
+
+			var warning = new TextTag ("warning");
+			warning.Underline = Pango.Underline.Single;
+			buffer.TagTable.Add (warning);
+
+			var error = new TextTag ("error");
+			error.Underline = Pango.Underline.Error;
+			buffer.TagTable.Add (error);
+
+			provider = new CssProvider ();
+			provider_reset = new CssProvider ();
+
+			var container = new ScrolledWindow ();
+			Add (container);
+			var view = new TextView (buffer);
+			container.Add (view);
+			buffer.Changed += OnCssTextChanged;
+
+			using (Stream stream = Assembly.GetExecutingAssembly ().GetManifestResourceStream ("reset.css"))
+			using (StreamReader reader = new StreamReader(stream))
+			{
+				provider_reset.LoadFromData (reader.ReadToEnd());
+			}
+
+			using (Stream stream = Assembly.GetExecutingAssembly ().GetManifestResourceStream ("css_basics.css"))
+			using (StreamReader reader = new StreamReader(stream))
+			{
+				buffer.Text = reader.ReadToEnd();
+			}
+
+			// TODO: Connect to "parsing-error" signal in CssProvider, added in GTK+ 3.2
+
+			ApplyCss (this, provider_reset, 800);
+			ApplyCss (this, provider, UInt32.MaxValue);
+
+			ShowAll ();
+		}
+
+		private void ApplyCss (Widget widget, CssProvider provider, uint priority)
+		{
+			widget.StyleContext.AddProvider (provider, priority);
+			var container = widget as Container;
+			if (container != null) {
+				foreach (var child in container.Children) {
+					ApplyCss (child, provider, priority);
+				}
+			}
+		}
+
+		private void OnCssTextChanged (object sender, EventArgs e)
+		{
+			var start = buffer.StartIter;
+			var end = buffer.EndIter;
+			buffer.RemoveAllTags (start, end);
+
+			string text = buffer.Text;
+			try {
+				provider.LoadFromData (text);
+			} catch (GLib.GException) {
+				// Ignore parsing errors
+			}
+
+			StyleContext.ResetWidgets (Gdk.Screen.Default);
+		}
+
+		protected override bool OnDeleteEvent (Gdk.Event evt)
+		{
+			Destroy ();
+			return true;
+		}
+	}
+}
+

sample/GtkDemo/Makefile.am

@@ -13,7 +13,7 @@ DEBUGS = $(addsuffix .mdb, $(TARGETS))
 CLEANFILES = $(TARGETS) $(DEBUGS)
 noinst_SCRIPTS = $(TARGETS)
 
-EXTRA_DIST = $(sources) $(image_names)
+EXTRA_DIST = $(sources) $(image_names) $(css_names)
 
 sources = \
 	DemoApplicationWindow.cs	\
@@ -21,6 +21,7 @@ sources = \
 	DemoButtonBox.cs		\
 	DemoClipboard.cs		\
 	DemoColorSelection.cs	\
+	DemoCssBasics.cs		\
 	DemoDialog.cs			\
 	DemoDrawingArea.cs		\
 	DemoEditableCells.cs	\
@@ -73,9 +74,18 @@ image_names = \
 	images/gtk-logo-rgb.gif \
 	images/floppybuddy.gif
 
+css = \
+	css/css_basics.css,css_basics.css \
+	css/reset.css,reset.css
+
+css_names = \
+	css/css_basics.css \
+	css/reset.css
+
 build_sources = $(addprefix $(srcdir)/, $(sources))
 build_images = $(addprefix $(srcdir)/, $(images))
-resources = $(addprefix -resource:, $(build_sources), $(build_images))
+build_css = $(addprefix $(srcdir)/, $(css))
+resources = $(addprefix -resource:, $(build_sources), $(build_images), $(build_css))
 
 GtkDemo.exe: $(build_sources) $(assemblies)
 	$(CSC) $(CSFLAGS) -out:GtkDemo.exe $(build_sources) $(references) $(resources)

sample/GtkDemo/css/css_basics.css

@@ -0,0 +1,21 @@
+/* You can edit the text in this window to change the
+ * appearance of this Window.
+ * Be careful, if you screw it up, nothing might be visible
+ * anymore. :)
+ */
+
+/* The content of reset.css has been applied to reset all properties to
+ * their defaults values and overrides all user settings and the theme in use */
+
+/* Set a very futuristic style by default */
+* {
+  color: green;
+  font-family: Monospace;
+  border: 1px solid;
+}
+
+/* Make sure selections are visible */
+:selected {
+  background-color: darkGreen;
+  color: black;
+}

sample/GtkDemo/css/reset.css

@@ -0,0 +1,67 @@
+/* Apply this CSS to get the default values for every property.
+ * This is useful when writing special CSS tests that should not be
+ * inluenced by themes - not even the default ones.
+ * Keep in mind that the output will be very ugly and not look like
+ * anything GTK.
+ */
+
+* {
+  color: inherit;
+  font-size: inherit;
+  background-color: initial;
+  font-family: inherit;
+  font-style: inherit;
+  font-variant: inherit;
+  font-weight: inherit;
+  text-shadow: inherit;
+  icon-shadow: inherit;
+  box-shadow: initial;
+  margin-top: initial;
+  margin-left: initial;
+  margin-bottom: initial;
+  margin-right: initial;
+  padding-top: initial;
+  padding-left: initial;
+  padding-bottom: initial;
+  padding-right: initial;
+  border-top-style: initial;
+  border-top-width: initial;
+  border-left-style: initial;
+  border-left-width: initial;
+  border-bottom-style: initial;
+  border-bottom-width: initial;
+  border-right-style: initial;
+  border-right-width: initial;
+  border-top-left-radius: initial;
+  border-top-right-radius: initial;
+  border-bottom-right-radius: initial;
+  border-bottom-left-radius: initial;
+  outline-style: initial;
+  outline-width: initial;
+  outline-offset: initial;
+  background-clip: initial;
+  background-origin: initial;
+  background-size: initial;
+  background-position: initial;
+  border-top-color: initial;
+  border-right-color: initial;
+  border-bottom-color: initial;
+  border-left-color: initial;
+  outline-color:  initial;
+  background-repeat: initial;
+  background-image: initial;
+  border-image-source: initial;
+  border-image-repeat: initial;
+  border-image-slice: initial;
+  border-image-width: initial;
+  transition-property: initial;
+  transition-duration: initial;
+  transition-timing-function: initial;
+  transition-delay: initial;
+  engine: initial;
+  gtk-key-bindings: initial;
+
+  -GtkWidget-focus-line-width: 0;
+  -GtkWidget-focus-padding: 0;
+  -GtkNotebook-initial-gap: 0;
+}

sample/sample.csproj

@@ -110,6 +110,7 @@
     <Compile Include="CairoPng.cs" />
     <Compile Include="valtest\Gtksharp\Valobj.cs" />
     <Compile Include="GtkDemo\DemoSpinner.cs" />
+    <Compile Include="GtkDemo\DemoCssBasics.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>